Cadastral survey is to measure and investigate the ownership, location, quality, quantity and utilization of land and its attachments.
Professional surveying and mapping. The traditional way of this work has a large workload, especially in control measurement, which is difficult to operate and easy to make mistakes. With the continuous development of modern science and technology, GPS technology has been widely used in cadastral survey, freeing cadastral survey from the routine manual work procedures. This paper mainly introduces the measurement method of control measurement using GPS technology.
I. Test Procedures
(1) preparatory work
L, data collection Before the investigation, it is necessary to collect the relevant investigation specifications, the basic map of the investigation area and the information of the big location.
2. Survey Area Reconnaissance According to the existing survey area data, the whole survey area should be surveyed, focusing on understanding the traffic situation of design points, the distribution of control points and the preservation of signs.
(2) net design
In order to fully meet the accuracy requirements of cadastral survey, the form of edge network should be adopted, and preliminary design should be carried out on topographic map according to the requirements of GPS regulation D network to ensure the high geometric strength of the whole network. In particular, the number of related points, observation period, repeated edges, asynchronous rings, synchronous rings, total baselines and independent baselines, as well as the average distance between adjacent points, the maximum distance and the minimum distance between adjacent points should be carefully and reasonably designed.
(3) Select some buried stones
1. On the basis of preliminary design and site selection map, site selection shall be conducted according to the following principles:
The position of (1) point is high, the instrument is easy to install and the field of vision is wide.
(2) The point target is obvious, with l5 around the visual field. Try not to have obstacles to reduce the GPS signal being blocked.
(3) The distance between the point and the high-power radio transmitter is not less than 200m, and the distance between the point and the high-voltage line is not less than 50m.
Avoid the interference of electromagnetic field to GPS signal.
(4) There should be no large area of water and other objects that strongly interfere with signal reception near the point, so as to weaken multipath.
The influence of path effect.
(5) The location should be selected in a place with convenient transportation, which is conducive to the expansion and joint measurement of other observation means.
(6) The foundation of the point is stable, which is convenient for the preservation of the point.
2. Buried stones shall be ordinary standard stones. The marker stones are prefabricated into general markers with concrete, buried on site, and building markers are made on some buildings. There is no iron center mark on each stone marker, but there is a clear and fine reticle, the diameter of the center point is less than 0.5arm, and all stone markers are unified.
Number. After the monument was buried, a little note was drawn on the spot.
(4) observation
L, formulate observation plan, after the completion of the stone buried in the selected point.
After the work, an observation plan should be made, including the following contents: (1) ephemeris forecast, main forecast, time measurement and visible satellites.
Number of stars, satellite altitude angle and azimuth angle. Ensure the actual measurement
The intensity factor (PD()P) of the geometric figure at this time point is less than or equal to.
At six o'clock.
(2) Work plan should be carefully prepared before actual measurement.
The GPS operation schedule and GPS survey field view are made.
Measurement notice, during operation, each observation group every day,
Instruments, vehicles, observation time, observation period and station number.
The observation route of each point transfer is explained one by one.
So as to ensure that the whole measurement process can be carried out synchronously and orderly.
2, unified observation operation requirements before actual measurement.
Instrument operators unanimously emphasize the operation requirements, as follows:
(1) Basic technical requirements: the basis of GPS survey.
The technical requirements shall be implemented in accordance with Class D network, as follows
Satellite scheduling angle (1. )& gtl5
Total number of effective observation satellites >; four
In' q (minutes) Effective observation time of any satellite in a time period >: l5
Number of observation cycles 2
Cycle length (minutes) 60
Data sampling interval 20
LPDOP & lt VI
(2) Antenna placement
(The D line is erected on a tripod, directly above the monument.
During calibration, the bubble of the circular level on the antenna base must be kept horizontal.
② The direction sign of the antenna points to the north, and the direction is wrong.
The difference is less than 5o to reduce the influence of phase center deviation.
Antenna erection is more than l meters from the ground. The antenna has been installed.
