International association of geodesy

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Report compiled by Michael G. Sideris



1. Positioning

1.1 Canadian geodetic long baseline interferometry

The Geodetic Survey Division (GSD) of Geomatics Canada, Department of Natural Resources (NRCan) in collaboration with the Space Geodynamics Laboratory (SGL) of the Center for Research in Earth and Space Technology (CRESTech) and the Dominion Radio Astrophysical Observatory (DRAO) has been actively involved in technology development and international VLBI observational programs. CGLBI activities can be summarized as follows:

Operation of the 46 m Algonquin radio telescope as part of the global fiducial network of observatories and the primary reference point of the Canadian Active Control System (CACS). A major overhaul of the telescope control system and installation of the PCFS were completed in June 1997 significantly improving the operational reliability and the quality of VLBI results. During 1999 the Algonquin 46 m antenna is scheduled to participate in 47 VLBI observing sessions (13 NEOS, 32 CORE and 2 NAVEX). In recent years it also participated in Mars Path Finder/Global Surveyor experiments where VLBI fringes were successfully detected for the baselines between Algonquin and other observatories.

Operation of the NASA 9 m MV-1 radio telescope at the Yellowknife Geophysical Observatory as part of the North American Plate Stability (NAPS) network and a fiducial reference point of the CACS and IGS networks. A new PCFS control system was acquired in spring of 1997 and the antenna has participated in CORE-B experiments in recent years. The loan of NASA Mark III instrumentation by the Space Geodesy Branch of GSFC for the Canadian observatories is appreciated and gratefully acknowledged.

The SGL/DRAO Technical Development Centers in close partnership with GSD continued the development and integration of the CGLBI S2 systems. The successful first fringe experiment on the baseline between Algonquin and Ottawa Shirley's Bay in September 1997 verified the critical functionality of all the essential CGLBI S2 components including the Recording/Playback Terminals (RT/PT), the Data Acquisition System (DAS), the Canadian VLBI Correlator and a 3.6 m transportable antenna. The 3.6 m antenna and a CH-75 Hydrogen Maser have been transported and installed at DRAO in preparation for the S2 geodetic mode experiments using DAS frequency switching.

A renewed effort to establish a state-of-the-art capability for CGLBI data reduction and analysis based on the latest GSFC Calc/Solve software has been under way since September 1997. The Calc/Solve package has been successfully installed at GSD and SGL with the intention to develop appropriate software interface for the Canadian S2 correlator.

1.2 GPS

The Geodetic Survey Division (GSD) continued its significant contribution to the International GPS Service (IGS). In addition to contributing GPS data for several sites, GSD continued to function as an IGS Regional Data Center, again attaining a high standard of consistency, reliability and quality control. GSD, in collaboration with the Pacific Geoscience Centre (PGC), is currently contributing data from 17 sites including several sites with collocated geodetic techniques. The Canadian stations are amongst some of the most reliable and timely IGS stations. In particular the station ALGO (Algonquin Park Observatory) has been used by many IGS Analysis Centers as a timing reference, due to its reliability, timeliness and data quality.

GSD also continued serving as a one of the seven IGS Analysis Centers (AC). The GSD AC contributes satellite orbits, precise clocks, Earth Orientation Parameters (ERP) including continuous UT, station coordinates, tropospheric delays and ionospheric grid solutions while maintaining consistent quality and timeliness. Contributions of the seven ACs are fundamental and essential for the IGS product combinations.

From 1994 to the end of 1998, GSD served as the IGS Analysis Coordination Center, producing the IGS satellite orbits, clocks and ERP combined products. The reliability, rapid response, efficient feed back mechanism and leadership provided by the IGS analysis coordination are well recognised internationally and greatly helped ensure timely and precise IGS products. In the fall of 1998, the IGS coordination and product combinations were successfully transferred to Dr. Springer of the Center for Orbit determination in Europe (CODE) at the Astronomical Institute of the University of Bern, Switzerland. GSD, through its representatives, has also made a strong contribution to the IGS Governing Board.

Since 1996, GSD has been active in the development of the SINEX (Solution INdependent EXchange) format and IGS station coordinates solutions. GSD has developed and made available to several ACs a SINEX converter and contributed SINEX multi-year station coordinates solutions to the International Terrestrial Reference Frame (ITRF) combinations. The GSD multi-year solutions have been computed using both NRCan only solutions as well as combinations of IGS AC solutions. Recently, as a result of this effort, GSD was invited and accepted to serve as the IGS Reference Frame Coordinator with the goal of producing IGS combined SINEX station coordinates solutions that will be an important component of the future IGS realisation of ITRF.

