Horizon Profile

What a Horizon Profile Actually Describes

A horizon profile is a line, not a point value: for every compass bearing (azimuth) around a site, it records the elevation angle above the true horizontal at which the visible sky is blocked by something far away. Walk a full circle around a site and plot “how high up the sky line sits” at each bearing, and the resulting curve is the horizon profile. Where that curve sits at 0° elevation, the sky is open down to the horizon; where it rises to several degrees, something distant — a ridge, a hill, a skyline of buildings — is cutting into the sky before the sun would otherwise appear or disappear.

This distinguishes horizon profile from the near-shading obstructions (shading analysis in general) that a site survey also has to capture. Near obstructions are close enough that their exact shape, height, and distance matter — a nearby tree can block one string of modules but not another. Distant obstructions are far enough away that only their angular elevation by azimuth matters; a mountain ridge either raises the effective sunrise/sunset for the whole site or it doesn’t, regardless of exactly how far away it is.

Why It’s Worth Surveying Separately

Because far obstructions only ever clip the very start and end of the sun’s daily path, their impact concentrates in low-sun-angle hours — early morning and late afternoon, and disproportionately in winter months when the sun’s arc is already shallow. A site can have a completely clear near-field (no trees, no adjacent structures) and still lose a measurable slice of annual yield to a ridgeline several kilometers away if that ridge happens to sit close to true east or west. This is exactly the kind of effect that shows up as a small but persistent gap between a naive irradiance estimate and a modeled one, and it’s part of why lenders expect a documented solar window analysis rather than a bare TMY lookup for anything beyond a small rooftop system.

Getting a Horizon Profile Into a Yield Model

In practice, the profile is built as a series of azimuth/elevation pairs — recorded in the field with a compass and clinometer, extracted from a DEM (digital elevation model) or LIDAR dataset, or estimated from panoramic site photos taken against a known sun position. Those pairs are then entered into PVsyst’s Horizon dialog as a closed curve around the full 360°, and the simulation engine reduces beam irradiance for any hour where the sun’s calculated elevation at that azimuth falls below the horizon line. The result folds into the same loss accounting used for near shading, but as a distinct line item — which is useful, because it lets a reviewer see at a glance whether a project’s shading losses are dominated by site-specific near obstructions (fixable with layout changes) or by terrain that no amount of layout optimization will change.

Key Takeaways

• Horizon profile = distant obstruction elevation by azimuth.
• Used for far-shading analysis in PVsyst.
• Distinct from near-shading (trees, buildings within site).
• Mountains and ridgelines can shade morning/evening hours seasonally.
• Site survey, LIDAR, or DEM data are the typical sources.

Related Reading

Horizon profile is one half of a shading analysis — the other half is near shading from obstructions inside the site, which is covered in more depth in our 3D near-shading scene builder walkthrough and in the broader survey of shading analysis software options. Because far-shading losses concentrate in specific low-sun hours, they also feed into the uncertainty bands lenders scrutinize in a P50/P90/P99 yield report, and into the modeling choices compared in PVsyst versus HOMER Pro for hybrid simulation. For readers weighing which platform actually handles shading modeling well, SurgePV’s shadow analysis tooling is built around exactly this near-versus-far distinction. On the services side, capturing an accurate horizon profile starts at the ground: our Site Survey & Land Feasibility team records field-measured horizon data that feeds directly into the far-shading input our Solar 3D Pre-Design engineers use when building out the PVsyst shading scene.