GEODESY(2)GEODESY(2)NAMEgeodesy - Geodesy module
SYNOPSIS
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;
DESCRIPTION
Geodesy provides routines to deal with (some) terrestrial coordinate
systems.
Eastings and northings are defined by the Eano adt and are measured in
metres and latitude and longitude (which should be in radians) by the
Lalo adt. Latitude is in the range -π/2 to π/2 radians and longitude in
the range -π to π radians.
OSGB36 (Ordnance Survey Great Britain 1936), Ireland65 (Ireland 1965),
ED50 (European Datum 1950), WGS84 (World Geodetic System 1984),
ITRS2000 (International Terrestrial Reference System 2000), and ETRS89
(European Terrestrial Reference System 1989) are the current datums
defined. Helmert transformations are used to convert between them. Note
that Ireland65 and ED50 are currently not supported and WGS84 and
ITRS2000 are considered equivalent.
Natgrid (National Grid), IrishNatgrid (Irish National Grid), UTMEur
(European Universal Transverse Mercator), and UTM (Universal Transverse
Mercator) are the current transverse Mercator projections supported.
The following functions are provided
init The module should always be initialized first. The parameters
are the required datum (default WGS84), transverse Mercator pro‐
jection (default Natgrid) and UTM zone (default 30) if appropri‐
ate. Negative values or out of range values are ignored.
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.
os2en Converts an Ordnance Survey National Grid reference to an east‐
ing, 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.
en2os Converts an easting, northing to an OS reference in the form
XYeeeeennnnn as above.
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 os2en.
lalo2str
Converts a latitude, longitude to string format as above. Sec‐
onds are given to two decimal places.
str2en Converts a string in OS or latitude/longitude format as above to
an easting, northing. Format errors indicated as in os2en.
en2lalo
Converts an easting, northing to latitude, longitude using the
current transverse Mercator projection.If the latter is UTM or
UTMEur the current zone setting will be used.
lalo2en
Converts latitude, longitude to an easting, northing using the
current transverse Mercator projection.
datum2datum
Approximate (Helmert) transformation of a latitude, longitude
between any of OSGB36, WGS84, ITRS2000 or ETRS89. The `from'
datum appears first in the parameter list.
SOURCE
/module/math/geodesy.m
/appl/math/geodesy.b
BUGS
The module is heavily biased towards Great Britain.
GEODESY(2)
