Public Types | Static Public Member Functions

GeographicLib::UTMUPS Class Reference

Convert between Geographic coordinates and UTM/UPS. More...

#include <GeographicLib/UTMUPS.hpp>

List of all members.

Public Types

enum  zonespec {
  MINPSEUDOZONE = -4, INVALID = -4, MATCH = -3, UTM = -2,
  STANDARD = -1, MAXPSEUDOZONE = -1, MINZONE = 0, UPS = 0,
  MINUTMZONE = 1, MAXUTMZONE = 60, MAXZONE = 60
}

Static Public Member Functions

static int StandardZone (real lat, real lon, int setzone=STANDARD)
static void Forward (real lat, real lon, int &zone, bool &northp, real &x, real &y, real &gamma, real &k, int setzone=STANDARD, bool mgrslimits=false)
static void Reverse (int zone, bool northp, real x, real y, real &lat, real &lon, real &gamma, real &k, bool mgrslimits=false)
static void Forward (real lat, real lon, int &zone, bool &northp, real &x, real &y, int setzone=STANDARD, bool mgrslimits=false)
static void Reverse (int zone, bool northp, real x, real y, real &lat, real &lon, bool mgrslimits=false)
static void DecodeZone (const std::string &zonestr, int &zone, bool &northp)
static std::string EncodeZone (int zone, bool northp)
static Math::real UTMShift () throw ()
Inspector functions

static Math::real MajorRadius () throw ()
static Math::real InverseFlattening () throw ()

Detailed Description

Convert between Geographic coordinates and UTM/UPS.

UTM and UPS are defined

Section 2-3 defines UTM and section 3-2.4 defines UPS. This document also includes approximate algorithms for the computation of the underlying transverse Mercator and polar stereographic projections. Here we substitute much more accurate algorithms given by GeographicLib:TransverseMercator and GeographicLib:PolarStereographic.

In this implementation, the conversions are closed, i.e., output from Forward is legal input for Reverse and vice versa. The error is about 5nm in each direction. However, the conversion from legal UTM/UPS coordinates to geographic coordinates and back might throw an error if the initial point is within 5nm of the edge of the allowed range for the UTM/UPS coordinates.

The simplest way to guarantee the closed property is to define allowed ranges for the eastings and northings for UTM and UPS coordinates. The UTM boundaries are the same for all zones. (The only place the exceptional nature of the zone boundaries is evident is when converting to UTM/UPS coordinates requesting the standard zone.) The MGRS lettering scheme imposes natural limits on UTM/UPS coordinates which may be converted into MGRS coordinates. For the conversion to/from geographic coordinates these ranges have been extended by 100km in order to provide a generous overlap between UTM and UPS and between UTM zones.

The NGA software package geotrans also provides conversions to and from UTM and UPS. Version 2.4.2 (and earlier) suffers from some drawbacks:

Definition at line 59 of file UTMUPS.hpp.


Member Enumeration Documentation

In this class we bring together the UTM and UPS coordinates systems. The UTM divides the earth between latitudes -80 and 84 into 60 zones numbered 1 thru 60. Zone assign zone number 0 to the UPS regions, covering the two poles. Within UTMUPS, non-negative zone numbers refer to one of the "physical" zones, 0 for UPS and [1, 60] for UTM. Negative "pseudo-zone" numbers are used to select one of the physical zones.

Enumerator:
MINPSEUDOZONE 

The smallest pseudo-zone number.

INVALID 

A marker for an undefined or invalid zone. Equivalent to NaN.

MATCH 

If a coordinate already include zone information (e.g., it is an MGRS coordinate), use that, otherwise apply the UTMUPS::STANDARD rules.

UTM 

Apply the standard rules for UTM zone assigment extending the UTM zone to each pole to give a zone number in [1, 60]. For example, use UTM zone 38 for longitude in [42, 48). The rules include the Norway and Svalbard exceptions.

STANDARD 

Apply the standard rules for zone assignment to give a zone number in [0, 60]. If the latitude is not in [-80, 84), then use UTMUPS::UPS = 0, otherwise apply the rules for UTMUPS::UTM. The tests on latitudes and longitudes are all closed on the lower end open on the upper. Thus for UTM zone 38, latitude is in [-80, 84) and longitude is in [42, 48).

