Australian examples of field and airborne AusCover campaigns

Authors:

1Kasper Johansen, 2Rebecca Trevithick, 3Matt Bradford, 4Jorg Hacker, 4Andrew McGrath and 4Wolfgang Lieff

1Biophysical Remote Sensing Group / Joint Remote Sensing Research Program
 Centre for Spatial Environmental Research
 School of Geography, Planning and Environmental Management
 The University of Queensland
 St Lucia, 4072 QLD
Email: k.johansen@uq.edu.au

2Remote Sensing Centre

Department of Science, Information Technology, Innovation and the Arts (DSITIA)

Queensland Government, Ecosciences Precinct, 41 Boggo Road,

Brisbane, 4102 QLD

3CSIRO, Sustainable Ecosystems

Tropical Forest Research Centre

PO Box 780, Atherton, 4883 QLD

4Airborne Research Australia / Flinders University
 Hangar 60, Dakota Drive, Parafield Airport, 5106 SA

List of Contents

Abstract and key points

Introduction

Campaign Planning and Coordination

Field Sampling Design

Campaign Example: Robson Creek

Robson Creek Study Area

Field Equipment

Field Data Collection

Field Data Storage

Airborne Data Collection

Data Availability

Summary

Acknowledgement

References

List of Acronyms

Appendices

Abstract

The AusCover Earth Observation facility has undertaken nine field and airborne campaigns within selected Australian biomes between January 2011 and June 2013 as part of the calibration and validation program to support the production of continental scale satellite based time-series of biophysical parameters. Many national and international approaches were reviewed during the development phase, and the field and airborne data collection approaches and protocols developed have been based on their suitability and adaptability to different Australian environments, while still upholding national and international standards. Another focus was also to ensure the data collected were suitable to multiple uses and purposes to support a wide range of ecosystem science, research and environmental management activities in Australia. This chapter will present an outline of the main activities involved in planning and executing the nine field and airborne campaigns and hence will provide a useful set of guidelines of things to consider when collecting field and airborne LiDAR and hyper-spectral data suitable for up-scaling to continental scale satellite based measurements.

Key points:

  1. Ensure consistency and compatibility of field and airborne data;
  2. Select data collection approaches that reduce errors, allow daily backups and can be made readily available as soon as possible (e.g. ODK forms);
  3. Always have contingency plans in case of weather, equipment breakdown or other unforeseen circumstances; and
  4. The type of environment being investigated will influence the way in which the most optical field and airborne data can be obtained.

Introduction

The AusCover remote sensing data archive and access capability (www.auscover.org.au) was formally launched in the first half of 2010 and is one of several facilities of the National Collaborative Research Infrastructure and Super-Science Education Investment Funded Terrestrial Ecosystem Research Network (TERN). The aim of AusCover is to deliver consistent national time-series of remotely sensed biophysical parameters to support ecosystem research and natural resource management communities in Australia. These remote sensing products are based on past, current and future satellite image data sets with deliverables designed for Australian conditions. Biophysical remote sensing data products are developed based on satellite image data captured by the Landsat, MODIS, AVHRR sensors among others. These products will enable assessment of how environmental variables change over time. National remote sensing time-series data sets are accompanied by consistently formatted metadata, which are considered to be equally important to the image data products. These data sets will be made publically accessible and retrievable through the online Auscover Portal. Another major focus area of AusCover is remotely sensed data calibration and validation of the continental scale time-series based on existing and new captures of high spatial resolution hyper-spectral and LiDAR airborne and field data.

AusCover has carried out nine extensive airborne and field campaigns in Australia (Figure 1). Each site was selected to represent a dominant and/or conservation significant biome (Table 1) suitable for scaling up from field and airborne measurements to continental scale map products for calibration and validation purposes. Another focus by AusCover has been to ensure that the collection of high quality and high spatial resolution field and airborne data of the selected biomes would encourage, foster and support ongoing and future research.

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Figure 1. Map of Australia showing the location of field and airborne campaign sites carried out by AusCover between January 2011 and June 2013.

Table 1. Site name, site location, data collection date, type of environment, and photos of each of the nine AusCover sites.

Site nameSite locationDateEnvironmentSite Photo
TumbarumbaSouth eastern New South Wales, 100 km south west of Canberra8-14 Jan 2011Temperature wet sclerophyll eucalypt forest with average tree height of 40 m. Eucalyptus delegatensis is the dominant species.2Q==
ChowillaNorth of the River Murray floodplains north of Renmark, South Australia30 Jan - 3 Feb 2012Semi-arid mallee ecosystem in dune and swale system covered with an open mallee woodland upper story with a chenopod and native grass understory.8H8JbNg3fumvcAAAAASUVORK5CYII=
Watts Creek70 km east of Melbourne, Victoria5-9 Mar, 13-20 Apr, 1-3, 7 May and 9-16 Sep 2012Open forest with a eucalypt overstorey greater than 40 m in height consisting mainly of mountain ash. AFiYfaz7E3ETAAAAAElFTkSuQmCC
Rushworth Forest120 km north of Melbourne, Victoria15 Apr, 3-6 May, 31 May and 6 Jun 2012Open forest of red iron bark, red stringybark, red box, long leaf box and grey box.Zz8AAAAAElFTkSuQmCC
Zig Zag CreekEastern Victoria 300 km east of Melbourne, Victoria16-20 Apr 2012Dominated by shrubby dry forest and damp forest on the upland slopes, wet forest ecosystems which are restricted to the higher altitudes and grassy woodlands, grassy dry forest and valley grassy forest ecosystems are associated with major river valleys.lNJQcZAk88cAAAAASUVORK5CYII=
CredoGreat Western Woodland 500 km north west of Perth, Western Australia12-18 May 2012Open woodland inter-dispersed with open, treeless areas. The main vegetation species are Salmon Gums reaching up to 20 m and Gimlet between 5-10 m, both with little understorySalt bush and similar shrubs are also prevalent.2A56n6g6GSBAAAAAElFTkSuQmCC
Robson CreekLamb Range in the Wet Tropics World Heritage area 25 km south west of Cairns, Queensland9-16 Sep 2012Upland rainforest region at 700 m elevation. Notophyll vine forest with a tall canopy at around 40 m and high species diversity.
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South East QueenslandMultiple sites in South East Queensland, located in the Samford Valley, Karawatha Forest, and two mangrove sites near Brisbane Airport.21 Jan 2013 - 6 Feb 2013

Samford site: on an improved (Paspalum dilatum) pasture with tall eucalypt species.

Karawatha Forest: bushland with tall eucalypt species and patches of heatlands and Melaleuca swamps.

Mangrove sites: Within Moreton Bay with Avicennia marina being the dominant mangrove.

