Portable dimensional reference for 3-D tower modeling
A portable dimensional reference (PDR) that is transportable to a tower site and deployable on site at ground level near a tower. The PDR includes a pair of target pads and multiple connecting segments, which may be attached end-to-end between the target pads. The target pads are marked with respective targets that enable photogrammetry software to identify the targets, their locations, and the distance between them with high precision, enabling the software to apply the known distance as a scale constraint for accurately scaling dimensions of imaged components of the tower.
1. A method of using one or more portable dimensional references (PDRs), the method comprising:
transporting a carrying bag to a location of a tower, the carrying bag including components of a PDR, the components including a first target pad having a first target formed thereon, a second target pad having a second target formed thereon, and a set of multiple connecting segments configured to connect end-to-end between the first target pad and the second target pad to establish a known distance between the first target and the second target;
removing the components of the PDR from the carrying bag at the location of the tower;
assembling the PDR at least in part by attaching the connecting segments of the set of connecting segments end-to-end between the first target pad and the second target pad at a location within a predetermined distance from the tower; and
performing photogrammetric measurements on the tower based at least in part on the known distance established by the PDR.
2. The method of claim 1 , wherein the PDR is a first PDR and transporting the carrying bag to the location of the tower includes transporting components of a second PDR, the components of the second PDR including a third target pad having a third target formed thereon, a fourth target pad having a fourth target formed thereon, and a second set of multiple connecting segments configured to connect end-to-end between the third target pad and the fourth target pad to establish a known distance between the third target and the fourth target.
3. The method of claim 2 , further comprising:
removing the components of the second PDR from the carrying bag;
assembling the second PDR at a second location within a predetermined distance from the tower by attaching the connecting segments of the second set of connecting segments end-to-end between the third target pad and the fourth target pad;
establishing a length reference based on photogrammetric images of the known distance between the first target and the second target;
photogrammetrically measuring, based on the length reference, a distance between the third target and the fourth target; and
alerting an operator of an error in assembling at least one of the first PDR and the second PDR responsive to detecting a mismatch between the measured distance and the known distance.
4. The method of claim 3 , wherein photogrammetrically measuring the distance between the third target and the fourth target is performed by a computer based on photographic images acquired by a camera of an unmanned aerial vehicle that flies around the tower.
5. The method of claim 1 , wherein assembling the PDR includes straightening the PDR so that the first target pad, the first set of connecting segments, and the second target pad all form a line on a common plane.