Saltmarsh Habitat Map

A saltmarsh habitat map derived from airborne data. The habitat map is a polygon shapefile showing site relevant habitat classes – this is a merged product of multiple sites across multiple years.

The habitat map is derived from CASI (Compact Airborne Spectrographic Imager) multispectral data, LIDAR (Light Detection and Ranging) elevation data, and other GIS products. The classification also uses ground data collected after the CASI capture.

The ground data is used to identify the characteristics of the different habitats in the CASI and LIDAR data. These characteristics are then used to classify the different habitats and fit them into one of the predefined classes.

The collection of ground data used in the classification has some limitations. It is not collected at the same time as the CASI or LIDAR; it is normally within a couple of months of CASI capture, therefore some variations between the CASI data and situation on site at the time of ground data collection are possible. A good spatial coverage of ground data around the site is recommended, although not always practically achievable. For a class to be mapped, there must have been samples collected for it on site. If the class is not seen on site or samples are not collected for a class, it cannot be mapped.

The habitat map was created using a supervised classification, which means ground data were used to train the model. The classifications had a quantitative accuracy assessment carried out on them in the form of a confusion matrix using ground data set aside and not used in training the classifier. Alongside this aerial photography captured simultaneously with the CASI data was used to check and make final improvements to the habitat map. Attribution statement: © Environment Agency copyright and/or database right 202022. All rights reserved.