Georeference tool

[qgib]

Author Name: doug_newcomb-fws-gov - (doug_newcomb-fws-gov -)
Original Redmine Issue: 523

Redmine category:projection_support
Assignee: Magnus Homann

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Tried to georeference a jpeg image to EPSG 32119 projection. The output jgw file looked like this:
24.5335
0
0
-24.5335
nan
26052543469100656972793667356933792334551124445385671982001717765625696361250852
63230640588410366355387916037395507101170807331933447168232048026256148650314170
68255704400035347073092961720361697046386861456890565381992582038014706635298444
962359964072945413053455317431577487218906213975588864.000000
The qgis - generated points file :

mapX mapY pixelX pixelY
551629.000000 119426.000000 1042.95 -1942.69
558297.000000 128803.000000 1320.27 -1560.28
561736.000000 142243.000000 1460.38 -1023.16
554963.000000 154641.000000 1185.99 -519.606
532042.000000 159226.000000 234.348 -329.862
539335.000000 147557.000000 536.478 -807.141
529333.000000 124635.000000 132.178 -1723.75

I converted the above y pixel coordinates from negative to positive and used the altered coordinates as gcp points in gdalwarp and got the following correct world file:
24.4658442217
0.0000000000
0.0000000000
-24.4658442217
526378.6525011690
167601.3482739714

My simplistic assumption is that the qgis georeferencer is passing negative y coordinates for a jpeg file when they should be positive instead.

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• PE_rockingham_westend.jpg.points (doug_newcomb-fws-gov -)

[qgib]

Author Name: Magnus Homann (@homann)

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Is it possible to supply the image?

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• status_id was changed from Open to In Progress

[qgib]

Author Name: doug_newcomb-fws-gov - (doug_newcomb-fws-gov -)

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Tried to add the original jpeg file, but was too large at 3.2 MB

[qgib]

Author Name: Magnus Homann (@homann)

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We had some issues where if proejction was turned on when you entered georeference tools, it wouldn't work. have you tried turning off projection?

Also, if you have the possibility try downloading the latest from SVN and try it there. I have done some work with it.

If this does/does not work, let me know. There is nothnig bad with negative coordinates as I see it (0,0) is upper left pixel according to world file specification. What happens if you use gdalwarp with the negative coordinates?

[qgib]

Author Name: doug_newcomb-fws-gov - (doug_newcomb-fws-gov -)

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I can go back and check, but I as I recall using negative line numbers with GCPs caused the image to flip upside down. ( I had tried it with a tiff version of the file as well)
the world file associated had the following contents:
24.6106913661
0.0000000000
0.0000000000
-24.6106913661
526364.0265134282
221911.9794584604

With a negative y pixel size

I thought image specs in general had the 0,0 in the upper left hand corner and positive x going right and positive y going down?

[qgib]

Author Name: Magnus Homann (@homann)

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The points in the .points file are in an internal format, and we do not use GDAL to generate world file. Have you tried to turn off projection?

See also #10619

[qgib]

Author Name: Magnus Homann (@homann)

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Fixed in / . Uninitialized variables made win32 behave differently.

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• status_id was changed from In Progress to Closed
• resolution was changed from to fixed

[qgib]

Author Name: doug_newcomb-fws-gov - (doug_newcomb-fws-gov -)

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Thanks!

[qgib]

Author Name: Anónimo (Anónimo)

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Milestone Version 0.8.1 deleted