Use cases Distance Overlay

This page describes how to set up a project to calculate the lot- or floor-size of a set of buildings within a distance of a waterway. See section [Variations] for other examples and inspirations how to model your distance calculations for your own use cases.

Introduction

Let us consider the following use-case. As an authority, I am interested in how to calculate the amount of water-edge friendly vegetation, within 20 meters of the water edge. Using TQL, it is already easy to calculate the amount of square meters of a specific function or category, but how to restrict counting the vegetatino within 20 meters of the water edge?

Distance Overlay

Preview Server version 2017.2.0 added the possibility to add multiple instances of the distance overlay and customize the attribute containing the distance. Originally this distance was used as safety distance or noise disturbance distance. These distances describe a negative impact. However, with the customizable attribute, it can also be used in a more positive way.

Use Case

Let us consider the usecase, where I, as an authority, want to calculate the amount of square meters of deciduous trees within 20 meters of the water edge. It is currently possible to model this calculation. It requires the following:

• An attribute representing the distance;
• A terrain type describing the water
• A function describing the deciduous trees
• An distance overlay, calculating the distances
• A TQL query calculating the lotsize of the deciduous trees within distance of the water

Step 1: Assigning the distance Attribute

First, for this use-case, let us name the distance attribute DISTANCE_TO_WATER_EDGE. Next, we find the type of object we want to assign this attribute to. Since we want to calculate the area size of trees within a distance of 20 meters of water, we have to configure the water terrain with this distance attribute. Take the following steps:

How to How to add an attribute to a type of Terrain:

1. Open the project in Editor Mode;
2. Select Geo Data in the ribbon header;
3. Select Terrain in the ribbon bar;
4. Select a Terrain. In this case Water;
5. Click on the tab Attributes;
6. Scroll down the list and fill in the attribute in the text field of Add new Attribute with Name. In this case DISTANCE_TO_WATER_EDGE;
7. Fill in the desired distance in the text field of Add new Attribute with Value. In this case 20;
8. Click on Save new Attribute;
9. Notice that the attribute has been added to the selected Terrain Type.

Step 2: Configuring the distance overlay

Configuring a distance Overlay is relatively easy. Currently, multiple Overlays of the same type can be created and customized. To add and configure a distance Overlay, use the following steps:

How to How to configure a distance Overlay:

1. Open the project in Editor Mode;
2. Select Geo Data in the ribbon header;
3. Hover Overlays in the ribbon bar to show the Overlays popup;
4. Select Add Distance Zone in the Overlays popup; This adds a new distance Overlay;
5. The overlays list should be shown on the left, and the newly added distance Overlay should be selected. If not, select it manually;
6. In the text field Attribute selected in first: Building, Terrain, Area or Neighborhood, write the attribute name. In our case fill in DISTANCE_TO_WATER_EDGE;
7. (Optional) Change the general grid size of grid Overlays in your project;
8. (Optional) Change the name of the Overlay

Notes

There are several things to consider:

• The distance Overlay is a Grid Overlay. The accuracy is determined by the size of the grid cells. For more information about the grid size and its limits and Grid Overlays in general, see Grid Overlay.