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GPStoOSGB

The Ordnance Survey (OS) is Great Britain's national mapping agency. OS maps are
based upon the OSGB36 ellipsoid and latitude and longitude shown on GB OS maps are
those of the OSGB36 ellipsoid. However the OS National Grid Reference is the primary
way that map locations are specified in the UK. The National Grid is printed on all
OS maps as a grid as the primary location mechanism. Lat/long is included but only
as small crosses at spot points for cross reference to the grid.

Latitude and longitude from GPS is usually that of the WSG84 ellipsoid. This differs
slightly from the OSGB36 ellipsoid.

Heights shown on GB OS maps are relative to mean sea level at the Newlyn Tidal Observatory,
known as the Ordnance Datum Newlyn (ODN) while altitude from GPS is usually relative to the
WGS84 ellipsoid.These altitudes differ across Great Britain by between 41 to 53 metres.

This library contains a GPStoOSGB object that can make transformations between WGS84 latitude,
longitude and altitude and OSGB36 latitude, longitude and ODN height, and to and from National Grid
coordinates.

List of types:

GPStoOSGB

GPStoOSGB

This is the GPStoOSGB object that can make transformations between WGS84 latitude,
longitude and altitude to OSGB36 latitude, longitude and ODN height and to National Grid
coordinates.

The methods use the Ordnance Survey specified 7 parameter Helmert transformation.
See http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesystemsinfo/guidecontents/index.html
While the absolute accuracy of conversion is stated by the OS to be within 5 metres the differential
accuracy is likely to be much higher.

Easting and Northing are the displacement in metres of a point from the origin of the National Grid
For a Grid reference the 100 km square in which the point is located is allocated a two character
reference and the location of the point in that sqare is given by 2,3,4, 5 or even 6 numerals.
The E/W location is always stated first.

Events:

None

Members:


  Easting As Double  [read only]

  NEtoNGR (easting As Double, northing As Double) As String

  NewAltitude As Double  [read only]

  NewLatitude As Double  [read only]

  NewLongitude As Double  [read only]

  NGRtoOSGB36 (ngr As String) As String

  Northing As Double  [read only]

  OSGB36toNGR (OSGBlat As Double, OSGBlong As Double) As String

  OSGB36toWGS84 (OSGBlat As Double, OSGBlong As Double, OSGBalt As Double) As String

  Version As Double  [read only]

  WGS84toOSGB36 (WGSlat As Double, WGSlong As Double, WGSalt As Double) As String

Members description:

Easting As Double  [read only]
Returns the Easting value resulting from the latest
NGRtoOSGB36 or OSGB36toNGR transformation.
NEtoNGR (easting As Double, northing As Double) As String
Converts a Northing and an Easting to a National Grid Reference.
Doesn't change any properties.
NewAltitude As Double  [read only]
Returns the Altitude value resulting from the latest
OSGB36toWGS84 or WGS84toOSGB36 transformation.
NewLatitude As Double  [read only]
Returns the Latitude value resulting from the latest
OSGB36toWGS84 or WGS84toOSGB36 transformation.
NewLongitude As Double  [read only]
Returns the Longitude value resulting from the latest
OSGB36toWGS84 or WGS84toOSGB36 transformation.
NGRtoOSGB36 (ngr As String) As String
Converts an OS national grid reference to OSGB36 decimal lat and long.
Returns a comma separated string.
The grid reference can be 2, 3, 4 or 5 digits precision, spaces are ignored
Also converts it to Northing and Easting which can be retrieved
from the Northing and Easting properties.
Northing As Double  [read only]
Returns the Northing value resulting from the latest
NGRtoOSGB36 or OSGB36toNGR transformation.
OSGB36toNGR (OSGBlat As Double, OSGBlong As Double) As String
Converts OSGB36 decimal lat and long to an OS national grid reference.
Sets the Northing and Easting properties.
OSGB36toWGS84 (OSGBlat As Double, OSGBlong As Double, OSGBalt As Double) As String
Converts OSGB36 decimal lat,long and ODN altitude to WGS84 decimal
lat, long and altitude. Returns a comma separated string.
Sets the NewLatitude, NewLongitude and NewAltitude properties.
S latitudes and W longitudes are -ve.
Version As Double  [read only]
Returns the version number of the library.
WGS84toOSGB36 (WGSlat As Double, WGSlong As Double, WGSalt As Double) As String
Converts WGS84 decimal lat, long and altitue to OSGB36 decimal
lat,decimal long and ODN altitude. Returns a comma separated string.
Sets the NewLatitude, NewLongitude and NewAltitude properties.
S latitudes and W longitudes are -ve.
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