Use of GPS-RTK technology

This article mainly introduces the application of real-time dynamic positioning technology (GPS- RTK ) in mine surveying. GPS-RTK technology is used in mine surveying work, mainly used for mining area control point encryption, topography survey, drilling, profile point, trench, exploration well, pit, sampling hole, geological point, near well point, pit location Coordinate stakeout and measurement, engineering operation scheduling, geological mapping, etc.

1 GPS-RTK system principle and composition

111 Basic principles

The RTK measurement technology is a real-time differential GPS (RTD GPS) measurement technology based on carrier phase observation. The basic principle of real-time dynamic measurement is to place a GPS receiver on the reference station, continuously observe all visible GPS satellites, and send its observation data to the user observation station in real time through radio transmission equipment. At the user station, while receiving GPS satellite signals, the GPS receiver receives the observation data transmitted by the reference station through a radio transmission device, and then calculates and displays the three-dimensional coordinates of the user station in real time according to the principle of relative positioning. Reach the centimeter level. In this way, through the positioning results calculated in real time, the quality of the observation results of the base station and the user station and the convergence of the solution results can be monitored to write a paper, so that the success of the solution results can be determined in real time to reduce redundant observations and shorten the observation time. .

112 Composition of RTK measurement system

The RTK measurement system is mainly composed of GPS receiving equipment, data transmission system and software system.

(1) GPS receiving equipment

On the base station and the user station, set up dual-frequency GPS receivers. The dual-frequency observations not only have high accuracy, but also help to quickly and accurately solve the unknowns of the whole week. When the base station serves multiple users, the sampling rate of its receiver should be consistent with the highest user receiver adoption rate.

(2) Data transmission equipment

Data transmission equipment, also known as data link, is composed of a base station's radio transmitter station and a user station's receiver. The choice of frequency and power depends on the distance between the user station and the reference station, environmental quality, and data transmission speed.

(3) Software system

The quality and function of the software system that supports real-time dynamic measurement are decisive for ensuring the feasibility of real-time dynamic measurement, the reliability and accuracy of the measurement results. The outstanding function of this software system is to be able to quickly solve the unknowns of the whole week, and can choose fast static, quasi-dynamic, and real-time dynamic operation modes to complete the quality analysis and evaluation of the solution results in real time.

2 Operation process of GPS technology in mine survey

211 Preparation of the internal industry Before implementing the GPS field survey, the survey area should be surveyed in advance, and the preparation of the internal industry should be completed according to the characteristics of the mine survey.

The work mainly includes the following aspects:

(1) Set the project name according to the project

(2) Parameter setting: The data sampling rate of the base station is generally 4 ~ 5S, the data sampling rate of the rover station is generally 1 ~ 2S, and the height cutoff angle is usually set to 10 degrees.

(3) If the coordinate conversion parameters are known, enter the handbook.

(4) Before implementing project lofting, the industry enters the design coordinates and line azimuth of each lofting point, so that the field can be staked out in real time and accurately.

212 Find the conversion parameters of the measurement area

Mine surveys are carried out on the Beijing coordinate system or independent coordinate system, which has the problem of coordinate conversion between the WGS-84 coordinates and the Beijing coordinate system or independent coordinate system. Because RTK operations require local coordinates to be given in real time, this makes coordinate conversion very important.

(1) For larger measurement areas, determine the conversion parameters in advance, and enter the parameters and coordinates of the base station directly during RTK operation. Conversion parameters obtained by using two kinds of coordinates at the same point of the high-level control point.

(2) Conversion parameters can also be obtained temporarily during RTK operations. First set up a base station in a place with a wide view of the sky and collect single-point positioning WGS-84 coordinates. Then, the rover station jointly measures more than 3 high-level control points to solve the coordinate conversion parameters.

213 Placement of reference station

In order to ensure the accuracy of observation and improve work efficiency, the placement of the reference station should meet the following conditions.

(1) The base station can be established on a known point with precise coordinates, or on an unknown point with better conditions

(2) The base station should be located in a place with high terrain, unobstructed view and good coverage area of ​​the radio station. The first choice is the central area of ​​the survey area.

(3) In order to prevent the multipath effect and the loss of data link, there should be no interference sources such as high-voltage wires, TV turntables, radio transmitters, etc. within 200 meters of the reference station, and no GPS signal reflection sources around.

(4) The antenna of the base station radio should be erected in the north of the GPS receiver host. Because near the north and south poles is a hollow area of ​​satellites.

RTK measurement and lofting

Based on the first-level control of the survey area, a point correction method is used to solve the conversion parameters of the coordinate system, and the reference station is better viewed in Tiantong, and there are no strong electromagnetic interference sources around the base station. When the measurement area shows that there are more than 5 GPS satellites, PDOP

When the value is less than 6, it usually takes 5 to 15 seconds to complete the initialization and get a fixed solution. Only one person is required for each mobile station to carry out the measurement operation. Every time the operation is started, the known control points should be checked to ensure that the system is correct, and the GPS electronic handbook can be used to collect the terrain features, exploration pits or exploration lines For the lofting operations of profiles and exploration engineering points, the collection and recording time of each point is about 1 to 10 seconds. Real-time dynamic RTK data processing is relatively simple. The measured coordinates collected by field surveys are directly downloaded to the computer through the data transmission system of the handbook. It can be edited graphically or printed out after finishing, sorting and judging to form a file. RTK can also provide navigation data in real-time for stakeout of exploration engineering points, which not only allows you to find points quickly, but also provides positioning accuracy. For example, if you add points and survey points on the survey line, the navigation data displayed on the GPS electronic handbook can also make you go online quickly. Using GPS-RTK stakeout, no need to communicate navigation data and directions on the intercom. The GPS electronic handbook navigation screen allows you to quickly point and go online, greatly improving work efficiency and reducing the work intensity of surveyors. 3 RTK application and positioning accuracy analysis

The topography of a mining area in Xingren, Guizhou is not very undulating, the sky is wide, and it has no significant impact on RTK operations except for certain places. The engineering control survey, the exploration profile line, and the lofting of exploration engineering points all use RTK operations. Repeatedly measure the statistical table of poor coordinates of the same control point, see Table 1. The comparison of the sampling distance of the total station and the RTK measured between adjacent observation points is shown in Table 2.

Table 1 Repeated measurement of the coordinate of the same control point is poor m

Table 1 Coordinate difference of measure the same

one control point repeatedlym

Point â–³ X â–³ Y â–³ Z

GPS3 01009 01004 01004

GPS10 01007 01003 01005

N1 01012 01002 01009

N8 01005 01003 01008

N21 01010 01002 01006

N35 01004 01011 01012

Table 2 The measured distance between the total station and the RTK measured between adjacent observation points is poor m

Table 2 Differentmeasurements of electronic total staTIon

and RTK between adjacent observaTIon pointsm

Dot

Total station measurement

distance

RTK measured

distance

Poor

5 6 1101235 1101231 01004

10 11 851638 851632 01006

11 12 1651700 1651707 01008

20 21 1151657 1151649 01008

29 30 1951623 1951612 01011

From the above table, RTK measurement can not only provide point coordinates and elevation in real time, but also know the measurement point accuracy in real time, which can greatly improve work efficiency. At the same time, from the measurement results, the accuracy of RTK measurement points can reach the centimeter level, which can fully meet the needs of mine measurement.

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