A subset of the Canadian GPS tracking stations make up what we refer to as the Canadian Active Control System (CACS). The CACS is being developed and maintained to provide positioning accuracy of better than one metre in real-time and better than three centimetres in post-processing over the Canadian landmass. It allows for efficient access to the national spatial reference frame without requiring occupation of monumented control points and provides an effective enhancement of GPS precision. By utilising stations that contribute to the ITRF, the CSRS compatibility with global standards is assured.

1.3 Canadian Spatial Reference System (CSRS)

GSD has been active in providing access, maintaining and improving the Canadian Spatial Reference System (CSRS) and its components, consistent with IAG resolutions at XX IUGG General Assembly in Vienna:

Redefinition and more accurate realisation of NAD83 in terms of a 6-parameter datum transformation from ITRF.

Definition, in cooperation with the US, of the North American Subcommission of Commission X (Global and Regional Networks).

Provision of a more accurate realisation of NAD83.

Elimination of the inconsistencies between Canadian and US realisations of NAD83.

Development of a transformation between GPS-derived ellipsoidal heights and the orthometric heights of the Canadian Geodetic Vertical Datum of 1928. This task involved the compilation and adjustment of all GPS surveys on BM across Canada since about 1987.

2. Gravity Field Approximation

2.1 Gravimetric geoid modelling

GSD continued to play a leading role in the area of geoid modelling, both at the national and international level. In 1996, GSD, the University of New Brunswick and the University of Calgary engaged in a three-year plan to develop an enhanced geoid model for Canada by the year 2000. This collaboration was extended to the U.S. National Geodetic Survey, NIMA, KMS and others for the development of a North American geoid model. GSD has since organised two geoid workshops with international participation and contributed to many other meetings and discussions for the coordination of the project.

In 1996-1997, GSD participated in the evaluation of the most recent geopotential model, the EGM96, and produced a comprehensive report with test results over Canada. GSD contributed to the creation of the Special Study Group SSG3.177 of the IAG “Modelling of the synthetic gravity field of the Earth” an essential venue that will result in significant enhancements in the area of regional geoid studies.

2.2 Airborne gravimetry

GSD has been active in the area of airborne gravimetry and in further developments of its dynamic gravimeter system. In 1997, GSD participated in “Airborne Gravity and the Polar Gravity Field” in Kangerlussuaq, Greenland and was involved in the planning of the flight lines for the airborne gravity surveys of the off-shore areas of Canada and Greenland. In 1998, GSD participated successfully in the Polar Margin Aeromagnetic Project (PMAP) with its dynamic gravimeter system. Other participating agencies included the National Imagery and Mapping Agency (NIMA), the U.S. Naval Research Lab (NRL), the National Survey and Cadastre of Denmark (KMS) and the National Research Council (NRC) of Canada. GSD contributes to the Arctic Gravity Project, an international effort of 10 countries to compile state-of-the-art detailed free-air and Bouguer anomaly grids.

2.3 Absolute Gravimetry

GSD continued its involvement and its leading role in the area of absolute gravimetry. Many instrument improvements have been accomplished:

  • 1995: new iodine-stabilised laser added to JILA-2

  • 1997: acquisition of second JILA instrument (JILA-4)

  • 1998: second iodine-stabilised laser acquired for JILA-4

  • 1998: acquisition of a new timing interface for gravity observations

  • 1998-99, new laser fiber optics system introduced in JILA-2

At the international level, in 1995, our team published the results of the analysis of the 1994 international inter-comparison data at the BIPM. Results showed a standard deviation of less than four microgals for all instruments. In 1996, we repeated the observations at IAGBN sites Schefferville and Yellowknife. In 1997 we participated in the fifth international comparison of absolute gravimeters at the BIPM. Results from this comparison show a standard deviation of less than two microgals for most instruments (including JILA-2).

