I'm hoping someone can point me to a step-by-step article or post on how to use LiDAR from 2 different years to detect changes in topography. I've found this Q&A; Forum answer...
https://knowledge.safe.com/questions/2487/lidar-feature-extraction.html
... but it's sort of a broad-strokes overview of the process, and not detailed enough for me to do anything with, having never tried this before (on any platform).
Thanks for any help you can offer!
P.S. - My organization is using FME 2016.
Hi @westdakota,
It depends exactly what you are looking for, the example you have linked is a bit more complex than a simple change detection as the answer suggests changing the data to 3D which I don't think is what you are after. Between two LIDAR datasets when you are looking for changes in the topography you are actually looking for whether there is a change in the value of the same cell between the 2 years. A good place to start might be: https://knowledge.safe.com/articles/1224/change-detection-with-the-rasterexpressionevaluato.html
Alternatively one transformer to explore would be the RasterCellValueCalculator which I believe essential performs the same operation as that in the article above without you having to set up the full equations. This transformer has an input port for each image and then you can select the operation to perform. For change detection I would use subtract where A-B is equal to New-Old. If there has been no change the output cell value will equal zero, and then where there is a value the positive/negative will indicate whether there has been an increase or decrease in elevation.
Note: In order to use this transformer the raster pairs much have the same number of rows and columns.