BOOK REVIEWS

Book review in this Article DIGITAL IMAGING. By R. Graham . Whittles Publishing, Caithness, 1998. ISBN 1 870325 12 5. 234 × 156 mm. 240 pages. 18 colour plates, 93 figures, 9 tables. Price £35.00 paperback. PARALLEL PROCESSING ALGORITHMS FOR GIS. Edited by R. Healey , S. Dowers , B. Gittings and M. Mineter . Taylor & Francis, London, 1998. ISBN 0 7484 0509 7. xviii + 460 pages. Price £24.95. FRAMEWORK FOR THE WORLD. Edited by D. Rhind . Geoinformation International, Cambridge, 1997. ISBN 1 8624 2021 1. 240 × 160 mm. 325 pages. Illustrated and 12 colour plates. Price £45.00 casebound. SEMANTIC MODELLING FOR THE ACQUISITION OF TOPOGRAPHIC INFORMATION FROM IMAGES AND MAPS. Edited by W. F$ourstner and L. Pl$uumer . Birkhäuser Verlag, Basel, 1997. ISBN 3 7643 5758 4. 235 × 160 mm. 227 pages. Diagrams and illustrations. Price CHF88.00. GEOGRAPHICAL INFORMATION SYSTEMS AND COMPUTER CARTOGRAPHY. By C. Jones . Addison Wesley Longman Ltd., Harlow, 1997. ISBN 0 582 04439 1. 190 × 245 mm. 319 pages. 16 colour plates, 202 black and white illustrations and 14 tables. Price £21.00 paperback. MAPPING: WAYS OF REPRESENTING THE WORLD. By D. Dorling and D. Fairbairn . (Insights into Human Geography Series.) Edited by P. Knox and S. Smith . Addison Wesley Longman Ltd., Harlow, 1997. ISBN 0 582 28972 6. 234 × 155 mm. vii + 184 pages. Price £11.99 softbound. MANUAL OF PHOTOGRAPHIC INTERPRETATION. Second edition. Editor-in-chief W. R. Philipson . American Society for Photogrammetry and Remote Sensing, Bethesda, MD, USA, 1997. ISBN 1 57083 039 8. 285 × 225 mm. xvi + 689 pages. 489 figures, including 87 in colour, and 75 tables. Price for non-members US$124.00. FLATTENING THE EARTH. TWO THOUSAND YEARS OF MAP PROJECTIONS. By J. P. Snyder . University of Chicago Press, Chicago and London, 1997. ISBN 0 226 76747 7. 235 × 165 mm. xviii + 365 pages. 173 figures and 6 tables. Price £15.95 paperback. EUROPEAN SPACE DIRECTORY 1998. Thirteenth edition. Edited by D. Shirvanian . Sevig Press, Paris, 1998. ISSN 0765–0574. 270 × 210 mm. 324 pages. 1 figure and 43 tables. Price FFr965 paperback. TERMINOLOGIE DE TÉLÉDÉTECTION ET PHOTOGRAMMÉTRIE. By S. Paul , G. Ducher , I. Jobard , C.-H. Latarche and M. Lenco . Conseil International de la Langue Française, Paris, 1997. ISBN 2 85319 270 9. 247 × 168 mm. 455 pages. Price FFr250 hardback. AUTOMATIC EXTRACTION OF MAN-MADE OBJECTS FROM AERIAL AND SPACE IMAGES (II). Edited by A. Gruen , E. P. Baltsavias and O. Henricsson . Birkhäuser Verlag, Basel, 1997. ISBN 3 7643 5788 6. 238 × 171 mm. ix + 393 pages. 241 figures and 25 tables. Price CHF128 casebound.     

