Electricity Tower Surveying
The Israeli Electric Company needed to survey a quad pod electricity tower and draft a 3D CAD plan with accuracy better than 2cm (0.05ft).
The estimated effort, using conventional surveying techniques, was 3 days:
- 2 field days using both prism and prism-less Total Station devices.
- 1 day office day to draft the detailed CAD plan, based on the Total Station measurements and a sketch done in the field.
The tower was photographed using a regular Sony NEX-7 camera (24-megapixel resolution) with a 16mm wide-angle lens, mounted on a small quadcopter that flew at 35 – 45 meters (120 to 150ft) above ground.
A total of 31 images of the tower were captured, from the perimeter around the tower toward its center, with an image taken about every 15 meters (50 feet).
Acquiring Ground Control Points
A total of 27 points were measured on the electricity tower and around it, using a prism-less Total Station device. 10 of these points were used as control points for geo-referencing the images.
The chosen control points were high-contrast, well-defined objects, such as corners of the tower, devices mounted on it, etc.
DatuSurvey™ Professional (formerly DatGram™3D) Savings
The actual time to survey and draft a 3D CAD model of the electricity tower was less than 1 day:
- 40 minutes in the field: 10 minutes to photoshoot the electricity tower, and additional 30 minutes to measure control points around it.
- 4 office hours to geo-reference the images and draft the 3D CAD model of the electricity tower directly on the images.
A 3D CAD model, in DXF format, was generated by drafting directly on the images, using the DatuSurveyTM Professional (formerly DatuGramTM3D) photogrammetry software.
A list of all measured points, in PNT format, was generated. This included point names, codes, descriptions, coordinates, and their measurement accuracies in all axes.
373 new measurements were made using the images. The measurement accuracy of all points was better than 2cm (0.05 ft.) in both position and elevation.