PPK Accuracy Evaluation of the Marlyn Cobalt Drone

PPK Accuracy Evaluation of the Marlyn Cobalt Drone

PPK Accuracy Evaluation of the Marlyn Cobalt Drone

PPK Accuracy Evaluation of the Marlyn Cobalt Drone


Thursday, March 30, 2023

The objective of this study is to verify the precision that can be obtained with the Marlyn Cobalt Drone in PPK mode, comparing the results with the ground control points (GCPs) in the generated orthophoto.

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Project Objectives

The objective of this study is to verify the precision that can be obtained with the Marlyn Cobalt Drone & PPK, comparing the results with the pre-measured check-points in the generated orthophoto.

Project Workflow and Instruments Used

GNSS Receiver

The GNSS receiver is a high-precision device used for satellite measurement and positioning. Designed with advanced technology, the receiver can receive signals from GPS, GLONAS, GALILEO and Beidou satellites, enabling it to provide accurate and reliable position even in weak signal conditions or harsh environments.

Ground Control Points (GCPs)

Ground Control Points (GCPs) are reference points that are established on the ground and are used in photogrammetry to correct for distortion that may be present in drone's images. GCPs are placed at strategic locations and measured with precise measurement equipment, such as GNSS receivers or total stations, to obtain their exact coordinates in the reference system used.

On this occasion, the GCPs will be used as check-points to check the accuracy of the orthophoto generated by the Marlyn Cobalt using its integrated Topcon PPK. The position of the GCPs measured in the field will be compared with the position of the same GCPs in the generated orthophoto, in this way it will be possible to determine how much error there is between the GCPs and what appears in the orthophoto. This information will be valuable to assess the accuracy of the drone and the photogrammetry process used to obtain the orthophoto.

Base station and GCPs
GNSS SATLAB SL700 / Ground Control Points (GCPs)

Atmos Marlyn Cobalt Drone

The Atmos Marlyn Cobalt is a fixed-wing drone used in surveying, mapping, and photogrammetry. With an aerodynamic design and an electric propulsion system, this drone is energy efficient, promising 40-50 minutes of flight time. The Marlyn Cobalt can support different sensors whether they are RGB, Multispectral or Thermal, allowing specific data to be captured and a detailed understanding of the terrain to be obtained. Capable of operating in a wide range of environments, this drone is easy to transport and assemble. With autonomous flight capability, you can follow a specific route and capture accurate data without a pilot on board.

Marlyn Cobalt surveying and mapping drone
Atmos Marlyn Cobalt Drone

SONY RX1RII Camera Sensor

The SONY RX1RII sensor is a compact, high-resolution camera was used as a component of the Atmos Marlyn drone. This sensor features a 35mm CMOS sensor with 42.4 megapixels, allowing you to capture sharp, detailed images in a wide range of light conditions.

The SONY RX1RII sensor is designed to work insurveying, mapping, and photogrammetry applications, as it features a fast f/2.0 aperture lens that allows for greater light collection and a wider depth of field. In addition, the sensor features advanced autofocus technology and manual adjustment options, allowing for greater control and customization of image capture. At the time of publication, Atmos has improved the end-of-life Sony RX1RII and replaced it with the A7RIV 61MP sensor, which offers improved area coverage and oblique imagery with a 21mm Zeiss Ventum lens. However the A7RIV is outside the scope of this study.

Marlyn mapping and surveying drone
Atmos Marlyn Cobalt Drone with Sony RX1RII Camera

Atmos Navigator (Flight Planning Software)

The Atmos Navigator is a software designed to plan and control flight missions for topography, mapping and photogrammetry applications. It offers a user-friendly user interface and allows users to create custom missions to capture accurate images. This software is an essential tool for drone mission planning and control, allowing users to efficiently and effectively obtain accurate data with the Marlyn Cobalt Drone.

Atmos Navigator
Atmos Navigator Software

Atmos Geotagger (Software)

Atmos Geotagger V2 software is a PPK georeferencing tool for images captured by Marlyn Cobalt that synchronizes and adjusts the GPS position of images to generate cm-accurate x,y,z geotags for each image. The application imports images and GPS log files from the mission, synchronizes the images with GPS position data, and geo-references each image precisely based on its position and orientation. In addition, it allows you to process large amounts of data efficiently and offers a preview of the processed images and the option to export them to other processing and analysis software programs. This is why Geotagger v2 software is a crucial tool for drone data management and for generating accurate results in surveying, mapping and photogrammetry applications.

Atmos Geotagger
Atmos Geotagger Software

Agisoft Metashape (Software)

Agisoft Metashape is a photogrammetry software used to create accurate orthophotos in surveying and mapping. The software processes digital images to create an accurate 3D model of the terrain and, from this model, generates a georeferenced orthomosaic that can be used for project planning and topographic feature analysis. In addition, the software offers tools for data processing and analysis, measurement, and report generation. Agisoft Metashape is a crucial tool in creating accurate orthophotos for surveying and mapping, with the ability to process and analyze data for detailed and accurate results.

