Today we would like to continue articles about experience of using the DJI PHANTOM 4PRO RTK PPK to build a high-precision three-dimensional model of urban area.

May 21-24, Topodrone specialists together with Finnish company Tasamitta Oy ( carried out a pilot project on aerial survey of the territory of the city of Joensuu in Finland.

Before aerial survey we measured ground control points (road marking, and other object well recognized on images) across the entire area

The measurements were carried out by a two-frequency Javad GNSS receiver from the NTRIP TRIMNET network in RTK mode.



The aerial survey itself did not take much time. It was enough one standard DJI battery to cover an area by double grid routs. Usually a modified Phantom 4PRO is able to fly 21 minutes + 20% of the energy reserve for save returning home and landing.


REACH RS GNSS receiver was used as the base station for flights, This equipment proved to be a reliable and easy to use tool providing sufficient accuracy for postprocessing.

After aerial photography and post-processing of GNSS measurements, the obtained coordinates of the photos centers were imported into EXIF tags using the Toposetter application. Thus, we replaced the navigation coordinates, defined by the «civil» GPS module of the drone, with high-precision ones, which subsequently greatly simplified the process of creating a project for photogrammetric data processing and building a digital terrain model.

Pic.2. toposetter


To process data in Photoscan or Pix4D software, it is enough to upload images to the project, set the accuracy of the coordinates of the images to 1 cm and start the automatic processing (photos alignment and dense cloud generation).

The accuracy of the model was verified by previously measured control points not participated in the alignment process (Table 1).




X/Longitude Y/Latitude Z/Altitude X_error Y_error Z_error
1 29.750268 62.594423 78.626 -0.076576 -0.051925


2 29.751747 62.593955 78.908 -0.035505 -0.053669



29.751656 62.593974 78.915 -0.032421 -0.089987 0.045332
4 29.750855 62.595417 81.68 0.062724 -0.020427



29.751278 62.595409 82.11 -0.041076 -0.073572 0.040098
6 29.751299 62.595422 82.061 -0.012024 0.003381


TOTAL RMS 0.04 0.05



After the automatic classification of the points cloud, a high precision & detailed digital terrain model and orthomosaic were created.

Pic.4. 3D-model


Pic.5. Classified points cloud. Brown color — terrain


Pic.6. DEM


Pic.5. Orthomosaic


The results of the project show the real possibilities of using DJI Phantom 4RPO RTK PPK upgraded by Topodrone team for UAV survey. The system provides a set of high accurate data which can be automatically turned to high-precision and detailed three-dimensional terrain model without need to lay ground control points.

With our advanced and low cost drone technology you can survey large areas of land more accurately and faster than conventional survey techniques, providing clients with contours and digital elevation models with rapid turnaround.

Our UAVs equipped with a high-precision GNSS receiver make it possible to automatically obtain 3D model of the territory with centimeter level accuracy and can provide you with much-needed details regarding the landscape and surrounding areas. This cuts down on equipment and manpower costs.

The resulting points cloud in its detail and accuracy corresponds to UAV LIDAR data. Algorithms of data classification provide recognition of terrain, trees, buildings, construction and other technological objects.

Our UAV products allows to obtain data for mapping and GIS up to scale of 1: 500  of a built-up area and have the following advantages over expensive UAV and LIDAR systems

  • Easy to use
  • No need in field work to measure GCP, save your time
  • High accuracy for low price
  • Save money by upgrading of your existing DJI Phantom 4PRO or ADV

Stay tuned about new project and products…

DJI Mavic PRO PPK RTK why not?

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