BOOK REVIEWS

Book review in this Article GIS DATA CONVERSION: STRATEGIES, TECHNIQUES AND MANAGEMENT. Edited by P. Hohl . Onword Press, Santa Fe, 1998. ISBN 1 56690 175 8. 180 × 228 mm. xiii + 416 pages. Illustrated. Price £33.95 paperback. GEOGRAPHICAL INFORMATION SYSTEMS FOR ECOLOGY: AN INTRODUCTION. By R. Wadsworth and J. Treweek . Addison Wesley Longman Ltd., Harlow, 1999. ISBN 0 582 24652 0. 156 × 234 mm. xiii + 184 pages. Four colour plates, appendix, references and index. Price £14.99 paperback. GENERATION OF DIGITAL ELEVATION MODELS THROUGH SPACEBORNE SAR INTERFEROMETRY. Remote Sensing Series, Volume 30. By D. Small . Remote Sensing Laboratories, Department of Geography, University of Zurich, 1998. 147 × 207 mm. xvi + 150 pages. 84 figures, including images, and 8 tables. Price SFr 40 paperback. TRIANGULATION. By P. Whitaker . Phoenix House, London, 1999. ISBN 1 816590 80 6. 140 × 200 mm. 272 pages. Price £12.99. OEEPE SURVEY ON 3D‐CITY MODELS. By C. Fuchs , E. G$uulch and W. F$ourstner . PERFORMANCE OF TIE‐POINT EXTRACTION IN AUTOMATIC AERIAL TRIANGULATION. By C. Heipke and K. Eder . OEEPE Official Publication No. 35. Bundesamt für Kartographie und Geodäsie, Frankfurt am Main, 1998. ISBN 3 88648 075 5. 175 × 245 mm. 198 pages. 42 figures, 27 tables and 7 appendices. Price DM47, paperback, plus DM7 for postage and packing and DM20 for foreign exchange charges, if applicable. EUROPEAN SPACE DIRECTORY. Fourteenth edition. Edited by D. Shirvanian . Sevig Press, Paris, 1999. ISSN 0765 0574. 210 × 270 mm. 316 pages. 1 figure and 30 tables. Price FFr990 (£150) paperback. CAMERA AT SEA. THE HISTORY OF THE ROYAL NAVAL PHOTOGRAPHIC BRANCH, 1919–1998. By N. Mercer . Airlife Publishing Ltd., Shrewsbury, 1999. ISBN 1 85310 889 8. 218 × 306 mm. 144 pages, including a 72 page portfolio of colour plates. Price £24.95 hardback. ESSENTIAL DARKROOM TECHNIQUES. Third edition. By J. Eastland . Cassell, London, 1999. ISBN 0 304 35086 9. 190 × 247 mm. 208 pages. 144 figures and 22 tables. Price £18.99 paperback. ADVANCES IN MOBILE INFORMATION SYSTEMS. (MOBILE COMMUNICATIONS SERIES.) Edited by J. Walker . Artech House, Inc., Norwood, USA, 1999. ISBN 0 89006 951 4. 159 × 235 mm. xxi + 468 pages. 104 figures and 42 tables. Price £67 hardback.     

