Question

Difference between two DEM (rasters) in an overlap area

  • 22 April 2022
  • 6 replies
  • 57 views
D
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I'm trying to make the difference between two DEM in an overlap area. 

Already how do I create the overlap area of the two DEM (raster) in FME. 

And how do I calculate the difference in pixel value height between raster 1 and raster 2?

 

thanks you!

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6 replies

nielsgerrits
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Userlevel 6
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This can be done using the RasterExpressionEvaluator.

D
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This can be done using the RasterExpressionEvaluator.

What do I put in the expression to get the elevation value of A minus that of B?

nielsgerrits
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Userlevel 6
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What do I put in the expression to get the elevation value of A minus that of B?

If the band is 0 then A[0]-B[0].

2022-04-22_16h37_41I attached a sample workspace.

M
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Hi @dona​, like already suggested by @nielsgerrits​ the RasterExpressionEvaluator is the right transformer for this purpose. As an addition, however: please note that the RasterExperssionEvaluator requires two rasters with the same dimensions. Please see this thread for a sample workspace.

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What do I put in the expression to get the elevation value of A minus that of B?

Thanks for the template but as I have two rasters that are not the same the function is not good. My two rasters are in two different files and what I want is to calculate the difference in elevation of the two rasters in the overlapping area. 

D
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Hi @dona​, like already suggested by @nielsgerrits​ the RasterExpressionEvaluator is the right transformer for this purpose. As an addition, however: please note that the RasterExperssionEvaluator requires two rasters with the same dimensions. Please see this thread for a sample workspace.

Hi @maayke​,

Indeed, I had found this post before asking my question but I can't use the RasterExpressionEvaluator transformers only on the overlap area because I will have two rasters of the same dimension in the overlap area. Do you know how to extract the overlap area between the two rasters so that I have the same dimension and use RasterExpressionEvaluator?

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