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Litchfield80 km south of Darwin, Northern Territory27 May - 2 Jun 2013Savanna, eucalypt open forests, dominated by Eucalyptus miniata and Eucalyptus tetrodonta.AFAAAAAElFTkSuQmCC

While the first field and airborne campaign in Tumbarumba, New South Wales was treated as a test site for development of field and airborne data collection approaches, field protocols, selection of suitable airborne data collection specifications, data post-processing procedures and data storage, the following eight campaigns have had a standard set of field and airborne data collected. While the field collection approaches and types of field data have been kept as consistent as possible, collection approaches have been refined and new types of field data added along the way (e.g. collection of Terrestrial Laser Scanning (TLS) data). The airborne data acquisition specifications and collection procedures have been kept consistent and carried out by Airborne Research Australia (ARA), Flinders University. The image processing approaches on the other hand have developed significantly to ensure the highest possible airborne data quality. Hence, a number of data versions have been supplied by ARA. As airborne data quality control and assurance are ongoing, new and refined airborne data post-processing approaches may be performed by ARA in the future to deliver new data versions consistently processed to the highest possible standard. These data sets will be made freely available via the online AusCover Portal.

All the field and airborne image data provided by AusCover are supplied with associated metadata. Well documented metadata for the airborne data have been developed and supplied by ARA. These metadata will also be freely accessible and retrievable via the online AusCover Portal to support future ecosystem research in Australia. The data acquisition specifications were set to suit a large number of product and research purposes and ensure that the quality of the data meets short and medium term specification requirements for potential future research of Australian ecosystems.

One of the field and airborne campaigns, representing a mature stage of the data collection procedures and processing, is the Robson Creek campaign. Hence, the Robson Creek campaign is in many cases used in this book chapter as an example to illustrate and demonstrate the activities and outputs associated with the AusCover field and airborne campaigns. The Robson Creek Supersite is part of the Far North Queensland Rainforest Biodiversity Node within the Northern Australian Hub of TERN. The site is locally managed by CSIRO Tropical Forest Research and overseen by James Cook University. The site was chosen as a representative upland (400-1000 m) rainforest site with high plant and animal diversity, homogeneity of forest type and parent material, and all weather access. The Robson Creek site is critical to remote sensing of continental scale products, as it represents an area with the highest biomass in Australia and hence can be used to constrain and validate remotely sensed models.


The two main aims of each of the AusCover field and airborne data collection campaigns have been:

  1. To demonstrate how hyper-spectral and LiDAR image data and field data can be collected in an accurate, timely and efficient manner to deliver products suited to AusCover calibration and validation activities as well as a range of TERN activities and international remote sensing calibration and validation work.
  2. To collect field and airborne LiDAR and hyper-spectral image data over the selected sites to enable the production of maps of biophysical parameters, including (a) forest height, foliage projective cover, plant projective cover, vertical profiles, tree density, and leaf area index (LAI) from the LiDAR data and (b) reflectance, nitrogen, water content, canopy chlorophyll content, and photosynthetic and non-photosynthetic cover from the hyper-spectral data. Fusion of the LiDAR and hyper-spectral image data, as well as AusCover derived field and image data, may be used for deriving additional data sets including land cover maps and for developing scaling methods.

Campaign Planning and Coordination

Each of the AusCover field and airborne campaigns has required a substantial amount of planning and coordination to ensure optimal data were obtained and that airborne data and field measurements could be acquired simultaneously. The main activities required for planning and coordinating each of the field and airborne campaigned have included:

The timing of the field and airborne campaigns was for most of the campaigns dictated by the season to increase the likelihood of cloud free conditions to enable high quality airborne data to be collected. The collection of field data was not as dependent on the weather condition but for most activities, rain made data collection difficult and time-consuming. Once a suitable season for the AusCover study sites had been identified, the selection of the dates of the field campaign were determined by the availability of the aircraft and ARA scientists operating them and suitable personnel within AusCover. Most of the campaigns have relied on the availability of local personnel, but personnel from interstate has participated in all campaigns to ensure that the required level of expertise for equipment handling and field data collection was available to ensure data collection consistency and quality.

As much of the required field equipment as possible was obtained locally, i.e. from universities, government agencies and non-government organisations involved in the campaign, with additional instrumentation, such as spectroradiometers, ground calibration targets, terrestrial laser scanner, sunphotometer, etc. couriered to the site ahead of time. Prior to each campaign, it was ensured that at least one person with extensive experience in each of the field data collection activities were present to ensure the guidelines of the field data protocols were followed and all required data were correctly recorded on field sheets or on androids using ODK forms.

Airborne data acquisition specifications were developed to ensure the airborne LiDAR and hyper-spectral data collected were suitable for a large number of research and biophysical mapping applications. ARA has also provided a significant contribution towards the development of the data acquisition specifications to ensure the specifications were feasible and optimised where possible. Prior to each campaign, AusCover and ARA agreed on the most suitable airborne data collection procedure and ARA has provided flight planning information prior to each campaign to ensure all personnel in the field were informed. As some of the field sites did not have open areas suitable for deployment of ground calibration targets and spectroradiometer measurements to be carried out, airborne data for additional sites outside the target areas have in many cases been collected by ARA. ARA was also responsible for setting up a total station at each of the sites to demonstrate the geometric accuracy of the airborne data. Hence, regular and open communication between AusCover personnel and ARA has been imperative to ensure the field and airborne data could be correctly integrated once collected.

A number of other logistics has been important for each of the AusCover campaigns. As 10-20 people have been participating in each of the campaigns, booking of accommodation, transport and meals were required prior to the campaigns. Distribution of field tasks and responsibilities has also been done prior to each field trip to avoid miscommunication and ensure all required data were collected. Hence, communication prior and during the campaigns has been imperative, with regular phone meetings prior to the campaigns and briefings and de-briefings on a daily basis during the campaigns. One item specifically highlighted prior to each of the campaigns was the need for daily backups of all collected data, proper data storage and assigning a responsible person for collecting and storing all collected data throughout the entire campaign. Occupational health and safety (OHS) requirements have been very important to follow, as a large number of people participated in the campaigns in often very remote locations. The OHS requirements included but were not limited to risk assessments of all activities, assessment of the level of hazard, mitigation plans of all hazards, ensuring communication (satellite phones, walkie talkies), never working alone, always carrying first aid equipment and always having access to transport.

Finally, backup plans were put in place before each of the campaigns in case of poor weather conditions. The importance of this was highlighted during the first AusCover campaign in Tumbarumba, New South Wales, where the weather prevented the acquisition of hyper-spectral data at the time of the field campaign. Hence, for all subsequent airborne campaigns, backup plans have been in place to ensure field measurements could be completed at a later stage if needed and that a team of people and equipment were available locally to collect spectroradiometer measurements of ground calibration targets at the time of a potentially delayed airborne hyper-spectral data collection.

Field Sampling Design

The general sampling design of AusCover campaigns has depended on existing data sets and research being carried out within the focus sites. Generally, the size of the areas has been 5 km x 5 km. The 5 km x 5 km sites have been selected based on a number of criteria, mainly to ensure the following criteria were fulfilled:

As can be seen in Figure 2, the 5 km x 5 km sites have generally been very homogenous in terms of vegetation cover and structure or at least consistently mixed, and therefore suitable for scaling-up to MODIS type satellite image data. At many of the selected sites, a flux tower was installed or planned to be installed within the 5 km x 5 km area, which will allow measurements of energy, carbon and water exchange between the atmosphere and the ground and vegetation to be integrated with the field, airborne and satellite data collected by AusCover. Pheno-cams have been installed on some of the flux towers to allow photos to be taken every hour of the day throughout the year to study canopy and leaf phenology.

