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 water, we have to configure the water terrain with this distance attribute. Take the following steps: