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GeographicLib::UTMUPS Class Reference

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

#include <GeographicLib/UTMUPS.hpp>

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 Transfer (int zonein, bool northpin, real xin, real yin, int zoneout, bool northpout, real &xout, real &yout, int &zone)
 
static void DecodeZone (const std::string &zonestr, int &zone, bool &northp)
 
static std::string EncodeZone (int zone, bool northp, bool abbrev=true)
 
static void DecodeEPSG (int epsg, int &zone, bool &northp)
 
static int EncodeEPSG (int zone, bool northp)
 
static Math::real UTMShift ()
 
Inspector functions
static Math::real MajorRadius ()
 
static Math::real Flattening ()
 

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. These are the algorithms recommended by the NGA document

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:

The GeographicLib::UTMUPS::EncodeZone encodes the UTM zone and hemisphere to allow UTM/UPS coordinated to be displayed as, for example, "38N 444500 3688500". According to NGA.SIG.0012_2.0.0_UTMUPS the use of "N" to denote "north" in the context is not allowed (since a upper case letter in this context denotes the MGRS latitude band). Consequently, as of version 1.36, EncodeZone uses the lower case letters "n" and "s" to denote the hemisphere. In addition EncodeZone accepts an optional final argument abbrev, which, if false, results in the hemisphere being spelled out as in "38north".

Example of use:

// Example of using the GeographicLib::UTMUPS class
#include <iostream>
#include <exception>
#include <string>
#include <iomanip>
using namespace std;
using namespace GeographicLib;
int main() {
try {
// See also example-GeoCoords.cpp
{
// Sample forward calculation
double lat = 33.3, lon = 44.4; // Baghdad
int zone;
bool northp;
double x, y;
UTMUPS::Forward(lat, lon, zone, northp, x, y);
string zonestr = UTMUPS::EncodeZone(zone, northp);
cout << fixed << setprecision(2)
<< zonestr << " " << x << " " << y << "\n";
}
{
// Sample reverse calculation
string zonestr = "38n";
int zone;
bool northp;
UTMUPS::DecodeZone(zonestr, zone, northp);
double x = 444e3, y = 3688e3;
double lat, lon;
UTMUPS::Reverse(zone, northp, x, y, lat, lon);
cout << lat << " " << lon << "\n";
}
}
catch (const exception& e) {
cerr << "Caught exception: " << e.what() << "\n";
return 1;
}
return 0;
}

Definition at line 75 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 110 of file UTMUPS.hpp.

Member Function Documentation

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

The standard zone.

Parameters
[in]latlatitude (degrees).
[in]lonlongitude (degrees).
[in]setzonezone override (optional). If omitted, use the standard rules for picking the zone. If setzone is given then use that zone if it is non-negative, otherwise apply the rules given in UTMUPS::zonespec.
Exceptions
GeographicErrif setzone is outside the range [UTMUPS::MINPSEUDOZONE, UTMUPS::MAXZONE] = [−4, 60].

This is exact.

Definition at line 42 of file UTMUPS.cpp.

References GeographicLib::Math::isnan(), and GeographicLib::Utility::str().

Referenced by 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]latlatitude of point (degrees).
[in]lonlongitude of point (degrees).
[out]zonethe UTM zone (zero means UPS).
[out]northphemisphere (true means north, false means south).
[out]xeasting of point (meters).
[out]ynorthing of point (meters).
[out]gammameridian convergence at point (degrees).
[out]kscale of projection at point.
[in]setzonezone override (optional).
[in]mgrslimitsif true enforce the stricter MGRS limits on the coordinates (default = false).
Exceptions
GeographicErrif lat is not in [−90°, 90°].
GeographicErrif lon is not in [−540°, 540°).
GeographicErrif the resulting x or y is out of allowed range (see Reverse); in this case, these arguments are unchanged.

If setzone is omitted, use the standard rules for picking the zone. If setzone is given then use that zone if it is non-negative, otherwise apply the rules given in UTMUPS::zonespec. The accuracy of the conversion is about 5nm.

The northing y jumps by UTMUPS::UTMShift() when crossing the equator in the southerly direction. Sometimes it is useful to remove this discontinuity in y by extending the "northern" hemisphere using UTMUPS::Transfer:

double lat = -1, lon = 123;
int zone;
bool northp;
double x, y, gamma, k;
GeographicLib::UTMUPS::Forward(lat, lon, zone, northp, x, y, gamma, k);
zone, true, x, y, zone);
northp = true;

Definition at line 67 of file UTMUPS.cpp.

References GeographicLib::PolarStereographic::Forward(), GeographicLib::TransverseMercator::Forward(), GeographicLib::Math::NaN(), GeographicLib::Utility::str(), GeographicLib::PolarStereographic::UPS(), and GeographicLib::TransverseMercator::UTM().

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

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]zonethe UTM zone (zero means UPS).
[in]northphemisphere (true means north, false means south).
[in]xeasting of point (meters).
[in]ynorthing of point (meters).
[out]latlatitude of point (degrees).
[out]lonlongitude of point (degrees).
[out]gammameridian convergence at point (degrees).
[out]kscale of projection at point.
[in]mgrslimitsif true enforce the stricter MGRS limits on the coordinates (default = false).
Exceptions
GeographicErrif zone, x, or y is out of allowed range; this this 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 118 of file UTMUPS.cpp.

References GeographicLib::Math::isnan(), GeographicLib::Math::NaN(), GeographicLib::PolarStereographic::Reverse(), GeographicLib::TransverseMercator::Reverse(), GeographicLib::Utility::str(), GeographicLib::PolarStereographic::UPS(), and GeographicLib::TransverseMercator::UTM().

