TOPOGRAPHIC SURVEYS AT GREAT SCALE IN LITTLE TIME THANKS TO AUTONOMOUS VEHICLE WINGQUAD 3.
Topography has been a science of measuring our land that has evolved in its techniques and methods over time. As the well-known French geographer P. Merli mentions, the topography “was born at the same time as private property”, so the need to measure more or less extensive regions has led to the development of new technologies that cover a greater surface area in surveys and thus be able to obtain quality results in less time and with cost savings.
Part of this new technology is drones, which with the help of GNSS (Global Navigation Satellite System) allows us to generate highly accurate large-scale results. WingQuad 5 can lift to 500 hectares per flight, and allows incorporating RTK - PPK systems that will allow us to obtain accurate and reliable information.
As an example, we have the case of a property located in the canton Esmeraldas, province of Esmeraldas belonging to a public institution in Ecuador. The property has an estimated area of 160 ha. Its main problem is to clarify the extensions of the land to verify that the property belongs to the said institution and subsequently carry out participatory projects for the benefit of the population.
EQUIPMENT USED: To perform the topographic survey of 160 ha. The WingQuad 3 drone was used, which due to its high flight capabilities and advanced GNSS navigation systems was defined as the right equipment for the project.
The survey was divided into 2 phases, the field phase where all the information gathering was carried out and the office phase where the information processing and generation of results and topographic plans were carried out, which are detailed below:
a) Field Phase.- The field phase lasted 3 days between June 20, 21 and 22, 2019, where the implementation of control points, construction of monumental type B landmarks, and the execution of the flight were executed. Visual recognition of the study area was carried out to observe aspects such as the shape of the terrain, the relief, accessibility to the study area, climatic conditions, among others. A site analysis was performed for the placement of the 6 control points in the field through the use of a double frequency precision GPS according to the fast static and static method. After that, the construction planning of 6 milestones with type B documentation established by the Military Geographic Institute was carried out.
- The implementation of fast static points as photogrammetric support points was carried out through the use of a double frequency precision GPS according to the fast static and static method and placement of canvases or objects visible from the air, which will serve as support points to perform photogrammetric processing with high positional accuracy, and achieve a correct reconstruction of the information.
-The limit of the study area was established, as it will serve as the basis for the respective flight planning. - Execution of flight plans with the UAVenture AirRails planning software, software that allows 2D and 3D planning. And finally the execution of the flight with WingQuad 5. Due to the characteristics of the terrain, two flight areas were established to maintain a similar GSD (Ground Sample Distance) in the data collection
Flight Plan: AirRails software
The survey of 6 geographical landmarks with type B milestones known as the “GPS” was carried out, these points were raised with a GNSS equipment referred to the UTM coordinate system, ITRF08 horizontal datum, SIRGAS vertical datum, GRS80 ellipsoid, Reference time 2016.4 , 5 more points were determined as photogrammetric support known as “GCP”.
“GCP” Ground Control Points
Results of the lifting of control points or photogrammetric support points.- The information processing was performed by entering geo-located images, each with its coordinate in x, y and z (longitude, latitude, and height), referring to the reference system SIRGAS, WGS94, zone 17 north.
- A 3D point cloud was obtained in .LAS format.
- An Ortomosaic was generated in Geo TIFF format with a GSD (Ground Sample Distance) of 4.43 cm/pixel.
- The DSM or Digital Surface Model in Geo TIFF format was generated with a GSD (Ground Sample Distance) of 4.43 cm/pixel.
- The DTM or Digital Terrain Model in Geo TIFF format was generated with a GSD (Ground Sample Distance) of 22.14 cm/pixel.
- Equidistant contour lines at 1 m were generated. in .SHP and .DXF format.
- The information processing in the PIX4D Mapper software allowed us to determine the level of confidence in the reconstruction of the information, obtaining a percentage of 97% of the calibrated images, with an average reprojection error of 0.18 - Georeferenced plans were generated at 1: 1,000 scale in digital format. DWG