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Geodesic laser system

#B-1173


Computer-Controlled Geodesic Laser System for City-Planning and Municipal Services

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics
  • INS-DET/Detection Devices/Instrumentation
  • OTH-BIT/Building Industry Technology/Other

Status
3 Approved without Funding

Registration date
11.08.2004

Leading Institute
B.I. Stepanov Institute of Physics, Belarus, Minsk

Supporting institutes

  • VNIIEF, Russia, N. Novgorod reg., Sarov

Collaborators

  • Gesellschaft fuer Spezielle Vermessung und Planung mbH, Germany, Bentwisch\nUniversity of Twente, The Netherlands, Enschede\nCharite Campus Benjamin Franklin / Institut für Medizinische Phyzik und Lasermedizin, Germany, Berlin\nUniversitat Autonoma de Barcelona, Spain, Barcelona

Project summary

The goal of the project is developing, building and demonstrating a prototype of a computer-controlled geodesic laser system for city-planning and municipal services, which is based on a novel, original technique allowing to establish an object location on terrains (including the terrains hidden from direct observation by obstacles).
State-of-the-art in the field. The accurate establishing the object position (that is, the determination of the Cartesian X, Y and H coordinates for an object on the earth surface) is a vital necessity for a wide range of applications such as construction of buildings, communication line laying and others. There are a number of modern techniques, including techniques based on the terrain object positioning with the help of satellite systems (such, for instance, as a global position system, GPS) developed to solve this geodesic problem. In spite of the high accuracy the application of the GPS-based technique is limited because of the cost. The technique can not be applied also for a number of cases when a so-called condition of 120 degrees is not satisfied and the line-of-sight between the object and a satellite is absent (for instance, in position fixing for the objects situated among urban buildings or on a rugged terrain). For a wider implementation in practice, therefore, the GPS-based approach should be complemented by other reasonably priced techniques. Then, the GPS may applied for establishing position for only few base points.
The classical theodolite-based approach to determination of the object coordinates with respect to base points is one of the best known and traditional techniques where modern laser systems find the application [Gottwald R. Kern. E2-SEE in neues Instrument nicht nur fur die Industrievermessung ”Allg. Vermess.-Nachr.”, 1987, No. 4, pp. 147-154]. However, the method does not allow to map the objects hidden from direct observation by various obstacles (by buildings, terrain elements, trees, etc.) since the method requires the line-of-sight between the object and the theodolite.
Recently project participants in cooperation with German researchers have patented a novel technique, which does not require such a line of direct observation. The technique is based on labeling of the required object by means of a laser beam (or a laser searchlight) pointed exactly upward. Due to the ‘side scattering’ effect the laser beam can be observed above the surrounding obstacles from desired points of registration. The unique properties of the laser beam (high power, monochromaticity, low pergence, etc.) make it possible to use the beam as a peculiar light label. Then the object’s coordinates could be found by analyzing this side scattered beam by several precision optic-mechanical systems (POMS).
The effect of the proposed project on the progress in the field. As a result of the project realization, a prototype of an original highly-computerized laser geodesic system will be created. The practical application of such systems will bring the solution of vital problems in city-planning and municipal services to a higher level. For instance, it makes possible to realize a direct computer-controlled positioning for the objects on large-scale urban areas at any time instant, avoiding the labor-consuming multi-path theodolite-based measurements.
Competence of the project participants. Project participants from Institute of Physics of NASB are well known specialists in the fields of atmospheric optics and laser physics. Participants from RFNC-VNIIEF are acknowledged experts in development of precise computer-controlled optic-mechanical positioners including the devices for laser systems. The leading specialists of the project have more than 20 publications of laser and optic subjects in prestigious scientific journals. The joint efforts of the Institutions will allow to solve the complex problems successfully and to realize completely the project goals.
Expected results. A prototype of a laser optical geodesic system will be developed and built. The system capability for the accurate computer-controlled establishing of the position will be demonstrated for objects hidden from direct observation by various obstacles on a real terrain with a size up to 5x5 km.
It is intended to study the ‘side scattering’ effect in detail both theoretically and experimentally. As a result of this study, the ‘urban aerosol’ model will be modified in order to describe adequately scattering of the laser radiation in the atmosphere over large-scale urban areas. The modification is important for optimization application of the proposed laser geodesic system.
A laser searchlight based on a self-contained, compact, powerful solid-state or semiconductor laser with a high pulse repetition frequency will be designed and made.
It is planned to design and to manufacture three POMS systems. Each of the systems will include a precise computer-controlled turning unit, a telescopic device and a high-sensitive spectral-selective photo-detector device.
It is proposed to develop an optical method for the accurate H coordinate determination and to design the device. The device will provide the precession of laser searchlight beam around the vertical axis.
A strategy and procedures of rapid and accurate coordinate determination with the help of computer-controlled measurements, acquisition and processing of obtained information will be elaborated.
