Equalization of geodetic networks based on the use of satellite technology
Geodetic networks, regardless of the technology of their creation, always contain redundant measurements. With the help of redundant measurements, poor-quality results are monitored and eliminated. In addition, redundant measurements are used to assess the accuracy of the measurements made. On the other hand, redundant measurements lead to ambiguous values of the coordinates and heights of geodetic networks. The adjustment process is performed in order to obtain unambiguous results and to increase their accuracy. As a rule, this problem is solved by the method of least squares by minimizing the expression. The correct choice of measurement weights leads to an increase in the accuracy of the adjustment results and, conversely, erroneously specified weights can lead to a decrease in the accuracy of the geodetic network.
An example of the determination of weights can serve as a fragment of a geodetic network, satellite observations in which are performed by six receivers during six sessions.
The scheme of a fragment of a geodetic network of 20 points, created using satellite technology
If we take as a unit the weight of a single measured line, then the weight of the line measured in two sessions should be set 1.4 times higher. In the case of a multi-point solution, if the weight of the coordinates of the point at which single measurements were made is taken equal to one, then the point participating in two or more sessions will receive weight 1.41; 1.73, etc.
In practice, the following technological schemes have been applied:
- equalization according to the program of the manufacturer of satellite receivers;
- adjustment by a specially developed program;
- equalization of satellite measurements, like trilateration networks.
Alignment on the program of the manufacturer of satellite receivers
The main blocks of the program involved in the adjustment process are:
- viewing and editing;
- coordinate transformation;
- service programs.
The data of the selected object can be viewed and edited in graphical and tabular form in the “View and Edit” block. Information related to the items, such as the item identifier, attributes, antenna offset, coordinates, etc., can be viewed and edited at any time. Using filters allows you to display only those items that meet certain criteria.
To obtain results in the user’s coordinate system, it is necessary to convert coordinates from one system to another. There are several possibilities for this purpose:
- create libraries of coordinate sets, ellipsoids, transformation parameters and sets of projections;
- define various types of coordinate transformation parameters;
- carry out various types of transformation;
- use different cartographic projections;
- combine programs for calculating map projections defined by the user.