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need help with ascii to grid header file in...   Nate Peterson Jul 19, 2007
Re: need help with ascii to grid header fil...   K. Gardiner Jul 08, 2008
Re: need help with ascii to grid header fil...   William Huber Jul 09, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Jul 09, 2008
Re: need help with ascii to grid header fil...   Brad Posthumus Jul 11, 2008
Re: need help with ascii to grid header fil...   William Huber Jul 11, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Jul 11, 2008
Re: need help with ascii to grid header fil...   Brad Posthumus Jul 11, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Jul 11, 2008
Re: need help with ascii to grid header fil...   Brad Posthumus Jul 11, 2008
Re: need help with ascii to grid header fil...   Allison Anderson Jul 11, 2008
Re: need help with ascii to grid header fil...   William Huber Jul 14, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Jul 14, 2008
Re: need help with ascii to grid header fil...   William Huber Jul 14, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Jul 14, 2008
Re: need help with ascii to grid header fil...   Brad Posthumus Jul 14, 2008
Re: need help with ascii to grid header fil...   Brad Posthumus Jul 14, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Jul 14, 2008
Re: need help with ascii to grid header fil...   Brad Posthumus Jul 14, 2008
Re: need help with ascii to grid header fil...   Alicia Venkatachalam Sep 24, 2008
Re: need help with ascii to grid header fil...   K. Gardiner Sep 24, 2008
Re: need help with ascii to grid header fil...   Alicia Venkatachalam Sep 25, 2008
Re: need help with ascii to grid header fil...   Nate Peterson Jan 20, 2009
Re: need help with ascii to grid header fil...   Nate Peterson Feb 13, 2009
Re: need help with ascii to grid header fil...   Brad Posthumus Feb 16, 2009
Re: need help with ascii to grid header fil...   Nate Peterson Feb 16, 2009
Re: need help with ascii to grid header fil...   William Huber Feb 16, 2009
Re: need help with ascii to grid header fil...   Brad Posthumus Feb 24, 2009
Re: need help with ascii to grid header fil...   Nate Peterson Feb 16, 2009
Re: need help with ascii to grid header fil...   James Casey Feb 20, 2009
Re: need help with ascii to grid header fil...   K. Gardiner Feb 20, 2009
Re: need help with ascii to grid header fil...   Brad Posthumus Feb 24, 2009
Re: need help with ascii to grid header fil...   Susan Rhea Mar 13, 2009
Re: need help with ascii to grid header fil...   Jacob Grinsted Mar 26, 2009
Re: need help with ascii to grid header fil...   Nate Peterson Mar 30, 2009
Re: need help with ascii to grid header fil...   Jacob Grinsted Apr 01, 2009
Re: need help with ascii to grid header fil...   Susan Rhea Apr 01, 2009
Re: need help with ascii to grid header fil...   Susan Rhea Apr 01, 2009
Re: need help with ascii to grid header fil...   Susan Rhea Apr 01, 2009
Re: need help with ascii to grid header fil...   Stephen King May 05, 2009
Re: need help with ascii to grid header fil...   Dave Tewksbury Nov 14, 2009
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Subject need help with ascii to grid header file in degrees 
Author Nate Peterson 
Date Jul 19, 2007 
Message I'm stumped. I'm trying to import an ascii grid of bathymetry/elevation. This data, General Bathymetric Chart of the Oceans (GEBCO), comes from the British Oceanographic Data Centre.
It's a 1 minute grid, in decimal degrees, with the following header:

Gridded data provided through the GEBCO Centenary Edition software interface
Data source GEBCO One Minute Grid version 1.02
Minimum longitude : 142.98333 degrees (+ve East)
Maximum longitude : 149.98333 degrees (+ve East)
Minimum latitude : -8.3499999 degrees (+ve North)
Maximum latitude : -3.1500001 degrees (+ve North)
Data spacing : 1 minute
Rows*Columns : 313x421
Units : Depths in Metres (terrestrial values are positive)
Points start at the North-West corner working eastwards across to the North-East before restarting in the West
Longitude Latitude Depth
142.9833 -3.1500 -756
143.0000 -3.1500 -762
...etc...

