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Woody Extent and Foliage Projective Cover - SPOT, OEH algorithm, NSW coverage
Last modified by Matt Paget on 2016/06/20 11:22
Link to the data
| Descriptor | Data link |
|---|---|
| Persistent URL | http://www.auscover.org.au/purl/spot-woody-extent-fpc-nsw-2011 |
| GeoNetwork record | |
| Maps | http://mapdata.environment.nsw.gov.au (search 'woody extent') |
| Data access | http://qld.auscover.org.au/public/data/spot/woody_fpc_extent/nsw-2011 ftp://qld.auscover.org.au/spot/woody_fpc_extent/nsw-2011 |
Data licence and Access rights
| Item | Detail |
|---|---|
| Rights | Copyright 2014-2016 OEH. Rights owned by the Office Environment and Heritage (OEH). Rights licensed subject to Creative Commons Attribution (CC BY). |
| Licence | Creative Commons Attribution 4.0 License, http://creativecommons.org/licenses/by/4.0. |
| Access | These data can be freely downloaded and used subject to the CC BY licence. Attribution and citation is required as described at http://www.auscover.org.au/citation. We ask that you send us citations and copies of publications arising from work that use these data. |
NSW woody vegetation extent 2011
Woody vegetation is a key feature of our landscape and an integral part of our society. We value it because it contributes to the economy, protects the land, provides us with recreation, and gives refuge to the unique and diverse range of fauna that we regard so highly. Yet it poses a significant threat to us in times of fire and storm. So information about trees is vital for a range of business, property planning, monitoring, risk assessment, and conservation activities.
The map of woody vegetation extent for NSW for 2011 has 5 metre pixels. It shows the location, extent, and density of foliage cover for stands of woody vegetation in NSW.
The resolution is good enough to identify small features such as trees in paddocks and scattered woodlands through to the largest expanses of forest in the State.
What can the maps be used for?
The maps are intended for use in rural landscapes and are suited to many applications including
- property planning
- vegetation mask for topographic maps
- local government planning
- risk assessment, such as in fire-prone areas
- native vegetation mapping
- habitat identification and mapping
What maps are available?
There are two different versions of the state-wide map:
- Woody vegetation extent. A presence/absence map showing areas of trees and shrubs, taller than two metres, that are visible at the resolution of the imagery used in the analysis
- Woody foliage projective cover (FPC). FPC is the fraction of the ground that is obscured by green leaf, and is a measure of canopy density
On the download server, the woody extent products are those with the 'bcu' code in the file name. The Woody FPC products are those with the 'bcv' code in the file name. Both mosaics and tiles are available. A shape file that identifies the location of the tiles is also on ftp server.
The satellite imagery used (left panel) in the creation of the two products (right panels)
How accurate are the maps?
OEH staff conducted two comparisons with independent observations of woody vegetation extent. The first comparison used fine-detailed maps of woody-vegetation extent derived from airborne Lidar surveys. The state-wide map of extent had an overall accuracy of 90.1%.
The second comparison used 6670 image-interpreted points of woody vegetation presence or absence. The points were gathered from images with 2.5 m pixels. The overall accuracy was 88%. The spatial variation in accuracy across the state, reported by Local Land Service region, is listed in the table below.
Care should be taken when interpreting the maps. Incorrect classification is most likely to occur where it is difficult to distinguish trees greater than two metres in height from other types of vegetation. Such vegetation includes sparse woodlands, low shrubs, chenopods, heath, wetlands, and irrigated pastures and crops. Also, woody vegetation is only detected about half of the time when the foliage cover within a pixel is less than 20%.
Overall accuracies of woody extent from the comparisons
| Local Land Service | Points | Lidar | Local Land Service | Points | Lidar |
|---|---|---|---|---|---|
| North Coast | 95.8% | 93.6% | Riverina | 89.0% | 93.0% |
| Northern Tablelands | 91.8% | 89.0% | Hunter | 88.7% | 85.3% |
| South East | 91.6% | 94.5% | North West | 88.3% | 89.0% |
| Central Tablelands | 91.0% | 86.8% | Murray | 84.8% | 90.3% |
| Greater Sydney | 90.6% | 89.1% | Western | 77.5% | 88.6% |
| Central West | 89.8% | 88.3% |
Key specifications
| Spatial resolution | 5 m |
| Spatial coverage | The state of New South Wales |
| Temporal resolution | Single image. |
| Sensor & platform | SPOT 5 HRG |
| Custodian | NSW Office of Environment and Heritage |
| Coordinate system | NSW Lamberts Conformal Conic (mosaic). GDA94 MGA zones 54, 55, and 56 (tiles) |
Image pixel values
| Woody extent product | Woody extent and FPC |
|---|---|
| 0 - not woody | 101 to 200 - woody FPC* |
| 1 - woody | 100 - not woody |
| 255 - null | 99 - not woody, ephemeral water |
| 98 - not woody, water body | |
| 97 - not mapped |
* FPC = pixel_value * 0.01 - 1
Acknowledgement
We owe a debt of gratitude to the numerous Science Division staff and volunteers who edited the maps. Thanks too, to the following organisations:
- Airbus Defence and Space for SPOT imagery data
- NSW Land and Property Information for ADS40 data
- NSW Land and Property Information and a number of commercial vendors for Lidar data
- Joint Remote Sensing Research Program
Contact
Contact the NSW OEH data broker for further information. data.broker@environment.nsw.gov.au
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