The Total Error Dialog appears beside the 3D Process Dialog during Global Optimization (i.e. it does not appear when orientation-only processing is done) or during Camera Calibration. The dialog shows a set of vertical bars where each bar shows the accumulated error within the 3D model in one iteration. A new vertical bar is added to the Total Error Dialog for every iteration of the global optimization solution. The bars should get shorter as processing proceeds (which shows reducing error in the model). See also Final Total Error.
The error values shown in this dialog are technically referred to as the ‘standard error of unit weight’ or the ‘a posteriori sigma0’. These values are unit-less and combine information from image residuals, camera parameter residuals, edge residuals, constraint residuals and control point residuals. If there are no control points, no constraints and calibration is not being done these values reflect closely the total weighted residual error in the photo markings.
If the bars get bigger instead of smaller or if there are more than ten vertical bars of the same height, then PhotoModeler is having trouble solving. A few bigger bars are generally OK as long as the bars start to get smaller. If the bars do not get smaller then the processing is failing. In this case PhotoModeler will eventually give up on the processing and tell you that the processing has failed. You can also click the "Quit..." button on the 3D Process Dialog to stop the processing early if you wish.
The Total Error Dialog will usually show two sets of bars separated by a gray area. The first set corresponds to the first Optimization phase and the second set of bars to the second Optimization and Camera Optimization phase. Sometimes the first vertical bar in the second set will be larger than the last bar in first set. This is normal and it does not mean that PhotoModeler is having trouble with the adjustment.
If the automatic high residual point removal feature is turned on (See Preferences - Processing and Cameras), the second set of bars at right may include a single green bar. This indicates that PhotoModeler has made changes to the project with the unreferencing of a high residual point. The Project Status Report will explain the change by indicating the point id and the photo on which the unreference occurred.
If the processing fails, no 3D model will result (or if previously solved there will be no change) and you will need to fix the problems. See the section called When processing fails or 3D results look bad for information on how to fix these problems.
You can think of the Total Error Dialog as the pulse of your project. While the most important thing is that the bars gets smaller as processing proceeds, one can get useful information by studying the shape of the error chart. The following examples show Total Error Dialog results for various types of projects along with hints of what is right or wrong:
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Successful two stage processing. Most projects that are set up well will have error dialogs that look like this. After the initial orientation only small optimizations are needed. |
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Successful two stage processing of a strong project that has probably been processed before (there is not much room for improvement). |
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Successful two stage processing where the initial orientation was good but not perfect. The optimizer was able to produce a good solution in the first stage and the second stage was used as a check. |
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Successful one stage processing where the initial orientation was ok but not perfect. The optimizer was able to produce a good solution in the first stage. A second stage was not run due to insufficient extra data or no camera optimization. |
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Somewhat successful one stage processing where the initial orientation was weak. While the processing might have succeeded the final error is quite high (7.6, when good values are under 1.0). A model might have resulted from the processing but it is suspect. Look for referencing errors or camera parameters problems. |
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Most processing failures will look something like this. You might see small decreases in the error bars or they may be all similar height. The error values will also be high. This implies some inconsistency in the project (perhaps a misreferenced point or camera parameters that are not quite correct). |
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The green bar indicates that the automatic high residual point removal feature (See Preferences - Processing and Cameras) made a change to the project. The Project Status Report will explain the changes by indicating the point id and the photo on which the unreference occurred. |
