CP 1 stands for reference control point; CP2 stands for the control point of off-line construction survey; CP3 stands for the special control point of ballastless track construction;

In the construction and acceptance survey of ballastless track, it is necessary to use the survey mark points (CP3 points) arranged every 60 meters on both sides of the line. The functions of these survey mark points are: as survey marks; Place reflective prism for automatic scanning of total station;

Layout of CPⅲ control points: check the continuity of field observation data and correct the obvious single wrong data. By using the adjustment software, the adjustment calculation is carried out on the observation data of total station and level at CPⅲ point in the field. Firstly, the independent coordinates of CPⅲ are obtained, and then the exact coordinate values of CPⅰ and CPⅱ are added, so that the absolute coordinate values of CPⅲ can be obtained through adjustment calculation.

Extended data:

CP 1 initial survey (dual-frequency receiver GPS, electronic level) and CP2 fixed survey (total station) are adopted in railway line construction;

Points for attention in observation of CP Ⅲ control points:

According to the CP ⅲ control network controlled in the first step, field data collection and observation are carried out, mainly including total station and level.

CPⅲ points are numbered uniformly, with odd numbers on the left and even numbers on the right;

In the process of operation, surveyors should strictly follow the specification requirements to avoid unnecessary thinking errors;

The prism constant should be set correctly. The bigger the prism, the stronger the reflection of light in the prism.

If the prism constant is set incorrectly in field observation, it will be a great workload in indoor data calculation.

During field observation, each station will observe 8 CP Ⅲ points, and each station will only move forward with a pair of prisms, so the pressure and temperature values must be correctly input. The instrument is free to set up stations, and the height of the instrument is not measured, and the instrument automatically calculates.

Note: every other pair of CP ⅲ prisms can be set freely; Observe 2×2 CP ⅲ control points in two directions;

Each CP Ⅲ control point shall be observed at least 3 times; Each station should observe at least two returns; Use CP ⅰ and CP ⅱ for connection measurement;

In the section where the center line of the railway line is stable, CP ⅰ control network can be established in the initial survey control network according to the requirements of fine survey network; In the section where the center line of the railway line is stable, the fixed survey control network is used to establish the CP ⅱ control network.

If the center line position of the railway line is unstable, establishing CP ⅰ and CP ⅱ in advance will increase a lot of repetitive work, bring some economic losses, and easily cause confusion of data and points.

References:

Baidu encyclopedia-railway engineering survey

References:

Baidu Encyclopedia-Line Measurement