DOCSLIB.ORG

Datum Transformations Using the Ntv2 Grid by Julie Lovesay, Chief Directorate: National Geo-Spatial Information (CD:NGI)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Datum Transformations Using the Ntv2 Grid by Julie Lovesay, Chief Directorate: National Geo-Spatial Information (CD:NGI) Visualisation technical Datum transformations using the NTv2 grid by Julie Lovesay, Chief Directorate: National Geo-spatial Information (CD:NGI) Prior to 1999, all geospatial data in South Africa was referenced to the Cape datum (Modified Clarke 1880 ellipsoid). Since the introduction of the Hartebeesthoek 94 datum (utilising the WGS84 ellipsoid) in 1999, GIS practitioners have faced challenges combining historical data in the Cape datum and more modern data in the Hartebeesthoek 94 datum. I have investigated an approach that can easily be used to transform data from the Cape datum to Hatebeesthoek 94. This is called the NTv2 grid which is software independent. However, it was tested within the ARC environment as this is one of the most widely used platforms. he transformation of point files from one datum to another is Trelatively simple, and can be done with a Helmert transformation, provided the area is smaller than 40 km and at least two points are known in both systems. In smaller areas of only a few kilometres, a straight shift is acceptable if surrounding trigonometrical (trig) beacons or town survey marks are consistent. However the transformation of GIS vector data such as shapefiles does not involve only point conversion, but rather points, polygons and lines. This makes the transformation more complicated as the polygons and lines may contain many vertices and can possibly be geographically extensive. Currently, the vast majority of GIS projects utilise WGS84/ Hartebeesthoek94 as the default Fig. 1: Left - Water pipes in Mossel Bay in Cape Datum overlaid on an image rectified in the datum. GIS practitioners are regularly Hartebeesthoek94 datum. Right – The water pipes after NTv2 transformation, vector data now faced with the problem of having correctly georeferenced. historic vector data in the another datum; mostly shapefiles in the "old" Cape Datum, while the rest of the data The National Transformation version 2 of the countries national control points, is in Hartebeesthoek94. When data (NTv2) is a datum transformation a regular spaced grid of shifts at an from two datums is combined and an method relatively unheard of within interval of 0,01 degrees (±1 km) was appropriate transformation strategy the South African surveying and GIS interpolated. This translated to roughly is not applied, a very visible shift will communities. It was originally created 1,55-million points, which are used to occur when the data is overlaid and by the Geodetic Survey Division of apply shifts to the shapefiles. displayed. Geomatics Canada to transform files Because the density of South Africa’s from NAD1927 to NAD1983. This This is easy to spot, as there is national control points is irregular, the method has now been extended to generally a difference of around 300 m accuracy of the transformation will accommodate Australia, New Zealand, in x (northing) and 50 m in y (easting) vary. In highly populated urban areas, France and South Africa. components. Applying this shift to it is possible to find over 5000 trig the shapefiles, or even the default The NTv2 method uses grid files to beacons and town survey marks in less transformation in ArcGIS will result in transform shapefiles from Cape Datum than a degree square; while rural areas very poor accuracies, as the horizontal to Hartebeesthoek94. The file contains such as the Northern Cape can have shift varies across the country by up binary information relating to the less than 200 trig beacons and no town to 80 m. ArcGIS’s default 3D shift will difference in the two (unprojected) survey marks in an equal area. As a produce results in the order of 15 m. coordinate systems. Using all 50 000 regular grid has been interpolated from PositionIT – April/May 2010 49 VISUALISATION technical (parent) grid, providing more accurate The accuracy of the NTv2 grid was transformations. NTv2 then checks tested by applying a transformation to all the grids, to find the one with the 91 trigonometrical beacons distributed highest density. Knowing which grid was throughout the country. By comparing used for the transformation can give the the transformed coordinates with the user an idea of the accuracy achieved. known Hartebeesthoek94 coordinates, South Africa does not currently use the conclusions could be drawn. A mean method of overlaying a sub-grid. variation of 1 cm with a standard deviation of 1 cm was achieved. This It is important to remember that the accuracy is suitable for both GIS and grid file applies to each vertex and no surveying applications and has the global rotation or scale factor is applied. potential to save time by reducing the The shifts in this grid have specifically need for re-digitising. been