Question

Writing geotif with PixelIsPoint Header

jkr_wrk
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Userlevel 3
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How do i set FME Workbench to write a GeoTiff with the PixelIsPoint header?

 

Every setting i try writes a world file with the coördinates of the middle of the top left corner pixel and a model tie point with the top left corner of the top left pixel and a PixelIsArea header.

 

QGis and Arcgis pro show the correct position with the current settings but Autodesk seems to shift the file half a pixel.

 

I tried to fix this with the "Ignore Raster Type Key" setting or the "Write esri compatible coordinate system". I tried setting the RasterCellOrigin to 0,0 or 0.5,0.5

 

But all files seem the same.

 

Loading an ASC file looks correct. This file contains the lower left corner of the file.

 

Center of the attached files is 155000 463000

 

 

 

Sample: Every Nth Feature (N=1)

4 replies

caracadrian
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I use both Autocad and QGis, all my world files are referenced like this World file - Wikipedia

Your 3 geotiff's are referenced via:

A = 1

B = 0

C = 154997.5

D = 0

E = -1

F = 463002.5

Your sample geotiff's are invalid in Autocad. What method do you use to insert the raster in Autocad? mapiinsert should do the job correctly. If you use some lisp for georeferencing you might have an error there.

Please provide a sample workspace, if it's ok with you, so we can figure something out.

jkr_wrk
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Userlevel 3
Badge +17

I have tested all kinds of settings in FME. Writing 2^8 files. Didn't test all in Autocad because i don't have much experience with the software.

 

But I understand that the file is loaded into Autodesk Civil3d as a triangulation. The ascii file i write is a working method. The Geotiff can be imported, as I understand both with and without the .tfw file.

 

The contents of the .tfw that FME creates:

1.0000000000
0.0000000000
0.0000000000
-1.0000000000
154998.0000000000
463002.0000000000

 This is the correct world file contents according to the Wiki you provided.

  • Line 5: C: x-coordinate of the center of the upper left pixel
  • Line 6: F: y-coordinate of the center of the upper left pixel

 

Both lines should reference the center of the cell and not the corner of the file. 

 

There is also a model tie point in the header of the tiff:

ModelTiepointTag = (...,I,J,K, X,Y,Z...)

https://www.awaresystems.be/imaging/tiff/tifftags/modeltiepointtag.html

 

This is set to:

Model Tie Point = 0 0 0 154997.5 463002.5 0

So the coordinate 0,0,0 of the raster lies on 154997.5 463002.5 0 in the world.

 

This seems to be correct.

 

 

 

 

Sample: Every Nth Feature (N=1)
caracadrian
Rank
Badge +20

I have tested all kinds of settings in FME. Writing 2^8 files. Didn't test all in Autocad because i don't have much experience with the software.

 

But I understand that the file is loaded into Autodesk Civil3d as a triangulation. The ascii file i write is a working method. The Geotiff can be imported, as I understand both with and without the .tfw file.

 

The contents of the .tfw that FME creates:

1.0000000000
0.0000000000
0.0000000000
-1.0000000000
154998.0000000000
463002.0000000000

 This is the correct world file contents according to the Wiki you provided.

  • Line 5: C: x-coordinate of the center of the upper left pixel
  • Line 6: F: y-coordinate of the center of the upper left pixel

 

Both lines should reference the center of the cell and not the corner of the file. 

 

There is also a model tie point in the header of the tiff:

ModelTiepointTag = (...,I,J,K, X,Y,Z...)

https://www.awaresystems.be/imaging/tiff/tifftags/modeltiepointtag.html

 

This is set to:

Model Tie Point = 0 0 0 154997.5 463002.5 0

So the coordinate 0,0,0 of the raster lies on 154997.5 463002.5 0 in the world.

 

This seems to be correct.

 

 

 

 

Upon inspecting your data, the .tfw file is actually right as the points you input are outputted as the pixel centers.

I am not familiar with the Model Tie Point header in geotiff so no comments on that regard.

 

jkr_wrk
Rank
Userlevel 3
Badge +17

Upon inspecting your data, the .tfw file is actually right as the points you input are outputted as the pixel centers.

I am not familiar with the Model Tie Point header in geotiff so no comments on that regard.

 

Thanks, I did not yet figure out what Civil uses to position the file. But after inspecting the wiki and awaresystems website I guess FME is writing the correct way and Autodesk interpreters wrong. Maybe writing no coords in header and using only a world file will help.

 

Still don't know what the setting "Ignore Raster Type Key" does in the writer. And still nothing found to set the "PixelIsPoint" setting. But i guess this does nothing in how Autodesk reads the file.

Sample: Every Nth Feature (N=1)

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