ConvertTOXYZ and ETOPO.

MOHID GIS general discussion forum
ricardog@satlink.com
MOHID Beginner
Posts: 3
Joined: Thu Jan 01, 1970 00:00

ConvertTOXYZ and ETOPO.

Postby ricardog@satlink.com » Wed May 26, 2010 18:29

I am trying to follow the \"create a model gridded bathymetry\" tutorial.
when I try to download the etopo2v2c data, in the directory \"raw-binary\" there are 2 options:

ETOPO2v2c_i2_LSB.zip - 2-byte integer grid with Least Significant Byte First (littleendian)
ETOPO2v2c_f4_LSB.zip - 4-byte floating pt grid with Least Significant Byte First (littleendian)

I downloaded the i2 version, I got a \".bin\" file. Anyway, I tried but that file is not working with ConvertToXYZ.

(in the tutorial, it mentions a .dat file)

I am downloading the f4 version to try.

Just to check:

¿can someone confirm me that converttoXYZ is still working with etopo2v2?. ¿Am I downloading the correct files?
¿is it possible to use ETOPO1? and if so, ¿which file has to be downloaded?

thank you.

ricardog@satlink.com
MOHID Beginner
Posts: 3
Joined: Thu Jan 01, 1970 00:00

Postby ricardog@satlink.com » Thu Jun 03, 2010 14:41

First I want to apologize because I realize now that this question should have gone in tools

I am still having problems with converttoxyz, but you can avoid using it.

you can get the data you need using this web site:

http://www.ngdc.noaa.gov/mgg/gdas/gd_designagrid.html#

save your grid as XYZ.

then you need to change sign of the Z value, and to add the <begin_xyz> and <end_xyz> lines in the file.

I am not sure about grid registration, and about extreme values, but the data you get is good enough to follow the tutorial. (and to create some preliminary models of your area of interest).


I took a look at the source code of converttoxyz, and it is reading the file as 15i6 data

\"read(Me%Unit,'(15i6)')(Me%Topography(i),i=1, iLongitude)\"

I am not sure because my knoweidge of fortran is weak, but I do not think that this corresponds with the raw_binary file that you get if you download the database.
The format of the file \"ETOPO2v2c_i2_LSB.zip\" is just two bytes per grid cell, without headers or record markers, (I create a simple C program and I could decode it)

regards, ricardo.

luis_at_mohid.com
MOHID Developer
Posts: 553
Joined: Thu Jan 01, 1970 00:00
Location: Instituto Superior Técnico - Technical University of Lisbon
Contact:

Postby luis_at_mohid.com » Tue Jun 08, 2010 08:38

Hi Ricardo,

I not sure exactly what might be the error. however when the ConvertToXYZ was developed this website did not exist. Nowadays you can automatically download the ETOPO data directly to XYZ via the website you've mentioned. Just make sure that for using the XYZ in MOHID GIS you need to follow the rules for XYZ points files.

See more here:
http://www.mohid.com/wiki/index.php?title=XYZ_Points

Regards,
Luis


Return to “MOHID GIS (discontinued)”

Who is online

Users browsing this forum: No registered users and 1 guest