At present, each survey and measurement vessel carrying out marine survey and measurement tasks operates in a single point mode independently. The basic functions of each survey and measurement vessel are survey sampling, data collection, and initial processing and storage of samples and data. After the vessel returns to the shore station processing center, the data is processed into information products and published. It cannot transmit real-time data to the shore station, other vessels, or marine observation methods, and there are shortcomings such as long product release cycles and slow data updates. This system builds hardware platforms and develops specialized measurement and control software in the monitoring center and measurement terminals based on the current status and operation modes of survey and measurement equipment. It utilizes the data communication function of the BeiDou system to transmit data and exchange instructions between the monitoring center and measurement terminals. The measurement status data collected by each measurement terminal is transmitted in real-time to the monitoring center as required. The monitoring center processes and analyzes the received data in real-time, and can issue control instructions to each measurement terminal according to task requirements to guide and monitor the measurement process of each measurement terminal. This forms a distributed measurement operation mode where multiple measurement ships are simultaneously controlled by the monitoring center, achieving the goal of improving the quality of measurement data and the efficiency of measurement operations.

1. Overall scheme design

Beidou Satellite is a satellite communication navigation and positioning system with independent intellectual property rights in China. The signal coverage range of 3500-92 136180-01 covers China’s territory and surrounding areas. The Beidou satellite system combines three major functions: navigation positioning, short message communication, and precise timing. It can provide satellite navigation information and short message transmission services 24/7, and can provide positioning and data communication services for road transportation, railway transportation, maritime operations, hydrology, meteorology, and other fields in China and surrounding areas.

This system mainly consists of two parts: a monitoring center and a monitoring terminal. In the development of this plan, inheriting the common technology of Beidou user computers, the user computers are divided into six major units: antenna, RF channel, baseband digital signal processing, data processing, power module, and structure. At the same time, in response to the specific application requirements of distributed ocean survey and measurement, it is necessary to develop application software and embedded data acquisition instruments for monitoring centers, and optimize data collection and subcontracting. The overall system design is shown in Figure 1.

Overall system design

The monitoring center is used to receive the collected data reported by the data acquisition devices of various monitoring terminals, and to classify, analyze, organize, and backup the data through upper layer application software; At the same time, it is necessary to monitor the positioning and communication information of each monitoring terminal, and have command and scheduling functions such as broadcast transmission, tracking selected targets on electronic charts, trajectory playback, roll call positioning, and electronic compass navigation.

The embedded data acquisition device should have a high-resolution color screen, large font, and high brightness to facilitate operators to visually observe the data collection work and equipment working status; At the same time, it is embedded with the WinCE operating system, which has a dual input mode of buttons and touch screen, making the operation simple and easy to use. The embedded data acquisition device is used in conjunction with the BeiDou user computer. The acquisition device has multiple serial ports and can simultaneously connect different devices for data acquisition. The collected data is sent to the monitoring center through the BeiDou user computer.

Ship Beidou monitoring and data acquisition require that the Beidou user machine has the characteristics of waterproofing, corrosion resistance, and strong salt spray resistance. At the same time, it can be connected to high-precision GPS and send positioning results, speed, heading and other collected information to the monitoring center through the Beidou link.

2 Key Technologies

2.1 Monitoring Center Design

The survey and measurement monitoring center adopts the Beidou-1 command type user machine, 3500-92 136180-01. This product can simultaneously receive signals from three Beidou satellites and six beams. The IC card is easy to disassemble and install, and has practical functions such as tracking selected targets on electronic charts, trajectory playback, roll call positioning, and electronic compass navigation. The operating interface is beautiful, simple, and easy to use. When the battery is out of charge, the AC adapter can be used directly to work, and its environmental adaptability meets the requirements for outdoor use. This product can be installed in two ways, as shown in Figure 2.

Two installation methods

2.1.1 Hardware Unit

This product adopts the “one line communication” design principle, and the antenna is connected to the host using a coaxial cable, making installation more reliable and convenient. The front of the host is equipped with a Samsung six beam indicator light, which is convenient for monitoring the working status of the user’s computer system. The whole machine is designed with a height of 1U, and can be installed in a standard 19 inch cabinet after towing.

2.1.2 Software Unit

The PC platform data collection software is loaded into the monitoring center to receive and process communication data from multiple remote devices, enabling data collection and control of remote devices. It can recognize and process the Beidou and GPS positions reported by remote devices, and achieve monitoring and command terminal device status and other functions. The PC platform data collection software adopts N-TIER layered architecture design, object-oriented software design and implementation methods. At the vertical architecture level, software systems provide three major layers: hardware parsing layer, data processing layer, and application layer. At each major level, there are several small levels of abstraction, implication, implementation, and encapsulation. This design minimizes the coupling of the software and has high reliability, maintainability, and upgradability. The overall design diagram of the software is shown in Figure 3.

The overall design diagram of the software

From top to bottom, it can be divided into the following functional modules:

(1) Collect data processing module. Capable of receiving BeiDou communication messages sent by remote devices, real-time processing and temporary storage of received collection data, real-time display of message reception status, automatic control of remote devices to resend lost data collection messages, and splicing received messages in the format of long message data exchange. After receiving correct and complete data collection, it is stored in the information storage module through an interactive interface for post collection data analysis.

(2) Beidou positioning module. Capable of receiving and processing all BeiDou positioning information requested by remote devices, and can be stored in the information storage module through interactive interfaces for subsequent analysis of positioning system applications such as positioning accuracy, usability, and applicability between BeiDou and GPS data.

(3) GPS data module. Capable of receiving and processing all GPS information reported by remote devices, and able to store it in an information storage module through an interactive interface for subsequent analysis of positioning system applications such as accuracy, usability, and applicability of BeiDou and GPS data.

(4) Device status module. Display the Beidou card information of the command terminal, monitor and display the equipment status of the command terminal in real time.

(5) Data storage module. Store and manage Beidou positioning, GPS positioning, and data collection, and can be exported to TXT or Excel format files according to user needs.