Marine remote sensing toolkit

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BRG The University of Queensland
Fundamentals

- Main page
- Pre-processing
- Field data collection
- Mapping approaches
- Change and trends
  - About
  - Image requirements
  - Mapping change
  - Trend detection
  - Example time series
  - Example change maps
- Delivery

# Mapping biophysical change

Change detection uses two sequential images of the same area to either:

1. identify regions of significant change in surface reflectance (pixel value) or a biophysical property; or
2. map the transition from one thematic class to another (e.g. seagrass to sand)

For both cases, it is essential that the two images meet ALL pre-processing requirements.

Mapping biophysical change: To generate a map of change in seagrass abundance, the 1999 abundance image was subtracted from the 2002 image.

If using two images, or image maps of a biophysical variable (e.g. SST), the successive images can be subtracted to divided to produce a difference image.

If using two thematic maps (e.g. benthic cover types), the post-classification comparison technique should be used to produce an output map showing the initial and final state of each pixel.

Note that the accuracy of the change product is a product of the accuracy of the two input images.