How to create a heightmap for a new neighborhood

This how-to describes how to create a new height map for a new neighborhood. Usually, when a new neighborhood is designed, the height of the current situation has to be adjusted. The steps to get from the current height map to the new height map are described.

Tygron Platform loads the project area's current elevation by default using the latest AHN. The layout of the area is loaded into the Tygron Platform using the BAG, the BGT, and for the terrain, the BRO.

The new design specifies height adjustments relative to the existing ground level for various components: In this example, the following classification has been made:

• Houses = 0.30 m + ground level
• Roads = 0.15 m + ground level
• Gardens = 0;
• Green structure = 0.15 m – ground level
• Water = 0.3 m – ground level.

Preprocessing of the design drawing

How to preprocess the design drawing:

1. In QGIS, the DXF file is converted to a GeoJSON. This results in: Points, Lines and Surfaces.
2. Two additional attributes are added to the surfaces, namely:

Hoogte_tov_mv (Height_relative_to_ground_level). This attribute represents the relative elevation of this surface. The value of this surface is derived from the design principles.

Verhoging (Elevation). This attribute is used to visualize the project area. This attribute is assigned the value 1.

Creating the project boundary in Tygron

How to create the project boundary in Tygron:

1. Import all design drawing surfaces within the project boundary into Tygron as an Area. Make sure to base the area names on a logical name from the GeoJSON.
2. Then group the areas based on the common attribute, namely Hoogte_tov_mv.
3. Using a Distance Overlay, this area is converted into a grid. We call this Grid_Project_Area. We use the following settings:

Select Input:

Attribute: Specific layer

Areas

Attribute:

Verhoging (Elevation)

Creating the height map for the groundworks map

How to create the heigth map for the groundworks map:

1. Add a Heightmap Overlay (DTM). We call this Height_Map.
2. Create a waterway filter by adding an Average Overlay named Water_Filter. We use the following settings:

   Set Input to Attribute: Specific layer

   Set Maplink to Terrains

   Set the Cell averaging distance (m) to 1

   Set attribute to WATER

3. Convert water cells to NO_DATA values using a Combo Overlay named Water_no_data. We use the following settings:

   Set Grid Overlay A to Water_filter

   Set Grid Overlay B to Height_Map

   Set the Formula to IF (GT(A,0), NO_DATA, B)

4. Close ditches by replacing NO_DATA values with surrounding slope heights using an Average Overlay named Ditches_Closed. We use the following settings:

   Set Grid Input Overlay to Water_no_data

   Set the Cell averaging distance (m) to 10

5. A cutout of the closed waterways is created for only the project area. This is done using a Combo Overlay, which we call Height_Map_Groundworks . We use the following settings:

   Set Grid Overlay A to Project_Area

   Set Grid Overlay B to Ditches_Closed

   Set the Formula to IF (GTE(A,0), B, NO_DATA)

6. Optional, set the Height_Map_Groundworks overlay as parent of the overlays mentioned in steps 1 to 4.
7. Finally, the **Height_Map_Construction_Ready** is exported as a grid. To verify the success of this operation, the height map can be further examined in QGIS.