Placement centre z

What it is

The height of the device centre: the rotation axis of a tracker, the middle of the module plane of a fixed rack, the height of the two faces' top edges on an east-west ridge. z places the device centre; there is no terrain surface in the scene. Lengths are in the scene's unit, the same for every length.

Typical values and how to get it

From the survey or a terrain model, in any datum that every placement and object shares: a site elevation of 150 is fine. Default 0. On flat ground give every device the same z. Only differences in z change the result: between neighbouring devices, where a device that stands higher than the one ahead of it is shaded less, and between devices and objects. A height above the ground, such as a KML altitude relative to the ground, is z itself on flat ground; on sloping ground add the ground elevation under the device. A tracker's layout polygon is its module plane at 0° rotation, which lies close to the axis: take its altitude as the axis height. For a rooftop array, z is the height of the array centre in the datum of the building's base, on or above the roof face it lies on: a device parallel to that face is not shaded by the prism under it, while a centre below the face puts it inside the prism, which can then shade it. The residential example sets each module centre 0.1 higher in z than the roof face under it, a vertical offset.

API

scene.placements.z