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Figure 2. Examples of AusCover campaign sites of 5 km x 5 km, including the (a) Chowilla site; (b) Robson Creek site; (c) Watts Creek site and (d) the Litchfield site.

Within each 5 km x 5 km site, AusCover has collected a variety of vegetation structural measurements over 100 m x 100 m areas at different locations (Figure 3). The locations of these 100 m x 100 m areas were determined based on the following criteria:

However, accessibility often restricted where sites could be located. For example, the Robson Creek site had significant elevation changes within the 5 km x 5 km area of around 700 m. As many areas were too steep to get to and to safely carry out the fieldwork, this limited the spread of sites to be within a few hundred metres of the two main dirt roads intersecting the study area.

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Figure 3. Layout of the 100 m x 100 m area within which vegetation structural measurements were obtained.

Within each 100 m x 100 m area, three 100 m tape measurements were lined up facing north (0°) – south (180°), 60° - 240° and 120° - 300° and intersecting at the centre, which created a star shape with each of the six arms being 50 m in length from the centre point (Figure 3). A Differential Global Positioning System (DGPS) was used to obtain the position of the centre point of each star transect. Point based observations were made for each 1 m of ground cover, mid-storey and over-storey, following the approach outlined in Muir et al. (2011). This produced a total of 300 point based observations, which can be converted into a measure of fractional ground cover and foliage projective cover. Basal area is estimated at the centre point, as well as the 25 m mark along each of the six arms of the star transect. Vegetation structure, i.e. DBH at 30 cm and 130 cm from the ground, tree height to first branch, total tree height, and length of the major and minor axes of the tree crown, was recorded for all trees included in the basal area count at the centre point of the star transect (typically 10-25 trees). LAI was measured using either the LAI-2200 or the CI-110 (depending on light conditions) at set intervals (typically every 1 m) along the three 100 m transect lines. Hemispherical photos, using a fisheye lens, were collected at three different exposure levels at the centre point, as well as the 25 m and 50 m marks along each of the six arms of the star transect (a total of 13 locations). At the centre point and at a distance of 10 m from the centre point in the north, east, south and west directions, terrestrial laser scans were collected. Reflectors were set up to allow the five different scans to be geo-referenced to each other.

In addition to the star transects covering a 100 m x 100 m area, additional sites were visited within the 5 km x 5 km sites to complete a rapid sample of structural measurements. These included DBH and hemispherical photos at some campaign sites and, at other more recent sites, one terrestrial laser scan and hemispherical photos collected at the location of the TLS and at a distance of 10 m from the TLS in the north, east, south and west directions. A GPS position was derived of the TLS location.

Additional field measurements, including the setup of pheno-cams, collection of spectroradiometer measurements of ground calibration targets, sunphotometer and ozonometer measurements and hemispherical sky photos at the time of the airborne data capture, were also collected. These measurements were not part of the star transect setup. During some of the AusCover campaigns (Tumbarumba, Robson Creek, South East Queensland, Litchfield) leaf sample collection, species identification and leaf chemistry assessment have also been undertaken.

Campaign Example: Robson Creek

The Robson Creek site is part of the Wet Tropics Bioregion with significant conservation value, representing the largest continuous stretch of rainforest in Australia. As part of the work conducted by the TERN Australian Supersites Network facility, site selection and surveying of a 500 m x 500 m focus plot commenced in August 2009 with the first trees measured and surveyed in October 2009. Approximately 25,000 tree species have been identified, and associated tree height, DBH and GPS position have been collected (Appendix 1). Vertebrate and invertebrate biodiversity and seedling surveys started in November 2009. Construction of a flux tower and associated soil and water sampling infrastructure commenced in June 2010, and was completed in mid-2013. Because of the extensive field based work within the area, the AusCover facility conducted an intensive field and airborne campaign between 9 and 16 September 2012 to collect further data in this area and complement existing research and data sets. A total of 18 people from the University of Queensland, James Cook University, Royal Melbourne Institute of Tecchnology, CSIRO and the Department of Science, Information Technology, Innovation and the Arts participated in the field campaign. In addition, a team of four people from ARA/Flinders University worked closely together with the AusCover team to ensure high quality airborne LiDAR and hyper-spectral data were collected coincidently with the field data.

Robson Creek Study Area

The TERN Robson Creek site is located approximately 30 km northwest of Atherton, in Far North Queensland, Australia (1701’ 12”S 14537’ 56”E, 700 m elevation). It lies in Danbulla National Park within the Wet Tropics World Heritage Area. Access to the site is 13 km past Tinaroo Falls township along Danbulla Forest Drive and approximately 1 km along the Mount Edith Presentation Road (Figure 4). The AusCover focus areas are shown in Figures 5 and 6. The climate of the area is considered seasonal with 61% of the annual rainfall occurring in the months of January to March (Danbulla Forestry). Mean annual rainfall at Danbulla Forestry (17009’36”S, 145037’35”E, 4.5 km south of the plot) is 1597 mm (1921 - 1991), at Tinaroo Dam township (17010’07”S, 145032’54”E, 10 km southwest) is 1255 mm (1954 - 2006), and at Kairi Research Station (17013’03”S, 145034’33”E, 11 km south-southwest) is 1248 mm (1913 - 2006). Mean monthly rainfall for Danbulla Forestry and Tinaroo Dam Township is shown in Figure 7. Mean monthly minimum and maximum temperatures for Kairi Research Station are shown in Figure 8 (BOM, 2006).

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Figure 4. Location of the TERN Robson Creek permanent plot on the Atherton Tablelands, Queensland, Australia. The red line indicates access route.

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Figure 5. Aerial view of the Robson Creek focus areas. AusCover conducted fieldwork within the white 5 km x 5 km area. The large yellow rectangle shows the outline of a WorldView-2 image captured on 19 September 2012. The small yellow square outlines the 500 m x 500 m plot, where all tree species have been identified and mapped. The red rectangle represents an additional area of LiDAR and hyper-spectral image data within which leaf samples were collected and ground calibration targets were deployed.

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Figure 6. Aerial view of the TERN Robson Creek 5 km x 5 km site and the nearby site from where ground calibration targets were deployed and leaf samples were obtained.

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Figure 7. Mean monthly rainfall for Danbulla Forestry () and Tinaroo Dam Township ().

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Figure 8. Mean monthly minimum and maximum temperatures for Kairi Research Station (11 km southwest of the plot).

The 500 m x 500 m plot is located at the southern base of the Lamb Range, which rises to 1276 m ASL. The western edge of the plot runs parallel to, and 50 m east of the Mount Edith Presentation Road, which is on an alluvial flat adjacent to Robson Creek. The landform of the plot is moderately inclined with a low relief (Speight 1990) with a 30 m high ridge running north/south through the middle of the plot and a 40 m high ridge running north/south on the eastern edge of the plot. Three permanent creeks flow through the plot, joining with Robson Creek which in turn meets the Barron River approximately one kilometre south of the plot.