I understand that a new header in a format suited for ArcGIS is necessary. So I made this one:
ncols 421
nrows 313
xllcorner 142.0
yllcorner -8.0
cellsize 0.0166666666
142.9833 -3.1500 -756
143.0000 -3.1500 -762
...etc...

Arc processes the grid but the values are garbage. I can kind of see the faint hints of elevation, but it's not even close to being good enough to work with.

Any tips out there on how I can fix up this header?

Cheers,
Nate Peterson
The Nature Conservancy
Brisbane, Australia 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 08, 2008 
Message Hi Nate,

Did you ever figure this problem out? We're having similar difficulties in our lab but we can't even get the ASCII file to show up (even with the alterations).

 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author William Huber 
Date Jul 09, 2008 
Message The problem is not the header, it's the data format: this file lists each cell value as a triple (x,y,z), one per line. What you need is the sequence of z-values only: the header implicitly determines what the x and y values will be.

For small files, strip the header, prepend a single header line like

"X", "Y", "Z"

and add the file as an ordinary text table. Convert that to a grid, one point per cell.

For larger files, pre-process them to remove the X- and Y-values (as well as the end-of-line characters if you can), tack on the usual grid header, and import that as an ASCII grid. Pre-processing is readily done with standard tools like AWK or PERL, programmable text editors, and many, many scripting environments, including Java, Python, etc. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 09, 2008 
Message Thanks Bill,

I'll give it a try and see what happens.

Cheers. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Jul 11, 2008 
Message The GEBCO world bathymetry (http://www.gebco.net/data_and_products/gridded_bathymetry_data/) can be converted to a ESRI ASCII grid using the Generic Mapping Tools (GMT).

1. Download and install these tools (basic Windows installation is sufficient - http://gmt.soest.hawaii.edu/)
2. Open up a command line window (Start->Run...->cmd)
3. Change directory to the location of the GEBCO data (*.grd file)
4. Use the "grd2xyz" command with the -E option for export to ESRI ASCII

e.g. grd2xyz GridOne.grd -E > bathymetry.asc

From there you can access it in ArcGIS and convert it to a raster if required. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author William Huber 
Date Jul 11, 2008 
Message Thanks for the link, Brad. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 11, 2008 
Message Thank you for helpful post. I downloaded the GMT basic Windows software and have run into a bump in the road. How do you change the directory to the location of the GEBCO data? I'm not used to using the command line windows.

Cheers. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Jul 11, 2008 
Message If necessary, type in the name of the drive where the folders containing the data exist, followed by a colon

e.g. C:

Use the "cd" command to change directory

e.g. cd \workspace\hydrology\bathymetry

Use "dir" to verify your data is in the directory, then run the grd2xyz command.

I've attached a screenshot showing how I navigate to the file and run the command on my desktop.
 
  grd2xyzTool.jpg (opens in new window)
 
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 11, 2008 
Message Thank you Brad for your help on this matter. I was able to change the directory and checked that my data was there (which is was). I then used the "grd2xyz" command but it was "not recognized as either an internal or external command, operable program or batch file". Also, when I checked my folder, the program had created an ASCII file without any data (0KB). Any ideas as to what is going on? 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Jul 11, 2008 
Message It sounds like something didn't work when you ran the installer.

When you download the Windows installer for GMT, you should get an executable with a name similar to "GMT_basic_install.exe". Running this program will create a GMT folder in whatever directory you select. Inside the GMT folder will be another folder called "bin" that contains all of the commands as executable files, including grd2xyz.exe. This bin folder should be automatically added to your user PATH environment variable (as seen in Control Panel->System->Advanced(tab)->Environment Variables) during the install. If the PATH variable doesn't include the GMT\bin variable, then try running the installer you downloaded again. Note that there should also be a user variable called GMT_SHAREDIR as well.

