Help!!: Raster Image to Topo Map 1

[PujanG]

Hi,
I don't know if it's a stupid question.
But i was longing to know, if its actually possible to convert a hardcopy of a topo. map to a digital map.

I've scanned a topo map & inserted it in CAD as a Raster Image.
Is it possible to draw polylines automatically along contour lines in the Raster Image??

Lets say we got the polylines along the contours as in Raster Image. Now can we assign elevation to these polylines & use them for the volume, watershed calculations??

Please feel free to post your ideas! Plz....

 

[brandonbw]

You can assign the polylines with elevations to calc out volumes.

But if you can't do this already by hand with a planimeter on the original drawing, I don't know why you would bring this into the computer not knowing how to do this already.

To begin with, do you know how to check that your topo's scale is correct in the X and Y directions once scanned in?

B+W Engineering and Design
Los Angeles Civil and Structural Engineering

http://bwengr.com

 

[IRstuff]

I would have thought that one would have done a websearch first:

http://3dfmaps.com/FaQ/convert.htm

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[dik]

IRStuff...
Have you used that contouring program? It looks really good and appears to only cost U$99.00.

Dik

 

[IRstuff]

Sorry, just trying the LMGTFY principle. While it looks simple, I can imagine that it's manually quite intensive. Digitizing contours, per se, seems to be reasonably doable, since that's just an extension of programs like Tracer 1.52. The catch would be getting all the contours assigned to the correct elevation. which, unless the topo map has certain formats that are consistent.

Alternately, I wonder if a digital elevation map might be easier to wrangle:

http://egsc.usgs.gov/isb/pubs/factsheets/fs04000.html

Overall, the accuracy and resolution is probably not as good as a topo map, but maybe it's good enough?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[brandonbw]

What are you using the topo for? Elevating contours in CAD is pretty simple. I am sure there are even free lisp routines that could elevate a pretty huge hillside map within minutes.

The easy way to check that is by using LDD which might take another 3 minutes. LDD can also elevate quickly like this as well, and label the contours.

B+W Engineering and Design
Los Angeles Civil and Structural Engineering

http://bwengr.com

 

[chicopee]

I don't know how extensive your JPEG file that you inserted into Autocad is, however, what I have done in the past is to first scale the JPEG drawing to actual dimensions within paper space, then use polylines to retrace contours. Use FIT option in PEDIT to smooth out polylines.
For intermediate contours not in the JPEG, do a search as there is a LISP program available.

 

[beej67]

Scan it, insert it, scale it, trace it, elevate the results.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[brandonbw]

beej67: Too easy! Unless that file is as large as some topos I have worked with. But those were basically new cities being built in the mountains and I would hope they would have digitized topos.

B+W Engineering and Design
Los Angeles Civil and Structural Engineering

http://bwengr.com

 

[beej67]

And on the 12th day, God said "let there be interns, and the development of their cad skills shall be beholden to their ability to trace raster data for a few hours at low hourly wages.."

Hell, when I was 16 years old and an intern, I was doing cut and fill calculations for landfills by the grid method by overlaying two vellums on a light board. Sometimes elbow grease is the best way to get something done.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[PujanG]

Thank u