BOOK REVIEWS

Book review in this Article GEOGRAPHICAL INFORMATION SYSTEMS AND THE LAW: MAPPING THE LEGAL FRONTIERS. By G. Cho . John Wiley & Sons Ltd., Chichester, 1998. ISBN 0 471 94857 8. 158 × 236 mm. xix + 337 pages. 19 figures and 7 tables. Price £70 hardback. UNDERSTANDING SYNTHETIC APERTURE RADAR IMAGES. By C. J. Oliver and S. Quegan . Artech House, Inc., Norwood, USA, 1998. ISBN 0 89006 850 X. 160 × 235 mm. xxvii + 479 pages. 125 diagrams and illustrations. Price £79 hardback. REMOTE SENSING OF TROPICAL REGIONS. By E. A. Sharkov . John Wiley & Sons Ltd., in association with Praxis Publishing Ltd., Chichester, 1998. ISBN 0 471 97171 5. 172 × 247 mm. xvii + 310 pages, plus 8 pages of colour plates. 78 figures and 24 tables. Price £65 hardback. ELEMENTS OF PHOTOGRAMMETRY, WITH APPLICATIONS IN GIS. By P. R. Wolf and B. A. Dewitt . McGraw Hill, New York, 2000. ISBN 0 07 292454 3. 160 × 235 mm. xiii + 608 pages. Illustrated. Price US$60 hardback. THE WESTERN FRONT FROM THE AIR. By N. Watkis . Sutton Publishing, Stroud, 1999. ISBN 0 7509 1338. 200 × 270 mm. ix + 130 pages. Illustrated. Price £20 hardback. ADVANCES IN REMOTE SENSING AND GIS ANALYSIS. Edited by P. M. Atkinson and N. J. Tate . John Wiley & Sons Ltd., Chichester, 1999. ISBN 0 471 98577 5. 174 × 251 mm. xiv + 273 pages, plus 4 pages of colour plates. Illustrated. Price £55 hardback. MANUAL OF REMOTE SENSING, THIRD EDITION, VOLUME 3. REMOTE SENSING FOR THE EARTH SCIENCES. Edited by A. N. Rencz . John Wiley & Sons Inc., New York, USA, in co‐operation with the American Society for Photogrammetry and Remote Sensing, 1999. ISBN 0471 29405 5. 184 × 260mm. xvi + 707 pages. 280 illustrations and tables and 53 colour plates. Price £128 hardback. MANAGING NATURAL RESOURCES WITH GIS. By L. Lang . SERVING MAPS ON THE INTERNET. By C. Harder . Environmental Systems Research Institute Inc., Redlands, California, USA, 1998. ISBN 1 879102 53 6 and ISBN 1 879102 52 8, respectively. Both 229 × 189 mm. ix + 117 pages and ix + 130 pages, respectively, both plus CD‐ROM. Illustrated. Price US$19.95 each, paperback. PASSIVE MICROWAVE REMOTE SENSING OF OCEANS. By I. V. Cherny and V. Yu Raizer . John Wiley & Sons Ltd., in association with Praxis Publishing Ltd., Chichester, 1998. ISBN 0 471 97170 7. 172 × 247mm. viii + 195 pages. 127 illustrations, including 8 pages of colour plates. Price £55 hardback. VIDEO CAMERA TECHNOLOGY. By A. C. Luther . Artech House Inc., Norwood, USA, 1998. ISBN 0 89006 556 X. 160 × 235 mm. xvi + 312 pages. Black and white illustrations. Price £59 hardback. DIGITAL PHOTOGRAMMETRY, VOLUME I. By T. Schenk . TerraScience, Laurelville, U.S.A, 1999. ISBN 0 9677653 0 7 perfect bound; ISBN 0 9677653 1 5 case bound. 235 × 162mm. xx + 421 pages. 179 figures and 15 tables. Price US$49 perfect bound, US$69 case bound, plus package and postage. INFINITE PERSPECTIVES: TWO THOUSAND YEARS OF THREE‐DIMENSIONAL MAP‐MAKING. By B. M. Ambroziak and J. R. Ambroziak , with an introduction by R. Bradbury . Princeton Architectural Press, New York, 1999. ISBN 1 56898 195 3. 382 × 325mm. 111 pages. 100 colour illustrations. Price £55 hardback. EVEREST—THE MAN AND THE MOUNTAIN. By J. R. Smith . Whittles Publishing, Caithness, 1999. ISBN 1 870325 72 9. 170 × 240mm. xiv + 306 pages. 45 figures and 5 appendices. Price £37.50 paperback. TEXT BOOKS ON REMOTE SENSING AND GIS. Remote Sensing Notes edited by Japan Association of Remote Sensing . GIS Notes by S. Murai . Asian Center for Research on Remote Sensing, Thailand, 1999. 140 × 130mm. Price unknown, CD‐ROM. REMOTE SENSING CHANGE DETECTION. Edited by R. S. Lunetta and C. D. Elvidge . Ann Arbor Press, Michigan, USA, 1998. ISBN 1 57504 037 9. 183 × 260mm. xviii + 318 pages. 20 colour plates, plus numerous illustrations. Price US$69.95 hardback. NORFOLK FROM THE AIR. VOLUME 2. Edited by P. Wade ‐Martins . Photography by D. Edwards . Norfolk Museums Service, Norwich, 1999. ISBN 0 903101 68 8. 212 × 284mm. 148 pages. 135 half page aerial photographs, 89 in black and white. Price £15.95 paperback.     