2.4 Superconducting gravimetry

In 1995, the Canadian Superconducting Gravimeter GWR-12 was refurbished with a new gravity sensor in preparation for the Global Geodynamics Project (GGP). In 1996, the consortium of five Canadian universities and GSD were awarded a Major Facilities Access grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) to support the operation, maintenance and upgrades of the CSGI and to fulfil the obligations towards the GGP. Since the official start of the GGP (1st of July 1997), GSD has been providing high quality and uninterruptible data to the International Center of Earth Tides (Brussels). GSD has also been contributing to the activities related to the GGP through active participation in workshops and other meetings (e.g. SEDI).

3. Geodetic Theory

In the field of tides and tidal corrections to geodetic observations, GSD, in collaboration with Geological Survey of Canada, has integrated numerous local/regional marine tide models around the Canadian coasts. These models complement the global ocean tide models (e.g. FES95.2) and enhance the evaluation of the ocean tide loading effects to geodetic quantities. The models and the software are available to the users via the GSD ftp site (Lambert et al., 1998).


Becker, M., L. Balestri, R. Bartell, G. Berrino, S.Bonvalot, G. Csapó, M. Diament, M. D'Errico, C. Gerstenecker, C. Gagnon, P. Jousset, A. Kopaev, J. Liard, I. Marson, B. Meurers, I. Nowak, S. Nakai, F.Rehren, B. Richter, M. Schnüll, A. Somerhausen, W. Spita, G. Szatmori, M. Van Ruymbeke, H.-G. Wenzel, H. Wilmes, M. Zucchi and W. Zürn (1995). Microgravimetric measurements at the 1994 International Comparison of Absolute Gravimeters. Metrologia V.32, N. 3, November 1995, p. 145 - 152

Beutler, B., J. Kouba, and T. Springer, 1995, Combining the Orbits of the IGS Analysis Centers, Bull. Geod. 69, pp. 200-222.

Beutler, G. and J. Kouba, 1999, State of the IGS by the End of 1998, Proceedings of 1998 IGS Network workshop, held in Nov. 98, Annapolis, Md.

Beutler, G., M. Rothacher, T. Springer, J. Kouba, R.E. Neilan ,1998. The International GPS Service: An Interdisciplinary Service in Support of Earth Sciences, Advances in Space Research.

Craymer, M., (1998). Integation of Local Surveys into the Canadian Spatial Reference System, Geodetic Survey Division, Geomatics Canada.

Craymer, M., R. Ferland, R. Snay, (1998), Realization and Unification of NAD83 in Canada and the U.S. via the ITRF, Proceedings of the International Symposium of IAG, Section II, “Towards and Integrated Global Geodetic Observing System (IGGOS)”, Munich, October 5-9, 1998.

Craymer, M.R., (1998). The Least Squares Spectrum, Its Inverse Transform and Autocorrelation Function: Theory and Some Applications in Geodesy, Ph.D. Disseration, Department of Civil Engineering, University of Toronto.

Craymer, M.R., P. Vanicek, R.O. Castle, (1995). Estimation of Rod Scale Errors in Geodetic Levelling. Journal of Geophysical Research, Vol. 100, No. B8, pp. 15129-15145.

Dragert, H., X. Chen, and J. Kouba, 1995, GPS Monitoring of Crustal Strain in Southwest British Columbia with the Western Canada Deformation Array, Geomatica, Vol.49, No.3, 1995, pp. 301-313.

Ferland, R., and J. Kouba, P. Tetreault and D. Hutchison, 1999, Recent contribution to the ITRF and its realization in Canada, submitted to the Proceedings for IAG, Section II Symposium"Towards an Integrated Global Geodetic Observing System (IGGOS)", Munich, Germany, October 5-9, 1998.

Ferland, R., J. Kouba, P. Tetreault, and J. Popelar, 1995, Variation in EOP and Station Coordinates Solutions from the Canadian Active Control System (CACS), IAG/IUUG Symposia, #115, Springer, pp. 42-46.

Heroux, P. and Jan Kouba, 1995, GPS Precise Point Positioning with a Difference, Proceedings of Geomatics'95, Ottawa, Canada, June 13-15.

Junkins, D.J., G. Garrard, (1998). Demystifying Reference Systems: A Chronicle of Spatial Reference Systems in Canada. Geomatica, Vol. 52, No. 4, pp. 468-473.

Kouba, J. and Y. Mireault, 1996, IGS Analysis Coordinator Report, 1995 IGS Annual Report , pp. 45-76.

