Does anybody here also experience what have happened to me. The result is somewhat odd because the result show a very curved tie points. In reality it is a relatively flat terrain.
Please check on the attached pictures as your reference. I also attached the flight path to show that this only happens when the project area is like a rectangle which the length is much greater than the width, e.g. road, rivers. It is also my second time showing this odd result. With different data sets but with same flight planning.
its hard to use the GCP because these are mostly fields. Please provide me with another solution.
Maybe the altitude is wrong in the project? Because it was aprox 140m above the takeoff level and the GPS gives numbers above the sea level - maybe thats the case?
Can you try something? Reduce the number of vertical and horizontal accuracy to 0.1 for all the images. Right-click on one cell and click on edit all accuracies. Process step 1 again.
I have also just processed a 3 mile long flat road project and had the same issue with the curving. I used all the same parameters i have used before and havent had this issue before. We are flying a phantom 4 pro V2. I have tried a few of the possible solutions from this thread and have not found a way to fix it yet. We are going to use survey GCP’s eventually. Would that fix the arcing that is being shown?
More than likely, you are experiencing the well know systematic Structure-from-Motion doming/dishing (elevation) error. Research literature attributes occurrences of this error to a) linear/parallel flight lines and b) accumulating lens calibration error. I have found that using gently curved, convergent, non-traditional (non-linear/non-parallel) flight lines does help mitigate the doming/dishing error.
Should we just always change this to .1, especially without the use of GCP’s, or if there aren’t enough photos? I have found that this works best for me since I am after only relative accuracy. So essentially reducing this to .1 tells Pix4D to process accuracy based most closely on the lat/long, even if this lat long could be off by 2-3 meters (no gcp’s), however it’s my understanding that this might at least increase relative accuracy, am I correct?
Hi @bkeane, you should not always change it to 0.1 meters. In general, we recommend to use realistic accuracy values.
However, if you see that setting the accuracy value lower helps with the project reconstruction and prevents the project from “breaking”, then fell free to do this as a workaround.
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