Inspection Services :: Geometric (caliper) survey A separate geometric (caliper) survey is not necessary with the Piglet system of A. Hak due to the fact that the ovality measurement is part of the standard measurements being performed. Dents or other ovalities are accurately measured and in combination with the distance such a feature can be clearly assessed. The Piglet system locates and measures the following features: Dents Wrinkles Ovality Girth welds Valves Tees Wall thickness change Change of diameter Partially closed valves And others, to give you full description of the pipeline