Working with Ground Control Points (AT309 Week 12)

In the lab, we worked with Ground Control Points which allow the data processing to be more accurate by spreading out "anchor points" throughout the area that contains known locations. Below is my notes is how to add GCPs into Pix4D Mapper software.


 -Download data from t drive/class data and put it onto the computer's C drive or an external hard drive.

-Open the turffarmNov2 Excel CSV file, copy columns A-E and paste it into a new excel file. Save it as Simplified Data, and as a CSV type file.

 

Figure 1- Simplified Data of GCP coordinates

 

Figure 2- Showing simplified data location

-Open Pix4D, start a new project and put in images from the lawnmower- patterned scan with the Mavic.

-Once at the processing screen, hit project -> GPC manager, and import the simplified data file that we just made with the A-E

 

Figure 3- GCP/MTP manager

 

Figure 4- GCP manager with imported data

-Once you import these GCPs, they will show up as blue crosses on the processing screen.

-Start the initial processing only by checking the “initial processing” box and unchecking the “point cloud and mesh” and “DSM, orthomosiac and index” boxes, and hitting start.

-You will need to wait for the initial processing to finish before continuing on to the next step. At the end of this, you will get your initial quality report.

 

Figure 5- Initial processing progress screen

-Once that is finished, go to the ray cloud tab, open up the GCP subfolder, and edit the GCP locations in about 4-5 of the smaller windows. Hit apply every time you relocate the GCP in one of the windows because this will calibrate the rest of the windows to be more accurate. To know where the GCPs are supposed to be located, open up the Mavicpronaider_ortho file in Arcpro.

 

Figure 6- Editing GCP location

 

Figure 7- Actual GCP location in ArcPro

 

Figure 8- GCP location file for ArcPro

-Repeat this process for all of the GCPs.

-Go to the process menu and hit “reoptimize” when you are done editing the GCPs. Otherwise, the location of the GCPs will not be saved.

 

Figure 9- Reoptimize after editing GCP

-Once you have reoptimized, uncheck the “initial processing” box and check the other two boxes and hit start.

  

Figure 10- Finish processing after reoptimizing

-Once the last two processes are finished, you can obtain an updated quality report by going to the process menu and clicking the “generate quality report” option.

 

Figure 11- Generating quality report after final processing

-After obtaining the updated quality report, the “quality check” category will show you the RMS error within the “Georeferencing” line. In my case, there was 0.041m of RMS error.

 


Figure 12- Updated quality report

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