Sun Above the Horizon

From Intervisibility submenu on calculate menu  or right click, Physical Geography menu.   Uses only the effect of topography (the DEM), and not vegetation or buildings not in the DEM.


Sky map, showing the elevation of the horizon versus azimuth.

Zero elevation is at the outer diameter of the diagram, directly overhead is the center of the diagram.

Brown line shows the local horizon

The four lines show the sun's path on the selected day (red), and the solstices and equinoxes.

Single Day Table
N28.89085751 E82.4991669

Solar Positions, Julian day: 111 (4/21/2018)

Sunrise: 4:59
Sun above horizon: 6:39
Sun below horizon: 15:03
Sunset: 17:58
Duration daylight: 12.99 hrs
Direct solar illumination: 8.41 hrs
Terrain masking: 4.58 hrs


Annual Table

  • DIRECT_ILL is the hours of sunlight with the sun above the horizon, taking the terrain into consideration.
  • DAYLIGHT is the number of hours the sun should be above the horizon.
  • TERR_MASK us Terrain masking, the hours that terrain blocks the sun and there will be no direct illumination.

Horizon Blocking Graphs.

Formula after:

Last revision 6/21/2004