Due to the rapid development of surveying and mapping technology, the application of total station is quite common. Compared with traditional flat mapping, it is a qualitative leap from white paper to digital mapping. The traditional measurement work procedure is “first control, rear crushingâ€, and sometimes it is affected by weather and visibility. Control measurement needs to be observed for a long time, thus affecting the measurement of the broken part. After more than 20 years of development, GPS technology has become more and more mature in its application. Due to its advantages of all-weather, no need for visibility, high positioning accuracy, short measurement time, and few measuring personnel, GPS applications are becoming more and more applicable. wide.
1 RTK positioning principle and requirements
1.1 positioning principle
RTK measurement technology is a real-time differential GPS measurement technology based on carrier phase observation. It breaks through the problems of conventional RTK differential operation system, such as relative independence, temporary station temporary and frequent erection, and realizes the dream of not setting up a base station. The system consists of three main parts: the base station, the rover (one or more), and the data link. In general, the base station is located at a high-level control point with known coordinates, continuously receives all visible satellite signals, and measures station coordinates, carrier phase observations, pseudorange observations, satellite tracking status, and receiver operation. The reference information such as status is sent to the rover through the data link, and the rover receives the data from the reference station while tracking the GPS satellite signal, and obtains the three-dimensional coordinate increment ΔX, ΔY between the reference station and the reference station through differential processing. ΔZ, from which the coordinates of the rover are calculated.
1.2 Observation requirements
1) The selection of the base station site and the instrument settings should meet the requirements of the Global Positioning System (GPS) Measurement Specification (CH2001-92, hereinafter referred to as the "Specifications"), and should also be combined with the actual situation of the test area, for example, considering the use. The relationship between the power of the station and the coverage, and the effectiveness of the data transmission between the stations, should be placed in the center of the test area and placed as high as possible; more than 50 m from the high-voltage line and the radio tower, Avoid interference from strong power sources; avoid large areas of water or densely populated areas to avoid multipath effects.
2) The instrument setting of the rover site also needs to meet the requirements of the "Specifications". When the graph root encryption measurement is performed, although the point selection has greater flexibility, it is required to have at least one viewing direction in the difficult viewing conditions. There should be 2 to 3 viewing directions in the open area.
2 RTK positioning accuracy
Since the data processing process of RTK positioning is a process of calculating the baseline vector, that is, the coordinate increment between the base station and the rover, there is no network adjustment processing, so the accuracy evaluation is similar to the accuracy evaluation of the static measurement baseline processing, generally using two Indicator: Whether the full-circumference ambiguity of the carrier phase is fixed and the RMS value of the rms. The former determines whether the coordinate value of the mobile station is a fixed solution or a floating solution. Within the effective range of the RTK, the accuracy of the floating solution is between the decimeter level and the meter level, and only the fixed solution can achieve the centimeter-level positioning accuracy; the latter directly determines The positioning accuracy is small, and the smaller the value, the higher the accuracy.
3 GPS implementation and application
3.1 Mining area control network layout
The Mazongling vanadium mine is a new mine under investigation. All the prospecting work is in progress. Due to the needs of the mine, 10 points are arranged in the mine area to form a GPS network, and 4 southern 9600 GPS receivers are used for observation. The data acquired synchronously constitutes the synchronous and asynchronous loops and the necessary repeating baselines. Set the inspection instrument acquisition parameters and the epoch interval and height cut-off angle before the observation. In the observation time, the synchronization time of the observation point at which the receiver receives the signal is one hour, and the observation time of the observation signal with weak reception signal is 2 hours, so as to ensure that the collected data can be solved by a fixed solution. When the adjustment is performed, the qualified fixed solution is obtained according to the collected data, and it is checked whether the synchronous ring and the asynchronous ring conform to the specification. After each baseline treatment is passed, a three-dimensional unconstrained adjustment is performed and the accuracy in the GPS network is evaluated, then the known coordinates are added, and the two-dimensional constraint adjustment is performed to obtain the plane coordinates and accuracy evaluation of each point.
3.2 Application of GPS RTK combined with total station in mine engineering measurement
In the past traditional measurement, after RTK, under the general topography, in the higher terrain, the station can measure the radius within 15 km, greatly reducing the number of control points required for traditional measurement. And the number of stations of the total station, only one person to observe the topography of the terrain, you can get the three-dimensional coordinates of the point. In the scope of the survey area, the designed points are calibrated in the field (such as drilling and stakeout). When using RTK technology to stake out, the efficiency of the field lofting will be greatly improved. Only the designed point coordinates should be input into the electronic hand sheet. The thin hand display will automatically remind you to go to the location where you want to stake out, which is quick and convenient.
When performing mine surveys, RTK measurements can reduce the workload, speed up the work, and improve the work efficiency for places with good terrain (no obstruction receiving signal and no loss of signal lock). Due to the high signal reception requirements of the receiver during RTK measurement, mine measurements often encounter steep mountains and dense vegetation. Where the receiver does not receive signals, the signal is prone to loss of lock. Initialization, the measurement accuracy will be greatly reduced, and sometimes the coordinates of the broken step point cannot be measured, which can not meet the needs of mine measurement. In order to improve the measurement accuracy, the total station should be used together, and the receiver signal is easy to lose lock. The total station is erected at the control point for direct measurement or stakeout, thereby improving the accuracy of the collected break points or staked points.
4. Conclusion
Disadvantages of GPS: When collecting the broken step, the receiver mainly relies on receiving signals, and has strong dependence on the signal. In some places where the mine is shielded, the signal is prone to loss of lock and cannot be accurately measured: in open areas, the signal loss will not be solved. Appears to achieve the required measurement accuracy, but it has the advantages of all-weather, no need to look at, high positioning accuracy, short measurement time, and fewer measuring personnel. Therefore, in the mine survey, the cooperation of the total station and other measuring tools is needed, and the advantages of GPS and total station and other measuring tools are fully utilized, which has great practical significance for speeding up the measurement progress of the mine and improving the measurement accuracy.
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