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. 2023 Oct 11;11:e16101. doi: 10.7717/peerj.16101

Figure 2. Schematic diagram of the PVC square and ground control points (GCP) used in the photogrammetric surveys.

Figure 2

The 1 m × 1 m PVC square was placed around a target colony prior to survey (top-down view, A). The PVC square featured two 1 m vertical extensions on opposite sides (side view, B). Colored electrical tape was added to the corners and vertical extensions of the PVC square, to provide additional GCPs for reconstruction. A PVC triangle and a color board equipped with a 12-inch ruler were also used as GCPs for each survey (triangle and square shown in A). Together, these GCPs provided consistent reference points to improve model alignment, orientation and scaling during photogrammetric reconstruction.