Complex processing of geodetic measurements

EasyNET

The EasyNET software is developed for user-friendly processing of accurate geodetic measurements. It is focused on automatic processing of variables measured by total stations, level instruments and gyro-theodolites. These measurements are automatically adjusted by the method of least squares. The result of this process is an adjusted spatial geodetic network. Originality and uniqueness of the software is based on application of advanced computing methods, which provide an exact evaluation of measurements and the best results. The software is designed for MS Windows in Czech and English language versions.

The most significant advantage of the present software is an method for automatic detection and rejection of outlying measurements. This method, which was designed and thoroughly tested by authors of the EasyNET software, is based on a robust adjustment of geodetic measurement.

The software combines all data (measurements and user settings) into a file (the project), allowing easy data transfer and collaboration between different users. In addition to many result spreadsheets, there is a graphical output showing adjusted geodetic network with error ellipses (Fig. 13) and a text protocol of a network adjustment (Fig. 14). The graphical output is possible to export to bitmap format or AutoCAD drawing exchange format (DXF).

Software features

Basic features of the EasyNET software are briefly described in the following paragraphs:

1. Detection of measurement sets

The EasyNET software processes accurate measurements, which are measured by a total station in both positions of telescope (first and second face) and they are grouped into the measurement sets. Measurement sets (specific sequences of survey variables) are identified and graphically highlighted (Fig. 1). If measurements are measured only in one telescope position, the software uses an automatic mirroring, i.e. adds records simulated in the opposite position (even with axis errors of a total station).

2. Measurement checking

The aim of the measurement checking process is a detection of gross errors, which are naturally present in survey data. This control mechanism checks whether measurements have real (expected) values and they fulfill user-specified critical values (limit differences between the first and second position of a telescope; limit differences between sets). If these limit differences are exceeded, all suspected measurements are marked (Fig. 1, Fig. 2, Fig. 3) and the network adjustment process is interrupted. For these cases, the user is equipped with many functions to edit the measurements.

3. Inclusion of supplementary measurement

Besides the main variables measured by total stations (slope distances, horizontal directions and zenith angles), the software is able to adjust supplementary measurement. They are independently measured slope distances, bearings measured by a gyrotheodolite, height differences (Fig. 4) and vertical plumbing measurements

4. Measurement reduction

The zenith angles and slope distances are reduced to direct line of network point marks (the height difference between an instrument and a target; the Earth’s curvature). The measured distances can be further reduced to the sea level and cartographic projection. It is possible to use different cartographic projections by different scale factors at the individual network points. In the case of an unscaled local geodetic network with minimally reduced distances, the sea level is set to a network elevation center.

5. Robust calculation of approximate coordinates of network points

The software uses an automatic calculation of approximate coordinates of geodetic network points. These coordinates are determined using the basic geodetic methods (forward intersection, resection, polar method, etc.), which are used repeatedly from individual network points in all possible combinations. For a maximum elimination of gross errors, the coordinates are finally determined as the median of all calculated values.

6. Detection of gross errors

The detection method is based on a comparison of differences between directly measured (reduced) values and values calculated from the approximate coordinates of network points. If the limit differences are exceeded, all suspected measurements are marked (Fig. 5).

7. A priori accuracy analysis of geodetic network

The aim of a priori analysis of geodetic network is to estimate a priori standard deviations of main measured values (slope distances, horizontal directions and zenith angles). This estimation is very important for determining the correct weights of measurements, which are necessary for correct setting of an outlier detection method. The software provides two types of estimation called the internal and external accuracy of network.

The internal accuracy method determines sample standard deviations. The samples include random values of variables repeatedly measured by a total station at individual standpoints (multiple measurement sets, Fig. 6). These standard deviations describe only random measurement errors.

The external accuracy method has two parts. The first is based on an adjustment of slope distances and zenith angles, which are measured between each two points of the geodetic network (values measured in opposite directions, Fig. 7). The second uses the adjustment of horizontal directions, which are measured among each trio of network points (angular misclosures, Fig. 8). These standard deviations describe both random and systematic measurement errors.

8. Detection of outliers

This advanced detection method evaluates a magnitude of measurement residuals determined by the iterative robust adjustment process (Fig. 9). This iterative process leads to gradual reduction of the influence of outliers, thus obtaining estimates of geodetic variables nearly independent of outlying measurements.

9. Adjustment of spatial geodetic network (by the method of least squares)

Since a total station generally measured slope distances, horizontal directions and zenith angles together, the software prefers a spatial geodetic network adjustment by the method of least squares. In this case all measured values are adjusted together, thus obtaining homogeneous estimation of coordinates of spatial network points (Fig. 10, Fig. 11, Fig. 12).

Depending on the number of fixed network points and supplementary measurement, the software provides the network adjustment in the following variants:

  • free geodetic network (free adjustment)
    • with inner constraints for translation and rotation of network
  • partly fixed geodetic network (minimally constrained adjustment)
    • with a fixed point and inner constraints for network rotation
    • with a fixed bearing and inner constraints for network translation
  • fixed geodetic network (fully constrained adjustment)
    • with two or more fixed points
    • with a fixed point and fixed bearing

10. Transformation of adjusted network

The software provides a linear transformation of coordinates of adjusted geodetic network points. It is spatial linear transformation, which consist of a horizontal congruent transformation and a vertical translation. Users choose between “Transformation with adjustment” method (Fig. 15, Fig. 16) or “Point and bearing” method (Fig. 18, Fig. 19). In the first case the transformation parameters are determined by the Helmert transformation (by the least square adjustment). It is possible to extend this method by the detection of outlying coordinates (Fig. 17). The “Point and bearing” method transforms coordinates so that the position of a selected point and his bearing correspond to user settings.

Documentation

Software documentation is published only in Czech language.

EasyNET documentation (in Czech)

Download

EasyNET Demo is provided only for scientific and educational purposes, i.e. it cannot be used for commercial purposes. This demo version processes no more than 200 measurement values and 7 network points.

Demo version (including demonstration data) download links below:

EasyNET Demo CZ

EasyNET Demo EN

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