Agisoft Metashape
Agisoft Metashape Software
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The project

In the development of this work, the first step was to select the place where the drone flight would take place. After evaluating the options, it was decided to carry out the flight in Laguna Caren, Santiago. This place was chosen because it is a large area, wide and far from the city, which would allow the drone to perform optimally, since it allows it to capture large amounts of land in a single session. With these characteristics, Laguna Caren became the perfect location to carry out the flight and obtain the necessary data for the project.

Once on the ground, the first step was to work with the GNSS instruments to capture the ground control points (GCPs) that had previously been located on site. With the technology of the GNSS receivers used, it was possible to obtain precise coordinates, with millimeter precision. For this process, the RTK modality was used, which implies the installation of a receiver as a base at a known point, and another mobile receiver to survey the control points. Thanks to the precision and reliability of this technology, it was possible to obtain a highly precise set of control points, which will later be used for the precision control of the orthophoto that we will obtain.

Subsequently, the drone was placed in a safe and stable place that would ensure a safe takeoff and landing. At this time, the workstation with the computer near the drone was established to review the safety parameters, create the flight mission and control the take off and landing of the drone, all thanks to the Atmos Navigator software.

Once the drone flight in the field is finished, the field work is concluded and the data obtained in the office is processed. The first step is to incorporate all the data captured during the flight, including the raw data from the GNSS Base receiver, the images captured by the drone and the GNSS information obtained. For this, the Atmos Geotagger V2 software is used, which allows integrating all the data obtained in a single file to carry out the process.

In the field (Chile)

Next, the image processing process begins, using the PPK (Post-Processing Kinematics) methodology to accurately geotag each captured image with respect to the known Base coordinate that we can include within the software. This process allows obtaining a precise position in the X, Y and Z system for each image, which is essential for the creation of the final model and the generation of future cartographic products.

Image processing with PPK is a technique that allows positioning errors that may arise during the flight of the drone to be corrected, thus ensuring that the images are georeferenced with high precision. This process is fundamental to achieve the necessary quality and precision in the generation of the orthophoto.

After having obtained the geotagged and corrected images, we proceed to work with the Agisoft Metashape software. In this program, we incorporate the images captured in the previous step to carry out the workflow. The first step is to orient the images so that they are correctly positioned.

Subsequently, we create the passing point cloud, which consists of a set of three-dimensional points in space that are going to be used for the creation of the dense point cloud. The latter is in charge of creating a three-dimensional model of the terrain, obtaining greater precision in its representation.

Next, we create the digital elevation model, which is a three-dimensional model that represents the elevation of the terrain. In this step, the highest and lowest areas of the terrain can be identified, allowing a better understanding of the topography of the area.

Finally, the orthophoto is generated, which is a digital model where the terrain is represented flat and corrected. This orthophoto is very useful, since it allows to extract precise and real measurements of the terrain. In this way, a more detailed analysis of the terrain characteristics can be carried out and valuable information for decision making can be obtained.

Project Results


The orthophoto is a product generated from the images captured by the Marlyn Cobalt Drone, which were precisely geotagged using the PPK methodology. This product was obtained thanks to the use of Agisoft Metashape software, and with this we were able to obtain a fully representative representation of the area of interest, which constitutes an area of 108 Ha.


Project Orthomosaic

In the product we can see the size of the GSD which is 1.3cm/px resolution at a flight height of 100 meters above the ground:

GSD Representation

Inserting the coordinates of the GCPs in the Agisoft Metashape software we can see that the difference between the coordinates of these and where the vertex of the GCP is located in the Orthophoto is 3.2 cm on average:

GCP in the software

In the following tables we can observe the error generated in the total of the 4 points and for each one of them respectively.

Number Error on X (cm) Error on Y (cm) Error on Z (cm) Error on XY (cm) Total (cm)
4 2.45612 1.08372 1.77130 2.68458 3.21628
Number Error on X (cm) Error on Y (cm) Error on Z (cm) Total (cm) Images (pix)
100 2.53248 -1.31494 -2.49093 3.78777 1.250(11)
101 2.26082 0.866184 -1.59563 2.89959 1.440(7)
102 3.24293 0.866184 -0.93669 3.46136 1.806(8)
103 1.44526 -1.27727 -1.70936 2.57723 1.610(8)
Total 2.45612 1.08372 1.7713 3.21628 1.52
Project Survey Results


After carrying out the entire work process, we can conclude that the results obtained were satisfactory. In particular, the accuracy obtained in the final product, the orthophoto, was truly excellent, achieving an accuracy of 3 centimeters when compared to the placed Ground Control Points (GCPs). This is a very remarkable result, since the area covered by the flight was 108 hectares and this precision was achieved in a record time of only 40 minutes. This clearly represents a great optimization in field worktime.

The speed of the flight is due to the fact that a fixed-wing drone was used, which gives it better aerodynamics. In addition, the quality of the images obtained was exceptional thanks to the SONY RX1RII sensor that was used. This camera is of high quality, which allowed to achieve a great resolution in the images.

It is important to note that this drone is very versatile for surveying large work areas, which makes it an ideal tool for surveying applications. In conclusion, the use of this technology allows to significantly improve the data collection process and generates accurate and reliable results, which greatly facilitates the work of professionals in the field of topography.

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