Show line of sight analysis in map

Perform a line of sight analysis in a map view between fixed observer and target positions.

Use case

Line of sight analysis determines whether a target can be seen from one or more observer locations based on elevation data. This can support planning workflows such as siting communication equipment, assessing observation coverage, or evaluating potential obstructions between known locations. In this sample, several predefined observer points are evaluated against a single fixed target to compare visibility outcomes side by side.

Note: This analysis is a form of “data-driven analysis”, which means the analysis is calculated at the resolution of the data rather than the resolution of the display.

How to use the sample

The sample loads with a map centered on the Isle of Arran, Scotland, and runs a line of sight analysis from multiple observer points (triangles) to a fixed target point (beacon icon) located at the highest point of the island. Solid green line segments represent visible portions of each line of sight result, and dashed gray segments represent not visible portions. Tap on each observer to see a callout that reports whether the target is visible and over what distance the line remains unobstructed. Use the toggle to show only results where the target is visible from the observer.

How it works

1. Create a Map and pass it to a MapView.
2. Create a GraphicsOverlay and add target and observer points to it, along with an appropriate symbol. Create another GraphicsOverlay that will display the line of sight result graphics.
3. Create a ContinuousField from a raster file containing elevation data.
4. Create a list of LineOfSightPosition from target and observer Points and a HeightOrigin.relative.
5. Configure LineOfSightParameters with ObserverTargetPairs, using the list of observer and target line of sight positions.
6. Create a LineOfSightFunction from the continuous field and line of sight parameters.
7. Evaluate the function to get LineOfSight results.
8. Create a Graphic from each result, using the geometry of the result’s visibleLine or notVisibleLine result, and an appropriate symbol.
9. Use LineOfSight.targetVisibility to determine if the observer position has a direct line of sight to the target position.
10. Get the length of the visible line result with GeometryEngine.geodeticLength(of:lengthUnit:curveType:) to report results.

Relevant API

• ContinuousField
• GeometryEngine
• GraphicsOverlay
• LineOfSight
• LineOfSightFunction
• LineOfSightParameters
• LineOfSightPosition
• ObserverTargetPairs

About the data

The sample uses a 10m resolution digital terrain elevation raster of the Isle of Arran, Scotland (Raster data Copyright Scottish Government and SEPA (2014)).

Tags

analysis, elevation, line of sight, map view, spatial analysis, terrain, visibility