Howdy! I'm having an issue using the WA clipped DRGs from - http://rocky2.ess.washington.edu/data/raster/drgclip/index.html - .
Some of the DRGs load fine, but the majority (especially the 24Ks) give an error of "compression algorithm does not support random access". After some Googling, it appears this means the tiff files were written in non-sequential format during the clipping process. I checked and it appears to be using PACKBITS compression and scanline mode. Based on my reading it appears the correct answer is to reprocess the files through TIFFCP and convert them. I'm unsure whether I should convert them to strips or tiles. It looks like scanline format is out since it doesn't allow random access when using compression. Between strips and tiles, is there a preference on which Xastir can process more efficiently for pan/zoom/update operations? At first glance I'm guessing tiles would be the most efficient. Along with the goes the question of recommended tile size. 16? 32? 64? 128? I tried using TIFFCP on one file and it dumped the GEOTIFF-specific tags as TIFFCP doesn't know what to do with them. is there an analog to TIFFCP buried somewhere in the GEOTIFF tools that I haven't found yet? Fortunately, there are already TFW files for each quad, but I'd like something a bit cleaner and standalone if at all possible. Once I've done a few more tests I can batch them up and do them all at once. Whatever method works best I'll post back to the group. Thanks in advance for any pointers and hints. 73 N5VFF - Brian _______________________________________________ Xastir mailing list [email protected] http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
