Home > 7. Bathy/Topo Data > 7.4 GEBCO Online
|1. Open the GEBCO website, and read about the program and its products.|
|2. Scroll down the page to find and click the DOWNLOAD DATA tab.|
|3. Read about the gridded dataset. This version ("GEBCO 2014") replaces a grid published in the 1990's that was essentially a gridding of all the XYZ coordinates of the vector contour lines. This new version is a compilation of all the best available grids, and has been recommended for use by the World Data Center for Geodesy and Geophysics (NGDC in Boulder, Colorado, USA).|
|4. Scroll down the page, below the map inform the coordinates for Liberia|
|5. This data selection screen appears with a global map|
|6. Expand the option GEBCO One Minute Grid (1 arc-minute interval) and choose the User-defined area option|
|7. Click on Add data to basket and then View basket.|
|8. Click in Checkout your request,
which will direct you to the Log in page.
note: To download the data you are required to be a registered BODC web user. If you have already registered, simply log in, alternatively register to become a new user."
|9. Once logged in, you can click on refresh and wait. When data is ready, click on Download.|
|10. Unzip the folder. The documentation has lots of important information you may want to read when working with your own data. For now, rename the nc file as gebco_1min_-23_-6_-3_9.nc and save it in the folder DATA > BASEMAP > RELIEF > GEBCO|
|11. Run Saga and open MODULES
> IMPORT/EXPORT GDAL/OGR > IMPORT NETCDF
Then click on OK.
|12. The grid now appears in your list of objects. Visualize it, as you see here, with ADD TO MAP. Check the LEGEND to make sure you have the correct grid values, as you see here.|
FILE > SAVE AS to save the new Saga format grid in the folder PRODUCTS > SAGA >
GRIDS with the filename relief_liberia_gebco14_online_saga_1min.sgrd. You
will need it later for other exercises.
If you need a NetCDF format grid, then follow these steps:
|14. The GEBCO 2014 global relief datasets will be merged into existing MDL exercises, replacing the old ETOPO1 relief grid. This will be a gradual process, and should not change any exercises radically. If you find ETOPO1 in an exercise, then replace it with GEBCO 08 or 14 (1 min). If you have the 30-sec version of GEBCO 08, then ask your instructor for special steps to deal with the change in resolutions.|