<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<DEFANGED_meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
Only a handful of commercial software packages are available for
generating DEMs from ASTER data. Each have their strengths and
shortcomings.<br>
A DEM generation module was added to ENVI (ITT Visual Information
Solutions) a little over a year ago and we at NSIDC have found that it
performs well and is somewhat more user-friendly than PCI Geomatica
Orthoengine. However, one thing it lacks, which PCI has, is control
over hole filling and interpolation. While the overall quality of DEMs
generated by ENVI is excellent, major anomalies (peaks, depressions)
can occur where the correlation between image pairs fails and the
algorithm interpolates across voids using poor elevation data on the
perimeter of these voids.<br>
<br>
I have requested to have a score channel added in the DEM generation
process. This would be a separate layer that carried information about
the quality of the DEM at each pixel location. Such a layer would allow
the user to selectively eliminate data that was suspect before
interpolating or doing further analysis. This was entered as change
request 44575. However, it has not yet been worked on.<br>
<br>
I then made a simpler request: to have the option of leaving the voids
and allowing the user to edit the raw DEM before applying whatever
smoothing and interpolation they thought was best. I got this response
from ITT VIS:<br>
<blockquote type="cite">
<pre wrap="">I will add your suggestion of a no smoothing/interpolation option to the existing feature request. If you know of any other individuals who use ENVI and whose work is negatively impacted by this issue, please pass along their names and I can add them to the list of affected customers. To be honest, there is a more or less direct relationship between the number of affected customers and the speed with which a requested feature is implemented.</pre>
</blockquote>
Thus the reason for this email. I am asking anyone who is an ENVI user
to write to <a href="mailto:support@ittvis.com">support@ittvis.com</a>
and request these features be added to the ENVI DEM extraction module.<br>
<br>
Thanks!<br>
<pre class="moz-signature" cols="72">--
Siri Jodha Singh Khalsa, Ph.D.
L-3 Communications GSI, Senior ECS Consultant
National Snow and Ice Data Center
University of Colorado
Boulder, CO 80309-0449 Phone: 1-303-492-1445
<a class="moz-txt-link-freetext" href="http://cires.colorado.edu/~khalsa">http://cires.colorado.edu/~khalsa</a> </pre>
</body>
</html>