Question

CsmapAttributeReprojector not recognizing negative y co-ordinate values

  • 23 April 2021
  • 1 reply
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F

I am using a CsmapAttributeReprojector to convert between a source coordinate system and my own local destination coordinate system.

 

I expect that the Y value should only change, however, this change does not take into account a negative value

 

So if the source Y value is -50

Instead of adding 200 to - 50, it adds 200 and 50 which results in 250 instead of 150.

 

I have a python script that reads the header of my CSV file and finds the Y column in the header and this value is given to the reprojector, this does find the right column but as said above, my transformations aren't subtracting

1 reply

daveatsafe
Rank
Userlevel 2
Badge +17

The user was in the southern hemisphere, which offers two different varieties of Transverse Mercator projections. One has the 0 northing at the South Pole, with Y increasing as you move north. The second has 0 northing at the equator, with Y increasing as you move south. In this case, the projection chosen was not the one desired, and so the offsets appeared to be applied the wrong way. Changing the projection in the coordinate system definition fixed the issue.

 

Fun fact: the Reprojector transformer will log the full definition of the chosen coordinate systems, which can help you find the resolution to coordinate system issues.

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