[GRASS-dev] v.surf.rst segment boundaries

Helena (or anyone else),

I really like the amount of control over interpolation that comes with v.surf.rst. But it always gives me artifacts at the segment boundaries (little “cliffs”). Is there some way to prevent that?

Michael


C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice: 480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)

www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Wed, Nov 18, 2015 at 1:29 PM, Michael Barton <Michael.Barton@asu.edu>
wrote:

Helena (or anyone else),

I really like the amount of control over interpolation that comes with
v.surf.rst. But it always gives me artifacts at the segment boundaries
(little “cliffs”). Is there some way to prevent that?

Could you perhaps share the command you use and what type of data (sparse
points or dense lidar) you run it for? From my experience, too low tension
or low npmin can cause that. Default settings are usually not producing the
segments, but it might be time inefficient.

Anna

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice: 480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu

_______________________________________________
grass-dev mailing list
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http://lists.osgeo.org/mailman/listinfo/grass-dev

Anna is right,
but there may be another case if you are interpolating from contours or isolines (such as isochrones as you may be doing)
make sure your optimize the number of points on the contour - click on the two last images on the page below
to see the difference
http://www4.ncsu.edu/~hmitaso/grasswork/interpgen.html

Vasek may have a better example for this - we had to use this approach when interpolating temporal
surface from time series of contours.

If you see the segments only in some spots that don’t have data (e.g. bare ground lidar where buildings were removed)
Anna has written a v.surf.rst wrapper that does two passes interpolation to minimize the visible segments.

Perhaps if you could share the data and the command that you have used we can suggest a solution.

Helena

On Nov 18, 2015, at 1:35 PM, Anna Petrášová <kratochanna@gmail.com> wrote:

On Wed, Nov 18, 2015 at 1:29 PM, Michael Barton <Michael.Barton@asu.edu> wrote:
Helena (or anyone else),

I really like the amount of control over interpolation that comes with v.surf.rst. But it always gives me artifacts at the segment boundaries (little “cliffs”). Is there some way to prevent that?

Could you perhaps share the command you use and what type of data (sparse points or dense lidar) you run it for? From my experience, too low tension or low npmin can cause that. Default settings are usually not producing the segments, but it might be time inefficient.

Anna

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice: 480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu

_______________________________________________
grass-dev mailing list
grass-dev@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-dev

Helena Mitasova
Professor at the Department of Marine,
Earth, and Atmospheric Sciences
and Center for Geospatial Analytics
North Carolina State University
Raleigh, NC 27695-8208
hmitaso@ncsu.edu
http://geospatial.ncsu.edu/osgeorel/publications.html

"All electronic mail messages in connection with State business which are sent to or received by this account are subject to the NC Public Records Law and may be disclosed to third parties.”

It is from points not lines. I just got out of class. But I’ll get the data together and send it on in a bit. Thanks much.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice: 480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Nov 18, 2015, at 1:12 PM, Helena Mitasova <hmitaso@ncsu.edu> wrote:

Anna is right,
but there may be another case if you are interpolating from contours or isolines (such as isochrones as you may be doing)
make sure your optimize the number of points on the contour - click on the two last images on the page below
to see the difference
http://www4.ncsu.edu/~hmitaso/grasswork/interpgen.html

Vasek may have a better example for this - we had to use this approach when interpolating temporal
surface from time series of contours.

If you see the segments only in some spots that don’t have data (e.g. bare ground lidar where buildings were removed)
Anna has written a v.surf.rst wrapper that does two passes interpolation to minimize the visible segments.

Perhaps if you could share the data and the command that you have used we can suggest a solution.

Helena

On Nov 18, 2015, at 1:35 PM, Anna Petrášová <kratochanna@gmail.com> wrote:

On Wed, Nov 18, 2015 at 1:29 PM, Michael Barton <Michael.Barton@asu.edu> wrote:
Helena (or anyone else),

I really like the amount of control over interpolation that comes with v.surf.rst. But it always gives me artifacts at the segment boundaries (little “cliffs”). Is there some way to prevent that?

Could you perhaps share the command you use and what type of data (sparse points or dense lidar) you run it for? From my experience, too low tension or low npmin can cause that. Default settings are usually not producing the segments, but it might be time inefficient.

Anna

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice: 480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu

_______________________________________________
grass-dev mailing list
grass-dev@lists.osgeo.org
grass-dev Info Page

Helena Mitasova
Professor at the Department of Marine,
Earth, and Atmospheric Sciences
and Center for Geospatial Analytics
North Carolina State University
Raleigh, NC 27695-8208
hmitaso@ncsu.edu
NCSU GeoForAll Lab (NCSU OSGeoREL)

"All electronic mail messages in connection with State business which are sent to or received by this account are subject to the NC Public Records Law and may be disclosed to third parties.”