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Correspondence between gstat and ArcGIS functionality?

5 messages · Prof. Jeffrey Cardille, Edzer Pebesma, Thomas Juntunen +1 more

Original
Edzer Pebesma
# 
Hi,

telling us what the drop-down menus tell you leaves me a bit of guess
work. Universal probably means universal kriging; linear drift a first
order trend in the coordinates (pass degree = 1 to krige, and something
like value~x+y to variogram, when long/lat are named x and y). Does the
first "Linear" in "Linear with linear drift" refer to a fitted linear
variogram model?
Prof. Jeffrey Cardille wrote:
Great idea!
Well, you have a license, doesn't that come with access to some sort of
documentation?
Not the things you mention; defining a local neighbourhood matters --
small neighbourhoods are faster, but at some stage also produce worse
interpolations.

For filling in missing strips in images I'd try to use segmented
neighbourhoods, to guarantee values are taken from all sides. Quadrant
search is available in the gstat C code, but not interfaced through the
R package. I will implement it if you volunteer to test it.
I'm interested in your findings!

BTW, just out of curiosity, why don't you do the whole thing with ArcGIS?

  
    

      
      
    

  


  


      

    

    

      
      

        
      

    

    

      
      

        


  

        

      Thomas Juntunen
    

    

      
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On Wed, 14 Apr 2010 15:47:01 -0400, Prof. Jeffrey Cardille wrote:

        

            

      
      
      
    

        
Hello,

I'm a graduate student at the University of Minnesota in the GIS program. For 
the past couple years I have been assisting a conservation biology doctoral 
student with GIS aspects of her dissertation, which involved acquiring Landsat 
data. I presume you are talking about the scan line corrector problem that 
developed in 2003 on Landsat 7 in the extended thematic mapper?

USGS engineers at EROS have tried several approaches to correcting the gaps, 
primarily by interpolation and filling in from other scenes from the same 
season. I don't have a reference handy, but I did read something that found 
that method had an unreasonable amount of cloud cover interference. However, 
the EROS folks eventually published a paper describing how their "multi-scale 
segmentation" technique worked that was then used for EROS terrain-corrected 
products. If you haven't read it, the paper has lots of valuable information on 
the exact nature of the problem. Here's a link to the citation from the ACM 
portal:

http://portal.acm.org/citation.cfm?id=1393487

For my purposes, the EROS corrected data were sufficient, but some applications 
such as permeability studies may require pixel-level precision.

Good luck with your endeavor and if you find a solution, I hope you'll post 
about it here.


Thomas Juntunen
MGIS Program, University of Minnesota

  
  


  


      

    

    

      
      

        


  

        

      Wesley Roberts
    

    

      
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Hi Jeff,

You may not need to use gstat or indeed R. NASA have kindly developed
the following software to take care of the gaps. Be aware though that
the method requires several images from different dates of the same
area. 

http://landsathandbook.gsfc.nasa.gov/handbook/software/gap_filling_software.html

Alternatively GRASS GIS has a function / module called r.fillnulls
which uses splines interpolation to fill the gaps.

http://grass.itc.it/grass65/manuals/html65_user/r.fillnulls.html 

Hope this helps,

Wesley

Wesley Roberts MSc.
Researcher: Earth Observation
Natural Resources & the Environment (NRE)
CSIR
Tel: +27 (0)21 888-2490
Fax: +27 (0)21 888-2693
"To know the road ahead, ask those coming back."
- Chinese proverb

            

      
      
      
    

        
9:47 PM >>>
Hello all,

This is my first posting to R-sig-geo; I looked for the answer in the
archives, but have not had any luck for my particular question. 

I have a newbie question about the correspondence between gstat and
ArcGIS.  I have a problem that gives very very satisfying results in
ArcGIS, and I would like to write a public function in R for others to
use that does the same thing.  The choice I used in Arc was "Universal"
and in the dropdown menu it says "Linear with Linear Drift".  My data
matrix is pretty standard:  2000 x 2000, with some NA, and values
between 0 and 255.

So I have a few questions.  Maybe I'll enumerate them.
1. Has anyone made a comprehensive list between ArcGIS functionality
and how to do it in gstat?

2. If not: does anyone know a simple correspondence between what ArcGIS
is doing and how to set up a gstat call for "Universal/Linear with
Linear Drift"?  I have looked online for precise details about Arc's
behavior, but haven't seen anything detailed enough.

3. Are there any tricks in gstat that make interpolation with gstat
especially fast or slow?  For example, if the numbers were treated
faster if they were between 0 and 1, or if NA should be recoded, or if I
should never use a data frame but always a matrix.  That sort of thing.

If not, I'll resort to trial and error and diving deeper into the gstat
documentation.  But it seems like a good idea to check in first.  For
anyone interested, I am trying to repair Landsat satellite photos, which
have big broken strips of nodata due to a mechanical failure.  The
strips are up to 14 pixels wide.  I need to do this 2000x2000
interpolation about 2000 times-- so speed differences of even a few
seconds or minutes are quite important..

Thanks!
Jeff

------------------------------------------
Prof. Jeffrey Cardille
jeffrey.cardille at umontreal.ca 

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