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Technical Evangelist
Posts: 213
Registered: ‎02-12-2016
Re: How do I perform change detection & generate a matrix table from Landsat classified (themati


Hi Debbie,


This is a two part inquiry, one is an inquiry for performing change detection and the other is an inquiry for using a matrix table for change analysis.


There are varying change detection methods available to create a Landsat classified thematic image in IMAGINE. Two of the more common methods would be supervised and unsupervised classification. There is an abundance of reference material that discusses these methods so I won’t use this forum to present them. IMAGINE offers online references from the Help tab > Reference Library group > Workflows menu > Classification Workflows.


The Hexagon Geospatial Real-Time documentation portal also provides procedural references for classification.



How are you looking to use a matrix table to measure the change analysis? The matrix table could be statistical or spatial. Raster tab > Thematic > Matrix Union creates a spatial matrix raster output. The spatial matrix example discussed below assumes:

  • identical landcover categories have been generated for both ‘before’ and ‘after‘ classified thematic images
  • the ‘before’ and ‘after‘ raster images are spatially coregistered (same geographical extent) with each other
  • the ‘before’ and ‘after‘ raster images have the same spatial resolution (e.g. 30m.)


Before and After landcover  categories.

  1. Urban, built-up land
  2. Agricultural
  3. Field and Rangeland
  4. Forest
  5. Water
  6. Wetland


The 6 x 6 matrix is constructed by where the columns represent the Before image landcover classes and the rows represent the After image landcover clases. The output pixel values represent the spatial coincidence between the pixels of the Before and After classes. There are 36 different possible change classes. For example, matrix output pixel value 4 represents the coincidence of Before class 4 and After class 1. This is interpreted as a change from Forest (4) to Urban, built-up land (1). Classes 1,8,15,22,29,36 represent classes of NO CHANGE between the Before and After images.


Just one example




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