GCPs Have High Error Values

[dronedrone]

Hello,

I am attempting to build a model with GCPs using the workflow suggested by SAV (https://www.agisoft.com/forum/index.php?topic=7851.0). I linked the GCP markers (associated with RTK GPS points) to drone photographs and unchecked all of the cameras in the reference pane before building a dense cloud. However, Agisoft Metashape calculated quite large errors for some of these linked markers (please see the screenshot attached). After building a dense cloud, I loaded a shapefile containing my rtk gps GCP points into Metashape and found that some of the points, like Pt_2 shown in the screenshot, did not have the exact same (or similar) altitude value. For instance, after Metashape built a dense cloud, it placed my Pt_2 marker ~7 m below the altitude that I specified the marker as having in the Reference Pane. Can someone please help me figure out how to reduce the error associated with the altitude values of my GCP markers?

Thank you!

[JasonR]

Are your targets unique in the sense that you didn't accidentally pick the wrong one when marking them? Are you optimizing your cameras with the GCPs selected? Those are some common errors to check.

[Alexey Pasumansky]

Hello egross,

Are you observing any high projection errors (in pixels) for any of markers? Also is this table shown before or after optimization operation, and if it is after the optimization, which coefficients have been adjusted?

[dronedrone]

Hello JasonR and Alexey,

Thanks for your replies!

Are your targets unique in the sense that you didn't accidentally pick the wrong one when marking them? Are you optimizing your cameras with the GCPs selected? Those are some common errors to check.

I double checked my targets and I didn't accidentally make any wrong picks necessarily. However, I must admit that while capturing the images, I did not have GCP targets placed all around the field site. Bushes and small, unique-looking rocks were essentially used as my GCP "targets". I feel that I picked these bush/rock targets quite accurately. Before posting here, I did unchecked my cameras and only selected the GCPs when I did the "Optimize cameras" option as that combo seemed to improve my accuracy.

Hello egross,

Are you observing any high projection errors (in pixels) for any of markers? Also is this table shown before or after optimization operation, and if it is after the optimization, which coefficients have been adjusted?

Please see the attached screenshot for the projection errors associated with each marker. This is my first time attempting to employ GCPs so I'm not too sure if the projection errors (in pixels) are too large. Both tables that I have attached in my forum posts associated with this topic show results after the optimization operation. For the optimization operation, I only selected "Adaptive camera model fitting" (Selecting this option grayed out all of the options listed in the General section of the Optimize Camera Alignment dialog box).

[BobvdMeij]

Assuming you've strictly followed SAV's workflow I reckon you've already done so, but just to be sure: can you please verify you've selected the correct coordinate system during import of the GCPs?