Question
How do I specify a land value in a dfs2 file?
Answer
When using the values in a dfs2 file to define a bathymetry, the dfs2 file contains a specific land value that cause all grid values above this value to be considered as land and the associated grid cells to not be included in the simulation or considered as input.
Dfs2 files created from Grid Editor will per default be given the land value 10, however it is possible to change this in the process. When converting GIS data to dfs2 (the Grd2Mike tool in MIKE Zero toolbox) the tool will per default assign the land value as 50, however it is possible to change this in the process.
Note: In MIKE+ the tool "Combine DEM Tiles" doesn't create a land value at all.
The land value for a given dfs2 file is saved in the M21_Misc custom block that is a part of the dfs2 file. The land value is saved in Element 4 in the custom block and can be modified by the user (see Fig. 1).
Fig. 1 - Value defining lower value of land points
In MIKE Zero you can access the custom block in two ways:
1. Open the dfs2 file in Data Utility (File->Data Utility...) and select the Custom Blocks entry (see Fig. 2). (In the examples below the land value is set to 4.4 m in the dfs2 file).
Fig. 2 - Example of Custom Block displayed in Data Utility
2. Open the dfs2 file in Grid Editor, select Edit->Custom Blocks and choose M21_Misc in the new dialog (see Fig 3).
Fig. 3 - Example of Custom Block displayed in Grid Editor
If the custom block "M21_Misc" doesn't exist yet, you can create it with the "New" icon. Write the land value in element 4 (the other elements are not relevant for the land value).
In MIKE+ you have the same two options for changing the custom block value.
First select the dfs2 file using the Grid Editor from the Results toolbar (see Fig. 4). Note: using Grid Editor from the 2D Overland toolbar requires the dfs2 file to be included in the domain.
Fig. 4 - Location of Grid Editor in the Results toolbar
This will open the dfs2 file in Grid Editor within a new MIKE Zero shell. From the toolbar in this MIKE Zero shell it is also possible to access the Data Utility dialog (File->Data Utility).
FURTHER INFORMATION & USEFUL LINKS
Manuals and User Guides
Online help for Edit Custom Blocks