Design and implementation of marine survey and measurement monitoring system based on Beidou satellite

0 Introduction
At present, all survey and measurement ships that perform marine survey and measurement tasks are operated in a single-point mode. The basic functions of each survey and measurement ship are survey sampling, data collection, and initial processing and storage of samples and data. After the ship returns to the shore station processing center, the data is processed into information products and released. It cannot transmit data in real time with shore stations, other ships or marine observation means, etc., and has shortcomings such as long product release cycle and slow data update. According to the current status and operation mode of survey and measurement equipment of survey and measurement ships, this system builds hardware platforms in the monitoring center and measurement terminals respectively, develops special measurement and control software, and uses the data communication function of the Beidou system to transmit data and command interaction between the monitoring center and the measurement terminal, that is, the measurement status data collected by each measurement terminal is transmitted to the monitoring center in real time as required. The monitoring center processes and analyzes the received data in real time, and can issue control commands to each measurement terminal according to the task requirements to guide and monitor the measurement process of each measurement terminal, thereby forming a distributed measurement operation mode in which multiple measurement ships perform measurements simultaneously under the centralized control of the monitoring center, so as to improve the quality of measurement data and the efficiency of measurement operations.

1 Overall design
Beidou satellite is a satellite communication, navigation and positioning system with independent intellectual property rights in China, and its signal coverage covers the territory of China and surrounding areas. Beidou satellite system has three functions: navigation and positioning, short message communication and precise timing. It can provide satellite navigation information and short message transmission services around the clock and in all weather conditions. It can provide positioning and data communication services for road transportation, railway transportation, offshore operations, hydrology, meteorology and other fields in China and surrounding areas.
This system mainly consists of two parts: monitoring center and monitoring terminal. In the development of this scheme, the general technology of Beidou user terminal is inherited, and the user terminal is divided into six units: antenna, RF channel, baseband digital signal processing, data processing, power module and structure. At the same time, in view of the specific application requirements of distributed marine survey and measurement, it is necessary to develop application software and embedded data acquisition instrument of the monitoring center to optimize data acquisition and subpackaging. The overall design of the system is shown in Figure 1.

The monitoring center is used to receive the collected data reported by the data collectors of each monitoring terminal, and classify, analyze, organize and back up the data through the upper application software; at the same time, it needs to monitor the positioning, communication and other information of each monitoring terminal, and have command and dispatch functions such as broadcast transmission, tracking the selected target on the electronic chart, trajectory playback, roll call positioning, and electronic compass navigation.
The embedded data collector should have a high-resolution color screen, large fonts, and high brightness to facilitate operators to observe the data collection work and the working status of the equipment intuitively; at the same time, it has an embedded WinCE operating system and has dual input methods of buttons and touch screen, making the operation simple and easy to use. The embedded data collector is used in conjunction with the Beidou user terminal. The collector has multiple serial ports and can be connected to different devices at the same time for data collection. The collected data is sent to the monitoring center through the Beidou user terminal.
Beidou monitoring and data collection for ships requires that the Beidou user terminal has the characteristics of waterproof, corrosion-resistant, and strong salt spray resistance. At the same time, it can be connected to high-precision GPS to send the positioning results, speed, heading and other collected information to the monitoring center through the Beidou link.
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0 Introduction
At present, all survey and measurement ships that perform marine survey and measurement tasks are operated in a single-point mode. The basic functions of each survey and measurement ship are survey sampling, data collection, and initial processing and storage of samples and data. After the ship returns to the shore station processing center, the data is processed into information products and released. It cannot transmit data in real time with shore stations, other ships or marine observation means, etc., and has shortcomings such as long product release cycle and slow data update. According to the current status and operation mode of the survey and measurement equipment of the survey and measurement ship, this system builds hardware platforms in the monitoring center and measurement terminal respectively, develops special measurement and control software, and uses the data communication function of the Beidou system to transmit data and command interaction between the monitoring center and the measurement terminal, that is, the measurement status data collected by each measurement terminal is transmitted to the monitoring center in real time as required. The monitoring center processes and analyzes the received data in real time, and can issue control commands to each measurement terminal according to the task requirements to guide and monitor the measurement process of each measurement terminal, thereby forming a distributed measurement operation mode in which multiple measurement ships perform measurements simultaneously under the centralized control of the monitoring center, so as to improve the quality of measurement data and the efficiency of measurement operations.

1 Overall design
Beidou satellite is a satellite communication, navigation and positioning system with independent intellectual property rights in China, and its signal coverage covers the territory of China and surrounding areas. The Beidou satellite system has three functions: navigation and positioning, short message communication, and precise timing. It can provide satellite navigation information and short message transmission services around the clock, and can provide positioning and data communication services for road transportation, railway transportation, offshore operations, hydrology, meteorology and other fields in China and surrounding areas.
This system mainly consists of two parts: the monitoring center and the monitoring terminal. In the development of this solution, the general technology of Beidou user terminal is inherited, and the user terminal is divided into six units: antenna, radio frequency channel, baseband digital signal processing, data processing, power module and structure. At the same time, in view of the specific application requirements of distributed marine survey and measurement, it is necessary to develop the application software and embedded data acquisition instrument of the monitoring center to optimize data acquisition and subpackaging. The overall design of the system is shown in Figure 1.

