The Compute TPU command computes Horizontal TPU (HzTPU) and Depth TPU (DpTPU) values for each sounding in the observed depths.
• DpTPU: The uncertainty associated with the depth value of a sounding. It is a random error and is scaled to 95% (1.96 sigma).
• HzTPU: The uncertainty associated with the position of a sounding. It is a random error and is scaled to 95% (1.96 sigma).
The HzTPU and DpTPU values are stored line-by-line with indexing to profiles and beams. You can view these specific error values for individual soundings in the Selection window, by querying the soundings in Swath, Single Beam, or Subset Editor.
Static errors, such as motion or position uncertainty, that are used to compute TPU are read directly from the project vessel file, sonar uncertainty is computed from the sonar settings maintained in the DeviceModels.xml, and tide and sound velocity from values set in the Compute TPU dialog box.
When present, real-time sonar uncertainty computed by the acquisition system, is recognized and automatically converted into HIPS. All other dynamic errors, such as from a motion sensor, can be loaded using the Import Auxiliary Data function.