Thank you Paul and Tom.
Tom: Thanks for clearing up my confusion about the two versions of BEDMAP2 data.
I tried your xyz2grd command, but it gives me error: xyz2grd: Cannot open file N-9999
Paul: I am also trying your suggestions, and will report back on how it went.
Post by Jordan, Tom A.R.M.Hi
The original script works with bm2_draft_bed.txt as it is an ascii
file with x, y, and z values.
However, bedmap2_bed.txt is an ascii grid file.
xyz2grd bedmap2_bed.txt -H6 -F -ZTLA N-9999
-R-3333500/3333500/-3333500/3333500 -I1000 -GBEDMAP2_GMT.grd
This should make you a GMT grid. You can then use grd2xyz to dump
out an x, y and z ascii file just like bm2_draft_bed.txt, and run it
through the original script, or follow Pauls suggestion below to
avoid gridding over the pole.
Tom
*Sent:* 25 June 2014 09:25
*Subject:* Re: [GMT-HELP] BEDMAP with GMT
I am surprised this ever worked.
Using surface to grid geographic data over a pole is a horrid idea
since surface is best for Cartesian data or latitude-banded data.
If you absolutely need to convert this polar stereographic grid to
1. Create a blank grid with desired resolution for -R-180/180/-90/-60
2. Dump via grd2xyz and project coordinates with the -Js projection
3. Sample the stereotraphic bedmap grid at the projected coordinates
4. paste the result with the grd2xyz output and send via xyz2grd to make the desired grid
Or something similar.
-p
Hi All,
Raising this topic again.
For some reason, the following solution does not works with the final
release of bedmap2 which is available at
https://secure.antarctica.ac.uk/data/bedmap2/
I have the old bm2_draft_bed.txt, and its output comes exactly as
what Tom has attached. However, when using bedmap2_bed.txt (which I
think, is the later version of bm2_draft_bed.txt), the output comes
as attached.
Can anyone help me understand what has changed since the draft
version to final version of BEDMAP2? Or is it that I am doing
something wrong in my code? I am using same code that Tom has given
in his email with minor changes like replacing the bm2_draft_bed.txt
by bedmap2_bed.txt, using the bedmap2_bed.txt as input, and changing
the -R to -180/180/-90/-60.
The code for bedmap2_bed and its output are attached.
#!/bin/sh
# bedmap_ant.sh
#
#
# Created by Sumant Jha on 12/27/12.
# Based on TOM JORDANs script, dated Nov 21, 2012 in [GMT-HELP] BEDMAP with GMT
# Modified on 06/24/2014
#
# script to get degree grid of BEDMAP2 data
# Note: For some reason, this script is only working on bm2_draft_bed.txt
# clean and order xyz data
echo "***********************************************"
echo Cleaning and Ordering X Y Z data in desired sequence"
awk ' NR>1 { print $1*1, $2*1, $3*1 } ' bedmap2_bed.txt | awk ' {
print $2, $3, $1 } ' > bedmap
# projecting bedmap data to degrees (default bedmap comes in UTM) NOTE -C option
echo " "
echo " "
echo "***********************************************"
echo " Projecting BEDMAP2 to Degrees"
mapproject bedmap -I -R-180/180/-90/-60 -Js0/-90/-71/1:1 -C -F -V> temp1
# Make new 1 min grid
echo " "
echo " "
echo "***********************************************"
echo " Creating 1 min grid for BEDMAP2"
surface temp1 -R-180/180/-90/-60 -I1m -V -Gbedmap_1min.grd
# make colour pallet
echo " "
echo " "
echo "***********************************************"
echo " Creating color pallett for displaying data"
grd2cpt -Z -V bedmap_1min.grd > bedmap1.cpt
gmtset PAPER_MEDIA A4
# Draw Antarctica Bedmap grid
echo " "
echo " "
echo "***********************************************"
echo "Drawing Antarctica BEDMAP grid"
grdimage bedmap_1min.grd -Cbedmap1.cpt -R-180/180/-90/-60
-Js0/-90/-71/1:50000000 -B30g300/15g15wEsN -K -V -P> BEDMAP_ant.ps
# Draw coast
pscoast -W1 -R -Js -O >> BEDMAP_ant.ps
# Create contours spaced at 200 intervals (optional)
#grdcontour Bedmap_ant.grd -J -R -W1/80/80/80 -C200 -P -S4 -O
-A1000+f3+k80/80/80+s8t -G2i/10 -Djunk -V -K >> BEDMAP_Ross.ps
echo " "
echo " "
echo "***********************************************"
echo "File Generated"
#View
gs BEDMAP_ant.ps
<BEDMAP_ant.png>
Hi All
One solution to the problem is below.
First get the XYZ data for BEDMAP2 from the same ftp site Roi
mentioned (its in a different directory).
ftp://ftp.bas.ac.uk/ptf/bm2_ftp/text_version_of_bed/
You can then re-project the data to degrees with mapproject, the trick is the C option.
Re grid the degree data and off you go.
Alternatively you could dump the coast line from pscoast (-m option).
Project the coast line to stereographic meters, same map project but no I.
Then simply plot the projected coast on top of the bedmap grid
extracted as Roi suggested using psxy Jx.
Hope this is useful.