If this PATH variable wasn't appended, then your options are:

1. Edit the PATH variable to include the GMT\bin folder (e.g. mine looks like "Q:\SYS;C:\temp\GMT\bin")
2. Copy the "grd2xyz.exe" file from the GMT\bin folder to the folder containing your data, and then run the command
3. Copy the data to the GMT\bin folder, change the directory to that directory, then run the command.

Hopefully there's not a strange permissions thing happening that's preventing it from working. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Allison Anderson 
Date Jul 11, 2008 
Message I've moved my data to the c:\programs\gmt\bin folder and checked the environment variables and am getting the following error: GMT Fatal Error: C:\GMT\share\PS_font_info.d: No such file or directory.

Any insights? Thanks 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author William Huber 
Date Jul 14, 2008 
Message Allison,

Could you enlighten us as to what relationship ought to exist between C:\GMT\share\PS_font_info.d and c:\programs\gmt\bin ? The only common ancestor they have is the root drive C:\. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 14, 2008 
Message Hi again,

I've tried all of Brad's suggestions but it still doesn't want to recognize the grd2xyz command (or any of the other commands in the bin folder). I also received the same error message as Allison when I copied the GridOne data to the bin folder. I thought maybe if I uninstalled and then re-installed GMT, it might work...but no such luck. Any other ideas?
 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author William Huber 
Date Jul 14, 2008 
Message I was able to reproduce the

GMT Fatal Error: C:\GMT\share\PS_font_info.d: No such file or directory

error. It is caused by a bad Windows installation program. Despite a quick search of the documentation, I was unable to discover any way to control this. However, a workaround is simple: copy the contents of the GMT "share" folder (installed by default in c:\programs\GMT\) into C:\GMT. The GMT executables will now run. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 14, 2008 
Message Thanks William,

I tried this method as well and for some reason, my computer does not want to work. Did you copy the gridone.grd into the bin folder as suggested by Brad or did you leave it in the GEBCO folder? 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Jul 14, 2008 
Message Something Bill mentioned sparked a potential solution here. I mentioned earlier there should be a GMT_SHAREDIR environment variable. If this variable is not set or is pointing to the wrong directory, then you will get the GMT Fatal Error message. Try setting it to your "share" directory and see if that helps.

Also, when appending a directory to an environment variable, be sure there are NO SPACES between the directories and the semi-colons.

See attached for a screenshot of my user variables that allow GMT to work properly. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Jul 14, 2008 
Message Forgot the attachment... 
  environmentVariablesGmt.jpg (opens in new window)
 
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Jul 14, 2008 
Message Thank you everyone for your help! I got it to work!

I managed to turn the ASCII into a raster in ArcMap, but now I can't seem to get it georeferenced. Also, the resolution is a bit off with all the Canadian Arctic Archipelago looking like one land mass. Is anyone else having this problem? 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Jul 14, 2008 
Message I defined the coordinate system as Geographic WGS 1984 (in ArcToolbox, use Data Management Tools->Projections and Transformations->Define Projection). That seemed to sufficiently align it with other world data.

I'm assuming the Canadian Arctic appears flat since in this dataset we're dealing with an elevation range from +8400 metres to -10500 metres. Depending on how you're symbolizing the dataset, this large range will force the Arctic Ocean to blend in with the islands.

 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Alicia Venkatachalam 
Date Sep 24, 2008 
Message Hello I see that K. Gardiner said they resolved this problem by converting the ASCII into a raster in ArcMap. Did you end up using the Generic Mapping Tools?...or did you find another way? I am also trying to import the GEBCO bathymetric data into ArcMap.

Many thanks,

Alicia 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Sep 24, 2008 
Message I did end up using the GMT to convert the data to ASCII. The previous posts give excellent detailed instructions on how to do this. I wouldn't have been able to figure it out with out the help of the other "posters" :).

Good luck! 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Alicia Venkatachalam 
Date Sep 25, 2008 
Message Great, thanks very much for replying so quickly! I will follow the instructions on the thread!

