Over time, sediment accumulation at the bottom of reservoirs reduces their effective capacity, affects water quality, and limits their usability.
This can decrease irrigation efficiency, interrupt water supply, and reduce flood control capacity. Accurate mapping and regular monitoring of bottom sediments are therefore essential for planning maintenance work and preventing further deterioration.
In this project, our Swiss partner Pix4D demonstrated how modern photogrammetry can significantly improve the efficiency and accuracy of reservoir sediment surveys.
During a project carried out in Japan, the combination of aerial drone imagery and terrestrial scanning with PIX4Dcatch RTK increased measurement accuracy by 70% compared with the traditional surveying method.
Read the original Pix4D case study at the following link.
Project overview
The study was conducted at an agricultural reservoir in the mountainous area of Toyama Prefecture, Japan.
Before data collection began, the reservoir was partially drained to expose the sediment accumulation area and make precise measurements possible.
The agricultural reservoir before draining, photographed by a drone, with trees obstructing parts of the site.
Data collection methodology
The project combined aerial and terrestrial data collection methods.
- Aerial imagery provided a comprehensive top-down view of most of the site.
- Some sections remained inaccessible to the drone because of surrounding trees and limited flight access.
- PIX4Dcatch with an RTK device was used to capture these areas from the ground with high positional accuracy.
- Aerial and terrestrial image sets were processed separately and then merged in PIX4Dmatic to create a unified 3D model.
Terrestrial data captured with PIX4Dcatch RTK is shown on the left, while aerial drone imagery is shown on the right.
This combined approach provided a more complete and accurate representation of the reservoir bed than either capture method could achieve independently.
Implementation workflow
- The coordinates of ground control points were determined using the single-point measurement function in PIX4Dcatch.
- This eliminated the need to use a total station or other bulky specialized surveying equipment for point measurement.
- By attaching an RTK device to a smartphone, the operator could collect accurate terrestrial data while walking around the site.
- Data processing was completed in PIX4Dmatic, which supported rapid project setup and straightforward placement of control points.
The completed 3D model created by merging terrestrial and aerial data.
Project results
- Measurement accuracy: Sediment measurement accuracy increased by 70% compared with the traditional method involving a surveyor and conventional equipment.
- Speed: Determining ground control points with PIX4Dcatch RTK required approximately 15 minutes instead of about 8 hours using conventional tools.
- Visualization quality: The resulting 3D model provided a detailed representation of the reservoir bed’s topography and offered substantially more information than conventional 2D drawings with points and lines.
- Reporting efficiency: The digital model made it easier to share project information and helped stakeholders understand the condition of the reservoir infrastructure.
Advantages of the combined workflow
The project demonstrated several practical advantages of combining drone mapping with terrestrial RTK capture:
- Complete coverage of areas that could not be surveyed by drone alone.
- Improved accuracy through RTK-based ground measurements.
- Reduced fieldwork time.
- Lower dependence on heavy surveying equipment.
- Detailed three-dimensional visualization of sediment accumulation.
- More efficient preparation of technical reports and maintenance plans.
Conclusion
The combination of PIX4Dcatch RTK and PIX4Dmatic significantly improves reservoir monitoring by increasing measurement accuracy, reducing labor requirements, and providing complete coverage in environments where drone access is limited.
This case demonstrates that modern photogrammetry is not only an alternative to conventional surveying methods. It is also an effective tool for infrastructure assessment, maintenance planning, sediment monitoring, and the management of agricultural and environmental facilities.
Futurology is an official distributor of Pix4D software. Pix4D products are available through the Futurology dealer network in the United States. For more information, please contact info@futurology.tech.