Kouba, J. and Y. Mireault, 1997 Analysis Coordinator Report, IGS Annual Report 1997, Vol. II, 1998.

Kouba, J., 1995, Analysis Coordinator Report, 1994 IGS Annual Report, pp. 59-69.

Kouba, J., 1996, IGS Combination of GPS Earth Orientation Parameters (EOP), Proc., IGS Analysis Center Workshop, March 1996, pp. 33-42.

Kouba, J., 1996, Status of the IGS Initiative to Densify the ITRF, 1995 IGS Annual Report, 77-86.

Kouba, J., 1997, Status of the IGS Pilot Project to Densify the ITRF, 1996 IGS Annual Report.

Kouba, J., 1998, Analysis Activities, IGS Annual Report 1997, Vol. I, pp.10-15, 1998.

Kouba, J., and Y. Mireault, 1997, IGS Analysis Coordinator Report, 1996 IGS Annual Report.

Kouba, J., G. Beutler and Y. Mireault, 1996, GPS Orbit/Clock Combination and Modeling, Proc. IGS Analysis Center Workshop, March 1996 pp. 3-8.

Kouba, J., G. Beutler, R.E. Neilan (1999). Coordination of IGS Analysis Centers, Proceedings of 11th International Workshop on Laser Ranging, Deggendorf, 21-25 September 1998.

Kouba, J., J. Ray and M.M. Watkins, 1998, IGS reference frame realization, the position paper #3, IGS Analysis Workshop, Darmstadt, Feb 9-11.

Kouba, J., Y. Mireault and F. Lahaye, 1995, 1994 IGS Orbit/Clock Combination and Evaluation, 1994 IGS Annual Report, pp. 70-94.

Kouba, J., Y. Mireault, G. Beutler, T. Springer and G. Gendt. 1998, A Discussion of IGS Solutions and their Impact on Geodetic and Geophysical Applications, GPS Solutions, Vol. 2, No. 2, pp. 3-15.

Kouba,J., G. Blewitt, C. Meertens and F. Webb, 1998, IGS Combined Products, their Use and IGS Realization of International Terrestrial Reference Frame (ITRF), Proceedings ofWEGNER98, States Kartwerk, Norway, July 98, .

Kouba. J. and Y. Mireault, 1997, IGS orbit, clock and EOP combined products: An update. Proceedings of the Symposium 1 - Advances in Positioning and Reference Frames, IAG97

Krakiwsky, E.J., D.J. Szabo, P. Vanicek, M.R. Craymer, (1999). Development and Testing of In-Context Confidence Regions for Geodetic Survey Networks, Contract Report, Geodetic Survey Division, Geomatics Canada, Revised February 1999.

Lambert, A., S.D. Pagiatakis, A.P. Billyard and H. Dragert, (1998). Improved ocean tide loading corrections for gravity and displacement: canada and northern United States. Journal of Geophysical Research, Vol. 103, No B12, pp. 30231-30244.

Liard, J, C. Gagnon and N. Courtier, (1995). Absolute gravity observations on BIPM site A3 during the 1989 and 1994 International Comparisons of Absolute Gravimeters. Metrologia V. 32, N. 3, November 1995, p. 153 – 158

Mainville, A., M. Craymer, S. Blackie, (1997). The GPS Height Transformation of 1997: An Ellipsoidal-Orthometric Height Transformation for Use with GPS in Canada, Geodetic Survey Division, Geomatics Canada.

Marson, I., J. E. Faller, G. Cerutti, P. De Maria, J.-M. Chartier, L. Robertsson, L.Vitushkin, J. Friederich, K. Krauterbluth, D. Stizza, J. Liard, C. Gagnon, A. Lothhammer, H. Wilmes, J. Makinen, M. Murakami, F. Rehren, M. Schnull, D. Ruess and G. S. Sasagawa, (1995). Fourth International Comparison of Absolute Gravimeters. Metrologia V. 32, N. 3, November 1995, p. 137-144.

Mireault, Y. and J. Kouba. 1999, IGS Combinations of Polar Motion, Length of Day and Universal Time, submitted to the Proceedings for IAG, Section II Symposium "Towards an IntegratedGlobal Geodetic Observing System (IGGOS)", Munich, Germany, October 5-9, 1998.