BOOK REVIEWS

Book review in this Article PHYSICAL MEASUREMENTS AND SIGNATURES IN REMOTE SENSING. Edited by G. Guyot and T. Phulpin . A. A. Balkema, Rotterdam, 1997. ISBN 90 5410 917 3. Two volumes, each 172.254 mm. Volume 1: xiii + 390 pages; volume 2: x + 411 pages. Price NLG 225. MANUAL OF REMOTE SENSING, THIRD EDITION, VOLUME 2. PRINCIPLES AND APPLICATIONS OF IMAGING RADAR. Edited by F. M. Henderson and A. J. Lewis . John Wiley & Sons, Inc., New York, in co-operation with the American Society for Photogrammetry and Remote Sensing, 1998. ISBN 0 471 29406 3. 221.287 mm. xxv + 899 pages. 76 colour plates. Price US$198 hardback. GEOGRAPHICAL INFORMATION SYSTEMS. PRINCIPLES, TECHNIQUES, APPLICATIONS AND MANAGEMENT. Second edition. Edited by P. A. Longley , M. F. Goodchild , D. J. Maguire and D. W. Rhind . John Wiley & Sons, Chichester, 1999. ISBN 0471 32182 6 hardback. Boxed set of two volumes. 200.270 mm. Volume 1: xcv + 580 pages, with 40 colour plates. Volume 2: xciii + 521 pages, with 66 colour plates. Price £195. FUTURE TRENDS IN REMOTE SENSING. Edited by P. GUDMANDSEN. A. A. Balkema, Rotterdam, 1998. ISBN 90 5410 933 5. 180.254mm. xii + 496 pages, including 18 pages of colour plates. Price NLG 205. INTERPRETATION OF AIRPHOTOS AND REMOTELY SENSED IMAGERY. By R. H. Arnold . Prentice-Hall, Inc., New Jersey, USA, 1997. ISBN 0 02 303924 8. 225.274 mm. xiv + 250 pages. 189 figures, including 17 in colour. Price £21.95 spiral bound. GEOCOMPUTATION: A PRIMER. Edited by P. A. Longley , S. M. Brooks , R. Mc Donnell and W. Mac Millan . John Wiley & Sons Ltd., Chichester, 1998. ISBN 0 471 98575 9 clothbound, 0 471 98576 7 paperback. 168.244 mm. xii + 278 pages, plus 8 pages of colour plates. Price £22.50 paperback. DIRECTORY OF AERIAL PHOTOGRAPHIC COLLECTIONS IN THE UNITED KINGDOM. Second edition. National Association of Aerial Photographic Libraries (NAPLIB), Dereham, 1999. ISBN 0 9530436 1 4. 210.297 mm. 132 pages. 8 plates and 3 figures. Price £40 (£20 to new members of NAPLIB and to members of the Photogrammetric Society). DIGITAL LANDSCAPE MODEL FOR EUROPE (DLME). By E. Blau , F. Boochs and B.-S. Schulz , with editorial assistance of P. R. T. Newby . OEEPE Official Publication No. 34. Institut für Angewandte Geodäsie, Frankfurt am Main, 1997. ISSN 0257 0505. 175.245 mm. 108 pages. 21 figures, 9 tables, 4 diagrams and 15 appendices. Price DM 40. THE AGI SOURCE BOOK FOR GEOGRAPHIC INFORMATION SYSTEMS 1998/99. Edited by C. Corbin . Association for Geographic Information, London, 1998. ISBN 1 847059 314. 210.297 mm. 396 pages. 43 trade directories and 21 reference tables. Price £39.50 paperback.     

