Instructions provided describe how to use CONVERTIMAGE to change or edit TIFF header information. ArcMap uses the header information in a TIFF to georeference that image, and occasionally the information in the header causes problems with scale and georeference in ArcMap. Editing the header information is typically the safest way to solve such problems. This can be done by using CONVERTIMAGE at an Arc prompt to create a new TIFF.
In the example below, the input image is converted to a bitmap. Bitmaps do not support any header information; therefore, the world files for the image are used for reference when the bitmap is converted back to TIFF.
- Open an ArcInfo Workstation Arc: prompt.
- Set the working directory to the storage location of the image.
- Use CONVERTIMAGE to convert the TIFF to a bitmap. The syntax is similar to:
CONVERTIMAGE input1.tif output1.bmp BMP
For specifics on the CONVERTIMAGE command, refer to ArcDoc.
If the TIFF is compressed, use the NONE option in CONVERTIMAGE to get an uncompressed TIFF before converting to a bitmap.
- Compare the original TIFF world file with the newly created bitmap's world file. Edit the bitmap's world file if it is different; it should match the original.
World files, *.tfw, *.bpw, and so forth, can be created, viewed, and edited with any text editor, such as Notepad.
- Use CONVERTIMAGE again to convert the bitmap back to a TIFF. This operation takes the information from the bitmap world file and includes it in the new TIFF header and world file. This operation removes any projection information in the TIFF header.
- Redefine the spatial reference for the image in ArcCatalog. The conversion in Workstation drops this information from the file.
- Check the final image in ArcMap.