Transformations and OSGM02 user guide - Leica Geosystems

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Where:1 the record number is a sequential number starting at 1 for the origin point (0,0) and finishing at 876 951 for thenorth-east corner (700 000, 1 250 000).2 ETRS89, National Grid projection, grid intersection easting coordinate in metres.3 ETRS89, National Grid projection, grid intersection northing coordinate in metres.4 the shift in eastings, at the intersection, between ETRS89 and OSGB36 National Grid, that isETRS89 east + OSTN02 east shift = OSGB36 National Grid easting.5 the shift in northings, at the intersection, between ETRS89 and OSGB36 National Grid, that isETRS89 north + OSTN02 north shift = OSGB36 National Grid northing.6 the height of the Geoid above the ETRS89 ellipsoid, in metres, at the intersection, that isETRS89 height – OSGM02 Geoid height = orthometric height above mean sea level.7 the Geoid datum flag is a number from 1 to 14, representing the geoid datum to which OSGM02 Geoid heightrelates, for example, this flag is 1 for Ordnance Datum Newlyn, the orthometric height datum used on the Britishmainland. See table 1 (page 17), for details of other datum flag references.OSGM02 within Northern Ireland – format and layout of the dataWithin Northern Ireland OSGM02 is released as a single data file using a 1 km grid. This grid covers an area 250 kmeast–west and 200 km north–south, the origin is offset by (550 000, 800 000) from the origin of the projected ETRS89coordinates (see appendix B). As with the data for Great Britain, the area to which the models are valid has beencookie cut to a polygon around the coastline and the border with the Republic of Ireland. This means that any positionmore than 10 km offshore or 2 km over the border with the Republic of Ireland will have fields 4 and 5 (see below) set tozero.It is strongly recommended that the transformation software be written to return an outside transformationboundary type error when a point outside this area is encountered.Transformations and OSGM02 user guide chapter 2v2.1 9/2002 © crown copyrightPage 13
Each record occupies a separate line with the south-west corner being the first record in the file. The format of eachrecord is indicated by the following table:Record no 1ETRS89easting 2 (m)ETRS89 northing 3(m)OSGM02 GeoidHt 4 (m)Geoid datumflag 51 550 000 800 0002 551 000 800 0003 552 000 800 000and so on and so on and so on251 800 000 800 000252 550 000 801 000253 551 000 801 000254 552 000 801 000255 553 000 801 000and so on and so on and so on50 448 797 000 1 000 00050 449 798 000 1 000 00050 450 799 000 1 000 00050 451 800 000 1 000 000Transformations and OSGM02 user guide chapter 2v2.1 9/2002 © crown copyrightPage 14
Page 2 and 3: PrefaceThis grid transformation sof
Page 4 and 5: Data copyrightUser guide copyrightT
Page 6 and 7: Appendix A Transforming ETRS89 GPS
Page 8 and 9: Orthometric heights in these system
Page 10 and 11: ETRS89 explainedBenefitsOrdnance Su
Page 12 and 13: Chapter 2Data overviewBasic princip
Page 16 and 17: Where:1 the record number is a sequ
Page 18 and 19: 4 the height of the Geoid above the
Page 20 and 21: For example, to find the record for
Page 22 and 23: Shifts for x, y are:se 0= east_shif
Page 24 and 25: The OSi/OSNI polynomial transformat
Page 26 and 27: The Ordnance Survey Geoid model: OS
Page 28 and 29: Chapter 4Quality statementCoverageO
Page 30 and 31: Appendix ATransforming ETRS89 GPS c
Page 32 and 33: The offset values are given by:dx =
Page 34 and 35: Appendix BConverting latitude and l
Page 36 and 37: ⎛ ⎛ 5 2 5 3 ⎞ ⎛2 21 3 ⎞
Page 38 and 39: Appendix CConverting easting and no
Page 40 and 41: Worked example using Airy 1830 elli
Page 42 and 43: Geoid modelA model of the level sur

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