Mireault, Y., J. Kouba and J. Ray, 1999, IGS Earth Rotation Parameters, submitted to GPS Solutions

Mireault, Y., J. Kouba, and F. Lahaye, 1995, IGS Combination of Precise GPS Satellite Ephemerides and Clocks, IAG/IUUG Symposia, #115, Springer, pp. 14-23.

Neilan, R.E., G. Beutler and J. Kouba, 1997, The International GPS Service in 1997: 5 years of practical experience; 3 years of official IAG service, Proceedings of the Special Session 1 - IAG Services, IAG97 Scientific Assembly of the International Association of Geodesy, Rio De Janeiro, Brazil, Sep. 3-9

Neilan, R.E., J.F. Zumberge, G. Beutler and J. Kouba, 1995, The International GPS Service for Geodynamics (IGS) and a Cooperative Partnership with the Global Sea Level Observation System (GLOSS), Report:IOC/GE-GLOSS-IV/27, February 2, 1995.

Neilan, R.E., J.F. Zumberge, G. Beutler and J. Kouba, 1997, The International GPS Service: A Global Resource for GPS Applications and Research, ION GPS-97, 10th International technical Meeting, Kansas City, Missouri, Sep. 16-19, pp. 883-889.

Scientific Assembly of the International Association of Geodesy, Rio De Janeiro, Brazil, Sep. 3-9,

Springer, T.A., J.F. Zumberge and J. Kouba, 1998, The IGS Analysis Products and the consistency of combined solutions, the position paper #1, IGS Analysis Workshop, Darmstadt, Feb 9-11.

Tetreault, P., C. Huot, R. Ferland, J. Kouba and J. Popelar, 1997, NRCan (EMR) Analysis Centre 1996 Annual Report, 1996 IGS Annual Report.

Tetreault, P., J. Kouba, R. Ferland and J. Popelar, 1995, NRCan (EMR) Analysis Report, 1994 IGS Annual Report, pp. 213-232.

Tetreault, P., R. Ferland, J. Kouba and J. Popelar, 1996, NRCan (EMR) Analysis Centre 1995 Annual Report to IGS, 1995 IGS Annual Report, 175-180.

Vanicek, P., P. Ong, E.J. Krakiwsky, M.R. Craymer, (1996). Application of Robustness Analysis to Large Geodetic Networks, Contract Report 96-001, Geodetic Survey Division, Geomatics Canada.

Zumberge, J.F., W. Gurtner, J. Kouba and T. Springer, 1999, Current performance of IGS Network, Proceedings of 1998 IGS Network workshop, held in Nov. 98, Annapolis, Md.



  1. Satellite Positioning and Navigation

A new approach to use a GPS reference station network to improve the performance of OTF carrier ambiguity resolution was proposed and tested [Raquet et al 1998]. Reliability and availability improvements through the augmentation of GPS with other satellite-based systems, ground-based pseudolites and on-board sensors were analysed [Morley & Lachapelle 1998, Ryan et al 1999, Hayashi & Lachapelle 1997]. The concept of using a pseudolite in an inverted mode where the pseudolite is mounted on moving plaftform was studied [Raquet et al 1996]. A new method to position cellular telephones using hyperbolic triangulation and GPS timing was developed [Klukas et al 1998]. The dynamic velocity determination performance of selected GPS receivers was analysed using a GPS simulator [Cannon et al 1997, Szarmes et al 1997]. The use of single-differenced GPS/GLONASS carrier measurements for attitude determination was investigated [Keong & Lachapelle 1998]. The use of precise post-mission GPS orbits and clock corrections derived from the IGS permanent tracking network for metre-level positioning was analysed [Lachapelle et al 1996, Henriksen et al 1996].

Approaches and testing of non-dedicated GPS receivers for precise aircraft attitude determination was carried out (Cannon and Sun, 1996) along with the integration of a two-antenna GPS system and low cost dead-reckoning sensors (Harvey and Cannon, 1997; Harvey and Cannon, 1999). The use of low-cost GPS sensors for real-time precise deformation monitoring was assessed using a network of receivers spaced 50-100 m apart (Kondo et al., 1996a; Kondo et al., 1996b). An investigation of ionospheric effects in the Auroral region along with the development of improved techniques for ionospheric error modelling was carried out and tested using data from the Natural Resources Canada (NRCan) Canadian Active Control Network (Skone and Cannon, 1997a; Skone and Cannon, 1998a; Skone and Cannon, 1998b). Techniques for precise kinematic positioning in real-time have been developed and tested (Land and Cannon, 1996), as well as the use of multiple antennas/receivers for improved ambiguity resolution in the marine environment (Weisenburger and Cannon, 1997). The use of wide area networks for metre-level positioning using a variety of receiver technologies was done using two networks (Skone and Cannon, 1997b; Fotopoulos et al., 1999). Multipath mitigation using multiple, closely-spaced antennas, has been investigated for application to reference stations (Ray et al., 1998). The application of GPS to precision farming and salinity mapping was developed and assessed on a number of fields in Alberta (Cannon et al., 1997; McKenzie et al., 1997).