BOOK REVIEWS

Book review in this Article THE ADVANCED VERY HIGH RESOLUTION RADIOMETER (AVHRR). By A. P. Cracknell . Taylor & Francis Lid., London, 1997. ISBN 0 7484 0209 8. 173 × 253 mm. xi + 534 pages. 8 colour plates. Price £60 hardback. SPATIAL DATABASE TRANSFER STANDARDS 2: CHARACTERISTICS FOR ASSESSING STANDARDS AND FULL DESCRIPTIONS OF THE NATIONAL AND INTERNATIONAL STANDARDS IN THE WORLD. Edited by H. Moellering . Published on behalf of the International Cartographic Association by Elsevier Science, Oxford, 1997. ISBN 0 0804 2433 3. 210 × 297 mm. 373 pages. Price $182 casebound. INTRODUCTION TO GEODESY. By J. R. Smith . John Wiley & Sons, Inc., New York, 1997. ISBN 0 471 16660 X. 156 × 230 mm. xv + 224 pages. 78 figures. Price £32.50 paperback. PHOTOGRAMMETRIE. Band 2, Verfeinerte Methoden und Anwendungen. Mit Beiträgen von J. Jansa und H. Kager. By K. Kraus . (Photogrammetry. Volume 2, Advanced methods and applications. With contributions by J. Jansa and H. Kager). Third edition. Dümmler Verlag, Bonn, 1996. ISBN 3 427 78653 6. 239 × 163 mm. 488 pages. 260 figures. In German. Price approximately 75 DM paperback. PHOTOGRAMMETRIE IN DER SCHWEIZ. Geschichte—Entwicklung. (Photogrammetry in Switzerland. History—Development). Edited by Schweizerische Gesellschaft FÜR Photogrammetrie , Bildanalyse und Fernerkundung (Swiss Society for Photogrammetry, Image Analysis and Remote Sensing). Dümmler Verlag, Bonn, 1996. ISBN 3 427 78721 4. 297 × 210 mm. 152 pages. 98 figures and an appendix with 8 colour maps. In German. Price approximately 60 DM hardback. GLOBAL POSITIONING SYSTEM: THEORY AND PRACTICE. By B. Hofmann -Wellenhof , H. Lichtenegger and J. Collins . Springer, Vienna and New York, 1997. Fourth revised edition. ISBN 3 211 82839 7. 240 × 165 mm. xxiii + 389 pages. 45 figures and 76 tables. Price US $54.95 paperback. MATHS FOR MAP MAKERS. By A. L. Allan . Whittles Publishing, Caithness, Scotland, 1997. ISBN 1 870325 91 5. 156 × 230 mm. xiii + 305 pages. 16 figures. Price £19.95 paperback. DIGITAL PHOTOGRAMMETRY: AN ADDENDUM TO THE MANUAL OF PHOTOGRAMMETRY. Edited by C. Greve . American Society for Photogrammetry and Remote Sensing, Bethesda, Maryland, USA, 1996. ISBN 1 57083 037 1. 286 × 225 mm. vii + 247 pages. 170 figures (7 in colour) and 33 tables. Price $90.00 (casebound), $62.00 ASPRS members, $35.00 students. AN ILLUSTRATED HISTORY OF 250 YEARS OF MILITARY SURVEY. By Y. Hodson and A. Gordon . Military Survey Defence Agency, London, 1997. ISBN 0 9529730 07. 210 × 295 mm. 40 pages, 106 illustrations. Price £7 paperback. Copies are available from Gordonwood Associates, 1 Majorca Avenue, Andover, Hampshire. SP10 1JW     

The reduction correction in North America

An inverse Poisson integral technique has been used to determine a gravity field on the geoid which, when continued by analytic free space methods to the topographic surface, agrees with the observed field. The computation is performed in three stages, each stage refining the previous solution using data at progressively increasing resolution (1^o×1^o, 5′×5′, 5/8′×5/8′) from a decreasing area of integration. Reduction corrections are computed at 5/8′×5/8′ granularity by differencing the geoidal and surface values, smoothed by low-pass filtering and sub-sampled at 5′ intervals. This paper discusses 1^o×1^o averages of the reduction corrections thus obtained for 172 1^o×1^o squares in western North America. The 1^o×1^o mean reduction corrections are predominantly positive, varying from −3 to +15mgal, with values in excess of 5mgal for 26 squares. Their mean andrms values are +2.4 and 3.6mgal respectively and they correlate well with the mean terrain corrections as predicted byPellinen in 1962. The mean andrms contributions from the three stages of computation are: 1^o×1^o stage +0.15 and 0.7mgal; 5′×5′ stage +1.0 and 1.6mgal; and 5/8′×5/8′ stage +1.3 and 1.8mgal. These results reflect a tendency for the contributions to become larger and more systematically positive as the wavelengths involved become shorter. The results are discussed in terms of two mechanisms; the first is a tendency for the absolute values of both positive and negative anomalies to become larger when continued downwards and, the second, a non-linear rectification, due to the correlation between gravity anomaly and topographic height, which results in the values continued to a level surface being systematically more positive than those on the topography.     

Comparison of mean gravity anomalies at elevation with corresponding ground anomalies

In support of requirements for the U.S. Air Force Cambridge Research Laboratories, gravity anomalies have been upward continued to several elevations in different areas of the United States. One area was 34⁰ to 40⁰ N in latitude and 96⁰ to 103⁰ W in longitude, generally called the Oklahoma area. The computations proceeded from 26, 032 point anomalies to the prediction of mean anomalies in 14, 704, 2.5′×2.5′ blocks and 9,284, 5′×5′ blocks. These anomalies were upward continued along 28 profiles at 5′ intervals for every 30′ in latitude and longitude. These anomalies at elevations were meaned in various patterns to form mean 30′×30″, 1⁰×1⁰, 5⁰×5⁰ blocks. Comparisons were then made to the corresponding ground values. The results of these comparisons lead to practical recommendations on the arrangement of flight profiles in airborne gravimetry.     

