12 replies to this topic

[georgew]

Hi, I am totally new to ArcGis and overwhelmed by its scope and not sure whether the following is possible:
I have a set of topographic maps in shapefile format containing contours and walking tracks. The track data does not include elevation (only lat. and long.), but the contour lines do include elevation. Is it possible (and how?) to create an elevation profile for the length of the walking track using the intersecting points between the track and the contour lines to obtain the elevation values?
Many thanks for any assistance you can give me.
George

[pradipgulekar]

Hi,

It is possible to give elevation to 2d data.
This process is called draping. You can assigned Z elevation to track by
using contour data.
You can move your data or Fix 2d data as per 3d elevated data without disturbing coordinates.

Regards,
Pradip L. Gulekar,
pradipgulekar@gmail.com

Note:- You can send me your files for testing.

[gregory]

Hi,
You will have to convert the countours to TIN first. Then use the TIN as the source of heights and convert tracks to 3d features, then generate profiles from 3d features. Depends on which version of Arc you're in disposition some extensions will be requied. I'm not sure which version (arceditor, arcinfo) allow create TIN from countours, but you will need for sure 3d analyst to create 3d lines and profiles from them. If you don't care to much about the accuracy you may also use upsampled SRTM '3 (vertical accuracy is about 20 meters) for you area of interest as the source of height and miss this way step with creating TIN from countours.
Hope it helps
Gregory

[georgew]

Hi,
You will have to convert the countours to TIN first. Then use the TIN as the source of heights and convert tracks to 3d features, then generate profiles from 3d features. Depends on which version of Arc you're in disposition some extensions will be requied. I'm not sure which version (arceditor, arcinfo) allow create TIN from countours, but you will need for sure 3d analyst to create 3d lines and profiles from them. If you don't care to much about the accuracy you may also use upsampled SRTM '3 (vertical accuracy is about 20 meters) for you area of interest as the source of height and miss this way step with creating TIN from countours.
Hope it helps
Gregory

Thank you both for your information. I was somewhat disappointed that it is so complicated. Why converting to 3D when the information is all available in the 2D tables. All I need is an intersection between the two files. Perhaps I have not been clear about the term "elevation profile". All I meant was a plot of height values over distance, not 3D imagery.
Does this make it easier?

[gregory]

Thank you both for your information. I was somewhat disappointed that it is so complicated. Why converting to 3D when the information is all available in the 2D tables". All I need is an intersection between the two files. Perhaps I have not been clear about the term elevation profile. All I meant was a plot of height values over distance, not 3D imagery.
Does this make it easier?


We're speaking about the same thing. Tracks while converting to 3d features get info about the height to each of point that creates the track. That's the reason.
There is no easier way to achive the profiles that the one I described. I mean having to disposition countours layer you have to do an extra step and create surface (TIN) from it. 3d features created from the track need as source of height surface that keeps heights info in it and you cannot get it directly from countours. It's pretty easy and shouldn't take you more than 5 minutes to do that. Pls consider the SRTM. If you need more assistance just ask.

regards
Gregory

[georgew]

We're speaking about the same thing. Tracks while converting to 3d features get info about the height to each of point that creates the track. That's the reason.
There is no easier way to achive the profiles that the one I described. I mean having to disposition countours layer you have to do an extra step and create surface (TIN) from it. 3d features created from the track need as source of height surface that keeps heights info in it and you cannot get it directly from countours. It's pretty easy and shouldn't take you more than 5 minutes to do that. Pls consider the SRTM. If you need more assistance just ask.

regards
Gregory

Thanks Gregory for the info and the offer of help, which I hasten to take up. I tried to edit my empty TIN to add the contours to it and received the following error:

"
Start Time: Mon Feb 23 19:11:57 2009
ERROR 999998: Unexpected Error.
Failed to execute (EditTin).
End Time: Mon Feb 23 19:15:01 2009 (Elapsed Time: 3 minutes 4 seconds)
"
All I can think of is that my contours file is too large, approx 120MB, and the error occurred after approx 8.5 million nodes had been processed. If this is the case, how can I reduce the size of the area to be TINned?
Your help is greatly appreciated.
regards
George
PS SRTM is not an option at this stage because of the error margin, my contours are 20m apart

[gregory]

There are two options that come to my mind and may let you reduce the size of the finall TIN.
First cut the countours exaclly (with small margin) to the extent of you profiles. You may want to generate the surface for bigger area that is necesarry (That's my guess from my experiences : ) ).
Simplify the countours. This will reduce the number of vertices, then try to create the TIN.
I'm not an Arcgis user at that moment so don't know where exaclly are the options I'm speaking about.

regards
Gregory

[aug_aug]

Assuming that you have 3D/Spatial Analyst extensions, if not ignore this comment, if the contour lines have an elevation, you could use "Topo to Raster" (3D Analyst) tool > then overlay your walking tracks on top of this new raster, and if they're made of many individual points, use the "Extract Values to Points" (Spatial Analyst) tool to apply z-values to each of the walking track nodes.

Hope that helps.

[frax]

I guess it would be possible, for a quick and dirty approach, to intersect the track with the contours, so that you get a rough profile that way (don't know exactly how to do it though!). If it is close between the contours, and if the trail is perpendicular to the contours, this will be a decent approximation. I think this may be what you are looking for.

[paul]

Try this arcscript:
http://arcscripts.es....asp?dbid=16031

You do not need 3D or Spatial Analyst extensions to use it, and it works with contours, TINs, and DEMs.

[georgew]

Try this arcscript:
http://arcscripts.es....asp?dbid=16031

You do not need 3D or Spatial Analyst extensions to use it, and it works with contours, TINs, and DEMs.

Thank you all for your help. The truth is I m having great difficulty getting this problem solved even with your assistance. I have not exhausted all avenues yet, but it is taking me longer than i anticipated.
I have not yet tried your script Paul, I am still trying the earlier suggestions as well as some I found in the ESRI support Centre. For instance:

http://support.esri....l...how&d=22597
http://support.esri....l...how&d=31629
http://www.esricanad...5.asp?QCount=36

all of which appear relevant, but none are working so far. The problem seems to me that none of the above techniques link the elevation field, contained in the contours file, with the tracks that intersect the contours. But I am guessing.
I will persevere however.
G.

[georgew]

Success finally, all my fault it took so long. I made two fundamental and wrong assumptions: one that the attribute table would contain the elevation points, until I realized there is only provision for one value per attribute in each line. The elevation points are created dynamically in the graph.
And the second assumption was that I assumed one did not have to select the features (eg the tracks in this case), but that all the features in the layer would be automatically selected. Which meant the graph button was never enabled. Now I know better.
Thank you all for your help, it has been a learning experience.

[johnnyh]

Check out Hawth's Analysis tools (free, and awesome), it's got a intersect lines (generates points) tool.

GlobalMapper has a really easy elevation profile tool, it might be available in the demo.