Web Exclusive: GeoMenu: Automation of Geodetic Measurements

August 1, 2000
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In recent years, geographic information systems (GIS) have been widely used as part of the information base of society development [1]. This article offers a solution to some of the problems that arise while making electronic cadastral maps for the topological base of those systems.

Such problems relate to changes in field operations and-more importantly-in the processing of geodetic measurements by software different from those used in GIS development.

Specialists have well-developed mathematical methods of processing field geodetic measurements. The creation of modern algorithms and applicable software must be adapted in order to automatically produce modern electronic cadastral maps.

This article presents a new software product useful in solving routine geodetic tasks faced by a medium-scale company active in engineering geodesy.

See Figure 1 for the program structure.

According to Figure 1, the program allows both separate and joint use of four modules.

A Universal Format

A field observation file includes the complete information received in the course of field measurements and can be entered into an office PC by means of modern information carriers connected to electronic tacheometers and program interfaces. The main problem is the proprietary formats that manufacturers of geodetic devices create for text files carrying field measurements data. The further processing of such files is hampered by these varying formats.

Certainly, a company buying a new device receives a modern software product and thus escapes the problem. However, since geodetic equipment lasts for a long time and can be expensive, not every user of an electronic tacheometer is willing to buy a modern program for processing and storing geodetic and survey data. In fact, some companies use devices produced by different manufacturers. The universal module offered in this article is developed especially for such cases. The module transforms text files of different formats into a universal format. The module works with files created by electronic tacheometers and memory units produced by the three most significant geodetic equipment manufacturers: Leica Geosystems, Topcon America Corporation and Sokkia Technology Inc.

To make it possible to place necessary points in the field, the module allows users to transform files containing lists of coordinates into text files made in formats compatible with electronic tacheometers of these companies.

Calculation Module

The calculating module provides for both manual and automatic entering of information, as well as for the subsequent calculating and adjustment of coordinates and heights of a separate traverse by the least squares technique. This solves the problem of receiving three-dimensional (3-D) coordinates of a completion survey point.

Catalogue Module

This module allows feed forward and feed back to the coordinates' catalogue since the meanings and quality of both the initial and calculated data presumably replenish the set of datum marks representing the base of geomatics data.

Specifically, the module implementing calculation and mathematical treatment of other geodetic constructions meets the basic up-to-date requirements of modern electronic devices and information carriers, including:

  • inverse position computation;
  • angular forward and backward intersections;
  • angular-linear intersection;
  • polar intersection;
  • offsets to baseline calculations;
  • re-calculation of the coordinate from one 2-D system into another.

These options enable a medium-scale company to carry out basic routine geodetic calculations and include an evaluation of exactness of the results received.

The coordinates catalogue presents a user's database with a comfortable search system. Each point is registered manually or from a text file containing coordinates with the point's class, location and other information.

It is possible to search for a point on three basic parameters: the "coordinate window" (the minimum and maximum meanings of coordinates x and y), the name and the place of the point.

Calculating the coordination of picket points

The last module relates to the calculation of the coordinates of picket points of a tacheometric survey. The data to be processed are placed in a text file of an original format we offer. The file is received directly from the memory unit of an electronic tacheometer after being appropriately transformed. One of the basic calculation aspects is the average value determination of the theodolite initial azimuth while orienting toward three and more known points of the geodetic completion survey, as well as of a mean value of the azimuth calculation. The program provides for the check of distances and heights including those known in advance and those received by measurement. The calculation protocol corresponds with the basic ISO requirements.

After the evaluation of the experimental data received by geodetic measurements in Israel, it was considered necessary by the Israeli specialists to include the use of mean sea level corrections and corrections for curvature of the earth and refraction. In Israel, the engineering geodetic surveys are carried out at a round-the clock temperature drop and pressure differential of 10 degrees C and 100 mm Hg respectively and at height differences exceeding 100 m. Therefore, taking these corrections into consideration elevates the exactness of jobs.

This software was chosen with regard for the fact that most software products used in making cadastral maps are based on Windows, Windows NT and Unix. Therefore, the newest programming languages of Visual C++ and Visual Basic have been considered and the choice was made for Visual Basic since it is relatively simple for the construction of program forms and databases. The transfer to Windows makes it possible to execute the program with graphical means and to create efficient dialogue menus.

This program has been preliminarily called "GeoMenu" and is now being tested by a number of licensed land surveying companies and manufacturers of software products for geodetic engineering surveys.

The first results of the production tests have shown that the GeoMenu program allows a quick, comfortable and qualitative process of various engineering geodetic constructions and-more importantly-presents to the specialists a mechanism for evaluation of exactness of the calculation results.

The first outcome of the program's use gives hope that it will be competitive in the software market for engineering geodetic surveys.

The next stage of its development is the creation of software modules for improving the geoinformation technology of making electronic cadastral maps in Visual C++ and AutoLisp in order to implement AutoCAD R14-R2000 programs.

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