Setting Object Elevation
Elevation of objects in the network can be set by using Digital Terrain Data.
Setting object elevation will only work for the United Kingdom. It is specifically designed to work with the Ordnance Survey Land-Form Profile 1:10,000 Digital Terrain Model data set issued in NTF format. Visit the Ordnance Survey website for more information.
Terrain data (.NTF) files covering the area to be updated are required. These files must all be in the same directory.
Elevation information can be applied to different types of network data:
- Nodes
- Customer Points
You can further limit the network data updated by the procedure by using a selection, preventing changes to objects with existing elevation data, or preventing changes to objects with a specified flag on the Elevation field.
You may want to store a copy of the original Elevation values before carrying out this procedure. See Backing Up Old Values below.
- Choose Set Elevation of Objects from the Model menu. This displays the Set Elevation of Objects dialog.
- Browse to the location of the Digital Terrain Model files. The DTM Files Required box on the right shows all the tiles required to cover the data in the model. Only one directory can be chosen. If more than one file is needed they all must be in the same directory.
- Once a directory has been selected, the colour of the tiles in the DTM Files Required box will change to green if the tiles are available. Tiles not found are shown in red. You can continue without all the required tiles. InfoWorks will gather data from all the available tiles.
- Choose the type(s) of data to which elevations should be applied. The options are Nodes, Customer Points, or Spatial Data Points.
- There are several ways to limit the objects affected by the changes:
- Check Selected Objects Only to limit the changes to the currently selected objects.
- Choose the Leave Existing Elevation Values Unchanged option to protect existing values in this field
- Choose the Overwrite Unless Have Flag option, and select a flag in the dropdown list. This prevents changes to any object where the Elevation field has the chosen flag.
- It is a good idea to create a special flag to mark Elevation values changed using this procedure. Select the flag in the Set Elevation Values Flag To box. This flag will be applied to all Elevation fields that have been changed.
Backing Up Old Values
It is very important to remember that the existing Elevation value is REPLACED when you carry out this procedure, unless you choose the Leave Existing Elevation Values Unchanged option. This replacement cannot be undone.
It is recommended that the Elevation values are backed up in some way so they can be reinstated if the automatically updated values are not appropriate.
One method would be to check the network in and then check out again so the old values are stored in the database in a previous version of the network.
A more appropriate method is probably to copy the data from the Elevation column of the grid and paste it into one of the User Number or User Text fields.
To copy the data:
- select all the cells in the column and choose Copy from the Edit menu or press Ctrl-C. If you select the entire column by clicking the column header, make sure you click No when asked if you want to include the column header.
- click the top cell of the User column where you want to paste the data. Make sure you scroll the grid back to the top if necessary.
- choose Paste from the Edit menu, or right click and choose Paste from the context menu, or press Ctrl-V to paste the data into the new column
- you could rename the column if you want to show what data it now contains. See Renaming Additional User Fields.
If you combine this procedure with a special flag set to mark changed values (see above), it is easy to see what the software has changed, and to go back to the old value if the change is inappropriate.
Moving the User Number column next to the Elevation column will make comparison even easier.
