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There's been a delay in adding the base mapping feature to the tiger2marker program due to the plethora of .tiff formats. After much thought, I've come to the conclusion that I should use a simpler format. I regret having to do this because every drg I've ever seen is in .tiff format. So, do I put a lot of time into handling all these different types of .tiff file, or use a simpler format and let the users convert their files to, say, .bmp format? The latter would eliminate the need to install the imaging ocx. The former would eliminate the need to convert the .tiff files to another format. I'm thinking I'll go with a simpler format and add a feature allowing users to georeference any image that's in the simpler format.Comments anyone?Lloyd Engle (when I decided to have a brain-child I had no idea I'd be in labor so long)
From what I've read, but without rechecking any of it now , there are two formats for the DRG .TIF files. One of the formats is used by the collarless DRGs and the other format is used by the collared DRG files.One of the formats is UTM, and I don't recall what the other format is, or which uses which format.I do my work with the DRG files by inserting them as images in AutoCAD, and then I have to manually scale them. The collarless files are far easier to work with than the collared files for this application, but for just plotting out map files, the collared work far better. MicroDEM can read both formats and print them at any given scale.Anybody know of a source, preferably free, of collarless DRG files for the state of Idaho? The P&L is about 2/3 in Washington and 1/3 in Idaho and I've got all the collared DRG files for the whole route, and collarless files for Washington, but the only DRG files I can find for Idaho, whether free or fee, are collared.David Beach.Palouse & Lewiston
Lloyd, After reading your post, If you have to convert to a different file format, I would suggest jpg, in the interest of saving hard drive space, some of the drg files Ive used, I tried to convert to .bmp, and man did they get huge!Dave
I would recommend NOT converting to jpg format. JPG is a lossy compression format and the fine detail will be lost and gone forever.David Beach.Palouse & Lewiston
That's why I ruled .jpg out early on, any conversion would have to be lossless. With respect to .tiff format, there are several different compression schemes in use. Whether they have collars or not is immaterial to the program as it stands, in fact stripping the collars within the program wouldn't be that difficult once they are read in, but should I rotate the result or fill in the wedges at the border from neighboring drg's? The drgs I got from http://www.mit.edu/afs/sipb/contrib/usgs-data/ use .zip compression, luckily the latest version of irfanview could read them (nothing else on my computer would open them, not even microdem) But when I tried to convert them to packbits compression, which is used by all the other drg's I've got (which load just fine) They wouldn't load! I guess irfanview doesn't get the tags right when writing.What I may do is chain to irfanview to read the .tiff files, that way only one at a time is converted, and the user just needs to make sure they have about 40 mb free hd space to use it. Looks like this is going to take a while longer yet.Lloyd
The USGS has a page with a fair amount of information on the DRG format(s). Also do a web search for "geotiff". The standard, published, tiff format leaves open the possibility of header information, without defining much of it. The geotiff format is an unofficial standard used by the geo community and the headers include which format (UTM or ??) the coordinates are in, the scale, and other useful information. What likely happened in your uncompress/recompress sequence is that something did not recognize the information in the internal headers and that information was lost. Do you have the latest version of MicroDEM? The author of that program seems to keep up on developments and would very likely have a means of dealing with a new format if one is out there.David Beach.Palouse & Lewiston
After further consideration, .jpg just might be the way to go, since a typical drg has only 12 colors, there's next to nothing to lose. I don't expect to make a final decision for at least another week though.
