toys/gps/docs/source/coord/gauss.cpp

#include "util/util.h"
#include "geo/private/math/math.h"
#include "geo/private/coord/gauss.h"

namespace ns
{
namespace geo
{

// BeiJing54 -> Gauss-Kruger
const char* Wgs84Proj4Init = "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs";

GaussConverter::GaussConverter(double centerMeridian, double bandWidth, double pm)
    : m_pm(pm), m_bandWidth(bandWidth)
{
    m_ctx = pj_ctx_alloc();
    // m_ctx=proj_context_create();
    m_beiJing54Proj = pj_init_plus_ctx(m_ctx, Wgs84Proj4Init);

    m_centralMeridian = unifyCentralMeridian(centerMeridian);

    char str[128] = {0};
    sprintf(str,
            "+proj=tmerc +ellps=WGS84 +lon_0=%.2fe +x_0=500000 +y_0=0 +lon_wrap=180 +units=m +k=1.0",
            m_centralMeridian);
    m_centralProj = pj_init_plus_ctx(m_ctx, str);
}

GaussConverter::~GaussConverter()
{
    if (m_centralProj)
        pj_free(m_centralProj);
    if (m_beiJing54Proj)
        pj_free(m_beiJing54Proj);
    if (m_ctx)
        pj_ctx_free(m_ctx);
    // proj_context_destroy(m_ctx);
}

int GaussConverter::reset(double centerLon, double bandWidth, double pm)
{
    if (are_equal(bandWidth, 0) && are_equal(pm, 0))
    {
        double c = unifyCentralMeridian(centerLon);
        if (are_equal(c, m_centralMeridian))
            return 0;
    }
    else
    {
        m_bandWidth = bandWidth;
        m_pm = pm;
    }

    pj_free(m_centralProj);

    m_centralMeridian = unifyCentralMeridian(centerLon);

    char str[128] = {0};
    sprintf(
        str,
        "+proj=tmerc +ellps=WGS84 +lon_0=%.2fe +x_0=500000 +y_0=0 +lon_wrap=180 +units=m +k=1.0",
        m_centralMeridian);
    m_centralProj = pj_init_plus_ctx(m_ctx, str);

    return 0;
}

bool GaussConverter::reset(std::string pjParamsStr)
{
    pj_free(m_centralProj);

    m_centralProj = pj_init_plus_ctx(m_ctx, pjParamsStr.c_str());

    if (m_centralProj)
    {
        return calcCenterLon(pjParamsStr, m_centralMeridian);
    }
    return false;
}

bool GaussConverter::calcCenterLon(std::string params, double& cenLon)
{
    std::vector<std::string> subs = util::split(params, " ");
    for (auto& s : subs)
    {
        if (util::startswith(s, "+lon_0="))
        {
            std::string numStr = s.substr(7);
            numStr = util::trim(numStr, " ");
            if (util::isNum(numStr))
            {
                cenLon = std::stod(numStr.c_str());
                return true;
            }
        }
    }
    return false;
}

double GaussConverter::unifyCentralMeridian(double lon)
{
    m_zone = static_cast<unsigned>(std::floor((lon - m_pm) / m_bandWidth)) + 1;
    return getCentralMeridian(m_zone);
}

PointD GaussConverter::wgs842Gauss(const PointD& p) const
{
    double x = p.x * DEG_TO_RAD;
    double y = p.y * DEG_TO_RAD;
    double z = 0.0;
    pj_transform(m_beiJing54Proj, m_centralProj, 1, 1, &x, &y, &z);
    return PointD(x, y, p.z);
}

PointD GaussConverter::gauss2Wgs84(const PointD& p) const
{
    double x = p.x, y = p.y, z = 0.0;
    pj_transform(m_centralProj, m_beiJing54Proj, 1, 1, &x, &y, &z);
    return PointD(x * RAD_TO_DEG, y * RAD_TO_DEG, p.z);
}

} // namespace geo
} // namespace ns