A detailed soil description of the CSIRO experimental plot 9, located 200 m to the north of the plot is given in Graham (2006). The parent material is a meta-sediment and soil fertility is considered low. The soil profile is described as having a Principal Profile Form Gn3.71 and affinities with the xanthozem Great Soil Group.

The plot is mapped as Regional Ecosystem (RE) 7.3.36a, complex mesophyll vine forest. The forest type changes to RE 7.12.16a, simple to complex notophyll vine forest, with increasing altitude to the north of the plot. Structurally the forest is very tall to extremely tall closed forest with canopy heights ranging from 23 to 44 m.

As is the case for all accessible areas of the Wet Tropics the plot has been selectively logged. The last logging in the Robson Creek area was undertaken between 1960 and 1969. The southern and central parts of the plot were logged in 1960-64, while the northeast and northwest corners were logged in 1964-1969. Silvercultural treatment of the surrounding Danbulla logging area was common place in the 1950’s. Treatments included cutting and poisoning of unwanted species and promotion of valuable species and seed trees. Although no written evidence exists of such treatments on the plot, the presence of such activity cannot be dismissed.

Severe tropical cyclone Larry crossed the coast near Innisfail on the 20th March 2006. The northern edge of the eye passed just south of Atherton. However some areas removed from the eye received severe disturbance. The plot area received moderate to slight disturbance (Bradford/Unwin scale: Category 3, Metcalfe et al. 2008) with the winds coming from a north-westerly direction. Damage from severe tropical cyclone Yasi in February 2011 was minimal with moderate leaf and branch loss and only few stems > 10 cm DBH being uprooted.

Field Equipment

Field equipment was provided by a number of institutions for the Robson Creek campaign. For most AusCover campaigns, the majority of the equipment used was obtained locally. However, for the Robson Creek campaign, Brisbane located Department of Science, Information Technology, Innovation and the Arts and the University of Queensland provided most of the equipment for the campaign. All field equipment used for the Robson Creek field campaign is presented in Table 2.

Table 2. List of field equipment used during the Robson Creek field campaign for each fieldwork activity.

Fieldwork Activities / MeasurementsField Equipment
Foliage projective cover and ground cover, including basal area and soil colour assessment (SLATS)
  • DGPS omnistar
  • Field laptop point based observations
  • Backup sheets for FPC/ground cover point observations
  • 6 x 100 m tape measures
  • Densitometer and laser pointer
  • Basal area optical wedges
  • Munsell charts
  • Pegs
  • Marking tape
  • Digital camera
Vegetation structure (height, DBH, crown dimensions)
  • Laser range finder
  • DBH tape measure
  • Tape measure
Leaf area index
  • Licor LAI-2200 Plant Canopy Analyzer
  • CI-110 Digital Plant Canopy Imager
  • 2 x SLR cameras
  • RGB fisheye lens
  • NIR fisheye lens
  • Tripod + monopod
Terrestrial laser scanning
  • Riegl VZ400 terrestrial laser scanner and accessories
Leaf samples and leaf chemistry assessment
  • 2 x Integrating sphere (for leaf optical measurements)
  • DGPS omnistar
  • Slingshot and attached rope
  • Leaf chemistry equipment (lab based)
Spectroradiometer measurements of ground calibration targets
  • 2 x ASD Spectroradiometer (including panel and accessories)
  • Spectralon panel (for instrument inter-calibration)
  • White, grey and black ground calibration targets (8 m x 8 m)
  • DGPS omnistar
Atmospheric measurements
  • Microtops Ozonemeter
  • Sunphotometer
  • Hemispherical photography (sky view)
Safety
  • Walkie talkies
  • Maps
  • 12 x Compasses
  • Handheld GPSs (and AA Batteries)

Field Data Collection

For each of the AusCover campaigns, a standard set of field based measurements has been collected. Because of equipment availability, field data collection protocol maturity and environmental variations between the times of data collection for the different AusCover campaign sites, slight differences in field data type and collection methods have occurred. The aim of each of the AusCover campaigns was to collect as much field data as possible using as many of the following field data collection approaches:

An example of the types of data collected during the Robson Creek campaign can be seen in Table 3. It should be noticed that vegetation structural measurements collected by AusCover for this campaign were limited because these were already available for many of the sites within the 5 km x 5 km area. Hence to save time and avoid duplication, tree height and DBH measurements were excluded, as the Australian Supersites Network had already collected these data (Appendix 1). Using the Licor LAI-2200 Plant Canopy Analyzer instrument for LAI measurements require a second sensor to be set up in an open area and the best results are obtained at dusk and dawn. Because of the canopy density within the Robson Creek site, no suitable open area was identified. Also, collecting the LAI-2200 measurements at dusk and dawn was deemed too dangerous because of the terrain and thorny plants. Hence, the CI-110 Digital Plant Canopy Imager instrument was used instead. At the time of the field campaign, the flux tower had not been installed. Therefore, no pheno-cams were installed at the time of the field campaign. Similar issues, affecting the type of field based measurements to be obtained, were encountered for the other AusCover campaigns.

Table 3. Daily field measurements and associated weather condition for the Robson Creek campaign.

DateWeatherField Activities
8 Sep 2012Cloudy
  • Leaf species identification and tree tagging
9 Sep 2012Cloudy
  • Leaf species identification and tree tagging
10 Sep 2012Cloudy
  • Site and safety induction
  • Site location
  • Star transect 1 (including TLS scans, hemispherical photography and LAI using CI-110)
  • Leaf sampling
  • Spectral analysis of leaves using integrating sphere
11 Sep 2012Rainy
  • Star transect 2 (including TLS scans, hemispherical photography and LAI using CI-110)
  • Leaf sampling
  • Spectral analysis of leaves using integrating sphere
12 Sep 2012Cloudy
  • Completed star transect 2
  • Star transect 3 (including TLS scans, hemispherical photography and LAI using CI-110)
  • Leaf sampling
  • Spectral analysis of leaves using integrating sphere
13 Sep 2012Mainly sunny, but some clouds
  • Completed star transect 3
  • Star transect 4 (including TLS scans, hemispherical photography and LAI using CI-110)
  • Leaf sampling
  • Spectral analysis of leaves using integrating sphere
  • LiDAR data collected for part of the site
14 Sep 2012Sunny
  • Spectrometer measurements of ground calibration targets
  • Irradiance measurements
  • Sunphotometer and Ozonometer measurements
  • Hemispherical sky photos
  • Leaf sampling
  • Spectral analysis of leaves using integrating sphere
  • LiDAR and hyper-spectral data collected for the whole site and the additional open area
  • Two rapid sites, including TLS and hemispherical photos
15 Sep 2012Cloudy
  • Leaf sampling
  • 10 rapid sites, including TLS and hemispherical photos

Measuring ground and canopy cover, basal area and assessing soil colour

The SLATS star transects are designed and used for collecting point based information on canopy cover, ground cover and basal area. The metric of overstorey vegetation cover adopted in many Australian vegetation classification frameworks is Foliage Projective Cover (FPC). Overstorey FPC is defined as the vertically projected percentage cover of photosynthetic foliage from tree and shrub life forms greater than 2 m height and was the definition of woody vegetation cover adopted by SLATS (Armston et al., 2009). Ground cover is the non-woody vegetation (forbs, grasses and herbs), litter, cryptogamic crusts and rock in contact with the soil surface.

