GCR

The GCR (Ground Coverage Ratio) is an indicator of the geometry of your PV array, basically defined as:

\[ G C R = \dfrac{\text{PV area}}{\text{Ground occupation area}} \]

However, the GCR cannot be universally defined as it depends on the exact definition of both areas:

The PV area may be the PV modules' sensitive area only, or the area occupied by the PV modules and their mounting structures (including spaces, inactive bands, etc.).
The ground area is difficult to specify in a general way: what area is included around a single table? Around the full system? Should the circulation ways be included? Etc...

Therefore, the GCR may be defined in slightly different ways depending on the PV installation type.

Arrays of Sheds or Trackers

The Ground Coverage Ratio is a relevant metric for regular arrays of trackers or sheds with fixed tilt. It represents the "density" of the PV sensitive areas. The higher the GCR, the higher the mutual shading losses.

When defining "Unlimited sheds" or "Unlimited trackers" in PVsyst's Orientation window, there is a 2D representation ignoring the extremities (inactive bands).

In this case, the ground area is defined as the area between the base of two consecutive rows, i.e., the pitch multiplied by the row length.

The PV area definition, however, depends on the exact system considered and the choice of shading type to simulate (mutual shadings, backtracking):

For sheds (regular fixed-tilt rows), the PV area is defined as the PV sensitive area + top inactive band, as both contribute to the shading factor. The bottom inactive band is ignored as it does not contribute to the shading factor.
For trackers, the PV area is defined as the PV sensitive area + left inactive band + right inactive band. Here, both inactive bands contribute to the shading factor.

For rather regular arrays defined in the 3D scene, PVsyst evaluates (and averages) the GCR of each array. This doesn't represent the additional spaces between arrays for circulation or other not-equipped areas in the plant's area.

Arrays of Tables or Independent Trackers

When importing 3D scenes (especially on a terrain), the tables do not necessarily have a regular arrangement. In this situation, the GCR can be hard to define and should be used with caution.

To compute the GCR, PVsyst tries to evaluate the average distance between each table and the next one in the 3D geometry. Cases of double pitches (or more) are rejected when computing the average. This is a fuzzy evaluation: the result may look a little bit strange in some special situations.
The terrain width for each table is the width of the table. Therefore, the eventual spaces between adjacent tables are not taken into account.
This evaluation also doesn't include the circulation areas and should be considered representative of the density of tables.

BIPV Systems

In Building-integrated Photovoltaics (BIPV) installations, the ground occupation doesn't make much sense: for example, a façade will have a null ground area.

Results in the Report

The GCR mentioned in the report may be different according to the situation (system, bifacial, etc.).
But don't worry: this is just an indicator; the GCR value is not used as such in the simulation.