Performing orthophoto plans of 7000 ha area of Saatli district and for the topographic planing in the area, the contract concluded between Client and The CASPIAN GEOMATICS scientific research and engineering company on January 29th 2018.
Investigation area in Saatli district where is located in an empty and flat area near by Moscow canal. The area is 7000 hectares. The relief of the area is flat, there are not an infrastructure and communication facilities, buildings and other situational elements on the site project. The vegetation consists of small shrubs.
Purpose of project.
The main objective of the project was to provide Geoinformation services on the site project. The issues raised include the following:
- Carrying out the topographic survey and mapping.
- Supplying the satellite data based on Earth Remote Sensing.
- Developing orthophoto map with 0.5 meter resolution based on satellite data.
- Performing topographic survey via a drone (aerophoto shooting).
- Conducting aerophotography, developing orthophotomaps with 3.5 cm resolution.
- Cameral processing and analysis of results etc.
Modern geodesic tools and geographic information systems (GIS) software have been utilized to achieve the ultimate goal.
The geoinformational works carried out on the project site was fulfilled by professional staff. In processing of Remote Sensing data, in creation of orthophoto plans, in carrying out operations on GIS, CASPIAN GEOMATICS has a professional team in implementation of Geodesy works as well.
Methodology of project.
Initially, the project area was explored based on aerospace data and it was decided that, start topographic planning of the area in the first stage and then provide remote sensing data for 7,000 hectares of the area, prepare the orthophoto plans with 0.5 m resolution across the entire project site based on these data as well.
The second stage of the issue was the planning via a drone of 2000 ha of the project area. On the basis of these aerial photography, it is planned to prepare orthophoto plans with 3.5 cm resolution.
In order to solve the above-mentioned issues, initially the visual inspection was carried out to the investigation area, specific areas have been identified as well. Later photogrammetric reference points were fastened in different areas of the project area to organize photogrammetric works. The coordinates and heights of those photogrammetric reference points were determined by the GPS receiver. And then, flight planning for Aerophoto planning works and implementation issues with its accuracy were considered (figure 1). After that, obtained aerophoto maps processed photogrammetry and processing results were mapped.
Photogrammetric reference points.
To ensure the accuracy of the products to be obtained during the photogrammetric processing and in order to their management, 9 photogrammetric reference points were fastened in the project area. The size of sides of these points are 50*50 cm and its surface consists of painted wooden boards. Their coordinates and elevation indicators were obtained by measuring real-time in kinematic mode using the Altus NR2 GNSS receiver. AzPOS service has joined for this purpose.The accuracy of obtained coordinate and height values during measurement was 2-3 cm.
Figure 1. Flight planning scheme via drone in 2000 ha area
Besides, 4 GNSS base station points were used as photogrammetric reference points to provide PUA with high precision coordinates during flight (figure 2). The measurements were performed in the UTM-39 \ WGS-84 coordinate system and EGM-2008 the geometric model in the orthometric altitude system.
Figure 2. Fastened photogrammetric reference points on the area of 2000 ha
Flight sensor is equipped with GNSS receiver and high-quality photo camera that allows measuring in kinematic mode. Since the area was large, the flight operation consisted of 4 parts. Each flight lasted for two hours and thirty-forty minutes and the flight height was approximately 270 m. Static mode measurements were performed with GNSS receiver during each point of the flight at known coordinates and altitude points at the same time to provide high precision coordinates for coordinates of the photo pictures during flight. Later, both receiver of flight sensor and as well as the collected GNSS observation information at the base station’s receiver was processed together with photographs. External orientation settings of pictures (x,y,h, Omeqa, Fi, Kappa) are set and they were added as meta information form to the picture files. The accuracy of the calculated coordinates and altitudes was 2-3 cm. Finally, as a result of aerophoto planning, about more than 14,000 photographs were obtained on all the area. Aerial photos were taken with 3.5 cm resolution quality (figure 3).
Aerial photos were processed, establishment and optimization of Aerotriangulation model has been resolved by photogrammetric reference points (figure 4). After the optimisation, the 3D surface model was established based on pictures, model are stored in such as points cloud and rastr, las and BigGeoTIF formats. Model has been set with 10 cm interval, Aerial photos have been ortho-transformation and mosaic, the orthophoto with 3.5 cm resolution was processed and maintained in “MrSID” format (figure 5-6).
Figure 3. Fragment from the aerial photo (2000 ha)
Figure 4. Optimised aerothrygulation block
Figure 5. 3D model and Cloud Points
Figure 6. The orthophoto plan with 3.5 cm resolution of 2000 ha area
After the work completion, in full of remote sensing data has been obtained of 2000 ha area and the orthophoto plans were prepared with 0.5 m resolution. During the preparation of orthophoto plans, the entire site was re-examined. Analyses were carried out in the laboratory based on satellite data for GCP (geodetic control points) points. As a result of the analysis, 10 GCP were identified on the project area (7,000 hectares). High-precision GPS equipment was used to determine coordinates and altitudes of those points in the area.
Despite the cold season and bad weather conditions during the work, topographer has been able to determine GCP points. Under laboratory conditions, the orthometric heights of the obtained data were determined and orthophoto plans were prepared for 7000 ha. Ellipsoidal and orthometric indicators of GCP points were specified.
So, the issues raised have been solved within the framework of the project of “ performing the project of orthophoto plans and carrying out the topographic planning of 7000 ha area in Saatli District”. So that, the following issues have been solved using modern geoinformation systems:
- Topographic planning works were carried out on the project site.
- The satellite data of 7000 ha area were obtained based on Earth Remote Sensing and on their basis, orthophoto plans have been processed with 0.5 m resolution covering the entire project area.
- GCP points have been determined by our specialists for the purpose of processing orthophoto plans with 0.5 m resolution and coordinates and altitude values of those control points in the field were measured by survey equipments.
- As a result of geodetic works, obtained ellipsoidal values and orthometric height values were calculated.
- Aerial photos of 2000 ha of the project area were carried out via the drone and as a result orthophoto plans with a 3.5 cm resolution were developed.
- Photogrammetric reference points for high-level photogrammetry work in 2000 hectares have been strengthened.
- Surface models based on aerial photos were created and points of cloud of the area was prepared.
- Results have been processed under laboratory conditions and the optimized aerotriangulation blocks have been constructed.
NOTE: A 27- page report has been prepared in related to the entire work done within the framework of the project. Models, maps, methodology and so on information have been more likely reflected in the report.
All rights reserved. https://caspiangeomatics.com/