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| To calculate FormU, perform the RMS of col 5 from the tmp80b output from [[get80.sh]]. So the equation will be of the form SQRT( [SUM( (col 5)^2 )] / (number of rows in tmp80b) ). Probably the easiest way to do this is to change tmp80b into a csv file and open it in Apple Numbers or Microsoft Excel, but the method doesn't matter. | To calculate FormU, perform the RMS of col 5 from the tmp80b output from [[get80]]. So the equation will be of the form SQRT( [SUM( (col 5)^2 )] / (number of rows in tmp80b) ). Probably the easiest way to do this is to change tmp80b into a csv file and open it in Apple Numbers or Microsoft Excel, but the method doesn't matter. |
FormU
FormU is so far the best way to reduce the uncertainty of an SPC model to a single number. It combines the pointing and overlap uncertainties from RESIDUALS.TXT that are extracted by get80.
Typically you will get FormU from the maplets with the best GSD, but sometimes it is worthwhile to calculate it for all maplets. Part of the Class B certification for the OSIRIS-REx mission was to determine FormU during various stages of shape model (i.e. global DTM) generation of testing model Shape 3. We found FormU was always within a factor of 2 of the actual error. The actual error of an SPC model is usually never known, but in this case we had a digital truth model for comparison (Weirich et al., 2022). This sort of testing was never performed for a regional DTM, but from a theoretical perspective there's no reason this factor of 2 relation wouldn't apply to a regional DTM.
To calculate FormU, perform the RMS of col 5 from the tmp80b output from get80. So the equation will be of the form SQRT( [SUM( (col 5)^2 )] / (number of rows in tmp80b) ). Probably the easiest way to do this is to change tmp80b into a csv file and open it in Apple Numbers or Microsoft Excel, but the method doesn't matter.
(Compiled by JRW)