1. Base Station Translation
After the base station moves or re-assumes in the “self-starting reference station” mode, the base station translation step must be carried out to make the point re-measured under the current base station consistent with that before the base station is shut down.
Base station translation method: Find a known point and measure the coordinates of the point to calculate the base station translation and apply it. Specifically, it refers to finding a known point (which can be a measuring point) to measure after the mobile station is fixed. After the measurement is completed, it is found that it is different from the known coordinates. At this time, it enters the “measurement-base station translation”, the GNSS point selects the newly measured point, selects the known coordinates of the point from the known point, and then clicks OK. In the displayed prompt, select yes “.
2. Point Correction
RTKs point correction is to convert WGS84 coordinates into the coordinate system of the current project and solve the conversion parameters. Point correction is divided into single point correction (three parameters), two point correction (four parameters), three point correction (seven parameters), and four point correction (seven parameters).
Generally speaking, three parameters are applied to small-scale measurement with poor accuracy.
The seven parameters generally adopt Boolean sand model, which uses translation, Y translation, Z Translation, X rotation, Y rotation, Z rotation, scale change K, and has a wide range of effects. However, the correction accuracy of seven parameters is directly related to the accuracy and distribution of known points. In order to carry out point correction operation more accurately, we usually need 3-5 high-grade control points, which should be evenly distributed around the measuring area and the center of the measuring area.
Pay extra attention to the followings:
Known points are best distributed at the edge of the entire work area, which can control the entire area and avoid the short side controlling the long side.
Avoid knowing points in the same line.
If an area is large and there are many control points, partition correction is required. Do not take part in the correction of more than a dozen points or more points in an area.
If there are more than 3 points for point correction, check the values of horizontal residual and vertical residual to see if they meet the measurement accuracy requirements of users. The residual should not exceed 2cm, if it is too large, check whether the input of the known point is incorrect. If it is correct, there is a problem with the matching of the known point. The known point needs to be replaced.
Note that only one point correction is required for a region, and only base station translation is required for subsequent remeasurement.
3. Point Setting-out
Point setting-out is the measurement work that sets the plane position and elevation of the engineering building on the design drawing paper to the ground with certain measuring instruments (such as RTKs) and methods. It is an inverse process of measuring coordinates.
Generally, the operation process is to import point lofting data → set up a base station or mobile station → point lofting → check.
1. How do I import point lofting data?
1) import the lofting point data into the excel table in the order of “Roll Call, x,y,h;
Change the suffix of the point file to. TXT;4) import the TXT lofting data file into the notebook.
Point lofting precautions: data collected by point lofting field should be backed up and checked by internal and external industries in a timely manner. The corresponding point coordinates saved when exporting lofting points are compared with the lofting point coordinates. It is enough that the poor does not exceed the engineering precision requirements.
4. Static Measurement
GPS static measurement is a kind of control measurement using measurement-type GNSS receiver (RTK), which is mainly used to establish coordinate control networks of various levels.
During the whole static measurement process, the GNSS receiver is stationary. The GNSS receiver is fixed on the point to be measured for a long time, and the data files transmitted by the satellite are collected according to a certain sampling interval. After that, baseline calculation and network adjustment are carried out through static data processing software.
Static measurement operations are divided into static external and internal operations. The process of field operation is basically a swing station → the height of measuring instrument → the startup of the instrument → manually record the information of the measuring station (the name of the measuring station, the number of the instrument, the height of the instrument, the start and end time, etc.)
The internal job flow is generally exported data → processed with static processing software.
Precautions for static measurement:
During site selection, the station should be in an open and non-interference position to avoid or reduce the multi-path effect.
If the observation conditions are very poor and cannot be changed, the observation time can be appropriately prolonged, and static observation can be carried out when there are many unobstructed satellites.
When processing static data, pay attention to whether the adjustment of free network exceeds the limit, and the selection of known points of constraint adjustment should follow the principle of long side controlling short side d amount
Static Control measurement has high positioning accuracy and simple operation, but it takes a long time.
5. Road Design and Point Setting-out
Road design: the function of “road design” is a simple tool for road graphic design. Standard roads are generally composed of straight lines, circular curves and comprehensive curves. Before building roads, first of all, the design unit needs to design the “straight curve table” of the highway, which is the parameter data of the highway, and then the survey party will carry out the survey and lofting work according to the “straight curve table, before the survey and lofting, the road design should be used. The direct curve table provided by the designer should be input into the software to generate the road design file, and the road design file should be used for the survey and lofting operation.
Common elements in straight curve table include coordinates and stake numbers, calculation of azimuth angle, straight line length between curves, rotation angle, radius, curve length, curve total length, broken chain, long chain, short chain, oval curve, turning back curve, etc.
Road lofting is actually a line expression of spot lofting, which takes the designed circuit diagram as the base map during spot lofting, displays the mileage of the mapping point on the current point line (the nearest point from the current point to the line) and the left or right offset of the forward direction in real time. At the same time, road lofting also includes middle-side pile lofting, cross-section measurement, culvert lofting, slope lofting, road inspection and free slope. Structure lofting, etc.