The State Vegetation Type Map: your questions

What information is available in the map?

Vegetation Type layer

Each map feature describes a homogenous area of native vegetation type including trees, shrubs, aquatic vegetation and for some maps candidate native grasslands.

Each unit is attributed with a code for all three tiers of the NSW vegetation type classification system:

  • Formations
  • Classes
  • Plant Community Types (PCTs).

PCTs

OEH has adopted PCTs as the finest level of vegetation classification in NSW.  They are intended to communicate local and regional patterns in species assemblages that can be used in vegetation maps, regulatory tools and local land use and management planning.

Given the similarity between some closely related PCTs within a Vegetation Class and the variable level of descriptive detail or site data for PCTs in NSW, the three most likely PCTs are also provided in the feature attribution.  

Areas that are not considered to be native vegetation are also mapped (by exclusion) and these may include: pine forests, plantations, weeds, open water, agricultural paddocks, built infrastructure, urban areas, roads, dams and exposed earth.

OEH is also undertaking a program to enhance and refine the list of Plant Community Types through more comprehensive analysis of new and existing site survey data.

Vegetation Survey Sites layer

Thousands of sites are used to define the State Vegetation Type Map. Some sites come from the OEH archives and others are recent and have been collected to help fill gaps in our knowledge. The location of each survey site and its registration code for the mapping region are included in this layer of the data package. Many of the more recent sites include a reference photograph.

Future online products

OEH is working with state and federal government agencies to design a new open data format for survey data. The NSW Bionet survey database will use this new standard to deliver web data services for flora survey data.   

The Office of Environment and Heritage aims to have most of the NSW vegetation information available as web services that can be accessed online or through mobile applications.

This will include the State Vegetation Type Map, all the NSW flora site survey records (location and data) and the detailed PCT profiles and photographs.

How are the maps created?

First we look at existing vegetation surveys and maps in the area of interest. All of the available survey site data are collated and we use the recorded data to allocate each survey site to a particular PCT. We then use sophisticated feature recognition software, originally developed for medical imaging technology, to analyse satellite imagery and aerial photography to delineate small patches of vegetation that have the same visual characteristics.

Segmentation 

This technique is generally known as segmentation because the process divides the image into segments and then draws polygons or lines around each of these regions of similarity according to a defined set of rules.

It effectively replicates what humans do when interpreting imagery but saves considerable time and cost compared with manually drawing lines. As the whole image is segmented, other non-vegetation features such as water bodies, infrastructure and buildings are also defined. So the segmentation data can assist with other mapping purposes.

Structural groups

Next, remote sensing interpreters and ecologists use their skills and experience to identify how the segmentation of native vegetation patterns can be aggregated into structural groups, similar to Vegetation Formations. They use a range of clues to help identify the vegetation structure such as survey sites, previous mapping, and topographic layers and, in some cases, time series images.

Using site survey information, the structural groups and other environmental determinants, we apply computer models to identify up to 3 of the most likely plant community types for each particular map polygon.

Experienced ecologists review and manually edit the modelled allocation of PCTs. This process may be repeated several times to develop the final release version of the map.

For more technical detail about how the maps are created, contact Bionet@environment.nsw.gov.au.

How should the regional scale map be used?

The State Vegetation Type Map is not referred to in legislation and it is not designed to be used as a stand-alone tool for defining what particular vegetation type is present at any given site. It can be best used to inform the likely range of PCTs to be found or where a type may be found elsewhere.

Each mapped polygon has a vegetation attribute for Formation, Class and PCT so users can decide what level of classification is best for their needs. Because some types are very similar or share species, the three highest probability PCTs are also provided. At the finest level, which is a single PCT, it is to be used as a guide. At broader floristic and structural levels (e.g. Vegetation Class, Formation and tree cover presence /absence) it is more reliable.

The State Vegetation Type Map will provide an estimate for the total extent of each PCT across NSW and identify which types are being most affected by clearing. It will also highlight gaps in our knowledge. As the map is progressively refined, the extant area can be adjusted.

With additional mapping of the predicted pre-clearing extent of PCTs, the relative level of clearing across NSW for every PCT can also be systematically calculated.

How will the State Vegetation Type Map be improved over time?

Incorporation of new more detailed mapping

The State Vegetation Type Map has been designed to more easily incorporate new data without the need for whole-scale remapping. In fact, the map already includes some selected mapping completed by other parties. These sources have used the same or equivalent vegetation types but may have mapped to higher levels of detail or had more intensive field verification.

Fine scale vegetation mapping is often undertaken independently and for highly specific purposes. OEH can assist other agencies, local government or private consultants to maximise their compatibility for incorporation into the State Vegetation Type Map.  

Additional flora survey to improve PCT definitions and distribution models

Field data is critical to the models used in the mapping process that guide where PCTs occur in the landscape. Consequently as these models are improved, the parts of mapping can be updated.

The preparation of the State Vegetation Type Map also helps identify where and which PCTs need more survey data. Having more survey data helps refine the diagnostic species characteristics for better mapping or field identification. After major additions to survey data, some types may be re-described or even merged with similar types.

Collaboration

OEH is collaborating with botanists and industry practitioners to improve the capture of systematic field data that can be used to improve classification. In addition OEH is targeting new survey effort in poorly sampled regions. Together this has significantly improved the availability of field data.

Exploring advanced modelling techniques as they become available

As new modelling techniques and approaches are developed and reviewed in the scientific literature this opens up opportunities to further improve the State Vegetation Type Map. OEH is currently working with the University of NSW to explore contemporary analytical techniques to enhance the definition and diagnosis of PCTs on the NSW East Coast and Tablelands.   

How reliable are regional scale vegetation maps?

The overall accuracy of a vegetation map depends on the number of vegetation classes being mapped and the quality and number of surveys available for each PCT. Some PCTs can be mapped with high overall accuracy, reliably representing their distribution. Others have very little survey information available so accuracy of the map will be limited. Some PCTs have so little survey data that they cannot be mapped at a regional scale.

 

Vegetation Unit Typical Model Accuracy
Keith Vegetation Formation and Class 60-75%
Plant Community Types (PCTs)

Individual PCTs 45-55%
Top 3 Ranked  PCTs 65-75%

 

Due to the variable quality of descriptive data for particular PCTs, the mapping accuracy can vary widely.

 

The three most likely PCTs are identified for each map unit.

 

 

 

 

 

 

The State Vegetation Type Maps represents the best available information about PCTs in NSW and will continue to improve over time.

How do we ensure the maps are prepared in a scientifically rigorous manner?

OEH takes scientific rigor very seriously. Peer review of our science at all stages of a project is central of our Scientific Rigor Statement.  At the commencement of the state-wide mapping project, an independent group of highly regarded and experienced scientists from across Australia and New Zealand were invited to form the Vegetation Information and Mapping External Scientific Advisory Committee (VIMESAC). The Committee has reviewed the methods, provided direction for improvements and confirms that the methods are being appropriately used.  

We also ensure that our models undergo rigorous internal validation and cross-checking and we regularly set aside a pool of samples to independently test model performance.
The methods we use have been supported by published scientific literature before we use them. In fact, species distribution modelling and feature recognition are both very active fields in science.

Many of the new analysis and mapping techniques developed for this project will be published for other scientists to benefit and build upon.

Finally, the maps are provisionally released to local and state-wide stakeholders to invite feedback and corrections before incorporation into the state wide layer.

an example map of NSW central west
Page last updated: 19 December 2016