Through use of a model-based solution, the SPAR 300 computes an estimated 3-D coordinate (horizontal and vertical position which is tied to the project survey control) on targeted underground utilities and qualifies each discrete observation with a derived “accuracy” metric that is based on the apparent circularity of the observed magnetic field.
A computed RMS (root-mean-square) between the fitted model solution and the observed magnetic field provides the reported SPAR 300 “accuracies” which are categorized as “VA, VB, VC, VD and VE”. Note: these are simply arbitrary measures of data confidence based on empirical methods and are not to be confused with Subsurface Utility Engineering (SUE) Standard (CI/ASCE 38-02) quality levels A-D which are professionally judged reliability designations.