Review Data

Now that all data has been downloaded, you can begin the Geotagging process. PPK geotagging combines the data streams you have collected into a cm-accurate location for each image.  

To begin, click on the ‘Geotag’ tab, which will display the screen shown.

You’ll notice that the data which has been downloaded in the previous tabs is automatically recognised here. An output is given for the number of images, PPK trigger events, and autopilot logs found within the project folder. It is advised to check that these align with your expectations. 

Post-Processed Kinematics (PPK)

Next, choose the output directory and insert the base station data into the box as shown (if not done already). For the RINEX files, ensure that you add all 3 files (xxg, xxo, xxn). Note that you can first choose the type of processing you wish to do;

  • Option 1 uses a CORS as reference, the location and antenna information will be read automatically from the RINEX observation.  
  • Option 2 uses a physical base station as reference, the location and antenna information will need to be entered manually. 
  • Option 3 computes a standalone solution.
  • Option 4 performs no PPK processing on the data, but generates a geotag based on the estimated position, this is the option you must use if the unit was purchased without an activated PPK system.  

It is worth noting that options 3 and 4 will only yield accuracies of around 2-3m for each geotag. 

In order to have most accurate results you need an accurate location for your base station, an antenna offset, and an antenna type. You can enter this data in manually using the options shown.

Output Options

Finally, choose whether you prefer to output the geotags as EXIF data within a new set of image files, or contained within a csv file. Writing to a csv file will allow the geotagging to proceed up to 10x faster depending on your PC speed, also writing to EXIF will mean that the angle and accuracy data is not included, so will be less accurate for photogrammetry! 

Marlyn’s PPK module collects all data in WGS84, however when processed with a base station, the coordinate system of the output data will be in the same coordinate system as the location of the base station.

Verify Information

Once all the data has been entered, you can verify your information in the map on the right side of the software as shown. Each PPK trigger event is mapped with a black dot, the track of the autopilot file is shown in grey, and the base station location is shown as a green point. Check that the autopilot and PPK triggers overlap and that no data is missing, and check that the location of the base station is as expected.

You will also see at the base of the map a text detailing the implications of the distance from the base station to the mapping area. Every 25km that the base station is away from the mapping area will result in around 1cm of uncertainty.

Septentrio Dongle

Before geotagging, also ensure that you have the Grey Septentrio Dongle plugged in to your PC. The Orange Septentrio dongle contains the license file which you need to extract and save to your PC the first time you use Geotagger.

Perform Geotagging

When you are ready to proceed, press ‘Geotag’. The software will then compare the data streams to create a set of image geotags, a time indication is given during this process also. 

A pop-up box at the end of processing will provide information on the quality of the processing which has been undertaken as shown below. 

Your Images have now been successfully geotagged and you can move on to photogrammetry.