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OSGB.cpp
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/**
* \file OSGB.cpp
* \brief Implementation for GeographicLib::OSGB class
*
* Copyright (c) Charles Karney (2010-2020) <karney@alum.mit.edu> and licensed
* under the MIT/X11 License. For more information, see
* https://geographiclib.sourceforge.io/
**********************************************************************/
#include <GeographicLib/OSGB.hpp>
#include <GeographicLib/Utility.hpp>
namespace GeographicLib {
using namespace std;
const char* const OSGB::letters_ = "ABCDEFGHJKLMNOPQRSTUVWXYZ";
const char* const OSGB::digits_ = "0123456789";
const TransverseMercator& OSGB::OSGBTM() {
static const TransverseMercator osgbtm(EquatorialRadius(), Flattening(),
CentralScale());
return osgbtm;
}
Math::real OSGB::computenorthoffset() {
real x, y;
static const real northoffset =
( OSGBTM().Forward(real(0), OriginLatitude(), real(0), x, y),
FalseNorthing() - y );
return northoffset;
}
void OSGB::GridReference(real x, real y, int prec, std::string& gridref) {
using std::isnan; // Needed for Centos 7, ubuntu 14
CheckCoords(x, y);
if (!(prec >= 0 && prec <= maxprec_))
throw GeographicErr("OSGB precision " + Utility::str(prec)
+ " not in [0, "
+ Utility::str(int(maxprec_)) + "]");
if (isnan(x) || isnan(y)) {
gridref = "INVALID";
return;
}
char grid[2 + 2 * maxprec_];
int
xh = int(floor(x / tile_)),
yh = int(floor(y / tile_));
real
xf = x - tile_ * xh,
yf = y - tile_ * yh;
xh += tileoffx_;
yh += tileoffy_;
int z = 0;
grid[z++] = letters_[(tilegrid_ - (yh / tilegrid_) - 1)
* tilegrid_ + (xh / tilegrid_)];
grid[z++] = letters_[(tilegrid_ - (yh % tilegrid_) - 1)
* tilegrid_ + (xh % tilegrid_)];
// Need extra real because, since C++11, pow(float, int) returns double
real mult = real(pow(real(base_), max(tilelevel_ - prec, 0)));
int
ix = int(floor(xf / mult)),
iy = int(floor(yf / mult));
for (int c = min(prec, int(tilelevel_)); c--;) {
grid[z + c] = digits_[ ix % base_ ];
ix /= base_;
grid[z + c + prec] = digits_[ iy % base_ ];
iy /= base_;
}
if (prec > tilelevel_) {
xf -= floor(xf / mult);
yf -= floor(yf / mult);
mult = real(pow(real(base_), prec - tilelevel_));
ix = int(floor(xf * mult));
iy = int(floor(yf * mult));
for (int c = prec - tilelevel_; c--;) {
grid[z + c + tilelevel_] = digits_[ ix % base_ ];
ix /= base_;
grid[z + c + tilelevel_ + prec] = digits_[ iy % base_ ];
iy /= base_;
}
}
int mlen = z + 2 * prec;
gridref.resize(mlen);
copy(grid, grid + mlen, gridref.begin());
}
void OSGB::GridReference(const std::string& gridref,
real& x, real& y, int& prec,
bool centerp) {
int
len = int(gridref.size()),
p = 0;
if (len >= 2 &&
toupper(gridref[0]) == 'I' &&
toupper(gridref[1]) == 'N') {
x = y = Math::NaN();
prec = -2; // For compatibility with MGRS::Reverse.
return;
}
char grid[2 + 2 * maxprec_];
for (int i = 0; i < len; ++i) {
if (!isspace(gridref[i])) {
if (p >= 2 + 2 * maxprec_)
throw GeographicErr("OSGB string " + gridref + " too long");
grid[p++] = gridref[i];
}
}
len = p;
p = 0;
if (len < 2)
throw GeographicErr("OSGB string " + gridref + " too short");
if (len % 2)
throw GeographicErr("OSGB string " + gridref +
" has odd number of characters");
int
xh = 0,
yh = 0;
while (p < 2) {
int i = Utility::lookup(letters_, grid[p++]);
if (i < 0)
throw GeographicErr("Illegal prefix character " + gridref);
yh = yh * tilegrid_ + tilegrid_ - (i / tilegrid_) - 1;
xh = xh * tilegrid_ + (i % tilegrid_);
}
xh -= tileoffx_;
yh -= tileoffy_;
int prec1 = (len - p)/2;
real
unit = tile_,
x1 = unit * xh,
y1 = unit * yh;
for (int i = 0; i < prec1; ++i) {
unit /= base_;
int
ix = Utility::lookup(digits_, grid[p + i]),
iy = Utility::lookup(digits_, grid[p + i + prec1]);
if (ix < 0 || iy < 0)
throw GeographicErr("Encountered a non-digit in " + gridref);
x1 += unit * ix;
y1 += unit * iy;
}
if (centerp) {
x1 += unit/2;
y1 += unit/2;
}
x = x1;
y = y1;
prec = prec1;
}
void OSGB::CheckCoords(real x, real y) {
// Limits are all multiples of 100km and are all closed on the lower end
// and open on the upper end -- and this is reflected in the error
// messages. NaNs are let through.
if (x < minx_ || x >= maxx_)
throw GeographicErr("Easting " + Utility::str(int(floor(x/1000)))
+ "km not in OSGB range ["
+ Utility::str(minx_/1000) + "km, "
+ Utility::str(maxx_/1000) + "km)");
if (y < miny_ || y >= maxy_)
throw GeographicErr("Northing " + Utility::str(int(floor(y/1000)))
+ "km not in OSGB range ["
+ Utility::str(miny_/1000) + "km, "
+ Utility::str(maxy_/1000) + "km)");
}
} // namespace GeographicLib
real
GeographicLib::Math::real real
Definition GeodSolve.cpp:28
OSGB.hpp
Header for GeographicLib::OSGB class.
Utility.hpp
Header for GeographicLib::Utility class.
GeographicLib::GeographicErr
Exception handling for GeographicLib.
Definition Constants.hpp:316
GeographicLib::Math::NaN
static T NaN()
Definition Math.cpp:277
GeographicLib::Math::real
double real
Definition Math.hpp:110
GeographicLib::OSGB::GridReference
static void GridReference(real x, real y, int prec, std::string &gridref)
Definition OSGB.cpp:34
GeographicLib::OSGB::CentralScale
static Math::real CentralScale()
Definition OSGB.hpp:206
GeographicLib::OSGB::EquatorialRadius
static Math::real EquatorialRadius()
Definition OSGB.hpp:182
GeographicLib::OSGB::FalseNorthing
static Math::real FalseNorthing()
Definition OSGB.hpp:225
GeographicLib::OSGB::Flattening
static Math::real Flattening()
Definition OSGB.hpp:197
GeographicLib::OSGB::OriginLatitude
static Math::real OriginLatitude()
Definition OSGB.hpp:214
GeographicLib::TransverseMercator::Forward
void Forward(real lon0, real lat, real lon, real &x, real &y, real &gamma, real &k) const
Definition TransverseMercator.cpp:355
GeographicLib::Utility::lookup
static int lookup(const std::string &s, char c)
Definition Utility.cpp:160
GeographicLib::Utility::str
static std::string str(T x, int p=-1)
Definition Utility.hpp:161
GeographicLib
Namespace for GeographicLib.
Definition Accumulator.cpp:12
std
Definition NearestNeighbor.hpp:806