I am following a workflow given by Aerotas to process data collected by a Phantom4 RTK with D-RTK2 Base station. Can anyone explain to me how to create dummy GCPs in Pix4D and apply a consistent XYZ offset to all of them. I have attached a pdf of the instructions given by Aerotas. The relevant section is Align with GCPs
Phantom 4 RTK Full Workflow.pdf (371.3 KB)
Also is there any other way to shift the computed data to align with the single GCP measured data. What I’m trying to do is apply a offset to the whole data in xyz direction.
I haven’t found a way to apply an offset to multiple GCPs in Mapper. My workaround is as follows: Create your GCPs in Mapper. Open the GCP window and export your GCPs. Import them into excel and add / subtract your offsets from the appropriate column(s). Save as .csv. Import the GCPs back into Mapper. When it asks if you want to overwrite the data of points with the same name, choose yes. I hope I understood your question and that this helps. Let me know if I completely missed it.
Thanks for the suggestion. I think this could work. Although how do I create GCPS in Mapper? Is it the same as Manual Tie Points?
Hi @survey3
You can create a .csv or .txt file with the names and coordinates of the GCPs. The format of this file should be as follows:
Later you can import this file in PIX4Dmapper, following these instructions: How to add / import GCPs in the GCP/MTP Manager
This is not the only way to add CGPs to a project. For more information, also see the following link: How to add / import GCPs in the GCP/MTP Manager
Other links that may be useful:
Have a very nice day!
Best regards
Hi @survey3
Is it the same as Manual Tie Points?
A Manual Tie Points (MTPs) are points without known 3D coordinates that are marked (clicked) by the user in the images. They can be used to assess and improve reconstruction accuracy.
MTPs are also used in PIX4Dmapper to assist the merging of projects.
Ground control points (GCPs) are used to georeference the model. A minimum of three GCPs is required to scale, rotate and locate the model, but we recommend that each project has between 5 and 10 GCPs distributed throughout the project area. We recommend measuring more GCPs, so some can be used as checkpoints to assess the accuracy of the project. GCPs improve the relative and absolute accuracy of the model.
There is more information in the following article: Tie points in photogrammetry project (ATP, GCP, MTP, and CP)
The creation is the same. Select your targets in multiple images. AFTER you do this, you can use the dropdown menu to change them from “Manual Tie Point” to “3D GCP.” Make sure to give the point the same name (exactly) as the corresponding point in the .csv file.
If you want to convert all of your MTPs to GCPs at the same time, you can do this in the GCP/MTP Manager by selecting all of your GCPs (shift+select or ctrl+select) then right-click anywhere in the “Type” Column and select “3D GCP” from the dropdown list.
Once you have all of your MTPs converted to GCPs, select “Import GCPs” from the GCP/MTP Manager Window.
Browse to your .csv file and import it. If all of the names are identical in the .csv and in Mapper, it will give you a warning that some points have the same name and ask if you want to replace the coordinates that are currently in Mapper with the coordinates in the .csv. Select yes or yes to all. (or something like that - I don’t have anything to import right now to snip a screenshot.) This will replace the coordinates of all the GCPs simultaneously and will most likely tell you that the project can now be georeferenced and ask if you would like to proceed. Again select “Yes.”
If you have any issues, feel free to reach back out. Let me know how it goes.
