Viewshed / Visibility Analysis

Determine which DEM cells are visible from an observer location using terrain line-of-sight analysis.

Terrain / ElevationEnd-User DocumentationTheory + Formula + Parameters

1. What This Feature Does

Determine which DEM cells are visible from an observer location using terrain line-of-sight analysis.

Cloud workflow: choose data → configure the scientific method → run → review the resulting layer/report. No programming is required.

2. Recommended Workflow

Choose DEM/elevation band and observer location. ↓ Set observer/target height. ↓ Set maximum distance and azimuth step. ↓ Run visibility analysis. ↓ Interpret with DEM resolution and Earth-curvature assumptions in mind.

3. Theory, Methods & Equations

Line-of-Sight Visibility

A target is visible when no intervening terrain has a higher elevation angle along the sight line.

α(r)=atan[(z(r)−zobs)/r]
Visible if α(r) ≥ max α(r′), 0<r′<r
Best used when: planning towers, sensors, visual impact or communications coverage.

4. Input Data

InputTypeRequirementDescription
DEM RasterrasterRequired
Observer Point LayervectorRequired

5. Parameters Available in the Application

ParameterDefaultChoices / RangeHow to Use It
Elevation Band——
Observer Height (m)1.70 to —
Target Height (m)00 to —
Maximum Distance (m)100001 to —
Azimuth Step (degrees)10.25 to 10

6. Output & Interpretation

The result should be interpreted according to the selected method and the physical meaning of the input data. Preserve source units, coordinate reference information, NoData meaning, acquisition date, and preprocessing level when comparing results.

Scientific interpretation: an algorithm can produce a numerically valid result even when the input data are unsuitable. Always check masks, units, sensor characteristics, spatial resolution and reference data.

7. Best Practices

  • Use analysis-ready inputs and remove invalid/cloud/noise artifacts that are not part of the target phenomenon.
  • Choose parameters from the physical scale of the data, not only from visual appearance.
  • Keep categorical and continuous rasters conceptually separate when selecting interpolation/resampling methods.
  • Compare the result with the source image and independent reference information.
  • Document the settings used when results will be compared across dates, sensors or study areas.
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