This article was provided by Lei, a colleague of the webmaster, edited by xiaokcehui
The full English name of the Moving Vessel Profiler (MVP) is the Moving Vessel Profiler. As a geophysical measurement, the speed of sound is obtained through temperature, conductivity and salinity, and the sound speed is corrected for acoustic equipment.
The navigating thermo-saline deep profile system has become one of the important methods in the field of obtaining sea temperature, conductivity, salinity and other elements, and calculating the speed of sound through the profile system to correct the sound velocity of multiple beams. The navigational thermohaline depth profile measuring instrument is a measuring instrument that can quickly and conveniently measure the conductivity and temperature profile of seawater. It provides a quick way to obtain thermohaline profile data for marine survey, scientific research, and military applications. There are mature navigational thermohaline profile measuring instruments abroad, which are widely used in marine scientific investigation and military marine environmental protection. In the beginning of the 21st century, my country started the development of the navigational temperature conductivity profiler, and imported navigational temperature and salt depth profile measuring instruments were used in marine surveys.
Winch system composition: The
winch system is mainly composed of 3 parts, namely the indoor control part, the winch, and the fish tow.
Experimental procedure:
Three tests were conducted on June 20, 2020, with fixed depths of 100, 500 and 1000m.
Among them, the 100-meter test retracted normally, and the winch failed during the 500-meter and 1,000-meter tests, which triggered the "topping alarm", causing the cable to stop. The manufacturer explained that it may be that the winch beacon system is too sensitive and triggered when the towed fish is up and down due to sea conditions.
Summary of other issues:
1. The winch recycling cable is not neat
2. The take-up speed is too low in the automatic state, 18m/min
3. The swing of the pulley at the end of the winch is too large
4. The winch arm is not tightly connected to the base and will swing
The above problems have been received by the manufacturers and they said they will make improvements. Our field team will no longer conduct winch experiments in the future.
Data accuracy:
In order to analyze the accuracy of sound speed data such as MVP winch, XCTD sound speed measurement was performed at the same time as the winch test.
This winch test obtained a total of 100m and 500m two sets of data, and the 1000m test failed to obtain data due to a winch failure. The sound velocity data obtained from the 500m test of the MVP winch is compared and analyzed with the xctd sound velocity of the same period. The difference in sound velocity is mostly about 0.5, the average difference is 0.8, and the maximum difference is 4. Among them, more than 95% have a difference of less than 2.5. According to this difference in sound velocity, the impact on the sounding accuracy at a depth of 6000 meters is about an order of magnitude lower than the 1% water depth required by the specification. From this indicator See the data is available.
However, according to the second-level standard of sound velocity accuracy in the "Marine Survey Specification Part V": the absolute error of sound velocity does not exceed ±0.75, only 65% of the data of this MVP sound velocity meets this requirement. Since both MVP and XCTD are sound speeds calculated by empirical formulas, the error standard is increased to 2 times that is ±1.5. Under this standard, 84% of the data in this test meets the requirements. From this index, it is considered MVP The sound velocity data is credible.
Considering comprehensively, it is believed that the sound speed data of the MVP winch is not bad, and there is a chance to compare it with the measured profile in the future.
Extended reading:
"The Application of MVP to Multi-beam Sound Velocity Correction in Comprehensive Commissioning" Chai Yongping
This article analyzes the accuracy of MVP sound velocity through multi-beam intra-coincidence accuracy
in conclusion:
Through the above comparison and analysis, the sound velocity profile data output by MVP is highly reliable, and the data correction of multi-beam sounding can meet the accuracy requirements of sound velocity correction, and the application effect is good in practice. Compared with the sound velocity profiler and the thermo-salt depth detector to collect sound velocity, the boat needs to be moored, and the MVP profile measurement can collect the profile data of different depths according to different speeds, which is useful for saving time and cost or when the boat is not suitable for mooring in sensitive sea areas. Compared with the XBT/XCTD disposable thermohaline deep profile system, it has the characteristics of high cost, poor stability, low accuracy and sensitivity, and it can ensure measurement accuracy and save economic costs.
"Handling the navigational ocean multi-parameter profile measurement system_Omit_VP_Method of temperature and conductivity hysteresis effect_Ren Qiang"
in conclusion:
MVP is a new oceanographic survey technology. Based on the salinity spikes that appear at the hypercline, on the basis of the F method, the GM method and the Grose method, a method is proposed to eliminate the inconsistency of the response time of the temperature sensor and the conductivity sensor. The MCT method for producing salinity spikes. Compared with other methods, the MCT method has certain advantages in the correction of MVP data in offshore China, which minimizes the salinity spike phenomenon at the thermohaline layer, and shows the temperature and salinity of the whole water layer in detail. structure. Comparing the MVP salinity data before and after the correction with the SBE-9 CTD salinity data, the result is that the salinity data of the two are basically consistent, and the accuracy of the data after the correction is higher. Comparing the data from the 35°N section, it is found that the low salinity phenomenon in the corrected procline area disappeared. The high-level spatial resolution data provided by MVP can do more in-depth research on the fine structure of ocean phenomena, which is of great significance to the study of regional oceans and fronts.
Some pictures cannot be uploaded, please pay attention to xiaok marine surveying and mapping network and the public account of the same name