calculated to transform Cape Datum to Hartebeesthoek94. Thus for Users using this file for surveying systems such as the old Gold Fields applications should be aware that Fig. 2: The grid system works by overlaying datum, the NTv2 grid is unsuitable, the shifts applied in the NTv2 file smaller and more accurate grids on top of and could not be used even if it was use the published Cape Datum and the parent grid. developed. Hartebeesthoek94 coordinates on 1 January 1999. Older publications of This conversion can be done in ArcGIS coordinates may contain variances from on any central meridian/longitude all control points, it is difficult to infer the latest issue, making it unsuitable of origin (Lo), by defining a specific information regarding the accuracy of for cadastral applications. The file is transformation and the location of the these shifts. freely available to the public, and can NTv2 grid (a .gsb file). A new shapefile be acquired from ESRI South Africa. In the future, in areas where there with the suffix _project.shp is created in are more control points, (such the same folder. The same conversion Contact Julie Lovesay, CD:NGI, as urban areas) smaller grids or can be applied to unprojected Tel 021 658-4479, sub-grids may overlay the main (geographical) shapefiles. [email protected] 50 PositionIT – March 2010.
Load more

Recommended publications
  • Implications for the Adoption of Global Reference Geodesic System SIRGAS2000 on the Large Scale Cadastral Cartography in Brazil
    Implications for the Adoption of Global Reference Geodesic System SIRGAS2000 on the Large Scale Cadastral Cartography in Brazil Vivian de Oliveira FERNANDES and Ruth Emilia NOGUEIRA, Brazil Key words: SIRGAS2000, SAD69, Global Geodesic System SUMMARY Since 2005 Brazil is going through a singular moment into Cartography. In January 2005, SIRGAS2000 began to be the geodetic official reference system for Geodesy and Cartography, with the concomitant use of SAD69. Since January 2015, only SIRGAS2000 will be official, and all cartographical products will have to be referenced into this Datum. The adoption of a geocentric reference system happens from the technological evolution that has favored an improvement of the Geodetic Reference System – SGR. Differently of a single alternative for the improvement of the SGR, the adoption of a new geocentric reference system is a basic necessity into the world-wide scenery to activities that depend on spatialized information. The technological advancements in the global positioning methods, specially in the satellite positioning systems. This change reaches more quickly the organs that need spatialized information in their infrastructure and planning activities, like town halls and services concessionaires like Telecommunications, Sanitation, Electric Energy among others, which need the real knowledge of the urban space: use and occupation of the soil, subsoil and air space, fiscal and housing technical register, generic plant of values, block plant, register reference plant, municipal master plan, among others that are derived from a cartographical basis of quality. Officially, were adopted these geodetic reference systems in Brazil: Córrego Alegre, Astro Datum Chuá, SAD69, and now SIRGAS2000. For legislation it is in transition for the SIRGAS2000.
    [Show full text]
  • Arcgis 10.1 Geographic and Vertical Transformation Tables
    ArcGIS 10.1 Geographic and Vertical Transformation Tables Note: Some numbers have been rounded for display. Area of use values are in degrees based upon WGS 1984. Table 1: Geographic (datum) transformations: well-known IDs, accuracies and areas of use ........................................................................................... 1 Table 2: Geographic (datum) transformations: Longitude rotation and unit change methods ......................................................................................... 43 Table 3: Geographic (datum) transformations: Geographic 2D offset method ................................................................................................................ 44 Table 4: Geographic (datum) transformations: Geocentric translation method ............................................................................................................... 44 Table 5: Geographic (datum) transformations: Coordinate frame (CF) and position vector (PV) methods .................................................................... 60 Table 6: Geographic (datum) transformations: Molodensky-Badekas method ................................................................................................................ 70 Table 7: Geographic (datum) transformations: HARN, NADCON, and NTv2 methods ................................................................................................. 71 Table 8: Geographic transformation methods: well-known IDs ......................................................................................................................................
