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# Module osgr

Ordnance Survey Grid References (OSGR) references on the UK National Grid.

Classes Osgr and OSGRError and functions parseOSGR and toOsgr.

A pure Python implementation, transcoded from Chris Veness' JavaScript originals OS National Grid and Module osgridref and Charles Karney's C++ class OSGB.

OSGR provides geocoordinate references for UK mapping purposes, converted in 2015 to work with the `WGS84` or the original `OSGB36` datum. In addition, this implementation includes both the OS recommended and the Krüger-based method to convert between OSGR and geodetic coordinates (with keyword argument `kTM` of function toOsgr, method Osgr.toLatLon and method `toOsgr` of any ellipsoidal `LatLon` class).

See Transverse Mercator: Redfearn series, Karney's "Transverse Mercator with an accuracy of a few nanometers", 2011 (building on "Konforme Abbildung des Erdellipsoids in der Ebene", 1912, "Die Mathematik der Gauß-Krueger-Abbildung", 2006, A Guide and Ordnance Survey National Grid.

Version: 25.04.12

Classes
| OSGRError Error raised for a parseOSGR, Osgr or other OSGR issue.
| Osgr Ordnance Survey Grid References (OSGR) coordinates on the National Grid.

Functions
parseOSGR(strOSGR, Osgr=<class 'pygeodesy.osgr.Osgr'>, **name_Osgr_kwds) Parse a string representing an OS Grid Reference, consisting of `"[GD] easting northing"`. |
toOsgr(latlon, lon=None, kTM=False, datum=Datum(name='WGS84', ellipsoid=Ellipsoids.WGS84, transform=Tran`...`, Osgr=<class 'pygeodesy.osgr.Osgr'>, **prec_name_Osgr_kwds) Convert a lat-/longitude point to an OSGR coordinate. |

Variables
| __all__ = `_ALL_LAZY.osgr`
| D = `_NG.datum`
| t = `0`
| i = `0`
| t2 = `0, 0, 0, 0`
| t1 = `0, 0, 0, 0`

Function Details

### parseOSGR (strOSGR, Osgr=<class 'pygeodesy.osgr.Osgr'>, **name_Osgr_kwds) |
Parse a string representing an OS Grid Reference, consisting of `"[GD] easting northing"`. Accepts standard OS Grid References like "SU 387 148", with or without whitespace separators, from 2- up to 22-digit references, or all-numeric, comma-separated references in meters, for example "438700,114800". Arguments: `strOSGR` - An OSGR coordinate (`str`). `Osgr` - Optional class to return the OSGR coordinate (Osgr) or `None`. `name_Osgr_kwds` - Optional `name=NN` (`str`) and optionally, additional `Osgr` keyword arguments, ignored if `Osgr is None`. Returns: An (`Osgr`) instance or if `Osgr is None`, an EasNor2Tuple`(easting, northing)`. Raises: `OSGRError` - Invalid `strOSGR`.

### toOsgr (latlon, lon=None, kTM=False, datum=Datum(name='WGS84', ellipsoid=Ellipsoids.WGS84, transform=Tran`...`, Osgr=<class 'pygeodesy.osgr.Osgr'>, **prec_name_Osgr_kwds) |
Convert a lat-/longitude point to an OSGR coordinate. Arguments: `latlon` - Latitude (`degrees`) or an (ellipsoidal) geodetic `LatLon` point. `lon` - Optional longitude in degrees (scalar or `None`). `kTM` - If `True`, use Karney's Krüger method from module ktm, otherwise use the Ordnance Survey formulation (`bool`). `datum` - Optional datum to convert `lat, lon` from (Datum, Ellipsoid, Ellipsoid2 or a_f2Tuple). `Osgr` - Optional class to return the OSGR coordinate (Osgr) or `None`. `prec_name_Osgr_kwds` - Optional `name=NN` (`str`), optional truncate precision `prec=ndigits` and additional `Osgr` keyword arguments, ignored if `Osgr is None`. Returns: An (`Osgr`) instance or if `Osgr is None` an EasNor2Tuple`(easting, northing)`. Raises: `OSGRError` - Invalid `latlon` or `lon`. `TypeError` - Non-ellipsoidal `latlon` or invalid `datum`, `Osgr`, `Osgr_kwds` or conversion to `Datums.OSGB36` failed. Note: If isint`(prec)` both easting and northing are truncated to the given number of digits.