It is intended to optimize the process of topographic survey and to demonstrate the capabilities of the prototype for a real urban area.
Fields of application for the project results – city-planning and municipal services, topographic survey on a terrain where the time of human presence must be limited, etc. Obtained results will be of interest for a number of basic research problems (for instance, in study of manifestation of aerosol and molecular atmospheric components in light scattering).
Meeting ISTC goals and objectives. The proposed project meets fully the purposes and the objectives of ISTC.
- The project will provide an alternative employment for the specialists from - IP of NASB and RFNC-VNIIEF, which were engaged in development, production and operation of high-power lasers for military applications and the equipment for nuclear weapon testing. The project will give a possibility for the participants to redirect their abilities to peaceful activity.
- The project will stimulate the involvement of the participants into the international scientific community due to close cooperation with foreign scientists and specialists, including the project collaborators.
- The project realization will support development of a peaceful technology, basic and applied researches.
- The project holds promise for a number of applications, which contribute to the solution of important national and international technology problems in such fields as, for instance, city-planning and municipal services.
- The expected results will stimulate participant’s conversion into the market economy answering to social needs and, undoubtedly, are of special interest from the commercial viewpoint for a number of municipal administrations (for instance, for the administration of Rostok in Germany).
Scope of activities. The project involves specialists from two Institutions with the great experience in teamwork. This experience will enhance the efficiency of the intended activity. The total effort will be 7625 person-days. The participation of 59 scientists and specialists (including 33 weapon ones) is implied. The total duration of the project will be 30 months. As a result of the project realization, we will solve some scientific and technical tasks. They are:
1. Performing calculation and measurements for study of the ‘side scattering’ effect;
2. Designing and manufacturing a laser searchlight;
3. Developing, designing and manufacturing a precision optic-mechanical system (POMS);
4. Developing an optic method for the H coordinate determination and creating a relevant device for the method realization;
5. Elaborating a strategy and algorithms for the computer-controlled position fixing with minimal error;
6. Optimizing the topographic survey and demonstrating the capabilities of a prototype model for realistic urban conditions.
The solution of Task 1 (that is, analyzing the dependence of the side-scattered radiation intensity on laser output parameters and atmospheric conditions) allows to create purposefully the main components of the prototype – the laser searchlight (Task 2) and the POMS (Task 3) with a required performance. The solution of Tasks 4 and 5 concerned with the methodology of coordinate fixing allows to elaborate physical principles of prototype operation and to exhibit the potential for the prototype. The potential will be demonstrated then through solution of Task 6. Tasks 1,2 and 6 will be solved, for the most part, by the specialists from IP of NASB. Tasks 3,4,and 5 will be accomplished mainly at RFNC-VNIIEF.
The role of the foreign collaborators lies in information exchange during the project realization, annotating to the technical reports (quarterly, annual and final ones) of the project participants, organization of joint seminars and working meetings, testing and estimating the designed equipment and the algorithms under the conditions of Rostok (Germany). Rostok is a city where Dr. L. Schrenk (a specialist in terrain object positioning and a project collaborator) lives. Dr. L. Schrenk will provide guarded rooms and a terrain area for demonstration of the capabilities of proposed technology. He will provide also the auxiliary equipment and the needed software.
Technical approach and methodology. The principle of the proposed system is based on an approach patented by the project’s participants. The main idea of the approach is the detection of a side-scattered laser beam directed above the surrounding obstacles. Such approach allows to establish the object coordinates on a terrain hidden from direct observation. Despite the low intensity of the beam, a reliable beam detection at long distances is provided with the help of an original high-sensitive ( ≥ 109 V/W) photo-detector device included in the POMS.
The accuracy of the X and Y coordinates is ensured by using the optic-mechanical stepper-motor-based units with a high precision (few angular minutes) of positioning. In order to obtain the H coordinate it is proposed to use a searchlight beam, which labels a desired object, to precess around the vertical axis and to generate the cone with a small vertex angle. The H coordinate can be associated unambiguously with the precession cone width as measured at a predetermined height. The efficiency of operation for the laser geodesic system will be provided by a computer control procedure of the position determination.
A number of theoretical and experimental studies have been carried out by participants at IP of NASB for testing the method. As a result, a working breadboard set-up has been created and successfully tested. The set-up is based on a low-power neodymium laser and a POMS including a photo-detector of relatively low sensitivity. Nevertheless, the experimental set-up finds the coordinates for the objects hidden from direct observation with an accuracy of ~ 10 cm at distances up to 0.5 km.
The proposed prototype of laser geodesic system can be created on the basis of commercial apparatus, devices and components. This reason argues for the feasibility of system implementation in the framework of the ISTC project.


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