Ultra-high degree spherical harmonic analysis and synthesis using extended-range arithmetic

We present software for spherical harmonic analysis (SHA) and spherical harmonic synthesis (SHS), which can be used for essentially arbitrary degrees and all co-latitudes in the interval (0°, 180°). The routines use extended-range floating-point arithmetic, in particular for the computation of the associated Legendre functions. The price to be paid is an increased computation time; for degree 3,000, the extended-range arithmetic SHS program takes 49 times longer than its standard arithmetic counterpart. The extended-range SHS and SHA routines allow us to test existing routines for SHA and SHS. A comparison with the publicly available SHS routine GEOGFG18 by Wenzel and HARMONIC SYNTH by Holmes and Pavlis confirms what is known about the stability of these programs. GEOGFG18 gives errors <1 mm for latitudes [-89°57.5′, 89°57.5′] and maximum degree 1,800. Higher degrees significantly limit the range of acceptable latitudes for a given accuracy. HARMONIC SYNTH gives good results up to degree 2,700 for almost the whole latitude range. The errors increase towards the North pole and exceed 1 mm at latitude 82° for degree 2,700. For a maximum degree 3,000, HARMONIC SYNTH produces errors exceeding 1 mm at latitudes of about 60°, whereas GEOGFG18 is limited to latitudes below 45°. Further extending the latitudinal band towards the poles may produce errors of several metres for both programs. A SHA of a uniform random signal on the sphere shows significant errors beyond degree 1,700 for the SHA program SHA by Heck and Seitz.     

INTERPOLATING FROM TRAVERSE TABLES TO SECONDS

Abstract

In the Empire Survey Review, no. 4, 1932, Mr. Clendinning has described a method of interpolating from traverse tables to seconds. Below is another method, due to Prof. Nekrassov, for use with traverse tables published by him. The method is described in The Geodezist, Moscow, 1936, no. I, pp. 47–52.     

The optimal Mercator projection and the optimal polycylindric projection of conformal type – case-study Indonesia

As a conformal mapping of the sphere S ² _R or of the ellipsoid of revolution E ² _A , _B the Mercator projection maps the equator equidistantly while the transverse Mercator projection maps the transverse metaequator, the meridian of reference, with equidistance. Accordingly, the Mercator projection is very well suited to geographic regions which extend east-west along the equator; in contrast, the transverse Mercator projection is appropriate for those regions which have a south-north extension. Like the optimal transverse Mercator projection known as the Universal Transverse Mercator Projection (UTM), which maps the meridian of reference Λ₀ with an optimal dilatation factor &ρcirc;=0.999 578 with respect to the World Geodetic Reference System WGS 84 and a strip [Λ₀−Λ _W ,Λ₀ + Λ _E ]×[Φ _S ,Φ _N ]= [−3.5^∘,+3.5^∘]×[−80^∘,+84^∘], we construct an optimal dilatation factor ρ for the optimal Mercator projection, summarized as the Universal Mercator Projection (UM), and an optimal dilatation factor ρ₀ for the optimal polycylindric projection for various strip widths which maps parallel circles Φ₀ equidistantly except for a dilatation factor ρ₀, summarized as the Universal Polycylindric Projection (UPC). It turns out that the optimal dilatation factors are independent of the longitudinal extension of the strip and depend only on the latitude Φ₀ of the parallel circle of reference and the southern and northern extension, namely the latitudes Φ _S and Φ _N , of the strip. For instance, for a strip [Φ _S ,Φ _N ]= [−1.5^∘,+1.5^∘] along the equator Φ₀=0, the optimal Mercator projection with respect to WGS 84 is characterized by an optimal dilatation factor &ρcirc;=0.999 887 (strip width 3^∘). For other strip widths and different choices of the parallel circle of reference Φ₀, precise optimal dilatation factors are given. Finally the UPC for the geographic region of Indonesia is presented as an example. Received: 17 December 1997 / Accepted: 15 August 1997     