    [Show full text]
  • Killet Software Ing.-Gbr
    History of the program TRANSDATpro Changes and Supplements of the last five years Worldwide geodetic Coordinate Transformations Detailed Information about the program TRANSDATpro: https://www.killetsoft.de/p_trda_e.htm Translation of this history to other languages: https://translate.google.com/ 01. 01. 2021: Program release TRANSDATpro 24.00 Changes and Supplements during the version TRANSDATpro 24.xx: 24.14: New help chapter "Selection of a Meridian Strip". 24.13: New round button to call the help "Selection of a Meridian Strip". 24.12: New Help link "What actually is a Coordinate Reference System?" 24.11: For calculations with the Mercator projection (1SP / 2SP) the International Date Line is considered. 24.10: New coordinate system "PDC Mercator (Pacific)". 24.10: EPSG code 3832 "WGS84 / PDC Mercator" implemented. 24.09: RefSys "ETRS89 (EU GPS measurements)" renamed to "ETRS89 (EU ITRS epoch 1989)". 24.09: RefSys "NAD83(US+CA GPS measurements)" renamed to "NAD83(US+CA ITRS epoch 1988)". 24.09: RefSys "GDA2020 (AU GPS measurements)" renamed to "GDA2020 (AU ITRS epoch 2020)". 24.08: Automatic language detection at the first program call adjusted. 24.07: Increased stability and speed with a new development system. 24.07: Delivered with new Dynamic Link Libraries (DLLs). 24.06: Error handling improved. 24.05: New NTv2 reference system for Belgium added. 24.05: New NTv2 reference systems for Portugal added. 24.03: New Language interface file for Bosnian, Croatian and Serbian added. 24.02: New language interface file for Italian added. 24.01: Restricted access to functions of the underlying GeoDLL fixed. 24.01: Link to the worldwide NTv2 files collection corrected.
    [Show full text]
  • Supported Coordinate Systems and Geographic Transformations
    Supported coordinate systems and geographic transformations This document contains information about the coordinate systems and geographic (datum) transformations supported in ArcGIS. The information is current as of version 8.1.2 of the Projection Engine. The tables include supported units of measure, spheroids, datums, and prime meridians. The supported map projections and their parameters are listed in one table. The geographic and projected coordinate system areas of interest are available. The geographic transformation tables include the method and parameters as well as the areas of interest. Earlier versions of the Projection Engine will not include all objects listed in these tables. Geographic (datum) transformations, three parameter Name Code Method dX dY dZ Abidjan_1987_To_WGS_1984 8414 Geocentric Translation -124.76 53.0 466.79 Accra_To_WGS_1972_BE 1570 Geocentric Translation -171.16 17.29 323.31 Accra_To_WGS_1984 1569 Geocentric Translation -199 32 322 Adindan_To_WGS_1984_1 8000 Geocentric Translation -166 -15 204 Adindan_To_WGS_1984_2 8001 Geocentric Translation -118 -14 218 Adindan_To_WGS_1984_3 8002 Geocentric Translation -134 -2 210 Adindan_To_WGS_1984_4 8003 Geocentric Translation -165 -11 206 Adindan_To_WGS_1984_5 8004 Geocentric Translation -123 -20 220 Adindan_To_WGS_1984_6 8005 Geocentric Translation -128 -18 224 Adindan_To_WGS_1984_7 8006 Geocentric Translation -161 -14 205 Afgooye_To_WGS_1984 8007 Geocentric Translation -43 -163 45 AGD_1966_To_GDA_1994 8189 Geocentric Translation -127.8 -52.3 152.9 AGD_1966_To_WGS_1984
    [Show full text]
  • MDT Versión 4
    Customization Manual Version 7.5 Aplitop, 2016 C/ Sumatra, 9 E-29190 MÁLAGA (SPAIN) web: www.aplitop.com e-mail: [email protected] Customization ............................................................. 3 Introduction ................................................................................. 3 General ........................................................................................ 4 Angles ........................................................................... 4 Measurement ................................................................ 5 User Blocks .................................................................. 5 Layers ........................................................................... 5 Project ........................................................................... 5 Printer ........................................................................... 5 Print in MS Word ......................................................... 6 Printing on Drawing ..................................................... 7 PDF Printing ................................................................. 7 Menus ......................................................................................... 7 Surveying .................................................................................... 8 Coordinate Reference Systems (CRS) .......................... 8 Corrections ................................................................... 9 Admissible Errors ........................................................