Point based observations using a laser pointer (for ground cover) and a densitometer (for canopy cover) are obtained for each 1 m along the three 100 m long transects (Figures 3 and 9). The star transect is located within a vegetation structurally homogenous area to ensure that the 300 point based observations are representative for the selected area. The 300 observations are converted into a single value of fractional ground cover and a single value of FPC. The GPS position is recorded at the centre of the star transect (Muir et al., 2011). As part of the SLATS star transect, an optical wedge prism is used to estimate tree basal area. Basal area defines the area of a given section of land that is occupied by the cross-section of tree trunks and stems at their base. This is measured at a person’s breast height (1.3 metres) and includes the entire diameter of every tree, including the bark. Basal area sweeps are recorded at the centre point as well as at a distance of 25 m from the centre point along each of the six transect arms (Figure 10). Soil characteristics and colour are also described as part of the star transect survey using Munsell Soil Color Charts.

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Figure 9. (a) Pole with laser pointer and densitometer attached for point based observations of ground and canopy cover. (b) The GPS position is recorded in the centre of the star transect.

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Figure 10. (a) Basal area sweep along transect line and (b) optical wedge inclusion and exclusion of trees. Source: http://en.wikipedia.org/wiki/Wedge_prism.

Vegetation structural measurements

When the basal area sweep is performed in the centre of the star transect, trees which are counted as 'in' in the sweep have their structural characteristics measured and recorded. Diameter at Breast Height (DBH) is measured at 1.3 m and at 0.3 m using a DBH tape measure. The crown diameter major and minor axes are also measured by two people using a tape measure to determine the crown diameter, with one person standing under the canopy border on one side of the tree crown and the other person under the other side of the canopy border. Tree height, defined as the vertical distance from ground level to the uppermost point is measured. The height from ground level to the first branch is also recorded. A laser range finder, hypsometer or clinometers and tape measure are be used.

Hemispherical photography

Hemispherical photography has been used in many studies of LAI (Chen et al., 1997; Robison & McCarthy, 1999). Hemispherical photos were collected from the centre point of the star transects, as well as at the 25 m and 50 m marks of each of the six transect arms. All photos are referenced to the central geographic location. A monopod may be used together with a level bubble to ensure the camera lens if facing vertically upwards (Figure 11). Three photos are collected at each sampling point, each with different exposures. Photos should be taken at dawn, dusk or during overcast conditions. During the time of the hyper-spectral data capture, hemispherical sky photos are taken every 10 minutes to record cloud cover during the airborne data capture (Figure 12).

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Figure 11. (a) Collection of hemispherical photo and (b) hemispherical photo example.

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Figure 12. Hemispherical sky photos collected during the airborne hyper-spectral data capture.

Leaf Area Index measurements using the CI-110 and LAI-2200 instruments

LAI data is collected at AusCover sites using two separate instruments, the LAI2200 and the CI-110. The LAI-2200 Plant Canopy Analyzer calculates LAI from radiation measurements collected both above and below the canopy with a fisheye optical sensor (148° field-of-view) (LI-COR, 2009). Hence, two sensors are needed, so one can be placed in an open area (above canopy measurements) (Figure 13) and the other one can be used for simultaneous below canopy measurements. The solar radiation is measured at five zenith angles. LAI estimates are based on four assumptions: (a) the foliage is black (no radiation is transmitted or reflected by the vegetation); (b) the foliage elements are small in comparison to the area of view of each sensor ring and the following guideline is applied: the distance between the sensor and the nearest leaf above it should be at least four times the width of the leaf; (c) the foliage is randomly distributed; and (d) the foliage is aziumuthally randomly orientated, in other words, leaves face all directions (LI-COR 2009). It is recommended that collection is carried out around dawn or dusk or during uniform overcast days. During AusCover campaigns, LAI measurements have been collected with the LAI-2200 Plant Canopy Analyzer along the three 100 m transects forming the star transects.

In situations where it has not been impossible to collect LAI-2200 measurements under the required conditions, the CI-110 Digital Plant Canopy Imager (Figure 14) has been used, as it allows a user-defined threshold to be set to discriminate between vegetation and sky, and hence can be used throughout the day, even in sunny conditions. A similar collection method, i.e. along the three 100 m transects forming the star transect, has been used.

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Figure 13. (a) Synchronising the clocks of both LAI-2200 sensors to ensure above and below ((b) within clearing seven times wider than the height of surrounding trees) canopy measurements can be related.

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Figure 14. CI-110 Digital Plant Canopy Imager used to derive LAI measurements.

Terrestrial Laser Scanning

Terrestrial Laser Scanning (TLS) data have been collected for most of the AusCover campaign sites. TLS data can be used to obtain more detailed structural characterisation of vegetation, including estimates of the number of trees per hectare, the distribution of stem diameters at breast height for assessing basal area, and estimates of tree height distributions, stem form, branching structure, the vertical distribution of foliage cover and plant area index (Figure 15). The sampling approach adopted by AusCover included five scan positions per site. One scan position was located in the centre of the star transect. The remaining four scans were obtained 10 m from the centre point in north, south, east and west directions. Reflectors visible in more than two scans were set up to ensure the scans could be geometrically related to each other (Figure 15).

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Figure 15. (a) Riegl VZ400 TLS, (b) high resolution scan of reflectors, (c) tilted TLS to obtain a full hemispherical scan, (d) intensity output image from the Robson Creek campaign, and (e) derived plant area volume density and plant area index from the Robson Creek campaign.

Leaf samples and leaf chemistry assessment 

High temporal frequency satellite observations of landscapes are necessary to capture highly dynamic spatio-temporal patterns of vegetation growth and productivity and landscape processes of carbon and water fluxes. Satellite observations of landscape seasonality include co-varying phenological changes in vegetation foliage quantity, phenological variations in foliage quality (leaf age, pigment contents, nitrogen, leaf stress, etc.), and external variations in clouds, aerosols, and sun-view angle geometries. During some of the AusCover campaigns (Tumbarumba, Robson Creek, South East Queensland, Litchfield) leaf samples have been collected to support phenology studies and to map individual species and their leaf chemical properties from hyper-spectral data. These measurements help to: (1) document, understand, and validate seasonality profiles and patterns of landscape productivity; (2) verify satellite observations of dynamic seasonal responses of the landscape to climate drivers (rainfall, temperature, radiation, etc.), disturbance, and land use activities; (3) and provide the scientific basis for spectral reflectance characterisation of vegetation and help understand reflectance patterns at the micro-scale.

During the AusCover campaigns, 3-5 samples of leaves per branch (youngest - middle and oldest leaf) and 3-4 branches (bottom to crown) were sampled from lower to upper branches to provide a proxy for age (Figure 16). The focus for these leaf samples was the dominant species within the AusCover campaign site. To determine if whole tree/canopy leaves seasonally change their optical/biologic properties, a spectroradiometer and integrating sphere was used to assess leaf spectral reflectance and transmittance (Figure 16). All collected leaves were frozen for subsequent laboratory analysis of their chemical properties, e.g. chlorophyll, nitrogen, tannin, lignin and water.

