Satellite Maps Replace Compasses in Quick Rooftop Solar Orientation Checks

Field teams assessing rooftops for photovoltaic (PV) projects have long relied on smartphone compasses, but the reading is often unsteady and hard to visualize on a sloped roof. A simpler field trick is gaining traction: open a satellite map and read the roof pitch against the map frame.

The method follows the basic cartographic rule — north up, south down, west left, east right. On a satellite view, if the two sloping roof planes sit side by side horizontally, the left plane faces west and the right plane faces east: an east-west roof. If the slopes stack vertically, the upper slope faces north and the lower slope faces south: a north-south roof. The approach needs no instrument calibration and works on a laptop or phone in seconds.

Orientation decides how a PV array performs. South-facing slopes in the Northern Hemisphere catch the most midday sun, while east and west slopes shift generation to morning and evening hours, which can match self-consumption or time-of-use tariffs. North slopes yield less but still count in mixed layouts. Knowing the aspect early avoids wrong quotes and wasted site visits.

The satellite trick is not a full engineering survey. Pitch, shade, roof age, and local array rules still need verification. But as Google’s Solar API, Project Sunroof, and open GIS tools show, bird’s-eye imagery is now the first screen in rooftop solar screening. For a quick pass, a compass is optional; a map is enough.