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I have rasters that are in UTM projection (of various zones, depending on the location of the raster) at 10-meter pixel spacing. The rasters are, on average, 29,000 by 21,000 pixels which covers a 290km-by-210km area.

Is it the case that since: (1) the rasters are in UTM projection and; (2) the rasters cover "local" areas, I can infer that true geographic north-south direction is perfectly vertical and true geographic east-west direction is perfectly horizontal anywhere in the raster?

[Edited to state "geographic" north.]

TCR
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  • By "true north", do you mean geographic north or grid north? If the former, no, there is a difference which increases the further from the central meridian you are. – Gabriel Aug 17 '22 at 19:26
  • I meant geographic north.

    Do you know any reference material (bonus if it includes Python/GDAL examples) that I can look into to figure out how to determine the geographic north in my rasters?

     – TCR Aug 17 '22 at 19:42
  • Honestly, this is above my level. The convergence angle value would be different for every pixel in your raster. – Gabriel Aug 17 '22 at 19:47
  • See this post for a solution: https://gis.stackexchange.com/questions/115531/calculating-grid-convergence-true-north-to-grid-north – GBG Aug 17 '22 at 19:54

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