For ETOPO2

ETOPO2 data is 2 minute resolution or about 4 km. 

Web page describing this data: http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html

To download entire data set data: see that web page

To get data from a subset area:

1. go to the data access site http://www.ngdc.noaa.gov/mgg/gdas/gd_designagrid.html
2. enter "Your Grid Id" (make up a name, up to 8 characters)
3. choose Database: "ETOPO2 2-minute Global Relief"
4. at top, click one of Windows, Macintosh, Linux LE x86, or Unix-BE. [little or big endian]
 (use unix-le for the UNAVCO converter on linux)
5. set Lat/Lon Area Bounds 
6. set Grid Cell Size to 2 minutes (default); you can increase the data spacing with other choices
7. note your choice of latitude and longitude limits

8. set Grid format to "ASCII Raster format," and "no header" 

Note the Number of Latitude Cells and Longtitude cells 
(save these numbers; you may need them later in conversion to NetCDF format file for IDV).

Click on the "Submit" button to make the data file.

In the next web page click on  "retreive individual files" (or "Compress and Retrieve")

Download the file ending in ".asc", or unzip and un-tar the ".tgz" data file on your system:

    In Linux, on your command line unpack the file with
    gunzip mynewfile.tgz
    tar -xvf mynewfile.tar ; 
    or use tar xvzf mynewfile.tgz

Find the actual ascii data file "[your Grid Id].asc,"  (2 subdirectories down now).

Look at the ascii file with an editor.
Number of rows in the file should be number of Latitudes.
Number of character columns is 7 * Number of Longitudes.
This is the only file from NGDC that the UNAVCO Converter needs.

To run the UNAVCO ascii to NetCDF file converter:

Follow instructions in http://geon.unavco.org/unavco/Converter/

cd to where the Coverter.jar is.

execute with java -Xmx512m -jar Converter.jar

See  following "Make a Configurator file."


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For NGDC "GLOBE" Topography data 

"GLOBE" data is 30 sec or about 1 km resolution.

web page describing the data: http://www.ngdc.noaa.gov/mgg/topo/globe.html

The NGDC subset region and data download service: 
http://www.ngdc.noaa.gov/cgi-bin/seg/ff/nph-newform.pl/seg/topo/customdatacd

Enter latitude -longitude limits

Use these choices to make a data file for use with the 
UNAVCO ascii to NetCDF file converter ( http://geon.unavco.org/unavco/Converter/ ) on linux:

FreeForm ND
int16
flat text
individual files
FTP

Make up a filename and title.

Download individual files. The ".dat" file is the one 
with the data for the UNAVCO converter. The  .hdr file
has the number of lat and lons you selected, and the starting lat (highest)
and lon (lowest).

delta lat and long is 0.00833333333 degrees for "GLOBE" 30 second data.

The data is in one line in the returned file. 
You  need to add one line return at the end of the line in the data file for the
converter to work, or use one few number of lats.

To run the converter:
Follow instructions in http://geon.unavco.org/unavco/Converter/

(cd to where the Coverter.jar is.

execute with java -Xmx512m -jar Converter.jar

Use file type "List file" in the UNAVCO converter.

Delta lat is negative; delta long is postive.

Lon changes faster than lat.)