A geodetic network is a combination of regular reference points fixed on the surface of the earth within the boundaries of a certain territory, which are called geodetic points. These points are used to relate objects to reference marks on the ground, as well as to scale measurements – from global networks to national and local (densification networks), which are located between them.
The condensation networks are called reference ones and are intended for surveyor’s construction of survey with subsequent execution of topographic plan of the terrain. Reference points can be flat (marked on the plan, have 2 coordinates), high-altitude (or level), as well as three-dimensional (or spatial).
Geodetic networks are characterized by the following principles, features and nuances:
- Planned geodetic points allow you to identify the coordinates of objects located directly on the surface of the earth.
- Leveling networks involve determining the position of an object or any point along the vertical axis from a previously recorded zero mark.
- Spatial networks imply determination, analysis and comparison of coordinates in three-dimensional measurement – on the plan and in height.
Without geodetic networks with different scales not a single map, site plan, topographic survey and other graphic materials that allow you to get detailed information about the geographical location and volumetric-planning characteristics of the object. All reference points are set in the ground in the form of stationary stakes, or applied to hard building surfaces with permanent paint compositions.
How are geodetic networks built?
Geodetic networks today are constructed using any of the following productive techniques:
- One of the most popular and basic methods of constructing geodetic networks is triangulation with predetermined pitch, which has been in use for over 300 years. In the command heights are fixed reference points in such a way that when they are connected by straight segments, triangles are formed. To obtain coordinate information for these points, you need to know exactly their position, the length of each side of the triangle and the values of directional angles between neighboring sides of the geometric figure.
- Modern geodesy also uses the technique of so-called dynamic triangulation, when one of the reference points is rigidly fixed on the ground, and from this point is observed synchronously moving other objects.
- Polygonometry is an effective way to build a geodetic network. Ripert points fixed on the ground are connected by straight segments in a certain sequence, using single geodetic strokes. This technique implies less high geodetic marks, which allows them to be applied in conditions of dense urban development. Most often, such points are displayed in the roadway or other hard surfaces in the form of marked steel elements.
- Trilateration is the most highly accurate technique, which is based on the calculation of Laplace azimuths using linear-angular techniques. In this case, it is necessary to initially know the coordinates of one or more reference points as well as the directional angles between the rays that depart from them to neighboring points. This technique, as a rule, is used only by professionals, as it requires time and labor costs, experience and special knowledge.
- Satellite method of constructing geodetic networks – can be geometric or dynamic. In the first case, the satellite fixes the connection between the receiving device and the defined coordinates for a particular point. In the second case, the reference point with coordinates is located directly on the satellite. The technique is used for the highest precision measurements, for example, for correct operation of the Glonass system.
- Radio interferometry is one of the most exotic methods of networking in geodesy – to determine the coordinates powerful radio telescopes are used, which receive signals, and the distance is calculated based on the duration of the delay between the reception of incoming information data by different devices located at a certain distance from each other.
The smallest scales from 1:100000 and less are used to construct geodetic reference networks from astronomical points, as in such cases, the distance between neighboring points can be up to 100 km. Thus, these scales are useless for construction and assembly work.
What are geodetic networks?
Given that geodetic networks are built on the principle of scaling from the largest to smallest, located within a particular plot of land, they are divided into the following categories:
- Global, which is a coordinate grid of parallels and horizontals that encircles the entire surface of the globe, defined by satellites.
- State – can be planned, high-altitude or spatial, allow to determine the exact position of the point in all three dimensions with reference to the global network.
- Condensed, or local networks, which are used at the scale of urban agglomerations, townships, and other endowed points. They are used for territory breakdown, land surveying, organization of building footprints, and drawing axes for exact location of capital construction objects.
In practice, there is a subset of condensed networks – survey networks, which are used to form a topographic plan of the area within the boundaries of the site in question. Exactly such networks are the basis for designing the object.
What tools will be needed to create geodetic networks?
To build a geodetic network during the survey of the area, you will need the following special tools and equipment:
- Theodolite – the simplest and most well-known geodetic instrument, which quickly determines the value of directional angles, both in plan and on the vertical plane. It is often used in the design of the topographic survey of the site in the given boundaries and binding of objects.
- Level is an electronic or optical device that allows you to determine the excess between different elevations, with a minimum error and with high accuracy.
- A tachymeter is a modern geodesic instrument equipped with a built-in GPS module, which combines the two previous devices and can accurately determine the position of any point in space in relation to the satellite.
Regardless of accuracy, category of complexity and technical characteristics, all geodetic equipment is professional, used to obtain official information, which requires its periodic verification with obtaining the appropriate certificate.