MAXPSEUDOZONE 

The largest pseudo-zone number.

MINZONE 

The smallest physical zone number.

UPS 

The zone number used for UPS

MINUTMZONE 

The smallest UTM zone number.

MAXUTMZONE 

The largest UTM zone number.

MAXZONE 

The largest physical zone number.

Definition at line 90 of file UTMUPS.hpp.


Member Function Documentation

int GeographicLib::UTMUPS::StandardZone ( real  lat,
real  lon,
int  setzone = STANDARD 
) [static]

The standard zone.

Parameters:
[in] lat latitude (degrees).
[in] lon longitude (degrees).
[in] setzone zone override (optional)

This is exact. If the optional argument setzone is given then use that zone if it is non-negative, otherwise apply the rules given in UTMUPS::zonespec. Throws an error if setzone is outsize the range [UTMUPS::MINPSEUDOZONE, UTMUPS::MAXZONE] = [-4, 60].

Definition at line 46 of file UTMUPS.cpp.

References INVALID, GeographicLib::Math::isnan(), MAXZONE, MINZONE, and UTM.

Referenced by Forward(), and GeographicLib::GeoCoords::SetAltZone().

void GeographicLib::UTMUPS::Forward ( real  lat,
real  lon,
int &  zone,
bool &  northp,
real &  x,
real &  y,
real &  gamma,
real &  k,
int  setzone = STANDARD,
bool  mgrslimits = false 
) [static]

Forward projection, from geographic to UTM/UPS.

Parameters:
[in] lat latitude of point (degrees).
[in] lon longitude of point (degrees).
[out] zone the UTM zone (zero means UPS).
[out] northp hemisphere of location (true means northern, false means southern).
[out] x easting of point (meters).
[out] y northing of point (meters).
[out] gamma meridian convergence at point (degrees).
[out] k scale of projection at point.
[in] setzone zone override.
[in] mgrslimits if true enforce the stricted MGRS limits on the coordinates (default = false).

The prefered zone for the result can be specified with setzone, see UTMUPS::StandardZone. Throw error if the resulting easting or northing is outside the allowed range (see Reverse), in which case the arguments are unchanged. This also returns meridian convergence gamma (degrees) and scale k. The accuracy of the conversion is about 5nm.

Definition at line 70 of file UTMUPS.cpp.

References GeographicLib::PolarStereographic::Forward(), GeographicLib::TransverseMercator::Forward(), INVALID, GeographicLib::Math::NaN(), StandardZone(), UPS, GeographicLib::PolarStereographic::UPS, and GeographicLib::TransverseMercator::UTM.

Referenced by Forward(), GeographicLib::GeoCoords::Reset(), and GeographicLib::GeoCoords::SetAltZone().

void GeographicLib::UTMUPS::Reverse ( int  zone,
bool  northp,
real  x,
real  y,
real &  lat,
real &  lon,
real &  gamma,
real &  k,
bool  mgrslimits = false 
) [static]

Reverse projection, from UTM/UPS to geographic.

Parameters:
[in] zone the UTM zone (zero means UPS).
[in] northp hemisphere of location (true means northern, false means southern).
[in] x easting of point (meters).
[in] y northing of point (meters).
[out] lat latitude of point (degrees).
[out] lon longitude of point (degrees).
[out] gamma meridian convergence at point (degrees).
[out] k scale of projection at point.
[in] mgrslimits if true enforce the stricted MGRS limits on the coordinates (default = false).

Throw error if easting or northing is outside the allowed range (see below), in which case the arguments are unchanged. The accuracy of the conversion is about 5nm.

UTM eastings are allowed to be in the range [0km, 1000km], northings are allowed to be in in [0km, 9600km] for the northern hemisphere and in [900km, 10000km] for the southern hemisphere. (However UTM northings can be continued across the equator. So the actual limits on the northings are [-9100km, 9600km] for the "northern" hemisphere and [900km, 19600km] for the "southern" hemisphere.)

UPS eastings and northings are allowed to be in the range [1200km, 2800km] in the northern hemisphere and in [700km, 3100km] in the southern hemisphere.