The monitoring center is used to receive the collected data reported by the data collectors of each monitoring terminal, and classify, analyze, organize and back up the data through the upper application software; at the same time, it needs to monitor the positioning, communication and other information of each monitoring terminal, and has the command and dispatch functions such as broadcast transmission, tracking the selected target on the electronic chart, trajectory playback, roll call positioning, and electronic compass navigation.
The embedded data collector should have a high-resolution color screen, large fonts, and high brightness to facilitate operators to observe the data collection work and the working status of the equipment intuitively; at the same time, it has an embedded WinCE operating system and has dual input methods of buttons and touch screens, making the operation simple and easy to use. The embedded data collector is used in conjunction with the Beidou user terminal. The collector has multiple serial ports and can be connected to different devices at the same time for data collection. The collected data is sent to the monitoring center through the Beidou user terminal.
Beidou monitoring and data collection for ships requires that the Beidou user terminal has the characteristics of waterproof, corrosion-resistant, and strong salt spray resistance. At the same time, it can be connected to high-precision GPS to send the positioning results, speed, heading and other collected information to the monitoring center through the Beidou link.

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2.2.1 Hardware unit
The display screen of the embedded data acquisition instrument adopts a 640×480 high-resolution color screen, large fonts, high brightness, and a simple and easy-to-use operation interface; it supports more than 3 serial ports, has an embedded WinCE operating system, and has dual input methods of buttons and touch screen.
The Beidou-1 communication terminal is an integrated user terminal developed and manufactured based on the use characteristics of various unattended data acquisition stations while retaining all the functions of the Beidou ordinary user terminal. In addition to retaining the Beidou positioning, communication and other functions, the core unit inside the host is integrated, which greatly reduces the size of the whole machine. At the same time, the equipment is encapsulated with a special shell, which is suitable for harsh working environments such as high salt fog, high humidity and heat. At the same time, the standby power consumption is further reduced to meet the needs of long-term work.
2.2.2 Software unit The
embedded platform data acquisition software is loaded on remote devices such as vehicle-mounted or data acquisition instruments to realize GPS location reporting; realize the sub-packaging of collected data, and automatically report the sub-packets to the command terminal according to the maximum processing capacity of the Beidou equipment; realize Beidou positioning; and detect and display the status of Beidou equipment in real time. The embedded platform data acquisition software uses Windows CE embedded operating system, and the interface operation should be intuitive and friendly.
The embedded platform data acquisition software adopts object-oriented software design and implementation methods. It is divided into three levels vertically: serial port data processing and parsing layer, data processing layer and application layer. Each level contains several small sub-modules. The overall design diagram of the software is shown in Figure 5.

The description of each sub-function module is as follows:
(1) Serial port driver module. Receives data from GPS receivers and collectors, uses redundant design to eliminate erroneous data, and has concurrent data processing capabilities.
(2) Data collection processing. Receives data collected from the collector, automatically packages the collected data according to the long message data transmission format and the communication level of the Beidou terminal, sends it to the command terminal according to the highest transmission frequency of the Beidou terminal, receives long message control instructions from the command terminal, automatically resends and reissues the collected data packets according to the Beidou device status; receives the data collection control instructions from the command terminal, and realizes the reporting of command terminal number changes, setting the collection data reporting method and frequency, and other collection controls.
(3) GPS data processing. Processes the GPS data submitted by the serial port driver module, packages the GPS positioning data according to the GPS data transmission format, and sends the GPS data when it meets the service frequency of the Beidou terminal.
(4) Device status module. Displays the user card information of the Beidou terminal, and monitors and displays the device status of the Beidou terminal in real time.
(5) Information storage. Realizes real-time storage of large-capacity collected data to facilitate subsequent collection information processing.
2.2.3 Main functions of embedded data acquisition instrument
(1) Data acquisition. Collect data from weather stations, high-precision GPS, etc., and forward them to the marine environment monitoring center through the Beidou link; equipped with display screen and buttons, can monitor the working status of connected equipment and can operate and control Beidou equipment; can display the working status of Beidou equipment in real time; can display the working status of data acquisition and transmission in real time.
(2) Basic functions of Beidou. Possess positioning and short message communication functions; have map roaming and display, SMS management, track playback and other functions.
(3) Information management function. All information should have corresponding automatic management and backup functions; have the function of classifying, counting and querying all stored historical data.

3 Conclusion
The system has initially realized the various functions of the monitoring center and monitoring terminal, but due to the current limited communication length of "Beidou", the use of "Beidou" to transmit massive data and fully realize the real-time transmission of various measurement data still needs further development of the "Beidou" navigation system to further improve the distributed marine survey and measurement system.