Preface: I'm a total GIS noob. Flame away. I'm learning GIS in my free-time and with free resources. I realize that is likely going to force me on the learn-fast-or-giveup track, but here it goes...
My first project: Create a laser cut 9-layer topographic map of the 7.5 minute area where I work.
1) Download SDTS DLG Hypsography data from USGS.
2) Unzip using Peazip.
3) Import into GRASS GIS.
4) Remove/edit unnecessary topo lines (I was able to do it with dlgv32 available at USGS website, but I can't export and don't want to pay $500 for a full version of global mapper).
5) Export to DXF or DWG
6) Open in Corel and create layers
7) Laser cut layers, glue them together.
I've gotten through steps 1, 2, and 3 with minimal frustration, although peazip throws an error on extract that says "data after archive", which I hope has no effect on the usability of my data. I'm at a loss on step 4.
That data set I'm working with is DLG STDS data in large format (7.5 minute quadrangles). Specifically, the data is from: http://dds.cr.usgs.gov/pub/data/DLG/LARGE_SCALE/I/indian_hills_CO/hypsography/1/
I can get the DDF files to import into GRASS and I can view the topomap in the display; however I'm having trouble manipulating what I'd like to see. Basically I want to display only the major topolines (for example, 6000', 6400', etc.). When I open this data set in Global Mapper, this is very easy to do. I imagine I can accomplish this with some kind of SQL select function in GRASS; however, I do not understand how the data is organized enough to do this. When I import the SDTS file, I get 10 database links. Most of the databases look 'empty', so I imagine there is just one file I need to be working with.
Do any of you have any experience in working with Hypsographic data? Do you know how I can simply delete the entries that do not correspond to the lines I want?