Additional research is this area was done by Dr. Yang Gao's group and includes the following:

(a) Development of a regional area differential GPS method for decimetre-level positioning and navigation (Gao et. al., 1997a; Li and Gao, 1998a).

  1. GPS ionosphere modelling (Gao and Li, 1998).

  2. Carrier phase data processing and ambiguity resolution algorithms (Gao and McLellan, 1996a; Gao et. al., 1996a, 1996d and 1996e; Li and Gao, 1997; Li et. al., 1997; Li and Gao, 1998b).

  3. Wide area differential GPS ( Gao et. al., 1995a and 1995b, Gao et. al., 1997b).

  4. Multi-sensor integration RTK systems (Gao and McLellan, 1996b, Gao el. al., 1996 and 1996c; Gao et. al., 1998; Gao and El-Sheimy, 1999)

2. Mathematical Modeling and Filter Design

Multi-resolution approximation, adaptive filtering, and ambiguity resolution methods were investigated. Multi-resolution methods using a discrete wavelet transform were applied to approximate the gravity field using data of different type, resolution, and accuracy, as well as data measured at different altitudes. An overview of the methodology is given in Li and Schwarz (1997), while a detailed discussion of the methods used, as well as numerical comparisons of this technique with least-squares collocation and multi-rate system techniques can be found in Li (1996). An extension of this approach to a more general set of problems in geomatics has been published in Li and Schwarz (1996a) with a specific example in atmospheric modelling presented in Li and Schwarz (1996b). Adaptive filtering has been studied by formulating the adaptive system as an interference canceler, see Bruton and Schwarz (1997), and by casting it in he form of an adaptive Kalman filter, see Mohamed (1999) and Mohamed and Schwarz (1999). In both cases, filter performance for kinematic trajectory determination was evaluated. Three different approaches to integer ambiguity resolution in carrier phase GPS were investigated. First a nonlinear integer programming method was used to obtain a global minimum, see Wei and Schwarz (1995). Second, a search algorithm based on genetic techniques was applied, see Li (1995). Finally, a whitening filter was used to come up with a simple and economic algorithm for short baselines, see Mohamed and Schwarz (1998). A broad-based comparison of these algorithms with others that have been published is still outstanding.

3. Airborne Gravimetry and Geoid Determination

Airborne gravity and geoid determination papers presented at the IAG symposium at the Boulder General Assembly were used as a starting point, see Schwarz et al (1995, ed) . As a follow-up, an assessment of the state of the art and future potential was published in Schwarz (1996b). Since then considerable progress has been made. Results of extensive system testing were used to improve error models and filtering procedures. The first detailed results of using a strapdown inertial system for airborne gravimetry were published in Wei and Schwarz (1998) and showed an accuracy comparable to that of the Lacoste/Romberg and Bell platform systems. This was confirmed in further tests where two different strapdown INS/DGPS systems were flown side by side over a 100km by 100km area in the Rocky mountains, see Glennie and Schwarz (1999). In addition, a direct comparison of the UofC strapdown system with the Lacoste-Romberg system was recently made, by flying them at low altitude on the same aircraft over a known sea gravity profile off the cost of Greenland, see Glennie and al (1999). A comparison of different mathematical models for airborne gravimetry is given in Wei and Schwarz (1997), and the effect of multiple system configurations on the error modelling is discussed in Schwarz et al (1998). Improvements in filtering techniques are reported in Hammada (1996) and in Hammada and Schwarz (1997); progress in trajectory modelling is discussed in Bruton et al (1999). The use of airborne gravimetry for geoid determination is discussed in Schwarz and Li (1996) and its place in the world of geodetic boundary value problems in Schwarz and Li (1997). First practical results of using airborne gravity for relative geoid determination in support of digital elevation models generated by airborne interferometric SAR have been reported in Glennie et al (1998) and in Tennant et al (1998). The development in this area is still rapid. For a detailed discussion of the current state of the art in strapdown airborne gravimetry Glennie (1999) is recommended.

