How to import a GeoJSON to change the elevation model

Spatial features such as levees or waterways, which are primarily features of an elevation model, may be known in the form of polygons or other types of vector data. It is possible to load in this data so that these features are "carved" (or raised) into (or out of) the existing elevation model. They can be loaded in by loading them in as Terrain. When loading in Terrain, especially when switching between land and water, the elevation model is altered automatically based on the Terrain Type's Attributes. The defaults can also be overwritten with a custom height and angle to precisely define the height (modifications) desired.

Required data

The following Attributes can be used to prepare a GeoJSON file, with which the elevation model can be altered. Each Attribute is effectively optional.

Attribute name	Unit	Description	Default behavior (when attribute is missing)
HEIGHT	m + datum	The maximum water depth (or terrain height) across the polygon.	Height is only changed when changing from land to water or vice-versa. The relative change in height is equal to the imported Terrain Type's WATER_DEPTH_M Attribute. When changing from land to water, the absolute terrain height is reduced by that amount. When changing from water to land, the absolute terrain height is increased by that amount.
ANGLE OF REPOSE	angle (0-90°)	The angle, relative to a horizontal plane, at which the feature should be "carved" (or raised) into (or out of) the terrain.	The ANGLE_OF_REPOSE Attribute of the underground Terrain Type already present there is used.
TERRAIN_TYPE	nominal value	A value identifying the desired terrain.	All features in the file can only be loaded in as a single type of terrain.

Steps

The elevation model can be changed with vector data, by importing the vector data as Terrains.

Editor → Current Situation (Ribbon tab) → Terrain (Ribbon bar) → Import geo data (Dropdown)

How to load in terrain height altering features:

1. Prepare a GeoJSON file with polygon features with HEIGHT, ANGLE_OF_REPOSE, and TERRAIN_TYPE Attributes.
2. Open the Geo Data Wizard via the Terrain dropdown.
3. Opt to import a GeoJSON.
4. In the feature location verification step, if you are importing line data (as opposed to polygon data), ensure you set an appropriate buffer.
5. In the "Assign Terrain type" step, select the default Terrain Type to import the features as.
6. If applicable, select "Terrain Type Mapping", and set up a mapping of Attribute values to Terrain Types.
7. In the "Adjust heights" step, if applicable, opt to override the height and angle of the Terrain, and select the appropriate Attributes.
8. Finalize and close the Geo Data Wizard.
9. The elevation model is now modified with the height changes defined by the GeoJSON file.

Notes

• This functionality works best when importing a file with polygons. For example, when importing waterways, using polygons ensures the exact aerial of the waterway is loaded in. Otherwise, all imported lines or points will be buffered with a single user-configurable value.
• The overriding Attributes for the height and angle do not need to be HEIGHT and/or ANGLE, as when they are used it's always neccesary to define which Attribute matches which parameter.
• When no specific depth is defined, the angle will also use the default behavior.
• Undoing this operation may be difficult, if the original terrain heights are not known.
• When using a mapping for Terrain Types, features are first checked for a match in the mapping. If none exists, the selected default Terrain Type is used.
• The Terrain Types listed in the "Assign Terrain type" step's dropdown include both above-ground and underground Terrain Types.
• When using the default WATER_DEPTH_M Attribute, the height change is relative to the existing terrain. When using an overriding height Attribute, the height change is relative to datum.
• If the sides of the elevation change meet before the target height is reached, the new elevation will fall short of the otherwise indicated target height.