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Figure 16. (a) Slingshot used to fire robe over branch to collect canopy leaves, (b) leaf sample, and (c) using a spectroradiometer and integrating sphere to assess leaf spectral properties.

Spectroradiometer measurements of ground calibration targets

Field spectroradiometer measurements have been collected for calibration and validation of at-surface reflectance of airborne hyper-spectral image data. Once the at-surface reflectance values of the hyper-spectral image data have been validated, the data can be used for scaling up to medium spatial resolution Landsat and MODIS data for calibration and validation of satellite based Nadir BRDF-Adjusted Reflectance (NBAR) products. Calibration targets should be large (ideally, calibration targets should cover an area of at least 3 x 3 pixels of the airborne hyper-spectral data), homogeneous, spectrally featureless in the part of the spectrum to be investigated, Lambertian and encompass a range of albedo levels (bright to dark). Calibration targets can either be natural ‘pseudo-invariant’ features (asphalt, concrete, salt, sand, gravel, limed and painted surfaces) at the site or artificial targets specifically placed into the flight lines. AusCover has used three 8 m x 8 m standard canvas calibration targets in white, grey and black colours (Figure 17a-b). The site chosen to place these targets should preferably in the centre of one of the flight lines (i.e. at the nadir view), flat and open. A spectralon reference panel was used every 5 minutes to optimize the spectrometer measurements to adjust the sensitivity of the detector according to the present illumination conditions (Figure 17c). In those cases where an additional spectroradiometer was available, irradiance was also measured (Figure 17d).

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Figure 17. (a) White, grey and black 8 m x 8 m ground calibration targets, (b) spectroradiometer measurements of ground calibration targets, (c) using the spectralon panel to adjust the detector to the present illumination conditions, and (d) irradiance measurements.

Atmospheric measurements using a sunphotometer and ozonometer

The acquisition of sunphotometer and ozonometer measurements is critical to capture data on atmospheric properties during airborne hyper-spectral imaging campaigns as well as for measurements coinciding with the overpass of satellite sensors. The atmospheric properties measured are used in the atmospheric correction of the remotely sensed image data. The Microtops instruments used by AusCover capture solar radiance data each in five wavelengths, which are used to extract information on aerosol optical depth, total column water vapour content, atmospheric pressure, temperature and total column ozone content (Figure 18). These observations are made regularly during the airborne hyper-spectral data capture at a set location within an open area.

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Figure 18. Setup of Microtops sunphotometer and ozonometer on tripod with GPS receiver.

Pheno-cams for ground and canopy cover phenology time-series observations

For some of the AusCover sites, pheno-cams, i.e. optical cameras, have been installed to automatically collect and store photos taken every hour throughout the year to study phenology of ground and canopy cover. Pheno-cams have been installed at about 3 m height on metal poles cemented into the ground for observation of ground cover, while pheno-cams for observation of canopy cover have been installed on flux towers present within the 5 km x 5 km AusCover sites.

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Figure 19. (a) Pheno-cam installed on pole to assess ground cover phenology and (b) on flux tower to assess canopy cover phenology.

Field Data Storage

The field data processing and storage for all the AusCover campaigns is managed within the AusCover field data management system. The details and evolution of this system are well documented in the chapter ‘Good Practice Field Data Management and Delivery’, so only a brief summary of the system is provided here. The AusCover field data management system consists of documentation, software/hardware and processes designed to facilitate the consistent collection, recording, storage and delivery of field data.

For the AusCover campaigns, field data were collected following standardised protocols developed prior to field data collection. Supporting ancillary data were collected using standardised field data collection forms. All data collected in the field were downloaded and backed up after collection each day of the campaings. Field forms were photographed and stored alongside instrument data in the backups.

On return from the field, data were collated and organised into a form enabling the data sets to be processed via Python scripts. These scripts are designed to upload ancillary data onto the AusCover PostGIS spatial database, as well as rename instrument filenames to fit the AusCover filenaming convention.

The AusCover PostGIS database directly links to the AusCover GeoServer, which in turn links to the AusCover Visualisation Portal. Delivery is therefore dynamic, with the information on the portal being the most up-to-date version of any given data set. Renamed instrument files are zipped and delivered by being placed within a directory linking to the AusCover THREDDS server. All data and relevant information are brought together both within the visualisation portal (through the use of pop up windows specific to each data set) or within the data set metadata records. Both mechanisms contain links to all relevant data and metadata.

Futher information on the AusCover data management system, including access to system documentation (protocols, field forms etc), tools and processes, can be found on the AusCover field data management home page on the AusCover xwiki (http://data.auscover.org.au/xwiki/bin/view/Field+Sites/WebHome). It should be noted, that the system is progressively evolving, so specific management steps may change over time.

Airborne Data Collection

The airborne data collection component of the first AusCover campaign was undertaken by Hyvista, who used their Hymap sensor to collect hyper-spectral data and sub-contracted Vekta to collect discrete return LiDAR data. The subsequent eight airborne campaigns were all undertaken by ARA, Flinders University. Hence, only the ARA airborne data collection approaches are described in this section.

For the last eight AusCover campaigns, airborne full waveform LiDAR and hyper-spectral data in the visible near infrared and shortwave infrared part of the spectrum were collected using the two research aircrafts of Flinders University – ARA (Figure 20). A Riegl Q560 LiDAR and two GPS/IMU systems (OXTS RT4003 and NovAtel SPAN / LCI) were mounted in an underwing pod of one of ARA's ECO-Dimona research aircrafts. A SPECIM AisaEAGLE II hyper-spectral scanner (VNIR) and a SPECIM AisaHAWK hyper-spectral scanner (SWIR) were mounted in underwing pods of the second of ARA's ECO-Dimona research aircrafts. Each scanner had its own OXTS RT4003 GPS/IMU navigation and attitude system. A NovAtel GPS Base station was set up within or close to each of the AusCover campaign sites to optimise the navigation data for the airborne data and to demonstrate the accuracy of the ensuing geo-referencing of all airborne data.

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Figure 20. Diamond Aircraft HK36TTC ECO-Dimona over the Robson Creek site in September 2012.

This LiDAR scanner setup resulted in an outgoing pulse rate of 240 kHz, scanned at 135 lines per second. Each scan line is an angular sweep through 45 degrees and contains 882 individual laser shots. The scan pattern is offset by 4 degrees from the vertical of the scanner coordinate system in order to compensate for wing dihedral and thus result in a symmetrical arrangement in aircraft coordinates. For a nominal flying height of 300 m above ground and a forward speed of 40 m/s, this setup yields a homogeneous surface point distribution of 0.30 m in along-track as well as across-track directions. At a nominal flying height of 300 m above ground the specified footprint of the laser pulse on the ground has a diameter of < 0.15 m, resulting in an a priori average uncertainty of the horizontal position of any encountered target of 0.075 m. Due to the extreme terrain for some of the AusCover campaign sites such as the Robson Creek site, a combination of north-south and east-west oriented flight lines were flown for the LiDAR data capture, in additional to a collection of terrain-following survey lines along the steepest slopes to ensure full coverage. For all other sites, either regular north-south or east-west patterns (with 125 m flight line spacing) were flown. The LiDAR surveys were usually flown in the early morning.

