Setting raster units to pixel coordinates

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07-14-2013 12:48 PM
RadekChuran
New Contributor
Hello,
I have a few raster images which I need to georeference and work further on with map and source coordinates. Everything works fine when I use a fresh raster image. It shows unknown units which are corresponding to the "pixel coordinates". I mean if the resolution of the image is 3000x2000 pixels then the units go from upper left corner with coordinates [0,0] to [2999,-1999] in lower right.
But if I am working on a raster which I've been working on before then the units are different even though the raster is not georeferenced or rectified yet. Probably it somehow stores the information about georeferencing from before. It shows units as decimal degrees. Which honestly I don't undestand what they mean in this case.
However, is there any way how to set the raster units to unknown/pixel again?
Thanks in advance.
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2 Replies
JimCousins
MVP Regular Contributor
Two thoughts:
If your map document has a coordinate system defined, any file with unknown units/coordinate system will be displayed using the map document's units. Check that the map document General tab shows units as unknown, and Coordinate System tab shows the Current Coordinate System as "No coordinate system."
Perhaps you need to go in and delete any pyramid layers or files created during your previous session. Go to the folder in a regular windows explorer/file browser, and delete any files with the same name, but different extensions than your original image. (ie: if your original image was picture.tif, delete picture.aux, picture.ovr, etc).
Regards,
Jim
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RadekChuran
New Contributor
Thanks for answer Jim,
I've checked the data frame properties already. It has neither the coordinate system nor the map units defined. Weird thing is that even though the map units are set as unknown the display units option (which is grey and unactive) is set to decimal degrees as default. If I set the map units to meters and then the display units to unknown it still shows the wrong units (the same as when the decimal degrees were set).
About the pyramids. I don't have any other files with the same name in the folder. However when I add the tif file to ArcMap it does not ask for building pyramids. Isn't it possible that it somehow stores the information within the tif file itself and not in other files with the same name?
Thanks for ideas.
Radek
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