Question

RasterExpressionEvaluator, variable gain to values depending on distance from one side.

R

Hello, I am looking at trying to build a transversal gain function for numeric rasters. I have several elongated rasters which form corridors. These rasters have a decreasing mean value from one side to the other. Since these rasters have varying orientation it is not simple to establish the row column relationship from side to side.

Do anyone have a tip for me how to be able to handle the distance relationship from side to side together with a custom built rasterexpressionevaluator to either scale up or down depending the spatial location in the raster.

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kailinatsafe
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Hello @rody​ , thanks for posting to the FME Community! I'm not too sure what the goal is here, apologies, maybe I am misunderstanding! If you could describe your use-case in more detail, or further explain what you're trying to use FME to accomplish, that would be great! Best, Kailin.

R

Hello @rody​ , thanks for posting to the FME Community! I'm not too sure what the goal is here, apologies, maybe I am misunderstanding! If you could describe your use-case in more detail, or further explain what you're trying to use FME to accomplish, that would be great! Best, Kailin.

Hello, what I wish to is to balance the images since they all have the same reoccurring imbalance in values. There is a gradient in values from one side to the other.

I have now found a way to do this in the point cloud which the raster was made from, currently I am looking at how to calculate a gradient which I can use to determine how to scale the values in order to balance them all to the same level. Do you have any idea how to calculate such a gradient on a pointcloud?

kailinatsafe
Rank
Userlevel 3
Badge +13

Hello, what I wish to is to balance the images since they all have the same reoccurring imbalance in values. There is a gradient in values from one side to the other.

I have now found a way to do this in the point cloud which the raster was made from, currently I am looking at how to calculate a gradient which I can use to determine how to scale the values in order to balance them all to the same level. Do you have any idea how to calculate such a gradient on a pointcloud?

Hello @rody​ , thanks for the reply! I hope my response makes sense, please let me know. If you know the gradient difference, you could potentially create an expression in the RasterExpressionEvaluator to calculate the correction for each pixel based on its location within the image. I think calculating the gradient difference would require determining intensity averages of several areas of the same landscape type over the image, which I’d imagine can get really complex. There aren't very many resources on this topic, so I don't have any real examples to share! Out of curiousity, have you considered doing this in a remote sensing application, prior to bringing your data into FME Workbench? Best, Kailin

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