The SPECIM AisaEAGLE and AisaHAWK hyper-spectral scanners were mounted underneath each wing of one of the ARA research aircrafts. The AisaEAGLE has a silicon CCD detector giving 965 spatial pixels across the aircraft track. The detector pixels are square, and from the nominal flight pattern altitude of 500 m above ground, these project to 0.33 m sampling. The AisaEAGLE was configured to return data in 252 spectral bands between 400 and 1000 nm, and exposure considerations led to a sampling rate of 30 - 45 lines per second for the AusCover campaigns. The AisaHAWK hyper-spectral line scanner also has a detector array with square pixels. It images 296 spatial pixels across the flight track, and the nominal pattern altitude of 500 m was selected to give a projected sampling interval of 1 m on the ground. Since the AisaEAGLE pixels are smaller, the AisaHAWK resolution was the driver for the flight pattern. The instrument was configured to return data in 241 spectral bands between 990 and 2494 nm. The AisaHAWK was operated at 45 lines per second, for Signal-Noise-Ratio considerations.

With 1 m cross-track sampling, the AisaHAWK was the limiting instrument for line spacing, with a nominal swath of 296 m. This dictates a flight line spacing of less than 150 m to allow for disturbances of aircraft attitude and position, and for convenience of flight line management the same 125 m-spaced lines were specified as for the north-south LiDAR pattern. The flight pattern planned and flown for the hyper-spectral data collection was based on the imaging geometry of the instruments, along with the consideration of desiring imaging angles as close to orthogonal to the sun's incidence angle as possible, with the highest solar illumination angle. This resulted in a set of parallel, north-south runs, to be flown as close to solar noon as practicable (Figure 21).

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Figure 21. Flight pattern for the hyper-spectral data collection of the Robson Creek campaign, showing take-off and landing at Mareeba Airport, the 5 km x 5 km AusCover campaign site, and the additional site towards southeast where leaf samples were collected and the ground calibration targets were deployed.

Data Availability

The AusCover field data sets typically consist of instrument files or measurements and a supporting shapefile of ancillary data (such as coordinates, date, and other observations). Associated metadata records for each data set contain details assisting users to determine the suitability of the data for their purposes, including abstract, licensing, contact details, spatial and temporal scales, etc. Additional information such as field collection protocols and associated reports are also publically available.

All field and airborne data collected, and associated metadata, can be freely downloaded from the AusCover data servers. This occurs through either the AusCover Visualisation Portal (http://data.auscover.org.au/Portal2/or via the product's metadata records. Exploration of the data is most easily accomplished through the AusCover Visualisation Portal (Figure 22). A brief tutorial on how to use this portal can be found on the AusCover xwiki: (http://data.auscover.org.au/xwiki/bin/view/Field+Sites/Access+Field+Data).

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Figure 22. AusCover Visualisation Portal displaying the locations of the airborne hyper-spectral data.

Most of the information is available by direct download from the portal or via links to online sources. For instrument data sets (imagery, scans, data files, etc.), users are directed to the AusCover THREDDS server (Figure 23) for download via http. For most of these data sets, this is the most accessible way to download the data. However, for some of the larger and more complex data sets this is too time-consuming and cumbersome. For this reason an anonymous FTP server has been setup to enable large scale transfer of the data sets (ftp://tern-auscover.science.uq.edu.au). Instructions on how to access the data sets via various FTP clients is provided on the AusCover xwiki: (http://data.auscover.org.au/xwiki/bin/view/Field+Sites/FTP+Access).

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Figure 23. Field and airborne data sets present on the AusCover THREDDS server.

It should be noted that the field data sets are dynamic and updated as more data becomes available either through data becoming publically available or subsequent site visits. At no time can a field data set be considered ‘complete’ and data sets may be improved or added to at any time. As ARA is a university-based group and not a commercial data provider, and as such has its own research interests in the airborne and other data, on-going improvement of the processing algorithms will continue and amended data sets will become available. A typical example is ARA's current initiative to transfer the LiDAR full waveform data into the new open-source Pulsewave format. Some other sensors were flown simultaneously on the ARA research aircraft for some of the campaigns, including a 15 MPixel aerial camera, a 2048 pixel wide Tri-Spectral line scanner (red, green, near infrared) and an experimental single band linescanner. Data from these sensors will be available in the near future.

Summary

The AusCover Earth Observation facility has undertaken nine field and airborne LiDAR and hyper-spectral campaigns between January 2011 and June 2013 as part of the calibration and validation program to support the production of Australian continental scale satellite based time-series of biophysical properties. This has resulted in the development of standardised field and airborne data collection approaches and protocols to ensure the consistency and quality of the data collected. While these approaches and protocols may be of use to others planning similar campaigns, it is worth highlighting that further improvements will still be made to existing approaches and protocols in the future. It should also be acknowledged that the type of environment being investigated will influence the way in which the most optical field and airborne data can be obtained. The field and airborne data collected by AusCover are anticipated for multiple uses and are freely available via the online AusCover Visualisation Portal to promote and support further ecosystem science and research in Australia in the future.

Acknowledgements

Many people and organisations have been involved in the AusCover field and airborne data collection campaigns. Every AusCover node and parties associated with the nodes are thanked for their input and participation in the field and airborne campaigns and for the post-processing and analysis of the obtained data. Also thank you to both Hyvista and Airborne Research Australia for the participation and involvement in the AusCover campaigns.

References

Armston , J.D., Denham, R.J., Danaher, T.J., Scarth, P.F., and Moffiet, T.N. (2009) Prediction and validation of foliage projective cover from Landsat-5 TM and Landsat-7 ETM+ imagery. Journal of Applied Remote Sensing 3, 033540.

BOM (2006) Bureau of Meteorology website. http://www.bom.gov.au/

Chen, J.M., Rich, P.M., Gower, S.T., Norman, J.N., and Plummer, S. (1997) Leaf area index of boreal forest: Theory, techniques, and measurements. Journal of Geophysical Research 102(D24), 29,429-29,443.

Graham, A.G. (ed.) (2006) The CSIRO Rainforest Permanent plots of North Queensland. Site, Structural, Floristic and Edaphic Descriptions. CSIRO and Cooperative Research Centre for Tropical Rainforest Ecology and management. Rainforest CRC, Cairns. 252pp. http://www.jcu.edu.au/rainforest/publications/permanent_plots.htm

LI-COR (2009). LAI-2200 Plant Canopy Analyzer Instruction Manual.

Metcalfe, D.J., Bradford, M.G. and Ford, A.J. (2008) Cyclone damage to tropical rainforests: species and community level impacts. Austral Ecology 33, 432-441.

