1. Downloading the ETOPO1 Grid

2. Importing ETOPO1 data

3. Converting ETOPO1 data to the Mercator Coordinates

4. Defining the 2500m isobath.

5. Defining the 2500m isobath + 100M limit line.

6. Generating a Bathymetric Profile from a grid

7. Calculating the Foot of Slope (FOS)

8. Generating a Bathymetric profile from another Bathymetric Profile

9. Joining FOS points together into one FOS data set

10. Adding 60M to the FOS points

• Open a web browser, and go to the following address:
  http://www.ngdc.noaa.gov/mgg/global/global.html
• Click the link: Create Custom Grids - in the dark blue line towards the top left of the page.

A new web page with the “GEODAS Grid Translator – Design- a – Grid” should appear

The GEODAS Grid Translator
• Enter a grid id (for example the name of your country)
• Select "ETOPO1 1-minute Global Relief - beta" as your Grid Database
• Enter the latitudes and longitudes of your area.
• Keep Grid cell size at 1 minute
• Select Grid format: Binary Raster Format
• Select Grid header: GRD98 Header
• Click the submit button on the top of the page
• A new page will appear, Click “Compress and Retrieve your grid”
• A new page will appear, Click "Retrieve". Store the data somewhere on your computer
• Once the data has been downloaded, decompress the files, and store them on your computer.

The following exercise can be used on most binary grids which Geocap support. You normally do not have to specify the grid file format. Geocap will automatically recognize the file format.

• Locate the folder called “Grids” in your Geocap project under “2. Seabed”
• Right click the folder and select “Import -> Generic…”
• The format should be set to “Automatic”
• Click the browse button: and locate the files you downloaded in Exercise 1. The data file is the file which ends with “.g98”, and is located in a sub folder. Select this file and click “Open”
• If “Specify import area” is checked, uncheck this option. This will import the entire grid.
• Click on the "Reader Options" tab and under polydata check the box next to "Invert" (The Grid we will import has negative values for sea depths, and positive values for heights above sea level. Usually most bathymetry data has positive values for depths. We therefore have to multiply the depth and height values by -1 with this option).
• Click execute.
• You will now be prompted with a question of the coordinate system and datum.
  Select:
  World Geodetic system 1984
  Geodetic

Geocap will report if the grid has been imported correctly, click OK and close the import dialog by clicking close. Observe that the new data set has appeared in the “Grids” folder.

The data is imported in Geodetic, with latitudes as Y coordinates and longitudes as X coordinates. In order to view the grid with the data we have already imported and converted to a Mercator coordinate system, we need to convert this grid to match the same coordinate system as the other data in the project (Mercator).

• Right click the dataset and select “shared commands-> convert to Mercator”
• Change the result combo box to “Replace input”
• Click execute

Schema type:
Check the schema of the data set is "seabed surface". If not then right click the dataset, choose Set Schema and choose seabed surface.
The data is now converted and ready to be displayed:

• Right click the dataset and select “Scale window to data”
• Right click the dataset and select “Map Sea”
• Right click the dataset and select “Map Land”
• When you have made changes to the project it is always a good idea to store your changes. Click the save button: in the project tool bar in order to save your project.

• Locate the data set you imported in Exercise 2, which should be located in “2. Seabed / Grids”. The data set should have the schema Seabed Surface. If it does not have this schema, right click it, and select “Set Schema -> Seabed Surface”
• Display the seabed by right clicking it and selecting "Map Sea"
• Right click the data set and select the command "Display contours"
• A menu will appear. We will just use the default settings. Click execute, and close
• Right click the data set and select the command "Generate Bathymetric Profile"
  A menu will appear.
• Click the "start" button. Then digitize the first point of the profile by clicking with the left mouse button where you want the profile to start on the seafloor in the display window.
• Digitize the last point of the bathymetric profile, by clicking with the left mouse button where you want the profile to stop on the seafloor.
  After you have digitized both the start and stop point, you will be notified where the resulting Bathymetric profile has been put. Click ok
• Locate the new profile in "2. Seabed / Bathymetric Profiles"
  This is the default position of bathymetric profiles. In order to structure our project we want to move the profile into a sub folder, and rename the profile.
• Right click the folder "2. Seabed / Bathymetric Profiles" and select "add-> folder"
• Change the name to "Etopo1" and click OK.
• Right click the profile and select "Cut"
• Right click the new folder and select "Paste"
  The profile is now moved into the new folder.
• Right click the data set and select "Rename"
  Give the profile a suitable name. for example the name of the area you are working in.