Alicia

 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Nate Peterson 
Date Jan 20, 2009 
Message Well it took me a while to get back around to this project, but I was glad to see all the activity following my original post.

I was able to follow the steps outlined on this thread and get a copy of GEBCO into an ESRI grid... but it was painful.

Looks like GEBCO is releasing an updated version in the next few months so I get to do it all over again!

Thanks for all your help folks.

Cheers
Nate
 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Nate Peterson 
Date Feb 13, 2009 
Message Now I have the new GEBCO 30 arc second data. It doesn't have a GRD extension, but instead it's NC.

I tried using grd2xyz but got an error:

GMT Fatal Error: grd2xyz could not allocate memory [3.48 gb, n_items = 933120000]

Ultimately I want this an ERSI grid so I can manipulate it with other data sets.

Thank you!
Nate Peterson
TNC - Australia

 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Feb 16, 2009 
Message Thanks for the update on the new dataset. I'll try downloading it today and see if it works. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Nate Peterson 
Date Feb 16, 2009 
Message I got word from the GMT folks that if I want to process the full GEBCO_08 datafile I would need to work on a "64-bit computer and compile GMT that way."

Which I don't have so I downloaded a subset of GEBCO_08 (25N, 25S, 90E, 180E) and used the grd2xyz with ease.

Cheers
Nate
 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author William Huber 
Date Feb 16, 2009 
Message Well, it's perfectly silly that you would need to buy a new computer and load it with gigabytes of RAM in order to perform a process that takes just a few bytes of RAM. My suggestion for larger files in the post above (http://forums.esri.com/Thread.asp?c=93&f=1740&t=228607&mc=26#793658 ) will do the job, even on an old 8086 DOS computer. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Feb 24, 2009 
Message Unfortunately this version of the bathymetry is in a binary NetCDF format, so it's not an easy text modification. I agree with the "perfectly silly" comment though, especially since GMT has a pretty robust suite of tools, including GRDREFORMAT which can be used to subset the data.

Here are the commands I used to split the GEBCO dataset into four subsets and then convert them to ESRI ASCII grid files. From there you can convert to raster and mosaic them in ArcGIS or ArcInfo workstation. 
 
grdreformat gebco_08.nc -Rd-180/0/0/90 gebco_08nw.nc
grdreformat gebco_08.nc -Rd0/180/0/90 gebco_08ne.nc
grdreformat gebco_08.nc -Rd0/180/-90/0 gebco_08se.nc
grdreformat gebco_08.nc -Rd-180/0/-90/0 gebco_08sw.n

grd2xyz gebco_08nw.nc -E > gebco_08nw.asc
grd2xyz gebco_08ne.nc -E > gebco_08ne.asc
grd2xyz gebco_08se.nc -E > gebco_08se.asc
grd2xyz gebco_08sw.nc -E > gebco_08sw.asc
 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Nate Peterson 
Date Feb 16, 2009 
Message I got word from the GMT folks that if I want to process the full GEBCO_08 datafile I would need to work on a "64-bit computer and compile GMT that way."

Which I don't have so I downloaded a subset of GEBCO_08 (25N, 25S, 90E, 180E) and used the grd2xyz with ease.

Cheers
Nate
 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author James Casey 
Date Feb 20, 2009 
Message Dear K. Gardiner,

I've been reviewing the conversations between you and Will Huber in an attempt to convert GEBCO ASCII files to grid files to upload to ArcMap. Can you lend some additional advice as to how you successfully ran the grd2xyz command? I must be missing a step or two because I continue to receive the message "fatal error".

Best,
James 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author K. Gardiner 
Date Feb 20, 2009 
Message Hi James,

I wish I could be of some help but it's been a while since I worked on this and I remember it was very glitchy. The best person to ask would be Brad Posthumus since he was the one who talked me through the tricky steps.

