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Question

Raster reprojection displacements

  • April 22, 2021
  • 2 replies
  • 26 views
r_huesken
Contributor
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Hi,

For a client we are developing a system to preview survey data (bathymetry) in a browser. Additionally, we also need to indicate differences between surveys over time. These survey data are supplied as rasters.

 

I have some troubles when reprojecting rasters with different extents to Web Mercator, please find attached a document with more information and screenschots.

 

Raster 1

  • CRS       EPSG:32643 - WGS 84 / UTM zone 43N - Projected
  • Extent  272800,2092300 : 276600,2097600
  • Unit      meters
  • Width   3800
  • Height  5300
  • Origin   272800,2097600
  • Pixel Size 1, -1

 

Raster 2

  • CRS       EPSG:32643 - WGS 84 / UTM zone 43N - Projected
  • Extent  261500,2088600 : 281600,2100300
  • Unit      meters
  • Width   20100
  • Height  11700
  • Origin   261500,2100300
  • Pixel Size 1, -1

 

 

I'm looking for a way to prevent small displacements using a correct combination of FME transformers, using FME 2020.1

 

Thanks,

 

Richard.

 

2 replies

nampreetatsafe
Safer
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Thanks for the question @r_huesken​! Just wanting to get clarification on the issue you are having. If you are comparing 2 rasters with different extents, I would assume there would be areas that aren't overlapped. Are you hoping to clip any of the areas that are only covered by one survey?

r_huesken
Contributor
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  • r_hueskenContributor
  • Author
  • Contributor
  • 33 replies
  • April 28, 2021

Hi, there areas that do not overlap, but that's not my concern, since I'm looking at areas where the surveys overlap. I find that the top left coordinate and the raster width and height are important for transformation fromEPSG:32643 to Web Mercator (EPSG:3857). These are different for both rasters, are transformed rasters give different outlines and z values in areas where they overlap...


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