5 replies to this topic

[destro tull]

Hopefully someone can help me with this. I'm trying to perform a slope analysis of an area. we have 2 metre contour lines in autocad that have the correct elevation data attached to them. So far i've been able to bring the contours into ArcGIS. If i use a colour ramp they display correctly (green=lowest, red=highest) so i know the data i need is there (each line has an "elev" attribute").

I guess it might be possible to calculate slope based on the proximity of the contour lines to each other, but i think that might be a bit over my head at the moment as i'm fairly new at this. All the slope analysis tutorials i've found involve DEMs. DEMs are not super easy to come by around here... I have only one that covers all of canada that is useless at the scale i need (roughly a square km).

Is it possible to creat a DEM file using arcGIS with an arcINFO license and autoCAD contour lines. I'd like to avoid involving another peice of software if it's an option.

Thanks in advance

[ProMapper]

The topo to raster tool which employs the ANUDEM program will generate hydrologically correct DEMs from contour data. You can try the tool and if you have been able to import the CAD file correctly then it should work.

Anu
http://www.mapsandlocations.com

[eli]

Have you checked out Geobase? It has DEMs for all of Canada, at 1:50k (and 1:250k). Might still be a bit rough for your scale, but just wanted let you know that DEMs are, in fact, relatively easy to come by in Canada.

In any case, I suggest you check out the Spatial Analyst toolbar. Perhaps you interpolate to raster or convert features to raster would help you (disclaimer: I haven't had to use these features for your puporses so I'm not sure).

[sjonni11]

Hopefully someone can help me with this. I'm trying to perform a slope analysis of an area. we have 2 metre contour lines in autocad that have the correct elevation data attached to them. So far i've been able to bring the contours into ArcGIS. If i use a colour ramp they display correctly (green=lowest, red=highest) so i know the data i need is there (each line has an "elev" attribute").

I guess it might be possible to calculate slope based on the proximity of the contour lines to each other, but i think that might be a bit over my head at the moment as i'm fairly new at this. All the slope analysis tutorials i've found involve DEMs. DEMs are not super easy to come by around here... I have only one that covers all of canada that is useless at the scale i need (roughly a square km).

Is it possible to creat a DEM file using arcGIS with an arcINFO license and autoCAD contour lines. I'd like to avoid involving another peice of software if it's an option.

Thanks in advance

Hi,

If you have 3d Analyst with your ArcGIS then its pretty easy to create a slope analysis using your contours.

You can start by creating TIN model using your contours as source. The next step is to convert the TIN to raster. Then you have your Surface layer which allows you to create Slope, Viewshead, Aspect, volume analyst and more.
I am sure there is a different way of doing this in ArcGIS but this is the method I use all the time.
Hope this has helped and/or you have any questions dont hesitate to ask. Good luck.

[destro tull]

@eli

thanks for the tip, geobase seems a tad more user friendly than geogratis (which i'd been using).

@promapper

Topo to raster worked perfectly, slope analysis is working well. I just needed someone to point me in the right direction.

now i'll look smart to my boss

[ProMapper]

@eli

thanks for the tip, geobase seems a tad more user friendly than geogratis (which i'd been using).

@promapper

Topo to raster worked perfectly, slope analysis is working well. I just needed someone to point me in the right direction.

now i'll look smart to my boss

Wow, Good to hear that. ArcGIS is a big software, even after years of work you kinda touch the surface only.