Cheers :) 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Brad Posthumus 
Date Feb 24, 2009 
Message I don't know if I can really add anything that's not already mentioned above. What's the complete FATAL ERROR message? 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Susan Rhea 
Date Mar 13, 2009 
Message Help Please. I want the same file - the newest gebco_08 raster file for use in ArcMap.

Lovely Posthumous fellow? Since you have done it, can you post the file geodatabase on an ftp site? There really is no need for all of us to go through this process. Perhaps the GEBCO people would let you send it there, and they would support a download? I'm still downloading the zip file from them, two hours later ...

Thanks! Susan Rhea 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Jacob Grinsted 
Date Mar 26, 2009 
Message Greetings

I'm currently working on processing the gebco_08.nc file to ESRI raster using the GMT tool and the commands listed above by Brad Posthumus.

But when I have the asc files in ArcMap 9.3 I get quite a problem whith the files. In all the files it's only the east and south border that have the correct coordinates.
An exampel of the nw part of the entire data:

Left: -180.000000
Right: -0.000072
Top: 89.999964
Bottom: 0.000000

The error of the right and top sides is like that in all four files.

the cell size is (X,Y)0.00833333, 0.00833333

Is there any who knows why I the files I get is not the entire data when I use the command

grdreformat gebco_08.nc -Rd-180/0/0/90 gebco_08nw.nc

I dont understand why some of it just disapears.. any suggestions?

Cheers
Jacob 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Nate Peterson 
Date Mar 30, 2009 
Message My only suggestion is to try a smaller subset of the raw GEBCO data. I couldn't get the entire globe processed either.

The GMT tools were a must!

Cheers
Nate
 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Jacob Grinsted 
Date Apr 01, 2009 
Message I've tried with dirrent and very small subsets of the data, but it still have the same error... I haven't changed any of the settings in the GMT tool, but maybe it's has something to do with that..

Cheers
Jacob 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Susan Rhea 
Date Apr 01, 2009 
Message I'm still working on this problem too. I have emailed Pauline at GEBCO, and I believe they would post the ArcGIS formatted data if someone sent it to them ... Brad, would you be willing?
Pauline Weatherall, GEBCO Digital Atlas Manager,
paw@bodc.ac.uk 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Susan Rhea 
Date Apr 01, 2009 
Message Small steps. Success with very small dataset.
Even though paths and enviro variables were set correctly on install, had to copy GEBCO_08.nc data to C:\GMT\bin, where I had installed program.

grd2xyz ran correctly.
opened ArcMap, opened Toolbox, opened Conversion Tools > To Raster > ASCII to Raster.
Entered input file, ran tool.
Output is correct although spatial reference is undefined.
Defined projection through Toolbox > Data Management Tools > Projections and Transformations > Define Projection.
Removed layer from ArcMap, and added again to get proper projection on the fly.

Now on to bigger datasets ... 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Susan Rhea 
Date Apr 01, 2009 
Message postscript - I am a USGS employee, and hence, must install programs as an administrator. I found I also have to run the grd2xyz inside C:\GMT\bin as administrator in order to have write permission. 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Stephen King 
Date May 05, 2009 
Message I'm not sure if this will help anyone in this discussion (and I haven't tried it out yet) but BODC have recently released a new version (2.11) of their GEBCO grid display software with a new option:

"An option to export data from the GEBCO gridded bathymetric data sets in an ASCII form suitable for conversion (using ESRI data conversion software) to a raster file for use with ESRI ArcGIS products".

It can be downloaded here: http://www.bodc.ac.uk/products/software_products/gebco_grid_display/ 
   
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Subject Re: need help with ascii to grid header file in degrees 
Author Dave Tewksbury 
Date Nov 14, 2009 
Message Stephen King mentioned that the new GEBCO software had the ability to export an ESRI compatible ASCII file.

Attached PDF describes how to download the GEBCO Grid Demonstrator software and associated global grids, export an ESRI compatible ASCII file and using ArcToolbox convert the ASCII file to a raster for use in ArcGIS.

Cheers,

Dave 
  GEBCO to ArcGIS raster.pdf (opens in new window)