This process contains four steps: 

1. Providing GCPs 
   
2. Marking GCPs
   
3. Reviewing Accuracy
   
4. Generating the Model

Starting the Process

When the model finishes pre-processing, and you have selected an option where it requires GCPs to be marked, your timeline will show the date of your flight with "Pending GCP Marking" underneath:

Step 1: Providing Ground Control Points

1. If this is your first flight or an additional flight
   
2. If it is an additional flight, and whether your GCPs are the same as the prior flights. 

For first flights or flights with new GCPs: Upload your GCPs.

Drag and drop your new file into the grey box below or click on "Select GCPs" to open your file explorer, where you can select the correct file to upload.

Tip: Use our File Template to save your GCPs in the correct format before uploading. 

For additional flights where your GCPs did not change: 

There will be an option to use the same GCPs from previous flights. 

Tip: If you have multiple previous flights, you can select which one to reference for consistent marking. This will serve as a guide for where your GCPs have historically been marked as you are marking them for your new flight.

Either click on one of the GCPs on your left-side list, or click one on the map to begin marking. 

Step 2: Marking Ground Control Points 

1. Center of Screen: The image you are marking
   
2. Top Right of Screen: Alternative images
   
3. Bottom Right of Screen: A view of the previous model, where you can zoom in on the previous GCP location
   

1. Use the buttons at the bottom of your screen: 
   

1. Use your arrow keys on your keyboard for quicker movement: 
   
1. Up arrow key = previous GCP
   
2. Down arrow key = next GCP
   
3. Left arrow key = previous image of the same GCP
   
4. Right arrow key = next image of the same GCP
   

1. Mark 5 images per GCP. Marking additional images will not increase accuracy. 
   
2. Mark photos where: 
   
1. The GCP is within the central 80% area of the photo, not on the edges. 
   
2. The GCP is seen straight down, not at an angle. 
   
3. The GCP is not covered or obscured. 
   
4. The GCP is clear, not blurry. 
   

1. Red Flag: If a GCP is destroyed or needs correction, mark it as a red flag. This will turn your GCP red on your map, and it will not be used in model generation.

         

1. Mark a GCP as a Checkpoint: These will not be used in the alignment of the model as it is being generated. Instead, it is used as a reference point after the model generates to correct any leftover alignment discrepancies. You will only need a few if it is decided to leverage checkpoints. For a model size of this example, one or none will suffice. 
   
1. You can mark a GCP as a checkpoint on the image as you are reviewing the GCP (as seen below): 
2. Or you can mark them on your list, when looking at all possible GCPs:
   

 

1. The GCP will turn blue on your map.
   

           

1. Additional Colors: 
   
1. Orange = marked GCP, used in the model generation
   

                      

1. Black = Unused/Unmarked
   

                     

1. Removing Marks
   
1. If a mistake is made when marking, you can remove a mark from an image:
   

1. You can also remove all marks from a GCP on your menu of GCPs, by clicking on the three dots next to your GCP:
   

           

1. GCPs in a Local Coordinate System
   
1. If you are working in a site that was established in a local coordinate system, it is possible your GCPs will be offset from your image pathway when you first upload them: 
   

                

1. Zoom into your map to find a GCP target. 
   
2. Use the GCP Moving Tool to align the black GCP mark as close as possible to the target.     
   

                 

1. Mark a few GCPs, evenly disbursed across the model. 
   
2. Check accuracy - Once this is done, it will keep the GCPs in the newly aligned area. 
   
3. Continue marking.

When you exit out of the GCP Wizard, your timeline will also show you the progress. 

Reviewing and Updating your GCP Markings

When DatuBIM has finished calculating the initial accuracy, it will say "Pending GCP Marking" on your timeline again. Click on it once more to open the GCP Wizard, which will now provide you with the residuals and any warnings. Well-marked GCPs should have residuals of ~0.1 ft (3 cm) or less. 

In this case, our residuals are significantly over 1/10th of a foot. If you see residuals this high, check the following: 

1. Click on the GCPs with the highest Diff to review the markings you made. 
   
1. It is possible there was more than one GCP in a photo, and the incorrect one was marked. 
   
2. It is possible that an image was unintentionally marked, due to an accidental click. 
   

Additional Accuracy Check

Once you review the above: 

1. If you have adjusted your markings, you will have the option to "revalidate accuracy". 
   
2. Even if you made no adjustments, you will have the "Improve and revalidate accuracy" button available here. This button will check a combination of several parameters and use the best one to improve accuracy of the markings.
   

Selecting "Improve and Revalidate Accuracy" is the most helpful next step, regardless of whether adjustments to your markings were made. 

DatuBIM will now work in the background to improve and revalidate the accuracy of your GCP markings and you can close the window, as it worked with the initial accuracy calculation.

   

After improving and revalidating accuracy, your residuals should look similar to the following. There are still two GCPs that have a difference above 1/10th of a foot, but still within a safe difference to generate your model accurately. 

Step 4: Generating the Model

Now that your GCPs are marked accurately, click "Generate Model" to begin the final step in the process. 

DatuBIM will provide you with a pop-up to confirm you are ready to generate the model. 

Once you select "Yes", you will see that model generation has started. You can close this window and continue your work. 

Model Generation time depends on image count and processing complexity. 

1. This could be used to supplement when GCPs are too far apart or destroyed. 
   
2. After the first flight, which was completed and geo-referenced with ground control points, Monuments can also be used in lieu of GCPs.