The CARIB97 high-resolution geoid height model for the Caribbean Sea

A 2×2 arc-minute resolution geoid model, CARIB97, has been computed covering the Caribbean Sea. The geoid undulations refer to the GRS-80 ellipsoid, centered at the ITRF94 (1996.0) origin. The geoid level is defined by adopting the gravity potential on the geoid as W ₀=62 636 856.88 m²/s² and a gravity-mass constant of GM=3.986 004 418×10¹⁴ m³/s². The geoid model was computed by applying high-frequency corrections to the Earth Gravity Model 1996 global geopotential model in a remove-compute-restore procedure. The permanent tide system of CARIB97 is non-tidal. Comparison of CARIB97 geoid heights to 31 GPS/tidal (ITRF94/local) benchmarks shows an average offset (h–H–N) of 51 cm, with an Root Mean Square (RMS) of 62 cm about the average. This represents an improvement over the use of a global geoid model for the region. However, because the measured orthometric heights (H) refer to many differing tidal datums, these comparisons are biased by localized permanent ocean dynamic topography (PODT). Therefore, we interpret the 51 cm as partially an estimate of the average PODT in the vicinity of the 31 island benchmarks. On an island-by-island basis, CARIB97 now offers the ability to analyze local datum problems which were previously unrecognized due to a lack of high-resolution geoid information in the area. Received: 2 January 1998 / Accepted: 18 August 1998     

Earth＇s Temporal Principal Moments of Inertia and Variable Rotation

Based on the gravity field models EGM96 and EIGEN-GL04C, the Earth＇s time-dependent principal moments of inertia A, B, C are obtained, and the variable rotation of the Earth is determined. Numerical results show that A, B, and C have increasing tendencies; the tilt of the rotation axis increases 2.1×10^ 8 mas/yr; the third component of the rotational angular velocity, ω3 , has a decrease of 1.0×10^ 22 rad/s^2, which is around 23% of the present observed value. Studies show in detail that both 0 and ω3 experience complex fluctuations at various time scales due to the variations of A, B and C.     

The geopotential value <Emphasis Type="Italic">W</Emphasis><Subscript>0</Subscript> for specifying the relativistic atomic time scale and a global vertical reference system

The TOPEX/Poseidon (T/P) satellite alti- meter mission marked a new era in determining the geopotential constant W ₀. On the basis of T/P data during 1993–2003 (cycles 11–414), long-term variations in W ₀ have been investigated. The rounded value W ₀ = 62636856.0 ± 0.5) m ² s ⁻² has already been adopted by the International Astronomical Union for the definition of the constant L _G = W ₀/c ² = 6.969290134 × 10⁻¹⁰ (where c is the speed of light), which is required for the realization of the relativistic atomic time scale. The constant L _G , based on the above value of W ₀, is also included in the 2003 International Earth Rotation and Reference Frames Service conventions. It has also been suggested that W ₀ is used to specify a global vertical reference system (GVRS). W ₀ ensures the consistency with the International Terrestrial Reference System, i.e. after adopting W ₀, along with the geocentric gravitational constant (GM), the Earth’s rotational velocity (ω) and the second zonal geopotential coefficient (J ₂) as primary constants (parameters), then the ellipsoidal parameters (a,α) can be computed and adopted as derived parameters. The scale of the International Terrestrial Reference Frame 2000 (ITRF2000) has also been specified with the use of W ₀ to be consistent with the geocentric coordinate time. As an example of using W ₀ for a GVRS realization, the geopotential difference between the adopted W ₀ and the geopotential at the Rimouski tide-gauge point, specifying the North American Vertical Datum 1988 (NAVD88), has been estimated.     

An alternative algebraic algorithm to transform Cartesian to geodetic coordinates

The algorithm to transform from 3D Cartesian to geodetic coordinates is obtained by solving the equation of the Lagrange parameter. Numerical experiments show that geodetic height can be recovered to 0.5 mm precision over the range from −6×10⁶ to 10¹⁰ m. Electronic Supplementary Material: Supplementary material is available in the online version of this article at     

