The following steps were originally provided by Steve Henry, Charles M Russell NWR, in the Region 6 GIS Newsletter.
DOQQs are scanned ortho-rectified photographs that, because they are georeferenced, are commonly used as background images to drape additional GIS layers over for viewing purposes. The extents of each image corresponds to 1/4 of a 7.5' USGS quadrangle map and images are generally provided by the USGS (at a cost) on a CD. In the past, DOQQs were provided in the JPEG format. Currently, USGS provides DOQQs in band interleave line format (BIL). Methods currently exist to use either format in ArcView, however, in the case of band interleave line format images, a header file must be created that contains information about the DOQQ.
To set up band interleave line images for use in ArcView, first, copy the file provided by USGS from the CD to a directory on the local computer and renamed the image to have a .bil extension. The header file to be created must be named the same as the related DOQQ but with a .hdr extension. Both of the files need to be in the same directory.
EXAMPLE: DOQQ name o4210908.sws provided on the CD by USGS
renamed: o4210908sws.bil
header file named: o4210908sws.hdr
The contents of the header file can be obtained by opening a DOS window and using the type command with the more option to display the header information.
EXAMPLE: type o4210908sws.bil |more
For most black and white band interleave line DOQQs, the contents of the header file typed into a text file are as follows. You can use a text editor such as Notepad or a word processor, but if you use a word processor be sure to save the document as an ASCII text file, not in the word processor format. Information identified in parentheses are for description purposed only and should not be included in the header file.
| nrows 7710 | (# of rows in the image) |
| ncols 5940 | (# of columns in the image) |
| nbands 1 | (# of bands - default is 1) |
| nbits 8 | (# of bits - should be 8) |
| layout bil | (file type) |
| skipbytes 0 | (# bytes to skip) |
| ulxmap 652989.291 | (upper left x coordinate) |
| ulymap 4755364.973 | (upper left y coordinate) |
| xdim 1 | (pixel dimension on x axis) |
| ydim 1 | (pixel dimension on y axis) |
For additional information regarding this Web page, contact Chris Lett, in the Division of Information Resources and Technology Management, at Chris_Lett@fws.gov
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Keywords=GIS, data, photographic, DOQ
Last Modified January 03, 2001 08:40 AM