Muir, J., Schmidt, M., Tindall, D., Trevithick, R., Scarth, P., and Stewart, J.B. (2011) Field measurements of fractional ground cover: a technical handbook supporting ground cover monitoring for Australia, prepared by the Queensland Department of Environment and Resource Management for the Australian Bureau of Agricultural and Resource Economics and Sciences, Canberra, November.

Robison, S.A. and McCarthy, B.C. (1999) Potential factors affecting the estimation of light availability using hemispherical photography in oak forest understories. Journal of the Torrey Botanical Society 126(4), 344-349.

Speight J.G. (1990) Landform. In. Australian Soil and Land Survey, Field Handbook. 2nd Edition. Inkata Press, Melbourne.

List of Acronyms

AcronymFull word
ARAAirborne Research Australia
ASLAbove Sea Level
AVHRRAdvanced Very High Resolution Radiometer
BRDFBidirectional Reflectance Distribution Function
CCDCharge Coupled Device
CSIROCommonwealth Scientific and Industrial Research Organisation
DBHDiameter at Breast Height
DGPSDifferential Global Positioning System
FPCFoliage Projective Cover
FTPFile Transfer Protocol
GPSGlobal Positioning System
IMUInertial Measurement Units
LAILeaf Area Index
LiDARLight Detection and Ranging
MODISModerate Resolution Imaging Spectroradiometer
NBARNadir BRDF-Adjusted Reflectance
ODKOpen Data Kit
OHSOccupational health and safety
RERegional Ecosystem
SLATSStatewide Landcover and Trees Study
TERNTerrestrial Ecosystem Research Network
THREDDSThematic Real-time Environmental Distributed Data Services
TLSTerrestrial Laser Scanner / Scanning

Appendix 1

Note: The following information in the appendix refers to a special 500 m x 500 m plot with intensive field sampling carried out by the Australian Supersites Network facility. The AusCover campaign site of 5 km x 5 km and includes the 500 m x 500 m plot with intensive field sampling.

Site establishment and survey

The TERN Robson Creek permanent plot is surveyed to a horizontal plan projection aligned to grid north. Unlike most other permanent plots around the globe that use a sight and measure method from an initial point to locate grid markers, the Robson Creek plot uses a GPS system to place each 100 m grid point independently.

ArcMap GIS was used to create a 500 m square grid broken into 100 m units based on Grid north (GDA94). For ease of navigation, the western edge of the plot was aligned with the easting 354250 and the southern edge of the plot was aligned with the northing 8106400. The locations of the 100 m intersection points were calculated and entered into a handheld Garmin high sensitivity GPS. The 36 x 100 m steel pickets were roughly placed on the grid with an independent error of 10 m. To position the 100 m steel pickets accurately, a survey grade DPGS unit (Trimble Pro XRT using the Omnistar DGPS signal) was used. Due to the lack of a clear signal under the forest canopy, a post-processing system was employed and positions were logged using the Terrasync software for 20 minutes. The Trimble pathfinder software was used to correct the positions using data from a base station operated by Measuretek in Cairns, 25 km away. Offsets from the roughly placed pickets were calculated and the pickets were moved accordingly. The independent precision of each point using this method is 2.3 m ± 1.8SD. This is considered the most accurate method using a GPS system under the forest canopy.

The 20 m grid points are marked with a white 20 mm poly pipe and are located by sighting and measuring off the 100 m steel pickets. The position of each point is checked by sighting and measuring from at least two points. The accuracy of these markers is considered to be ± 1.0 m within the hectare.

Location of the 100 m steel pickets on the TERN Robson Creek plot.

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Plot hectare numbering pattern.

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Tree measuring methodology

The tree census started in the southwest corner of the plot (0N,0E) and was done in units of 20 m x 20 m (subplot) within each hectare. Subplot numbering also starts in the southwest corner of each hectare and the order of subplot within each hectare is west to east, then east to west, etc. Subplot numbering is continuous across the 25 ha plot, ending at 625 in the northeast corner of the 25 ha. Tree numbering is sequential within each hectare. Hectare 1 has tag numbers 01-0001 through to 01-1000 and hectare 25 will have tag numbers 25-0001 through to 25-1000.

Stems surveyed in the first round of measurements are:

Stems ≥ 10 to ≤ 30 cm diameter at DBH are marked with a tag attached to a wire encircling the stem. A line completely encircling the stem is painted at the point of measurement (POM). Stems > 30 cm DBH have the hectare number and tree number painted on the northern side of the stem. A line completely encircling the stem is painted at the POM, except when the stem is extremely large in which case a line is painted partly around the stem.

Stems are mapped within each 20 m x 20 m subplot to a positional accuracy of 0.5 m. Each subplot was temporarily divided into 10 m x 10 m quadrats to assist in mapping. Heights are recorded to the nearest 1 m for each measured stem and are recorded as the length of the stem from ground to highest leaf. Heights for easily visible and larger stems are measured using a Nikon laser range finder. The heights of all other stems are estimated by comparing to the measured stems.

Rules for measuring

  1. Stems are measured in cm diameter at 1.3 m (breast height) from the ground on the uphill side of the stem.
  2. Stems leaning > 45 degrees are measured 1.3 m along the stem along the underside of the stem.
  3. Vines are to be pulled away from the stem before measuring where possible. Where a vine cannot be pulled away from a stem or the tape cannot be slipped under the vine, the stem is to be measured with callipers.
  4. Stems with a swelling or deformity that precludes taking a normal DBH measurement at 1.3 m will be measured above or below the deformity. If the deformity continues to < 1 m above the ground then the measurement is to be taken above the deformity. The POM is noted and painted.
  5. Stems with buttresses are to be measured at least 1 m above the highest buttress. Smaller specimens of particular species that are known to exhibit buttressing when they grow larger are measured at a higher POM to account for future buttressing. In this case the POM is decided on by the team leader.
  6. Where the trunk is irregular, deformed or fluted at all heights, the POM should be at 1.3 m.
  7. If there is a reason why no measurement can be made, a DBH must be estimated and noted. This occurs when stems have large and high buttresses and when large stems have many vines or strangler figs around them.
  8. Stems that fork above 1.3 m will be measured below the fork where the stem is not swollen or deformed.
  9. Stems that fork below 1.3 m will be measured at each stem as separate stems, at or close to 1.3m. Order of measurement in this case will be from largest to smallest stem. A multi-stemmed code is noted.
  10. Palms are included if the stem is ≥ 10 cm DBH (at 1.3 m) below the lowest living leaf base.
  11. Dead stems are to be measured and mapped but not painted and tagged.
  12. Lianas are measured 1.3 m along the stem after they leave the ground. The height of a liana will be the estimated length of the stem and will generally be higher than the host stem. They are mapped where they are considered to originate.
  13. The total DBH of strangler figs with more than one stem (the usual case) will be estimated and the POM noted and painted.
  14. Codes are recorded for unusual measurements: leaning > 45(L), snapped above 1.3 m (S), near dead or sick (N), rough hollow or dead side at POM (R), multi-stemmed (M), estimated DBH (E), callipers used for DBH (C).

(a) Corners of the 500 m x 500 m plot, (b) marked trees within the plot that can be related to species, DBH and tree height, and (c) subset of the table based information collected for each of the approximately 25,000 trees within the plot.

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