Survey Stations
Definition
A survey station is a fixed point on the ground, permanently or temporarily marked, from which survey measurements are taken or to which they are referred for locating other points, lines, and features in surveying.
Main Content
1. Types of Survey Stations
Main stations and subsidiary stations
- Main stations are the primary control points that define the framework of the survey. Subsidiary stations are intermediate points used to capture details or to assist in locating features accurately. For example, in chain surveying, the corners of a plot may be main stations, while points used to locate a building edge or tree are subsidiary stations.
Permanent and temporary stations
- Permanent stations are fixed with lasting marks such as concrete pillars, iron pegs, or reference stones. Temporary stations are used only for the duration of the survey and may be marked with wooden pegs, nails, flags, or ranging rods. Permanent stations are commonly used in control surveys and large engineering projects, while temporary stations are common in detailed field surveys.
2. Characteristics of Good Survey Stations
Intervisibility and accessibility
- Survey stations should generally be visible from one another if angular or line measurements are required between them. They should also be easily accessible so that instruments can be set up and measurements can be taken conveniently. A station hidden behind obstacles or located in unsafe terrain makes surveying difficult and inaccurate.
Stability and permanence
- A good station should be located on stable ground where the mark will not shift due to soil movement, traffic, erosion, or construction activity. If the station moves even slightly, the survey data may become inaccurate. For this reason, permanent stations are often protected and referenced carefully.
3. Selection and Marking of Survey Stations
Proper location based on survey purpose
- Stations are selected according to the type of survey and the shape of the area. In chain surveying, stations are usually chosen to form well-conditioned triangles with lines that are as long and straight as possible. In traversing, stations are selected so that the survey line covers the boundary or route efficiently, such as along roads, canals, or property limits.
Clear marking and referencing
- Once selected, stations must be clearly marked so they can be identified later. This may be done by driving a peg into the ground, painting a mark, setting a nail in concrete, or using a stone. Reference measurements to nearby objects are often recorded so the station can be recovered if the mark is disturbed. For example, a station may be located by measuring its distance from a boundary wall and a tree.
Working / Process
1. Reconnaissance and station selection
The surveyor first inspects the area and identifies suitable points based on visibility, accessibility, stability, and the purpose of the survey. The arrangement should allow efficient measurement and reduce errors. For example, in a road survey, stations are chosen along the centerline or route at suitable intervals.
2. Marking and numbering the stations
After selection, each station is physically marked on the ground using pegs, nails, stones, or paint. Stations are then given clear identifiers such as A, B, C, or 1, 2, 3. This numbering helps in field notes, plotting, and coordination of different survey teams.
3. Observation, measurement, and preservation of station records
Measurements such as distances, angles, and levels are taken between stations and to other features. The surveyor records all station details, sketches, and reference ties in the field book. If the survey is permanent or long-term, station details may also be preserved through reference marks or coordinates so that the points can be relocated in future work.
Advantages / Applications
Provides a reliable reference framework
- Survey stations act as the backbone of surveying work, allowing all measurements to be linked to known points. This improves accuracy in plotting and computation.
Useful in many surveying operations
- They are used in chain surveying, traversing, triangulation, leveling, route surveys, cadastral surveys, and construction layout. For example, building corners are set out from control stations.
Helps in long-term control and re-establishment
- Permanent survey stations make it possible to re-check, extend, or repeat surveys in the future without starting from scratch. This is valuable in land development, engineering projects, and map updating.
Summary
- Survey stations are fixed reference points used to control and support surveying measurements.
- They may be permanent or temporary and are selected based on visibility, stability, and the purpose of the survey.
- Proper marking, numbering, and recording of stations are essential for accurate fieldwork and future reference.
- Important terms to remember: survey station, main station, subsidiary station, permanent station, temporary station, intervisibility, reference mark