2011 NSW woody vegetation extent: maps

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 has been upgraded and is the most detailed to date (5 metre pixels). It shows the location, extent, and density of foliage cover for stands of woody vegetation in NSW for the year 2011. 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.

woody vegetation extent map

 

 

 

 

 

 

 

 

 

 

 

 

 

 

State-wide map of woody vegetation extent and foliage cover.
The darker the green, the denser the vegetation.

What can the maps be used for?

The maps are intended for 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 versions of the state wide map:

  • Woody vegetation extent, a map of woody vegetation presence or absence, where woody vegetation is defined as trees and shrubs taller than two metres and visible at the resolution of the imagery used in the analysis (5 m by 5 m pixels)
  • Woody foliage projective cover (FPC), FPC is the fraction of the ground that is obscured by green leaf, and is a measure of density.
Satellite imagery used

The satellite imagery used (left panel) in the creation of the two map products (right panels).

How accurate are the maps?

We conducted two comparisons with independent observations of woody vegetation extent. The first comparison used independently-derived, 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
by Local Land Service

 Local Land service

 Points

 Lidar

 North Coast

 95.8%

 93.6%

 Northern Tablelands

 91.8%

 89.0%

 South East

 91.6%

 94.5%

 Central Tablelands

 91.0%

 86.8%

 Greater Sydney

 90.6%

 89.1%

 Central West

 89.8%

 88.3%

 Riverina

 89.0%

 93.0%

 Hunter

 88.7%

 85.3%

 North West

 88.3%

 89.0%

 Murray

 84.8%

 90.3%

 Western

 77.5%

 88.6%

Techncial details

 Data type

 Raster

 Pixel size

 5 m

 Base imagery

 SPOT 5 HRG, 10 m  multispectral and 2.5 m panchromatic

 Coordinate reference system

 GDA94 / MGA zones 54, 55, and 56. EPSG codes 28354, 28355, and 28356.

 

 Pixel value

 meaning

 Woody extent product

 0

 Not woody

 1

 Woody

 255

 Null

 Woody extent and FPC product

 101-200*

 Woody FPC

 100

 Not woody

 99

 Not woody, ephemeral water

 98

 Permanent or semi- permanent water

 97

 Not mapped

 96

 No observations

 0

 Null

*A pixel value of 101 is an FPC of 0.01, 200 is an FPC of 1.0.

 

More about how the maps were created.

Acknowledgements

We owe a debt of gratitude to the numerous Science Division staff and volunteers who edited the maps.

Thanks too, to the following organisations:

  • AirbusDefence and Space for SPOT data
  • NSW Land and Property Information for ADS40 data.
  • NSW Land and Property Information and a number of commercial vendors funded from various sources for Lidar data
  • The Joint Remote Sensing Research Program for staff and research expertise

Data access

The maps may be requested through the Office of Environment and Heritage’s Spatial Data Online catalogue: http://mapdata.environment.nsw.gov.au. Search for woody vegetation.

Contact

For product information and data access queries email the data broker: data.broker@environment.nsw.gov.au

Page last updated: 25 May 2015