  1. Mobile Multi-Sensor Systems

Mobile multi-sensor systems, both van-mounted systems and airborne systems, have been studied for a variety of mapping and GIS applications. The general concept of such systems is described in Schwarz (1995, 1998). A high-accuracy van-mounted system for urban surveying and mapping has been presented in a number of publications, see for instance El-Sheimy (1996), Schwarz and El-Sheimy (1995, 1996), El-Sheimy et al (1995, 1997). The system is now fully operational in an industrial setting. In airborne mapping integration of the imaging sensors with INS/DGPS is increasingly used to georeference each image for immediate use without the need for ground control. Such systems have been tested for integration with conventional photogrammetric cameras and have shown that the in-flight camera position and orientation can be determined with accuracies of 0.1-0.2 m in position and 10-20 arcseconds in orientation, see for instance Skaloud et al (1996) and Skaloud and Schwarz (1998). Further improvements of the filtering techniques applied have been reported in Skaloud et al (1998) and in Skaloud (1999). The potential of a fully digital airborne system that would considerably reduce the overall cost of airborne mapping have been investigated in Mostafa and Schwarz (1997) and Mostafa et al (1998a, 1998b). Recent results indicate that ground positions can be determined at the decimeter level of accuracy without the use of ground control, using a CCD camera with 1500 by 1000 pixel resolution. If that resolution is not needed, as in many resource mapping applications, low-cost inertial systems can be used in the integration, see Zhang et al (1995) and Skaloud et al (1997). First results of using such systems in real time, for instance for forest fire control, have been published in Schwarz and Sun (1998).

Additional research in this area was done by Dr. Naser El-Sheimy's group and includes the following:

(a) Study on the “The Future of Positioning and Navigation (POS/NAV) Technologies: developing a road map for POS/NAV technologies as applied to land navigation”. The study was for the US Army Topographic Engineering Center (TEC).

(b) The development of INS Simulations for Pipeline Surveys.

(c) The Development of a Backpack Mobile Mapping System: developing a lightweight low-cost MMS for mapping and GIS application (under devlopment).

(d) The Development of Real-time Airborne Mapping (RAM): RAM will integrates Digital Color Cameras, the Global Positioning System (GPS), and Inertial Navigation System (INS). RAM can be used to produce seamless georeferenced color digital image strips of the area flown in real-time for utility companies, oil companies, and department of transportation applications. In order to achieve that, new algorithms and procedures that can georeference, process, and store the image and also tie them to ground coordinate framework in real-time will be developed.

(e) The development of a commercially successful Mobile Mapping System (MMS) that integrate navigation sensors (GPS and INS) and digital imaging sensors (full-frame digital cameras). The MMS VISAT van (Video-INS-SATellite) system was developed at the University of Calgary as a part of the Department of Geomatics Engineering research on multi-sensors systems. The VISAT van (see the opposite figure) is a precise post-mission MMS that can be operated at speeds of up to 60 km per hour and achieves a positioning accuracy of 0.3 m (RMS) for features within the images. The VISAT system integrates GPS, INS, and eight digital cameras. The GPS and INS are used to solve the georeferencing parameters necessary for mapping from the digital images.

(f) Research and Development of a Softcopy Photogrammetric Workstation (SPW) for GIS applications from Mobile Mapping Systems (See Figure 2). The SPW is mainly designed to extract features from the GPS/INS georeferenced-images collected by land mobile mapping systems or any other georeferenced media.

(g) The development of an Expert Knowledge System for GPS/INS Kinematic Mapping Systems (See Figure 3). The expert knowledge system is mainly concerned with alerting the operator to cases of poor GPS satellite geometry, signal blockage, or cycle slips, and using INS aiding in fixing these problems.

  1. Precise Geoid Determination, Satellite Altimetry, and Optimal Combination of Heterogeneous Data

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Современное видение глобальных перспектив развития магниевой индустрии Greg Patzer, International Magnesium Association, США
International association of geodesy iconInternational Association for Vegetation Science “Vegetation Processes and Human Impact in a Changing World” Chania, Crete (Greece)

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