These ranges are 100km larger than allowed for the conversions to MGRS. (100km is the maximum extra padding consistent with eastings remaining non-negative.) This allows generous overlaps between zones and UTM and UPS. If mgrslimits = true, then all the ranges are shrunk by 100km so that they agree with the stricter MGRS ranges. No checks are performed besides these (e.g., to limit the distance outside the standard zone boundaries).

Definition at line 119 of file UTMUPS.cpp.

References INVALID, GeographicLib::Math::isnan(), MAXZONE, MINZONE, GeographicLib::Math::NaN(), GeographicLib::PolarStereographic::Reverse(), GeographicLib::TransverseMercator::Reverse(), GeographicLib::PolarStereographic::UPS, and GeographicLib::TransverseMercator::UTM.

Referenced by GeographicLib::GeoCoords::Reset(), and Reverse().

static void GeographicLib::UTMUPS::Forward ( real  lat,
real  lon,
int &  zone,
bool &  northp,
real &  x,
real &  y,
int  setzone = STANDARD,
bool  mgrslimits = false 
) [inline, static]

UTMUPS::Forward without returning convergence and scale.

Definition at line 232 of file UTMUPS.hpp.

References Forward().

static void GeographicLib::UTMUPS::Reverse ( int  zone,
bool  northp,
real  x,
real  y,
real &  lat,
real &  lon,
bool  mgrslimits = false 
) [inline, static]

UTMUPS::Reverse without returning convergence and scale.

Definition at line 242 of file UTMUPS.hpp.

References Reverse().

void GeographicLib::UTMUPS::DecodeZone ( const std::string &  zonestr,
int &  zone,
bool &  northp 
) [static]

Decode a UTM/UPS zone string.

Parameters:
[in] zonestr string represention of zone and hemisphere.
[out] zone the UTM zone (zero means UPS).
[out] northp the hemisphere (true means northern, false means southern).

For UTM, zonestr has the form of a zone number in the range [UTMUPS::MINUTMZONE, UTMUPS::MAXUTMZONE] = [1, 60] followed by a hemisphere letter, N or S. For UPS, it consists just of the hemisphere letter. The returned value of zone is UTMUPS::UPS = 0 for UPS. Note well that "38S" indicates the southern hemisphere of zone 38 and not latitude band S, [32, 40]. N, 01S, 2N, 38S are legal. 0N, 001S, 61N, 38P are illegal. INV is a special value for which the returned value of is UTMUPS::INVALID. Throws an error is the zone string is malformed.

Definition at line 174 of file UTMUPS.cpp.

References MAXUTMZONE, MINUTMZONE, and UPS.

Referenced by main(), and GeographicLib::GeoCoords::Reset().

std::string GeographicLib::UTMUPS::EncodeZone ( int  zone,
bool  northp 
) [static]

Encode a UTM/UPS zone string.

Parameters:
[out] zone the UTM zone (zero means UPS).
[out] northp the hemisphere (true means northern, false means southern).
Returns:
string represention of zone and hemisphere.

zone must be in the range [UTMUPS::MINZONE, UTMUPS::MAXZONE] = [0, 60] with zone = UTMUPS::UPS, 0, indicating UPS (but the resulting string does not contain "0"). zone may also be UTMUPS::INVALID, in which case the returned string is "INV". This reverses UTMUPS::DecodeZone.

Definition at line 217 of file UTMUPS.cpp.

References INVALID, MAXZONE, MINZONE, and UPS.

Math::real GeographicLib::UTMUPS::UTMShift (  )  throw () [static]
Returns:
shift (meters) necessary to align N and S halves of a UTM zone (107).

Definition at line 229 of file UTMUPS.cpp.

static Math::real GeographicLib::UTMUPS::MajorRadius (  )  throw () [inline, static]
Returns:
a the equatorial radius of the WGS84 ellipsoid (meters).

(The WGS84 value is returned because the UTM and UPS projections are based on this ellipsoid.)

Definition at line 298 of file UTMUPS.hpp.

static Math::real GeographicLib::UTMUPS::InverseFlattening (  )  throw () [inline, static]
Returns:
r the inverse flattening of the WGS84 ellipsoid.

(The WGS84 value is returned because the UTM and UPS projections are based on this ellipsoid.)

Definition at line 307 of file UTMUPS.hpp.


The documentation for this class was generated from the following files: