Grid Data

Overview

Grid Data items relate to 2D or 3D information referenced to a grid. Grid data is stored in an ASCII text file and has multiple and flexible formatting options. In order to view a Grid Data file in Mohid GIS the file must contain grid information. In Mohid, the grid information is not used except for bathymetry file to Mohid Water, or the input topography file to Mohid Land where the simulation domain is defined. Grid Data items can be used to initialize 2D or 3D fields (e.g. temperature, salinity) via Module FillMatrix.

Header Section

The header section contains some specifications on the type of organization of the information.

FILL_VALUE         : -9.9e15    
TYPE_ZUV           : z         

FILL_VALUE specifies a value for points with no data.

TYPE_ZUV specifies if the data is located in the center of the grid cell or referenced to the faces of the grid cell. It can be z for centered data, u for east-west faces or v for north-south faces.

Data Section

Grid Data 2D

The data section contains the values of the Grid Data item. The data is stored inside a block defined by the following keywords: <BeginGridData2D> and <EndGridData2D>. Note that these keywords are case sensitive.

Filling data for all grid cells

You can specify the values by giving a list of all values of all the grid cells. Each value must be stored in a single line. The values are read from the lower left corner to the upper right corner of the grid that is values reading is done by row-column order. The first grid data values are read in the following order: (ILB, JLB), (ILB, JLB+1), … (ILB, JUB), (ILB+1, JLB), …, (IUB, JUB-1), (IUB, JUB). Note that the index “i” refers to the Y-axis and the “j” index to the X-Axis. In this case, if you have a (IUB x JUB) grid then the list must have (IUB x JUB) values.

<BeginGridData2D>
12.5
13.1
10.2
...
...
<EndGridData2D>

Filling data for some grid cells only

If you don't want to define all the values in the grid but only in a subset of cells in the grid (for example, if you want to simulate a bump in a flat bathymetry. Everywhere is 1000 m depth except in the bump area, so you want to define only the bump area); then you can also use "i j value(i,j,:)". Values not specified in the list will be given the DEFAULTVALUE.

<BeginGridData2D>
2   1   12.8
2   2   13.4
5   1   11.3
..  ..  ..
<EndGridData2D>

If the array is 3D and you wish to specify that in the vertical direction all the values are constant then use i j value(i,j,:). In the following example, if you have 3 layers, then grid cells (1,1,1), (1,1,2) and (1,1,3) will all be given the value of 10.2. Values not specified in the list will be given the DEFAULTVALUE.

<BeginGridData2D>
2   1   12.8
2   2   13.4
5   1   11.3
..  ..  ..
<EndGridData2D>

Grid Data 3D

The data section contains the values of the Grid Data item. The data is stored inside a block defined by the following keywords: <BeginGridData3D> and <EndGridData3D>. Note that these keywords are case sensitive.

Between these keywords, for each grid cell, a value must be supplied (.e.g. for the bathymetry file write the bathymetry value).

If the array is 3D and you which to specify that in the vertical direction the values are constant then use "i j value(i,j,:)". In the following example, if you have 3 layers, then grid cells (1,1,1), (1,1,2) and (1,1,3) will all be given the value of 10.2. Values not specified in the list will be given the DEFAULTVALUE.

<BeginGridData3D> 
    1   1   10.2
    1   2   12.3
    2   5   10.7
    ..  ..  ..
<EndGridData3D>

If the array is 3D and you wish to specify to each grid cell a specific value the use i j k value(i,j,k). Values not specified in the list will be given the DEFAULTVALUE.

<BeginGridData3D>
    1   1   1   10.2
    1   1   2   10.1
    1   1   3   9.9
    1   2   1   12.3
    ..  ..  ..  ..
<EndGridData3D>

You can also specify the values by giving a list of all values of all the grid cells. In this case, if you have a (IUB x JUB x KUB) grid then the list must have (IUB x JUB x KUB) values.

 <BeginGridData3D>
    10.2
    10.1
    9.9
    12.3
    12.1
    ...
 <EndGridData3D>