    [Show full text]
  • Guidance Note 7 Part 2
    IOGP Publication 373-7-2 – Geomatics Guidance Note number 7, part 2 – September 2019 To facilitate improvement, this document is subject to revision. The current version is available at www.epsg.org. Geomatics Guidance Note Number 7, part 2 Coordinate Conversions and Transformations including Formulas Revised - September 2019 Page 1 of 162 IOGP Publication 373-7-2 – Geomatics Guidance Note number 7, part 2 – September 2019 To facilitate improvement, this document is subject to revision. The current version is available at www.epsg.org. Table of Contents Preface ............................................................................................................................................................5 1 IMPLEMENTATION NOTES ................................................................................................................. 6 1.1 ELLIPSOID PARAMETERS ......................................................................................................................... 6 1.2 ARCTANGENT FUNCTION ......................................................................................................................... 6 1.3 ANGULAR UNITS ....................................................................................................................................... 7 1.4 LONGITUDE 'WRAP-AROUND' .................................................................................................................. 7 1.5 OFFSETS ...................................................................................................................................................
    [Show full text]
  • Coordinate Conversions and Transformations Including Formulas
    OGP Surveying and Positioning Guidance Note number 7, part 2 – May 2009 To facilitate improvement, this document is subject to revision. The current version is available at www.epsg.org. Surveying and Positioning Guidance Note Number 7, part 2 Coordinate Conversions and Transformations including Formulas Revised - May 2009 Page 1 of 118 OGP Surveying and Positioning Guidance Note number 7, part 2 – May 2009 To facilitate improvement, this document is subject to revision. The current version is available at www.epsg.org. Index Preface 4 Revision history 5 1 MAP PROJECTIONS AND THEIR COORDINATE CONVERSION FORMULAS 8 1.1 INTRODUCTION 8 1.2 MAP PROJECTION PARAMETERS 9 1.3 MAP PROJECTION FORMULAS 20 1.3.1 LAMBERT CONIC CONFORMAL 21 1.3.1.1 Lambert Conic Conformal (2SP) 21 1.3.1.2 Lambert Conic Conformal (1SP) 23 1.3.1.3 Lambert Conic Conformal (West Orientated) 24 1.3.1.4 Lambert Conic Conformal (2 SP Belgium) 24 1.3.1.5 Lambert Conic Near-Conformal 25 1.3.2 KROVAK OBLIQUE CONFORMAL CONIC 27 1.3.3 MERCATOR 30 1.3.3.1 Mercator (Spherical) 32 1.3.3.2 Popular Visualisation Pseudo Mercator 33 1.3.4 CASSINI-SOLDNER 35 1.3.4.1 Hyperbolic Cassini-Soldner 36 1.3.5 TRANSVERSE MERCATOR 37 1.3.5.1 General Case 37 1.3.5.2 Transverse Mercator Zoned Grid System 40 1.3.5.3 Transverse Mercator (South Orientated) 41 1.3.6 OBLIQUE MERCATOR AND HOTINE OBLIQUE MERCATOR 41 1.3.6.1 Laborde projection for Madagascar 46 1.3.7 STEREOGRAPHIC 49 1.3.7.1 Oblique and Equatorial Stereographic cases 49 1.3.7.2 Polar Stereographic 52 1.3.8 NEW ZEALAND MAP GRID 57 1.3.9 TUNISIA
    [Show full text]
  • Arcgis® 9 Understanding Map Projections Copyright © 1994–2001, 2003–2004 ESRI All Rights Reserved
