Problem with SURFACE command

[Mr Abhash Kumar]

Hi,

I am plotting velocity deviations (tomography results) and absolute velocity contours. I have non-zero velocity deviations only at those grid points where the hit count for each grid is more than 10 (hits125.ps) . I have both positive and negative velocity deviations. I am using SURFACE, GRDGRADIENT and GRDIMAGE to plot the deviation as below:



system "surface pdev125.txt -Gdev.125.grd -S3 -I10k -A0.966 -T1 -V $rflag\n";

system "grdgradient dev.125.grd -A225 -Gdev.125.shadow -Nt -V\n";

system "grdimage dev.125.grd $jflag $rflag -Sb -B -K -O -Cdv.cpt >> $psfn\n";


I am getting artificial deviation even at those grid points where there were no deviation in the original file (pdev.125.txt) and it may be due to SURFACE command. The top right corner (fading yellow) of the deviation map (map.125.ps) has artificial deviation. I am having this problem for other depth sections (map.165.ps). I was wondering to use GRDCLIP with -Sb or -Sa flag to create NaNs for those grid points but sign of velocity deviation (both positive and negative) is making it difficult to choose any threshold. I want to plot deviation only in those regions where I have good resolution. I would be extremely grateful for any advice in this regard.


Thanks

Abhash kumar

University of North Carolina at Chapel Hill, USA

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[Paul Wessel]

If the colored dots in hits125.ps is your surface input then I would think grdmask on those would be best, i.e., set to nan nose nodes that are too far away since the solution there is unconstrained. If you cannot do something automatic like that then digitize a polygon and use that to set the mask.
-p

Post by Mr Abhash Kumar
Hi,
system "surface pdev125.txt -Gdev.125.grd -S3 -I10k -A0.966 -T1 -V $rflag\n";
system "grdgradient dev.125.grd -A225 -Gdev.125.shadow -Nt -V\n";
system "grdimage dev.125.grd $jflag $rflag -Sb -B -K -O -Cdv.cpt >> $psfn\n";
I am getting artificial deviation even at those grid points where there were no deviation in the original file (pdev.125.txt) and it may be due to SURFACE command. The top right corner (fading yellow) of the deviation map (map.125.ps) has artificial deviation. I am having this problem for other depth sections (map.165.ps). I was wondering to use GRDCLIP with -Sb or -Sa flag to create NaNs for those grid points but sign of velocity deviation (both positive and negative) is making it difficult to choose any threshold. I want to plot deviation only in those regions where I have good resolution. I would be extremely grateful for any advice in this regard.
Thanks
Abhash kumar
University of North Carolina at Chapel Hill, USA

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To formally report bugs or request features, please register and add New Issue on gmt.soest.hawaii.edu
To unsubscribe, send the message "signoff gmt-help" to ***@lists.hawaii.edu
Note: gmt-help will become obsolete on Sept 1, 2014 - please use forum on gmt.soest.hawaii.edu instead.