boost geometry precision loss - c++

Question

#include <iostream>
#include <vector>
#include <boost/geometry.hpp>
#include <boost/geometry/strategies/cartesian/distance_pythagoras.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/geometries/linestring.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>
#include <boost/foreach.hpp>
int main(int argc, char *argv[])
{
typedef boost::geometry::model::d2::point_xy<double> point;
typedef boost::geometry::model::polygon<point> polygon;
std::stringstream ss;
std::string sstring;
char *poly1 =
"POLYGON((45.4602851 9.1146293,45.4602851 9.1196293,45.4652851 9.1196293,45.4652851 9.1146293,45.4602851 9.1146293))";
char *buffer = NULL;
int poly1StrLen;
double tmp;
polygon poly, newPoly;
point p1;
boost::geometry::read_wkt(poly1, poly);
boost::geometry::correct(poly);
BOOST_FOREACH(point const & p, boost::geometry::exterior_ring(poly))
{
// ss << boost::geometry::wkt(p);
// p1.x(p.y());
// p1.y(p.x());
boost::geometry::append(boost::geometry::exterior_ring(newPoly), p);
}
ss << boost::geometry::wkt(newPoly);
sstring = ss.str();
buffer = (char *)malloc(sstring.length());
buffer = strcpy(buffer, sstring.c_str());
printf("%s\n", buffer);
free(buffer);
}
Result is :
POLYGON((45.4603 9.11463,45.4603 9.11963,45.4653 9.11963,45.4653 9.11463,45.4603 9.11463))
Is loosing too much precision for geo-coordinates, what I have to do to leave the same precision?

Answer 1

Just set the output precision on the stream, e.g.
std::cout << std::setprecision(12) << boost::geometry::wkt(newPoly);
This is a lot simpler. You don't have to do the whole buffer dance either!
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#include <iostream>
#include <vector>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>
#include <boost/foreach.hpp>
int main() {
typedef boost::geometry::model::d2::point_xy<double> point;
typedef boost::geometry::model::polygon<point> polygon;
char const *poly1 = "POLYGON((45.4602851 9.1146293,45.4602851 9.1196293,45.4652851 9.1196293,45.4652851 9.1146293,45.4602851 9.1146293))";
polygon poly, newPoly;
boost::geometry::read_wkt(poly1, poly);
boost::geometry::correct(poly);
BOOST_FOREACH(point const & p, boost::geometry::exterior_ring(poly)) {
boost::geometry::append(boost::geometry::exterior_ring(newPoly), p);
}
std::cout << std::setprecision(12) << boost::geometry::wkt(newPoly);
}
Prints
POLYGON((45.4602851 9.1146293,45.4602851 9.1196293,45.4652851 9.1196293,45.4652851 9.1146293,45.4602851 9.1146293))