    ArcGIS® 9 Understanding Map Projections Copyright © 19942001, 20032004 ESRI All rights reserved. Printed in the United States of America. The information contained in this document is the exclusive property of ESRI. This work is protected under United States copyright law and other international copyright treaties and conventions. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage or retrieval system, except as expressly permitted in writing by ESRI. All requests should be sent to Attention: Contracts Manager, ESRI, 380 New York Street, Redlands, CA 92373-8100, USA. The information contained in this document is subject to change without notice. U.S. GOVERNMENT RESTRICTED/LIMITED RIGHTS Any software, documentation, and/or data delivered hereunder is subject to the terms of the License Agreement. In no event shall the U.S. Government acquire greater than RESTRICTED/LIMITED RIGHTS. At a minimum, use, duplication, or disclosure by the U.S. Government is subject to restrictions as set forth in FAR §52.227-14 Alternates I, II, and III (JUN 1987); FAR §52.227-19 (JUN 1987) and/or FAR §12.211/12.212 (Commercial Technical Data/Computer Software); and DFARS §252.227-7015 (NOV 1995) (Technical Data) and/or DFARS §227.7202 (Computer Software), as applicable. Contractor/Manufacturer is ESRI, 380 New York Street, Redlands, CA 92373-8100, USA. ESRI, ArcGIS, the ArcGIS logo, ArcInfo, ArcGlobe, and www.esri.com are trademarks, registered trademarks, or service marks of ESRI in the United States, the European Community, or certain other jurisdictions.
    [Show full text]
  • Working with Projections and Datum Transformations in Arcgis
    Werner Flacke / Birgit Kraus Working with Projections and Datum Transformations in ArcGIS Theory and Practical Examples First impression 2005 Points Verlag Norden*Halmstad Table of Contents VII Table of Contents Introduction 1 Introduction to coordinate systems 4 2.1 The significance of coordinate systems 4 2.2 Measurement units 6 2.3 Basic terminology of coordinate systems 7 2.4 Coordinate system data models 11 2.5 Standards: EPSG/POSC/ISO 19111/OGC/WKT 13 2.6 Coordinate system syntax in ArcGIS Desktop 14 Working with ArcGIS Desktop - first steps 18 3.1 The Desktop Help System in ArcGIS 18 3.2 A quick start for the practically minded 20 3.2.1 Loading data 21 3.2.2 Adding graticules 22 3.2.3 Setting the display units for the coordinates 25 3.2.4 Changing / setting the output CRS 27 3.2.5 Addendum to the measurement experiment 31 3.3 Area and length attributes 32 3.4 Projecting with ArcMap 33 3.4.1 New warning in ArcGIS 8.3 when editing 35 3.5 Coordinate systems in ArcCatalog 35 3.6 Associating coordinate systems with datasets 40 3.6.1 X/Y, Z and M Domains 41 3.6.2 Coordinate systems in a geodatabase and in ArcSDE 43 3.6.2.1 Coordinate systems of raster data in ArcSDE 43 3.6.3 Coordinate systems of shapefiles 44 3.6.4 Coordinate systems of raster data 44 3.6.5 Coordinate systems and image catalogs 48 3.6.6 Coordinate systems and Grids 48 3.6.7 Coordinate systems and TINs 48 3.6.8 Coordinate systems and CAD data 49 3.6.9 Coordinate systems and SDC files 49 3.6.10 Coordinate systems and X/Y coordinate tables 50 3.7 Georeferencing raster data
    [Show full text]
  • Ellipsoidally Referenced Surveying for Hydrography
    FIG GUIDE FIG PUBLICATION NO 62 Ellipsoidally Referenced Surveying for Hydrography INTERNATIONAL FEDERATION OF SURVEYORS (FIG) Ellipsoidally Referenced Surveying for Hydrography Jerry Mills David Dodd INTERNATIONAL FEDERATION OF SURVEYORS (FIG) Copyright © The International Federation of Surveyors (FIG), May 2014. All rights reserved. International Federation of Surveyors (FIG) Kalvebod Brygge 31–33 DK-1780 Copenhagen V DENMARK Tel. + 45 38 86 10 81 E-mail: [email protected] www.fig.net Published in English ISSN 1018-6530 (printed) ISSN 2311-8423 (pdf) ISBN 978-87-92853-09-7 (printed) ISBN 978-87-92853-16-5 (pdf) Published by International Federation of Surveyors (FIG) Cover images: David Dodd Layout: Lagarto Printer: 2014 Hakapaino, Helsinki, Finland CONTENTS LIST OF FIGURES ...................................................................................................................................vi ACRONYMS .............................................................................................................................................vii FOREWORD ...........................................................................................................................................viii PREFACE ....................................................................................................................................................ix 1 INTRODUCTION .............................................................................................................................1 2 VERTICAL POSITIONING ...........................................................................................................3
