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gpligc/src/projection.cpp

198 lines
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/*
* (c) 2002-2016 Hannes Krueger
* This file is part of the GPLIGC/ogie package
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
#include "projection.h"
#include <string>
#include <iostream>
#include <cmath>
#include <cstdlib>
//const std::string rcsid_projection_cpp =
// "$Id: projection.cpp 3 2014-07-31 09:59:20Z kruegerh $";
//const std::string rcsid_projection_h = PROJECTION_H;
Projection::Projection()
{
sphere_radius = 6371.0;
// this is 1 in km on a great circle
degree_dist = (2 * M_PI * sphere_radius) / 360.0;
// this is the default
projection = PROJ_PSEUDO_CYL_NO1;
// 9999 is the "not set"-flag
center_lat = 9999;
center_lon = 9999;
}
void
Projection::get_xy(float lat, float lon, float &x, float &y)
{
//std::cout << "ENTERING proj::get_xy" << std::flush;
//std::cout << "ENTERING proj::get_xy" << center_lat << " " << center_lon << std::endl << std::flush;
if (center_lat == 9999 || center_lon == 9999) {
std::
cerr << "Projection class: get_xy: center isn't set!"
<< std::endl;
return;
}
if (lat > 90)
lat = 90;
if (lat < -90)
lat = -90;
// This pseudo cylindrical projection has true lengths on meridians and latitude circles...
if (projection == PROJ_PSEUDO_CYL_NO1) {
float latdiff = center_lat - lat;
float londiff = center_lon - lon;
y = latdiff * degree_dist;
x = londiff * degree_dist * cos((M_PI / 180.0) * lat);
return;
}
// This cylindrical projection has true lengths on meridian only
if (projection == PROJ_CYL_NO1) {
y = (center_lat - lat) * degree_dist;
x = (center_lon - lon) * degree_dist;
return;
}
// platt(?) (Flaechentreu)
if (projection == PROJ_CYL_PLATT) {
float aequatdist_center =
sin(center_lat * (M_PI / 180.0)) * sphere_radius;
float aequatdist_point =
sin(lat * (M_PI / 180.0)) * sphere_radius;
y = aequatdist_center - aequatdist_point;
x = (center_lon - lon) * degree_dist;
return;
}
if (projection == PROJ_CYL_MERCATOR) {
x = sphere_radius * (center_lon * (M_PI / 180.0) -
lon * (M_PI / 180.0));
//x = (center_lon - lon) * degree_dist;
//std::cout << x << std::endl;
float sign = 1.0;
if (lat < 0)
sign = -1.0;
float aequatdist_point =
-sign * sphere_radius *
log(tan
((M_PI / 4.0) +
((fabs(lat) * (M_PI / 180.0)) / 2.0)));
float sign_c = 1.0;
if (center_lat < 0)
sign_c = -1.0;
float aequatdist_center =
-sign_c * sphere_radius *
log(tan
((M_PI / 4.0) +
((fabs(center_lat) * (M_PI / 180.0)) / 2.0)));
y = -(aequatdist_center - aequatdist_point);
return;
}
std::cerr << "No valid projection....." << std::endl;
exit(1);
}
void Projection::get_latlon(float x, float y, float &lat, float &lon)
{
if (center_lat == 9999 || center_lon == 9999) {
std::
cerr <<
"Projection class: get_latlon: center isn't set!" <<
std::endl;
return;
}
// this is 1 in km on a great circle
degree_dist = (2 * M_PI * sphere_radius) / 360.0;
if (projection == PROJ_PSEUDO_CYL_NO1) {
lat = center_lat + (y / degree_dist);
lon =
center_lon +
(x / (degree_dist * cos((M_PI / 180.0) * lat)));
return;
}
if (projection == PROJ_CYL_NO1) {
lat = center_lat + (y / degree_dist);
lon = center_lon + (x / degree_dist);
return;
}
if (projection == PROJ_CYL_PLATT) {
lon = center_lon + (x / degree_dist);
float aequatdist_center =
sin(center_lat * (M_PI / 180.0)) * sphere_radius;
lat =
asin((y +
aequatdist_center) / sphere_radius) / (M_PI /
180.0);
return;
}
if (projection == PROJ_CYL_MERCATOR) {
lon = center_lon + (x / degree_dist);
float sign_c = 1.0;
if (center_lat < 0)
sign_c = -1.0;
float aequatdist_center =
-sign_c * sphere_radius *
log(tan
((M_PI / 4.0) +
((fabs(center_lat) * (M_PI / 180.0)) / 2.0)));
float northing = aequatdist_center - y;
lat =
-(2.0 * atan(exp(northing / sphere_radius)) -
(M_PI / 2.0)) / (M_PI / 180.0);
return;
}
std::cerr << "No valid projection....." << std::endl;
exit(1);
}