CW-25E UAV Rubidium Optical Pump Aeromagnetic System Project Case


On June 16, the 2nd Geological System Geographic Information Industry (UAV Photogrammetry) Vocational Skills Competition was grandly opened in Rizhao City, Shandong Province, China. JOUAV, as a technical support unit, participated in this event.

the 2nd Geological System Geographic Information Industry Vocational Skills Competition

Unmanned aeromagnetic data collection

Recently, China Lanzhou Institute of Resources and Environment Technology and JOUAV, and other companies completed the unmanned aeromagnetic data acquisition project. It is verified that the CW-25E rubidium optically pumped aeromagnetic system meets the requirements of the corresponding technical specifications and can be used for geological survey and ore prediction.

Technical route

CW-25E rubidium optically pumped aeromagnetic system, using CW-25E UAV as a flight platform, integrates chip-level rubidium optically pumped magnetometer, high-precision fluxgate three-component magnetometer, GPS signal receiving system, laser altimeter, nine-axis attitude sensor, and barometric altimeter. It has real-time and post-flight aeromagnetic compensation technology for fixed-wing aircraft.

JOUAV series vertical take-off and landing(VTOL) fixed-wing UAV, the flight control can automatically realize the four-sided aeromagnetic maneuvering of the fixed-wing UAV, which is crucial to calculating aeromagnetic compensation parameters. At the same time, the system can be equipped with a 42-megapixel orthophoto aerial survey camera, which can acquire high-precision geomagnetic data while simultaneously collecting high-resolution orthophoto data, which is convenient for later data analysis. It greatly simplifies aerial geophysical exploration, improves the degree of automation and accuracy of the results, and achieves the goals of shortening the measurement period and reducing costs. It becomes a high-precision, high-efficiency, stable, and reliable aerial geophysical tool.

Fieldwork

Field Delivery Ceremony of CW-25E Rubidium Optically Pumped Aeromagnetic System

Aeromagnetic compensation of CW-25E rubidium optically pumped aeromagnetic system:
At an altitude of at least 800 meters above the ground, make fixed-point maneuvers in the four directions of 0°, 90°, 180°, and 270° to record aeromagnetic data records, as shown in the figure below. Enter the maneuvering lead distance of 400 meters to ensure that the aircraft state is stable, and the maneuvering operation is carried out in each flight direction with three pitches (maneuver angle ±5°), three rolls (maneuver angle ±10°) and three yaws (maneuver angle) ±5°) maneuver. The action cycle is 4 seconds, and the action interval is 1 second. The software calculates the corresponding aeromagnetic compensation parameters and evaluates the aeromagnetic compensation results. After the aeromagnetic compensation result meets the requirements, it will be collected by flying along the designed survey line until all survey lines are completed, and the single flight test is over.

Schematic diagram of aeromagnetic compensation trajectory
Schematic diagram of aeromagnetic compensation trajectory, data profile before and after optical pump compensation, and fluxgate

CW-25E rubidium optically pumped aeromagnetic system aeromagnetic survey line data collection:

CW-25E rubidium optically pumped aeromagnetic system for aeromagnetic data collection. A total of 2 sorties were carried out, four side maneuvers, cross lines, and 29 survey lines were completed. The flight survey lines were completed from west to east. Among them, L101-L129 were the main survey lines, and T1001-T1004 were the control lines.

Aeromagnetic survey flight path map
Note: All results pictures are released according to requirements with hidden coordinates

 

Project completion

The area of the survey area is estimated to be about 30 square kilometers. The survey scale is planned and designed according to the demand at 1:20000, the route interval is designed to be 200m, the length of the main survey line is estimated to be 150km, and the length of the control line is estimated to be 24km. The total effective route is about 180km. The total flight length is about 240km, and it is flown at a safe altitude of 2 sorties. The altitude range is about 170m, and the maximum is not more than 200m. The flying speed is 20 meters per second, and the sampling speed is 10 Hz.

Static noise data curve of optical pump magnetometer
Static noise data curve of optical pump magnetometer
Static ground noise: 0.0091nT (comply with the first-class noise level calculated according to 8.3.1 specifications).

 

Dynamic noise data curve of optical pump magnetometer in the air
Dynamic noise data curve of optical pump magnetometer in the air
Dynamic noise of the survey line in the air: 0.07nT (the survey line L101, according to standard 8.3.2, is the first-class noise level).

Aeromagnetic survey repeat line check and compare magnetic anomaly curve

Aeromagnetic survey repeat line check and compare magnetic anomaly curve1
Aeromagnetic survey repeat line check and compare magnetic anomaly curve

Total aeromagnetic accuracy:

The number of intersections between the cutting line and the survey line: 232, the aeromagnetic data is calculated after various corrections. The calculation method of the total accuracy before aeromagnetic leveling adopts the total mean square deviation σ of the magnetic field difference at the intersection of the cutting line and the survey line is 0.1nT.

Data mapping

After the flight compensation, the survey line and the tie line data are imported into the database. After daily correction, IGRF correction, the tie line is leveled into a magnetic field grid map as follows (all results maps are released as required to retain the scale and hide the coordinates):

polarization abnormality
The following are the plan view before compensation, after compensation, after leveling, and polarization abnormality.

It can be seen from the above figure that the plane anomaly map before compensation is striped, which is a typical aeromagnetic anomaly feature. But better than the previous aeromagnetic data, the stripe shape is improved after compensation. After simple leveling, the linear stripe disappears, which can be used as a basic image for anomaly interpretation.

The final result of aeromagnetic surveying polar anomaly plan
All the results are published in accordance with the requirement to retain the proportion and blow out the coordinate

In conclusion

The CW-25E rubidium optically pumped aeromagnetic system complies with the national standard "Aeronautical Magnetic Survey Technical Specification DZ/T0142-2010" quality requirements. It can provide practical information and interpretation results for mineral resources survey and evaluation, marine geological survey, engineering geology, environmental survey, basic geology, and research.

From software communication to hardware integration, the aeromagnetic measurement system is deeply integrated into the CW-25E flight platform, providing industry users with a one-stop solution for aeromagnetic and aerial surveys.