PrecisionMapper desktop app is an offline desktop tool which creates an Orthomosaic of your survey. It provides a
step-by-step approach which is used to create the various essential layers for the formation of an Orthomosaic. 

These layers are as follows.

                 1. Camera Layer

2. Sfm Layer

3. Dense Point Cloud Layer

4. Grid Point Cloud Layer

5. Mesh Layer

6. Ortho Layer

To create an orthomosaic with the help of PrecisionMapper desktop app in Advanced Mode, follow these steps.

1. Navigate to PrecisionMapper desktop app.
      Click 
Start in Advanced Mode (Figure 1).
      PrecisionMapper desktop
 will ask you to start a project in Advanced Mode. Click Ok.

Figure 1: Opening PrecisionMapper Desktop in Advanced Mode


2. In File menu, click New Project.
      
Provide appropriate details like project name, location and click OK (Figure and Figure 3).

Figure 2: Creating a new project



Figure 3: Selecting a project name and location


3. Click Add Photos and select survey images (Figure 4).

Figure 4: Selecting survey images


4. If your survey is carried out with multispectral sensor, then click Manage Multiband Calibration to calibrate multispectral bands. 

Otherwise, click OK to confirm your selected survey images and continue with next steps (Figure 5).

Figure 5: Confirming Survey Images



Note: While adding a survey, the survey images must be provided with their GPS data. 

GPS data consists of parameters like latitude, longitude, and altitude.
Depending upon the type of your drone, your survey images may possess inbuilt GPS data or it might be available in a separate file.
If no GPS data is detected, you need to import a separate GPS file (.dat or .csv format file) available in your respective survey folder.

5. In the absence of inbuilt GPS parameters, click Import GPS and select GPS parameters file
      (
telemetry file for PrecisionHawk drones) (Figure 6
).

Figure 6: Selecting GPS parameter file (telemetry for PrecisionHawk drones)

6. Adjust the GPS table (Figure 7).

   6.1 In Table Formatting section,
          i. Select the checkbox if the GPS file possesses a header.
         ii. 
Select column separator as White Space or comma depending upon your GPS file type.

    6.2 In Position Input section,
          i. Select the column numbers as per respective GPS values.
             (For example, as per your 
telemetry file table, if the Latitude is present in the 4th column,
             then select 
4 in Latitude starting from Column drop-down box. Similarly, select respective column
             numbers for 
Longitude and Vertical).


Figure 7: Adjusting GPS values



7. To add ground control points (if available), in Batch Setup sidebar, click 2.Add Control Points (Figure 8).


 Generating Camera Layer

8. After adding GCPs, click 3. Start Aligning Photos (Figure 8).

Figure 8: Batch Setup Sidebar


 
Generating SFM Layer

9. In Batch Options dialog box, enter following processing details and click OK (Figure 9),
      Maximum features to use per photos = 40000
      Preferred feature Size Range = 4 to 100
      GPS matching radius (Meters= 50           
      RANSAC threshold (Pixels) = 12

Figure 9: Entering recommended values in Batch options dialog box



Note: Following three steps are involved while aligning photos.

                          1. Feature Detection (Figure 10)
                          2. Feature Matching (Figure 11)
                          3. Sfm (Structure From Motion) (Figure 12)
                          All of the above three steps are auto-processed and you can view their status below
                          the Thumbnail window.



Figure 10: Step 1 – Feature Detection in progress



Figure 11: Step 2 – Feature Matching in progress



Figure 12: Step 3 – Sfm in progress



10. If you find the scene to be satisfactory, click Go To Next Step.
          Enter GCP entries (if available) and click Next (Figure 13).

Figure 13: Absence of GCPs



11. In Bundle Adjustment dialog box, keep the parameters at their default values and click OK.


 Generating Dense Point Cloud Layer

12. Click Generate Dense Point Cloud.
         In Dense Point Cloud Dialog box, select dense point cloud layer resolution level as 2 = Medium Resolution.
         Keep the remaining parameters at their default values and click Ok (Figure 14).

Figure 14: Selecting Dense point cloud resolution


Note: Following two steps are involved in the generation of Dense Point layer.

                   1. Undistort Images (Figure 15)
                   2. Dense Points (Figure 16)
                   Both the above steps are auto-processed and you can view their status below the Thumbnail window.

Figure 15: Generating Dense Point Cloud layer - Step 1 (Undistorted Images in progress)




Figure 16: Generating Dense Point Cloud layer - Step 2 (Dense Points in progress)





 Generating Grid Point Cloud Layer

13. After generating Dense Point Cloud layer, click Generate Grid Point Cloud.
         In Grid Resample Dialog box, click OK (Keep the Cell size parameter to its default value which is 1 meter)
         (Figure 17).

Figure 17: Default value for generating Grid Point Cloud layer



 Generating Mesh Layer

14. Click Generate Mesh and in Mesh Dialog box, keep the parameters to their default values and click OK
         (Figure 18).

Figure 18: Default values for generating the Mesh layer



 Generating Orthomosaic Layer

15. Click Generate Orthos and in Orthos Dialog box, enter details as follows (Figure 19).

     Output Pixels size/GSD (meters) = Median value

     Photo Blend Distance (meters) = 2

                 Down sample = Original Resolution

Figure 19: Selecting values in Orthos dialog box


Note: Following three steps are involved in the generation of an Orthomosaic layer.

                  1. Orthos (Figure 20)
                  2. Combine Orthos (Figure 21)
                  3. Stitching camera overlap mosaic (Figure 22)
                  All of the above steps are auto-processed. You can view their status below the Thumbnail window.


16. After completion of Step 3, the orthomosaic will get stored in the results folder of your survey folder
          (Figure 23 and Figure 24).

Figure 23: Generated Orthomosaic in results folder



Figure 24: Generated Orthomosaic




Generating A DSM (Height map) layer 


You can create a Digital Surface Model (DSM) that is a height map using
DataMapper Local.-Advanced Mode. In order to create this, make sure that you have
successfully created the Final Mesh layer and follow the steps mentioned below.


1. Select the Final Mesh layer checkbox from the Files pane located at the right side (Figure 25).


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Figure 25: Selecting Final Mesh layer checkbox


2. Click Layer. In Mesh, click Export As Height Map (Figure 26).


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Figure 26: Selecting Export As Height Map



3. Provide name and save the file. The file will be saved in .TIF format.


4. Select appropriate Ground Resolution value and Click OK (Figure 27).

     

Note_symbol.pngNote: Select Resolution value as the Median Value (Refer Figure 19 for knowing the Median Value).


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Figure 27: Selecting height map resolution



5. Once the DSM file is generated you can quickly view it in 2D View tab located at the
      top of the Display pane.


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Figure 28: DSM [Darkest spot indicates Deepest region of the survey area]


Note_symbol.pngNote: For any further analysis, you can view this DSM output in other GIS software like,
                 QGIS, ArcGIS and so on. All you need to do is access the .TIF file with the GIS software.