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How to create a model gridded bathymetry?

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How to create a model gridded bathymetry?

Step 1 - Extract Ocean bathymetry data from ETOPO 2'

Google Earth

Make sure you have Google Earth correctly configured!!

  • Obtain the ETOPO 2' extraction domain limits by reading the Max and Min values of Longitude and Latitude for your domain from Google Earth.

Etopo data file

  • The internet address where to download the data is;
  • Download the ETOPO2V2 raw binary data to use with the ConvertToXYZ program OR, if possible, rather use the intranet address which is \\kepler\DataCenter1\DataCenter\DadosBase\Oceanografia\Batimetria\Etopo\Etopo2\Data

A sample configuration file ConvertToXYZ.dat is:

FILE_TYPE                   : 2
INPUT_FILENAME              : \\kepler\DataCenter1\DataCenter\DadosBase\Oceanografia\Batimetria\Etopo\Etopo2\Data\etopo2.dat
OUTPUT_FILENAME             :
TOP                         : 17
BOTTOM                      : 14
LEFT                        : -18
RIGHT                       : -14
MAXIMUM                     : 1
MINIMUM                     : -9999
CONVERT_TO_HDF5             : 0

  • Sample of XYZ data extracted from ETOPO 2'. How the bathymetry XYZ file should look like.


  • Open new project in Mohid GIS

  • Give name and location to new project, then save

  • Add new data item

  • Select data item and open

  • Right-click data, zoom select, right-click, properties

  • Click on settings to set the colar palette and color range

  • Choose min depth (negative if above sea level), max depth and color palette

  • IMPORTANT: Click Save All from the Data Items menu. Otherwise you risk to loose all your work!

Step 2 - Create a coast line

Create coast line in Google Earth

  • Create a polygon shaped like the line of the coast

  • Right-click on polygon, then "save as"

  • Save the file in Kml format (NOT in Kmz format)

Run Kml2mohid

  • Get the Kml2Mohid program, edit a batch file, and run the program

  • Sample polygon (.xy) file

Import coastline polygon in Mohid

  • Click Data Items menu, then select Add Data Items...

  • Select folder, select polygon file type, select file and click open

  • Right-click polygon data, then select Properties

  • Click on settings

  • Select Constant and choose a color

  • Very important: Save All from the Data Items menu

  • General look of ETOPO points data layer and coastline polygon layer

Step 3 - Create the model domain regular grid in MOHID GIS

Define the grid

  • Choose bottom-left origin for the model domain

  • Click on Data Item menu, then select New Data Item

  • Select Simple Grid, then click on Browse

  • Give name, select Grid file as file type, click on Save

  • Click Ok

  • Right-click the Grid layer, then select Properties from the menu

  • Define origin, define resolution, define grid size, choose Simple Geographic coordinates type (and NOT Geographic as seen in the figure. CAUTION!)

  • Very important: Save All from the Data Items menu

  • General look of a bathymetry points data from ETOPO, a coastline and land polygon, and a model domain grid

Create Digital Terrain from Mohid GIS

  • Click on menu Tools, select Create Digital Terrain ...

  • Select grid layer, data points layers, land polygon layers. Then click Browse

  • Choose Options menu, select Triangulation, select All points, click on Run

  • Successful Done message

Admire the result

You can now proceed to create a model simulation after you create the tidal gauges

Next steps

Previous steps

About the screen capturing tool

The screen capturing tool used for this tutorial was the Jing Project.