I am digitizing contours off of USGS quad maps right now. Tracing over them in CAD. This works, of course, but there must be a better way of getting these contours for my projects.
Any ideas are appreciated.
Ficer67
Does your county or city have a GIS department? You may be able to get them there (we sell ours).
If all you’re interested in is the USGS maps, you can obtain these digitally from many firms. We use this.
You might also check out this website:
However, in my business, we generally have to obtain more detailed contours for our water and sewer design projects. (We typically do this work for municipalities.)
Basically, you first determine if the municipality already has the data, typically in the municipal Engineering or GIS departments.
If this fails, you have to obtain the data yourself by field survey, or for larger projects, by aerial mapping by a firm like this. Neither of these options are cheap. Both options generally start at about $10,000 and go up from there.
As a matter of fact, I have used Topozone before. Louisiana State University sponsors a programs called Atlas http://atlas.lsu.edu/, which allows me to download all of the quad maps for Louisiana, in tif format, free of charge. This is good. But I have to take it to the next level.
What I am doing manually is to trace over the contours of each quad map in CAD, for each of our projects. If there is no better way, I am going to keep doing this. However, I suspect that people have done this already. There ought to be a way that I can get a copy of these CAD drawings.
So how ‘bout it people,
What are you downloading. 7.5 min quads?
What contour interval do you need 40’?
There are programs that will auto digitize .tif’s based on the color of the cell. I have not had great luck with them though (its’ been a few years, I bet they are better now). It might help.
Check out what you can download from the USGS. Apparently they’ve stopped offering DEM (Digital Elevation Model) files, but you can still download DLG (Digital Line Graph) quads that include what you’re after, hypsography. I used to use them for hydrography. They downloaded as gzip compressed SDTS (Spatial Data Transfer Standard, IIRC) format files and I used a shareware utility called sdts2dxf to convert them to DXF files that could be used in AutoCAD.