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

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

UTMUPS::Forward without returning convergence and scale.

Definition at line 272 of file UTMUPS.hpp.

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

UTMUPS::Reverse without returning convergence and scale.

Definition at line 282 of file UTMUPS.hpp.

void GeographicLib::UTMUPS::Transfer ( int  zonein,
bool  northpin,
real  xin,
real  yin,
int  zoneout,
bool  northpout,
real &  xout,
real &  yout,
int &  zone 
)
static

Transfer UTM/UPS coordinated from one zone to another.

Parameters
[in]zoneinthe UTM zone for xin and yin (or zero for UPS).
[in]northpinhemisphere for xin and yin (true means north, false means south).
[in]xineasting of point (meters) in zonein.
[in]yinnorthing of point (meters) in zonein.
[in]zoneoutthe requested UTM zone for xout and yout (or zero for UPS).
[in]northpouthemisphere for xout output and yout.
[out]xouteasting of point (meters) in zoneout.
[out]youtnorthing of point (meters) in zoneout.
[out]zonethe actual UTM zone for xout and yout (or zero for UPS); this equals zoneout if zoneout ≥ 0.
Exceptions
GeographicErrif zonein is out of range (see below).
GeographicErrif zoneout is out of range (see below).
GeographicErrif xin or yin fall outside their allowed ranges (see UTMUPS::Reverse).
GeographicErrif xout or yout fall outside their allowed ranges (see UTMUPS::Reverse).

zonein must be in the range [UTMUPS::MINZONE, UTMUPS::MAXZONE] = [0, 60] with zonein = UTMUPS::UPS, 0, indicating UPS. zonein may also be UTMUPS::INVALID.

zoneout must be in the range [UTMUPS::MINPSEUDOZONE, UTMUPS::MAXZONE] = [-4, 60]. If zoneout < UTMUPS::MINZONE then the rules give in the documentation of UTMUPS::zonespec are applied, and zone is set to the actual zone used for output.

(xout, yout) can overlap with (xin, yin).

Definition at line 180 of file UTMUPS.cpp.

References Forward(), MATCH, and Reverse().

Referenced by GeographicLib::GeoCoords::AltUTMUPSRepresentation(), and GeographicLib::GeoCoords::UTMUPSRepresentation().

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

Decode a UTM/UPS zone string.

Parameters
[in]zonestrstring representation of zone and hemisphere.
[out]zonethe UTM zone (zero means UPS).
[out]northphemisphere (true means north, false means south).
Exceptions
GeographicErrif zonestr is malformed.

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 (or "north" or "south" spelled out). For UPS, it consists just of the hemisphere letter (or the spelled out hemisphere). 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° ≤ lat < 40°. n, 01s, 2n, 38s, south, 3north are legal. 0n, 001s, +3n, 61n, 38P are illegal. INV is a special value for which the returned value of is UTMUPS::INVALID.

Definition at line 214 of file UTMUPS.cpp.

References GeographicLib::Utility::str().

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

std::string GeographicLib::UTMUPS::EncodeZone ( int  zone,
bool  northp,
bool  abbrev = true 
)
static

Encode a UTM/UPS zone string.

Parameters
[in]zonethe UTM zone (zero means UPS).
[in]northphemisphere (true means north, false means south).
[in]abbrevif true (the default) use abbreviated (n/s) notation for hemisphere; otherwise spell out the hemisphere (north/south)
Exceptions
GeographicErrif zone is out of range (see below).
std::bad_allocif memoy for the string can't be allocated.
Returns
string representation 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 258 of file UTMUPS.cpp.

References GeographicLib::Utility::str().

void GeographicLib::UTMUPS::DecodeEPSG ( int  epsg,
int &  zone,
bool &  northp 
)
static

Decode EPSG.

Parameters
[in]epsgthe EPSG code.
[out]zonethe UTM zone (zero means UPS).
[out]northphemisphere (true means north, false means south).

EPSG (European Petroleum Survery Group) codes are a way to refer to many different projections. DecodeEPSG decodes those refering to UTM or UPS projections for the WGS84 ellipsoid. If the code does not refer to one of these projections, zone is set to UTMUPS::INVALID. See http://spatialreference.org/ref/epsg/

Definition at line 274 of file UTMUPS.cpp.

int GeographicLib::UTMUPS::EncodeEPSG ( int  zone,
bool  northp 
)
static

Encode zone as EPSG.

Parameters
[in]zonethe UTM zone (zero means UPS).
[in]northphemisphere (true means north, false means south).
Returns
EPSG code (or -1 if zone is not in the range [UTMUPS::MINZONE, UTMUPS::MAXZONE] = [0, 60])

Convert zone and northp to the corresponding EPSG (European Petroleum Survery Group) codes

Definition at line 291 of file UTMUPS.cpp.

Math::real GeographicLib::UTMUPS::UTMShift ( )
static
Returns
shift (meters) necessary to align north and south halves of a UTM zone (107).

Definition at line 302 of file UTMUPS.cpp.

static Math::real GeographicLib::UTMUPS::MajorRadius ( )
inlinestatic
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 407 of file UTMUPS.hpp.

References GeographicLib::Constants::WGS84_a().

Referenced by GeographicLib::MGRS::MajorRadius(), and GeographicLib::GeoCoords::MajorRadius().

static Math::real GeographicLib::UTMUPS::Flattening ( )
inlinestatic
Returns
f the flattening of the WGS84 ellipsoid.

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

Definition at line 416 of file UTMUPS.hpp.

References GeographicLib::Constants::WGS84_f().

Referenced by GeographicLib::MGRS::Flattening(), and GeographicLib::GeoCoords::Flattening().


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