In some projects, the following error message may show up:
RMS is short for "Residual Means Square" and is an estimate of the error that each point has after being extracted and correlated by the software. RMS is shown in pixel values and usually indicates how much a point on the ground is different than its location in the image. Larger values indicate more errors in the project and will lead to problems in the output products. Therefore, the software looks at the RMS values and stops the process if the values are higher than 25 pixels to prevent incorrect results.
There could be several reasons for high RMS values in a project:
- Ground elevation values are incorrect. The software uses ground elevation above sea level to trys and “anchor” the model and if these values are grossly incorrect it could result in high RMS. Check your input data and modify the reference elevation (see "Appendix E - Editing Z values" in the OneButton user manual).
- Images have little or no connections – the algorithm relies on correlation between images and in certain projects where the overlap between images is low these connections could be very hard to find. You can try to change some parameters to increase the number of connections for your project. To change a parameter, press the "Edit" button in the OneButton main window and then select the "Advanced Processing" tab. In this tab, you can change one of the following parameters:
- "Number of neighbouring images to consider for matching" - The software looks at adjacent images and in projects with high overlap or inconsistent overlap the adjacent images may only represent part of the images which need to be matched. Raise the value of this parameter to increase the number of adjacent images that need to be matched. NOTE: A higher value may result in longer process times.
- "Uniqueness of features in images" - Certain projects (such as wheat fields, for example) may not have enough unique features to help the software correlate between the images. In these cases, you can lower the value of this parameter to try and extract more features in the images.
- "Relative Elevation Variance" - Projects that have rapidly changing ground elevation (such as mountainous areas) or sharp changes in the elevation of objects above grounds (such as dense urban areas) may cause the software to not correlate adjacent images. In these cases, you can raise the value of this parameter so that more points in the images are correlated and the overall error is reduced.
- If the above parameters have not improved the results you can upgrade to our OneButton Professional software which allows you to manually add points between images.
- Sensor angle is above 70 degrees from nadir. Our software currently supports angles up to 70 degrees but we are planning to have support for all angles in our next major release.
- Sensor rotation angles were defined incorrectly - if you are loading a GPS file please verify that the column names are defined correctly. The software expects the GPS file to have the columns arranged in the following order:
- Image Name
If you did not arrange the columns in this order follow these steps to change the columns:
- Right click on the column and select the “assign column as” option and then the correct column name.
- Repeat this step for every column that you need to change.
- If you are not sure about the rotation angle definitions we recommend that you "clear" the definition for these columns:
- Right click on the column
- Select the “Clear column assignment” option