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Hypsometric Curve Out of a DEM   Juan Nogues Jan 14, 2004
Re: Hypsometric Curve Out of a DEM   Dan Patterson Jan 14, 2004
Re: Hypsometric Curve Out of a DEM   Xander Bakker Jan 14, 2004
Re: Hypsometric Curve Out of a DEM   Juan Nogues Jan 15, 2004
Re: Hypsometric Curve Out of a DEM   Xander Bakker Jan 15, 2004
Re: Hypsometric Curve Out of a DEM   Alessandro Sorichetta Jul 02, 2004
Re: Hypsometric Curve Out of a DEM   Xander Bakker Jul 04, 2004
Re: Hypsometric Curve Out of a DEM   Tom colson Jan 20, 2006
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Subject Hypsometric Curve Out of a DEM 
Author Juan Nogues 
Date Jan 14, 2004 
Message Hi!

I would like some help if possible on how to derive a hypsometric curve out of a DEM in ArcGIS 8.x

A hypsometric curve plots in the x axis the percent of total area of a watershed and in the y axis the percent of highest elevation.

Using GRIDPOINT in Arctoolbox I can export basically a text file with all the points and elevations, however the DEM I have has about 139000 points and excel just doesn't like that. I was wondering if there is a tool in ArcGIS that would let me do the curve inside ArcGIS 8.x.

If I can get the data (elevation and points) into an attribute table I guess I can work from there but how do I get an attribute table out of a DEM?

Thanks

Juan 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Dan Patterson 
Date Jan 14, 2004 
Message raster to xyz
http://arcscripts.esri.com/details.asp?dbid=12622

other related stuff on hypsometric/gis stuff but no direct solution for 8.x

http://www.geocomputation.org/2001/papers/boggs.pdf
http://forums.esri.com/Thread.asp?c=93&f=995&t=62565&mc=6#msgid161857
http://forums.esri.com/Thread.asp?c=93&f=992&t=91025&mc=0#msgid251104 
  Geomatics, Carleton University, Ottawa, Canada 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Xander Bakker 
Date Jan 14, 2004 
Message Hi Juan,

Recently we developed an application for a client to calculate hypsometric curves, sedimentation/erosion curves and volume change curves based on a series of DEM (different moments in time) and someadministrative units.

They use this application to monitor change water depths near shore. I can imagine this process can be used to determine the hypsometry of watersheds.

This method is based on a vectorization (polygons) of the DEM (the client uses DEM's with height values as integers expressed in cm) which is then clipped by the administrative unit. In vector format it is easy to loop through the features and calculate the area.

We actually went a little further by gathering the area information for several DEM's of the same area in order to be able to calculate the difference between two hypsometric curves (both in cumulative area and volume) to be able to show the sedimentation/erosion.

If you don't mind loosing a little precision you could convert your DEM to integer values and try the same procedure.

 
  Xander Bakker
Grontmij Nederland bv
GIS&ICT department
De Bilt, The Netherlands
http://www.grontmij.com 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Juan Nogues 
Date Jan 15, 2004 
Message Thanks Xander:
That is very helpful but if you could just tell me how you go about vectorizing a DEM I will be on my way. I pressume that is through ArcToolbox or something like that.

Thanks again

Juan 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Xander Bakker 
Date Jan 15, 2004 
Message Hi Juan,

You can do this with Spatial Analyst. Please notice that to reduce the amount of polygons you should convert you DEM to integer.

The can also be done in the Spatial Analyst, in the Raster Calculator.

Use: INT ( [the name of the layer DEM] )

Then in the spatial analyst menu, you will find "Convert" / "Raster to Features". Switch the "generalize lines" option off.

The output polygon file will have a "GRIDCODE" column which contians the height values.

Clip the new polygon map with you watershed (use the geoprocessor for this purpose). Then in the clipped polygon file, calculate the area for each polygon (use the free EasyCalculate tools from http://www.ian-ko.com/ ). In this case use "polygon_Return_Area.cal"

After this you can summarize on the GRIDCODE column and sum the area.

Open this table and create new column and cumulate the area (the list will already be sorted on GRIDCODE) by use another EasyCalculate script call "field_CumulateValues.cal". Edit the line:

sourceField = [A]
and change it to:
sourceField = [your summed area field]

Use the (limited) datagraph tools to show the graph or export the table to a package like Excel where you can create the graph...

Good luck! 
  Xander Bakker
Grontmij Nederland bv
GIS&ICT department
De Bilt, The Netherlands
http://www.grontmij.com 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Alessandro Sorichetta 
Date Jul 02, 2004 
Message Hi I'm trying to use your procedure to obtain hypsometric curve, but when I export the table with gridcode and comulate area in excel, in the graph I don'thave all the value and so I don't obtain the rigth curve! Maybe there is something I don't understand in the procedure, could anyone help me, I will really appreciate it.
Thank you very much 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Xander Bakker 
Date Jul 04, 2004 
Message Hi,

What do you mean with "I don't have all the values"? What values are written to the table and what values you expected were not written?


 
  Xander Bakker
Grontmij Nederland bv
GIS&ICT department
De Bilt, The Netherlands
http://www.grontmij.com 
   
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Subject Re: Hypsometric Curve Out of a DEM 
Author Tom colson 
Date Jan 20, 2006 
Message http://wwwbrr.cr.usgs.gov/weasel/ 
 
Tom Colson
North Carolina State University
College of Natural Resources
Center For Earth Observation
Raleigh, North Carolina, 27695
(919) 673 8023