# GCR with vertical or dual axis trackers

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When you have an array of vertical single axis trackers or an array of dual axis trackers, how do you calculate the GCR? See two examples below.

Example 1: 4x arrays of dual axis trackers, each with 15m pitch E-W and 0m pitch N-S

Example 2: 4x arrays of dual axis trackers, each with 15m pitch E-W and 10m pitch N-S

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For the report GCR:

When you are using arrays such as in your scene: if I am not mistaken the GCR is computed as the ratio table width / pitch of the array, and then an average is done between arrays. In principle your scenes should have a different GCR (higher for the first one).

Note for two axis trackers: by default the EW pitch is taken into account. If the EW pitch is zero the NS pitch is taken into account. This is not always accurate, it is mostly meant to give an approximate value.

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I understand that, with unlimited sheds, or unlimited trackers, the GCR is the width/pitch, because the only gap is between each rows. But with heliostat systems (with a rotating table on a vertical axis or on dual axis), there are gaps in two directions (NS pitch, EW pitch), so I was wondering how we could compute the GCR for those systems.

I'm asking because I find the GCR to be a good indicator of the use of the land. For instance, we might have vertical axis trackers that are more effective than horizontal one, but if the space they occupy in order to avoid mutual shadings is too big, the question remains if it's really worth it -> which is where I find the GCR to be a good indicator for land occupation, but not sure how to estimate it when we have a pitch in two directions.

... after some thinking, I believe an appropriate answer for the GCR/land occupation indicator in this situation could be:   (Coll. Width * Coll. Length) / (NS pitch * EW pitch)

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Yeah that seems a good notion of GCR.! I will file a ticket to assess this change 🙂