World Geodetic Datum 2000

 Based on the current best estimates of fundamental geodetic parameters {W ₀,GM,J ₂,Ω} the form parameters of a Somigliana-Pizzetti level ellipsoid, namely the semi-major axis a and semi-minor axis b (or equivalently the linear eccentricity ) are computed and proposed as a new World Geodetic Datum 2000. There are six parameters namely the four fundamental geodetic parameters {W ₀,GM,J ₂,Ω} and the two form parameters {a,b} or {a,ɛ}, which determine the ellipsoidal reference gravity field of Somigliana-Pizzetti type constraint to two nonlinear condition equations. Their iterative solution leads to best estimates a=(6 378 136.572±0.053)m, b=(6 356 751.920 ± 0.052)m, ɛ=(521 853.580±0.013)m for the tide-free geoide of reference and a=(6 378 136.602±0.053)m, b=(6 356 751.860±0.052)m, ɛ=(521 854.674 ± 0.015)m for the zero-frequency tide geoid of reference. The best estimates of the form parameters of a Somigliana-Pizzetti level ellipsoid, {a,b}, differ significantly by −0.39 m, −0.454 m, respectively, from the data of the Geodetic Reference System 1980. Received: 1 February 1999 / Accepted: 31 August 1999     

National height datum,the Gauss–Listing geoid level value w0 and its time variation 0 (Baltic Sea Level Project: epochs 1990.8, 1993.8, 1997.4)

 A methodology for precise determination of the fundamental geodetic parameter w ₀, the potential value of the Gauss–Listing geoid, as well as its time derivative ₀, is presented. The method is based on: (1) ellipsoidal harmonic expansion of the external gravitational field of the Earth to degree/order 360/360 (130 321 coefficients; http://www.uni-stuttgard.de/gi/research/ index.html projects) with respect to the International Reference Ellipsoid WGD2000, at the GPS positioned stations; and (2) ellipsoidal free-air gravity reduction of degree/order 360/360, based on orthometric heights of the GPS-positioned stations. The method has been numerically tested for the data of three GPS campaigns of the Baltic Sea Level project (epochs 1990.8,1993.4 and 1997.4). New w ₀ and ₀ values (w ₀=62 636 855.75 ± 0.21 m²/s², ₀=−0.0099±0.00079 m²/s² per year, w ₀/&γmacr;=6 379 781.502 m,₀/&γmacr;=1.0 mm/year, and &γmacr;= −9.81802523 m²/s²) for the test region (Baltic Sea) were obtained. As by-products of the main study, the following were also determined: (1) the high-resolution sea surface topography map for the Baltic Sea; (2) the most accurate regional geoid amongst four different regional Gauss–Listing geoids currently proposed for the Baltic Sea; and (3) the difference between the national height datums of countries around the Baltic Sea. Received: 14 August 2000 / Accepted: 19 June 2001     

Integration of Landsat ETM+ Data with Field Measurements for Mapping Leaf Area Index in the Grasslands of Central Kazakhstan

A fine-resolution leaf area index (LAI) data set over a 150 km × 150 km region in central Kazakhstan is retrieved using Landsat ETM+ imagery and ground-based LAI inferred from hemispherical photography and direct measurements. Regression analysis and geostatistics are applied for developing empirical models of LAI from Landsat ETM+ data. The best accuracy is achieved using a model employing a canonical index that combines all the contributions of individual Landsat ETM+ bands into a single index (R ² = 0.67; RMSE = 0.21). This model is then applied for mapping LAI at a regional scale.     

THE HEIGHT CLOSING ERROR IN MULTIPLEX BRIDGES CAUSED BY NON-FLAT DIAPOSITIVES

Abstract

A recent investigation into the flatness of Multiplex diapositive slides has shown that flatness errors occur ranging from 0 to 0·03–0·04 mm. referred to the flat projector stage. In a first attempt to ascertain the effects of errors of this kind on Multiplex bridges, the flatness values of two sets of nine diapositives each were measured using a simple interferometric method and the vertical (wants of correspondence) and horizontal parallaxes introduced by these flatness errors were subjected to computational bridging. The resulting height errors at the end of the two strips proved to be of noticeable size, as large as +0·6 and ?0·9 mm. respectively. Indicative as these figures may already be, it seems useful to abstract the investigation from the vagaries of the individual case and to put it on a more general footing.     

Code as Cartography

Abstract

Provincial Atlas of People's Republic of China (Chung hua ien min kung wo kuo fên shêng di t'u chi). 190 x 265 mm. pp. 251 (84 pages of maps). Peking: Map Publishing Society (di t'u ch'u p'an shê), China, Oct., 1974. 6.30 Yuan