5:15 PM - 7:15 PM
[SVC32-P20] Measurement of vertical wind direction and speed distribution using UAV for highly accurate estimation of volcanic gas emission rate
Keywords:unmanned aerial vehicle; UAV, multicopter, hovering, Aircraft attitude
1. Background and purpose of this study
One method of measuring the amount of volcanic gas released is the DOAS method, which uses a compact ultraviolet spectrometer to measure the amount of sulfur dioxide released. In this method, a major issue in determining measurement accuracy is the measurement of wind speed.
Abe et al. (2025, in press) report on the results of measurements of sulfur dioxide emissions using a traverse DOAS system that has been periodically carried out on the prefectural road northeast of Mt. Hakone Owakudani since 2017. In this observation, the wind direction and speed at Owakudani estimated from Mesoanalysis data were used to calculate the amount of emissions. However, it has been reported that there will be a large error in the measurement results from 2022 onwards, when actual wind speed and direction data from the Owakudani Ropeway Station building are used. In this observation, the route traversed was approximately 0.7 to 2.3 km horizontally from the fumarole, and about 200 m in altitude. Depending on the wind direction, volcanic gas generated in the valley may diffuse beyond the ridge.The complex topography means that the wind direction and speed vary greatly depending on the location and altitude, which is thought to be the key factor contributing to the large error.
Therefore, in this study, with the aim of improving the observation accuracy of volcanic gas emissions by simply and inexpensively measuring the wind direction and wind speed at any point, altitude, and time in areas around volcanoes, we investigated methods for measuring wind direction and wind speed at multiple vertical altitudes using UAVs and methods for observing volcanic gas emissions.
2.Measurement principle and measurement method
To measure the wind direction and speed using a UAV, we used a method that takes advantage of the characteristic of a multicopter flying tilted in the direction of travel, and measures the wind direction and wind speed from the aircraft's attitude while hovering.
In this research, by using aircraft attitude data that is measured and recorded in the UAV system itself, there is no need for additional measurement equipment, and as a result, measurements can be made even with small UAVs with small payloads. In this study, we used DJI's Mavic2 Enterprese Dual and Mavic3 Thermal, which are small UAVs with a weight of less than 1kg, to measure the wind direction and speed from the aircraft attitude data stored in the flight record data.
3.Results
In order to obtain the relational expression between aircraft attitude and wind speed, a flight test was conducted using the method described below.
When a UAV flies in a windless environment, assuming that the aircraft is stationary, the assumption is that the flight direction is equal to the wind direction and the flight speed is equal to the wind speed. In order to perform the test in a windless environment, we conducted an indoor test on the relationship between flight speed and aircraft attitude.
The relationship between the inclination of the aircraft and the flight speed obtained through this test was distributed almost on a linear regression line, and the relationship ware expressed by the following equation.
Y = 0.563 X ( R2 =0.963)
Using the relational expression between wind speed and aircraft attitude obtained above, wind speed was measured by UAV. Measurements were carried out from 14:00 to 15:00 on February 12, 2025, and the wind direction and wind speed were measured by hovering for 5 minutes each at six altitudes: 5, 15, 25, 35, 45, and 55 meters above the ground. The wind direction and wind speed were averaged at each two adjacent altitudes to calculate the 10-minute average wind direction and wind speed at 5 altitudes: 10, 20, 30, 40, and 50 meters.
One method of measuring the amount of volcanic gas released is the DOAS method, which uses a compact ultraviolet spectrometer to measure the amount of sulfur dioxide released. In this method, a major issue in determining measurement accuracy is the measurement of wind speed.
Abe et al. (2025, in press) report on the results of measurements of sulfur dioxide emissions using a traverse DOAS system that has been periodically carried out on the prefectural road northeast of Mt. Hakone Owakudani since 2017. In this observation, the wind direction and speed at Owakudani estimated from Mesoanalysis data were used to calculate the amount of emissions. However, it has been reported that there will be a large error in the measurement results from 2022 onwards, when actual wind speed and direction data from the Owakudani Ropeway Station building are used. In this observation, the route traversed was approximately 0.7 to 2.3 km horizontally from the fumarole, and about 200 m in altitude. Depending on the wind direction, volcanic gas generated in the valley may diffuse beyond the ridge.The complex topography means that the wind direction and speed vary greatly depending on the location and altitude, which is thought to be the key factor contributing to the large error.
Therefore, in this study, with the aim of improving the observation accuracy of volcanic gas emissions by simply and inexpensively measuring the wind direction and wind speed at any point, altitude, and time in areas around volcanoes, we investigated methods for measuring wind direction and wind speed at multiple vertical altitudes using UAVs and methods for observing volcanic gas emissions.
2.Measurement principle and measurement method
To measure the wind direction and speed using a UAV, we used a method that takes advantage of the characteristic of a multicopter flying tilted in the direction of travel, and measures the wind direction and wind speed from the aircraft's attitude while hovering.
In this research, by using aircraft attitude data that is measured and recorded in the UAV system itself, there is no need for additional measurement equipment, and as a result, measurements can be made even with small UAVs with small payloads. In this study, we used DJI's Mavic2 Enterprese Dual and Mavic3 Thermal, which are small UAVs with a weight of less than 1kg, to measure the wind direction and speed from the aircraft attitude data stored in the flight record data.
3.Results
In order to obtain the relational expression between aircraft attitude and wind speed, a flight test was conducted using the method described below.
When a UAV flies in a windless environment, assuming that the aircraft is stationary, the assumption is that the flight direction is equal to the wind direction and the flight speed is equal to the wind speed. In order to perform the test in a windless environment, we conducted an indoor test on the relationship between flight speed and aircraft attitude.
The relationship between the inclination of the aircraft and the flight speed obtained through this test was distributed almost on a linear regression line, and the relationship ware expressed by the following equation.
Y = 0.563 X ( R2 =0.963)
Using the relational expression between wind speed and aircraft attitude obtained above, wind speed was measured by UAV. Measurements were carried out from 14:00 to 15:00 on February 12, 2025, and the wind direction and wind speed were measured by hovering for 5 minutes each at six altitudes: 5, 15, 25, 35, 45, and 55 meters above the ground. The wind direction and wind speed were averaged at each two adjacent altitudes to calculate the 10-minute average wind direction and wind speed at 5 altitudes: 10, 20, 30, 40, and 50 meters.