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My Total Error is much higher (or my precision values are different) after I upgraded PhotoModeler but my project has not changed.

*This applies to PhotoModeler Pro 5.2.3 and later versions only. Three significant changes were made in the PhotoModeler Pro 5.2.3 release in the area of post-processing statistics. These are important changes that make PhotoModeler’s output more useful, as well as to align PhotoModeler with photogrammetric standards.

For PhotoModeler users that do not use precision values or are not worried about photogrammetric subtleties , only the first change will be of interest.

The first change was to the Processing Total Error. This is the value you see in the vertical bars during processing. This value is calculated differently now and on average the total error will appear to be bigger in PM 5.2.3+ vs previous releases. The actual project accuracy or precision has not changed – just the way we compute total error. The important value for total error is now 1.0. Try to get your error under 1.0 for most projects (inverse camera projects: this will still be difficult). The smallest Total Error is still better.

In more detailed photogrammetric terms: this change has made PhotoModeler’s Total Error equivalent to the photogrammetric standard called ‘a posteriori sigma0’ (sigma-naught after adjustment) (or “total error of unit weight”). The accuracy of projects after processing does not change with 5.2.3; only the way the total accumulated error is reported changed. The new sigma0 value is not only more consistent with standards but is also now more useful feedback on project quality. Please see the section called “Final Total Error” in the 5.2.3+ help file.

The second change was to post-processing precisions. Precisions are values computed by Processing to help you estimate the precision and accuracy of the project. The precisions are now multiplied by the a posteriori sigma0 value (which is now correctly computed). This will make the precision values independent of input precision estimates. The precision values (found on object point x,y,z coordinates, camera station parameters, and camera parameters in calibration) are more useful as a result.

While we feel these changes are correct for most PhotoModeler users, some users may find the change too big. If you depend on seeing the total error the way it was prior to 5.2.3 (perhaps you have some internal procedure documentation or you depend on the value in some external program), and you also do not use the output precision values then you can switch back to the old calculation methods. To do this, open the PhotoModelerPro5.ini file in your Windows directory and in the [Process] section add or change the following two entries to: CorrectSigmaVarianceScaling=FALSE CorrectTotalErrorScaling=FALSE

The third change was to fix a problem with how post-processing precisions were rotated when a project had a Scale/Rotate set up. Starting with the 5.2.3 release the precisions are now rotated using a different method which makes them consistent and useful regardless of the project’s coordinate system.

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