Then, at the dish antenna interval l20. These three directions are
When measuring the antenna height, the difference between the three measurements should not exceed.
3mm, take the average of the three results as the final antenna.
High, and recorded in the measurement manual, antenna high recorded value is
0.00 mm
(3) Observation point
(1) The observation group shall strictly abide by the dispatching orders and the regulations.
Set up the machine ten minutes before the scheduled operation and do it according to the specified time.
Industry, synchronous observation.
(2) When confirming external power cables and antennas, etc.
Only after the connection is completely correct can the power supply be turned on and the receiver be started.
(4) The receiver displays normally, and the post is qualified.
After that, enter the site and time control information and set the sampling rate.
(4) After the receiver starts to record data, it shall, at any time
Pay attention to the number of observation satellites, PDOP value and storage medium.
Quality record, power supply.
⑤ The antenna height should be measured once before and after observation.
And input the instrument and record the measurement manual in time.
6. When there is a thunderstorm during the observation, it should be
When contacting, close the test and remove the antenna at the same time.
⑦ During the observation period, it is not allowed.
Operation: turn off the instrument and restart it; Change satellite altitude
Degree angle; Change the antenna position; Changing the data sampling interval;
Other operations to close or delete the observation period.
3. On-site performance record
(1) Observation records The observation records are received by GPS.
The machine is automatically recorded on the PC card, and its main contents
There are: ① phase observation value and ② corresponding carrier phase observation value.
GPS time, GPS satellite ephemeris parameters and stations.
Control information and receiver working state information.
(2) The measurement manual requires that the measurement manual must be available now.
Fill in the fields, and it is not allowed to write them down or make them up afterwards. Field completion
After that, the manual will be numbered uniformly and bound into a book.
Second, the calculation in the office.
(A) the original data transmission
After writing the field observation every day, check each one.
After the data collection of the operation group meets the operation requirements, it shall be collected uniformly.
Relevant professional data transmission software using GPS receiver
Transmitting observation data to a portable computer, and at the same time
Check the antenna height and station number with the observation manual of each point, and then
Edit and distribute data, eliminate invalid observation information,
Form ephemeris file, observation file, station information file,
According to the instrument number for storage and management.
(2) Data preprocessing
Data preprocessing is mainly to input the original data file.
The adjustment calculation of line baseline vector is baseline solution.
The selection of data preprocessing software should include the following main contents
Functions include:
1. unify the data file format and set the antenna radius.
2. Satellite orbit standardization, using polynomial fitting.
Method: Smoothing the orbital parameters sent by GPS satellites every hour.
Number, to standardize the observation period of satellite orbit.
3. Detect cycle slips and repair carrier phase observations.
four
、
Tropospheric correction is added to the observation.
Through multiple processing and optimization of the baseline, all the bases
All lines have got double difference fixed solutions, and the ratio is 95%.
The above sum baseline residual is less than 2 cm.
(3) network adjustment
On the basis of daily data preprocessing, it should be in the whole
After the measurement is completed, all baseline documents shall be designed according to the layout.
Pick them out and adjust the whole network. First of all, all independence
Vertical baseline forms a closed figure, three-dimensional baseline vector and its
The corresponding variance covariance matrix is used as observation information, and one point is used as observation information.
Based on the three-dimensional coordinates of WGS-84 system, the calculation is carried out.
Free adjustment of GPS network Free adjustment provides all points in
w(one {； Three-dimensional coordinates below 4, three for each baseline vector.
Total correction number, baseline side length and coordinate difference observation point.
And the accuracy of the side length. Then determine the validity in free adjustment.
According to observation, in Beijing 1954 coordinate system.
Three-dimensional constraint adjustment of line. Take the joint survey of the three countries as the first class
Position coordinates, as a fixed value of mandatory constraints. balance
Results Through coordinate transformation, the final output of each point was 1945 Beijing.
Plane coordinates and elevation of the Yellow Sea.