ref: 60ecd07e6d3f5786c8723dc9172c35d580fdadc8
dir: /man/2/geodesy/
.TH GEODESY 2 .SH NAME geodesy \- Geodesy module .SH SYNOPSIS .EX include "geodesy.m"; geodesy := load Geodesy Geodesy->PATH; # easting, northing Eano: adt{ e: real; n: real; }; # latitude, longitude in radians Lalo: adt{ la: real; lo: real; }; OSGB36, Ireland65, ED50, WGS84, ITRS2000, ETRS89: con iota; Natgrid, IrishNatgrid, UTMEur, UTM: con iota; init: fn(d: int, t: int, z: int); format: fn(d: int, t: int, z: int); os2en: fn(s: string): (int, Eano); en2os: fn(en: Eano): string; str2lalo: fn(s: string): (int, Lalo); lalo2str: fn(lalo: Lalo): string; str2en: fn(s: string): (int, Eano); en2lalo: fn(en: Eano): Lalo; lalo2en: fn(lalo: Lalo): Eano; datum2datum: fn(lalo: Lalo, f: int, t: int): Lalo; .EE .SH DESCRIPTION .B Geodesy provides routines to deal with (some) terrestrial coordinate systems. .PP Eastings and northings are defined by the .B Eano adt and are measured in metres and latitude and longitude (which should be in radians) by the .B Lalo adt. Latitude is in the range -π/2 to π/2 radians and longitude in the range -π to π radians. .PP .B OSGB36 (Ordnance Survey Great Britain 1936), .B Ireland65 (Ireland 1965), .B ED50 (European Datum 1950), .B WGS84 (World Geodetic System 1984), .B ITRS2000 (International Terrestrial Reference System 2000), and .B ETRS89 (European Terrestrial Reference System 1989) are the current datums defined. Helmert transformations are used to convert between them. Note that .B Ireland65 and .B ED50 are currently not supported and .B WGS84 and .B ITRS2000 are considered equivalent. .PP .B Natgrid (National Grid), .B IrishNatgrid (Irish National Grid), .B UTMEur (European Universal Transverse Mercator), and .B UTM (Universal Transverse Mercator) are the current transverse Mercator projections supported. .PP The following functions are provided .TP .B init The module should always be initialized first. The parameters are the required datum (default WGS84), transverse Mercator projection (default Natgrid) and UTM zone (default 30) if appropriate. Negative values or out of range values are ignored. .TP .B format Parameters as above. Alters the current settings at any time though care must be taken to ensure existing coordinates are still treated as in their original form. .TP .B os2en Converts an Ordnance Survey National Grid reference to an easting, northing. The formats XYen, XYeenn, XYeeennn, XYeeeennnn, XYeeeeennnnn, eenn, eeennn, eeeennnn, eeeeennnnn and eeeeeennnnnn are allowed. Here X and Y are upper case letters, e is an easting digit and n is a northing digit. The reference can therefore be rounded to the nearest decakilometre, kilometre, hectometre, decametre or metre. The first element of the returned tuple is zero if the string has an incorrect format. .TP .B en2os Converts an easting, northing to an OS reference in the form XYeeeeennnnn as above. .TP .B str2lalo Converts a latitude/longitude string to a latitude, longitude. The string may have the formats deg[N|S], deg:min[N|S] or deg:min:sec[N|S] for latitude, deg[E|W], deg:min[E|W] or deg:min:sec[E|W] for longitude. The latitude must come first, then optional white space, then the longitude. Degrees, minutes and seconds may be integer or real. Format errors are indicated as in .B os2en. .TP .B lalo2str Converts a latitude, longitude to string format as above. Seconds are given to two decimal places. .TP .B str2en Converts a string in OS or latitude/longitude format as above to an easting, northing. Format errors indicated as in .B os2en. .TP .B en2lalo Converts an easting, northing to latitude, longitude using the current transverse Mercator projection.If the latter is .B UTM or .B UTMEur the current zone setting will be used. .TP .B lalo2en Converts latitude, longitude to an easting, northing using the current transverse Mercator projection. .TP datum2datum Approximate (Helmert) transformation of a latitude, longitude between any of .B OSGB36, .B WGS84, .B ITRS2000 or .B ETRS89. The `from' datum appears first in the parameter list. .SH SOURCE .B /module/math/geodesy.m .br .B /appl/math/geodesy.b .SH BUGS The module is heavily biased towards Great Britain.