Tom
# script to get degree grid of BEDMAP2 data, its slow but works
# clean and order xyz data
awk ' NR>1 { print $1*1, $2*1, $3*1 } ' bm2_draft_bed.txt | awk ' {
print $2, $3, $1 } ' > temp
# project data to degrees NOTE -C option
mapproject temp -I -R0/360/-90/0 -Js0/-90/-71/1:1 -C -F > temp1
# Make new 5 min grid
surface temp1 -R0/360/-90/-60 -I5m -Gbedmap_5min.grd
# make colour pallet
grd2cpt -Z bedmap_5min.grd > temp.cpt
# draw grid
grdimage bedmap_5min.grd -Ctemp.cpt -R0/360/-90/-60
-Js0/-90/-71/1:50000000 -K > temp.ps
# draw coast
pscoast -W1 -R -Js -O >> temp.ps
# view
gv temp.ps
*From:*World-Wide GMT Usage and Help Mailing List
*Sent:*20 November 2012 17:49
*Subject:*Re: [GMT-HELP] BEDMAP with GMT
There is a new Bedmap compilation
ftp://ftp.nerc-bas.ac.uk/ptf/bm2_ftp/readme%20and%20data%20files/
dal_translate -of GMT bm2_draft_bed.tif bedmap2.grd
grdimage -Jx-.000001/-.000001 -Ibedmap2.grd.int -B5000000
-R-3333500/3333500/-3333500/3333500 bedmap2.grd -Cbed.cpt -V >
bedmap2.ps
Roi
Dr. Roi Granot
Department of Geological & Environmental Sciences
Ben Gurion University of the Negev, Beer Sheva
P.O.Box 653 Israel 84105
Tel: 972-8-6477-509
Hi Sumant,
http://www.antarctica.ac.uk//bas_research/data/access/bedmap/download/ <http://www.antarctica.ac.uk/bas_research/data/access/bedmap/download/>
Then used xyz2grd to convert to grid. If you already have the grid
then it might be fine. What do you get when you run
grdinfo BEDMAP_groundbed.grd
groundbed.grd: Title: groundbed.grd
groundbed.grd: Command: xyz2grd groundbed.asc -E -Ggroundbed.grd
groundbed.grd: Pixel node registration used
groundbed.grd: Grid file format: nf (# 18) GMT netCDF format (float)
(COARDS-compliant) [DEFAULT]
groundbed.grd: x_min: -2661600 x_max: 2678400 x_inc: 5000 name: x nx: 1068
groundbed.grd: y_min: -2149967 y_max: 2195033 y_inc: 5000 name: y ny: 869
groundbed.grd: z_min: -2495.36010742 z_max: 4364.85400391 name: z
groundbed.grd: scale_factor: 1 add_offset: 0
So you can see that the x and y are not in latlon but metres relative
to the south pole so in my script I just set -R to the min and max.
As this is already projected data you should then just need to
overlay the appropriate latlon grid using psbasemap -Js with the
appropriate parameter to match the projection of the grid. The docs
give "we used the Polar Stereographic projection with 71°S as the
latitude of true scale and 0°E as the central meridian" although I'm
not sure what parameters you therefore need for -Js
Marcus.
----------------------------------------------------------
Dr Marcus Badger
Lecturer
School of Earth Sciences
University of Bristol
Wills Memorial Building
Queen's Road
BRISTOL BS8 1RJ
U.K.
Office: G40
Tel: +44 (0) 117 95 45491 or +44 (0) 117 33 16795
Mobile: +44 (0) 774 07 96811
----------------------------------------------------------
Hi Markus,
Pardon my ignorance on this, as I am very new to GMT. Do we need
to convert the BEDMAP grid to some other format? Where are you
getting the xyz data for the same?
I was using the BEDMAP grid that came with Geoware.
You are right about the -R values. I noticed the same but was not
sure, how to go about converting my -R values to that of BEDMAP
values. Your version is something what I am trying to achieve,
and then overlay the lat/longs. Not sure how to do that.
Sumant
On Nov 15, 2012, at 2:41 AM, Marcus Badger
Hi Sumant,
How far have you got? ie in what way is it not coming out
right? I've managed to make this into a grid using xyz2grd
and plot it using
grdimage groundbed.grd -V -Cpalette.cpt -B2000000NseW
-R-2661600/2678400/-2149967/2195033 -JX5i -Yc -Xc -P -K
but the grid is not in lat-lon but from the docs page "In
this system, coordinates are expressed in metres with the
origin at the South Pole." (which might be where you problems
start) and so I am unsure how to convert this to something
you can overlay coastline and gridlines. My version attached.
Marcus.
----------------------------------------------------------
Dr Marcus Badger
Lecturer
School of Earth Sciences
University of Bristol
Wills Memorial Building
Queen's Road
BRISTOL BS8 1RJ
U.K.
Office: G40
Tel: +44 (0) 117 95 45491 or +44 (0) 117 33 16795
Mobile: +44 (0) 774 07 96811
----------------------------------------------------------
Guys - I fear this question has been asked a lot before -
but, i cannot
seem to find an answer to it. I am trying to use the
BEDMAP data in GMT.
The problem it seems to me is the projection. I tried
using Jx and then
Js to overlay the lat-longs - but, somehow, it did not
come out right. I
am hoping if someone out here have worked with GMT and
BEDMAP data - and
could may be help me solve this issue.
grdimage
/Users/sumantjha/Documents/Geoware/DATA/misc/BEDMAP_groundbed.grd
-V
-C/Users/sumantjha/Documents/Work/GMT/GMT4.5.8/share/cpt/GMT_gebco.cpt
-B20NseW -R155/180/-80/-75 -Jx10i -X1.2i -Y6i -K -V -P >
Antarctica.ps
pscoast -R -Js0/-90/50i/1 -W -Df -Ir/.5/114/187/243
-G30/144/255 -V -O
-K -P >> Antarctica.ps
Any help will be appreciated.
Thanks
Sumant
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