12-29-2016 03:49 AM
Can somebody advise me of how I can perform change detection and then generate a matrix table (post-classification change analysis i.e. 'from to' change) with Landsat classified (thematic) images in ERDAS IMAGINE 2016.
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01-04-2017 07:45 AM
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:
Before and After landcover categories.
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
01-14-2017 10:40 PM
Thank you Jeff for the explanation. I have performed supervised classification in ArcGIS and now have an image with 9 landcover classes which I exported as an .img file. However when I try to load the file into Matrix Union I receive the error message "Input files must be thematic" - can you assist me with this problem
01-16-2017 05:47 AM
Try changing the layer type for your images from continuous to thematic. You can accomplish this by passing your images through the Subset tool. You will not subset the data, but simply change the output layer type to thematic.
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