    [Show full text]
  • Geodesy Matters at Esri Melita Kennedy Thank You to Our Sponsors
    Geodesy Matters at Esri Melita Kennedy Thank You to Our Sponsors GOLD SPONSORS SILVER SPONSORS Map projections Our Map Projections Aitoff Equidistant conic Mollweide Vertical near side perspective Albers Equidistant cylindrical Natural Earth Wagner IV Aspect-Adaptive Flat polar quartic Natural Earth II Wagner V Azimuthal equidistant Fuller New Zealand map grid Wagner VII Behrmann Gall stereographic Ney modified conic Winkel I Berghaus Star Gauss Kruger Orthographic Winkel II Bonne Geostationary Satellite Patterson Winkel Tripel Cassini Gnomonic (ellipsoidal) Plate Carree Compact Miller Goode Homolosine Polar Stereographic (A, B, C) Azimuthal equidistant auxiliary sphere Craster Parabolic Hammer-Aitoff Polyconic Eckert IV auxiliary sphere Cube Hotine oblique Mercator Quartic authalic (ellipsoidal) Eckert VI auxiliary sphere Cylindrical equal-area IGAC Plano Cartesiano Rectified skew orthomorphic Equidistant cylindrical auxiliary sphere Double stereographic Krovak Robinson Gnomonic auxiliary sphere Eckert Greifendorff Laborde oblique Mercator Sinusoidal Lambert azimuthal equal-area Eckert I Lambert azimuthal equal-area Stereographic auxiliary sphere Eckert II Lambert conformal conic Times Mercator auxiliary sphere Eckert III Local Transverse cylindrical equal-area Miller cylindrical auxiliary sphere Eckert IV Loximuthal Transverse Mercator Mollweide auxiliary sphere Eckert V Mercator (+ scale factor) Two point equidistant Orthographic auxiliary sphere Eckert VI Miller cylindrical Van der Grinten I Van der Grinten I auxiliary sphere New projections
    [Show full text]
  • PROJ4 Issues the Case of Romania: Increasing Transformation Accuracy Through Grid Shift Files
    PROJ4 Issues The case of Romania: increasing transformation accuracy through grid shift files Daniel Urdă 17.07.2014 Outline • National Reference System of Romania • Reference transformation: TransDatRo • Current implementations • Open source software • Proprietary software • Towards increased precision (in FOSS) • Conclusion PROJ4 Issues - The case of Romania 2 1 Romanian National Projection System PROJ4 Issues - The case of Romania 3 Romanian National Projection System • S-42 National Reference System – “Stereo70” • Characteristics: • Krasovski 1940 ellipsoid • Stereographic projection “1970” PROJ4 Issues - The case of Romania 4 Transformation issues • No simple mathematical formula • Existing attempts produce inconsistent errors, with accuracy depending on actual location of the dataset • Reprojection to/from other systems result in topological errors PROJ4 Issues - The case of Romania 5 Why bother with it • De jure standard for topo-geodesic measurements • Large existing database of geographic information using the projection (both classical maps and GIS systems) • Regulation No. 1089/2010 (EU) on the implementation of the INSPIRE directive as regards interoperability of geodatasets and services recommends using ETRS89 PROJ4 Issues - The case of Romania 6 2 Reference transformation: TransDatRo PROJ4 Issues - The case of Romania 7 TransDatRO • “Dumb” application provided by the Romanian Cadaster Agency (ANCPI) • Reprojects from/to ETRS89 (LAEA and Transverse Mercator projections available) • Declared planimetric precision: ±10+15 cm
    [Show full text]