[Proj] False Easting & Northing for LAEA?
support.mn at elisanet.fi
support.mn at elisanet.fi
Tue Apr 10 02:53:13 PDT 2012
Hello,
here we again face this problem that Proj.4 should
have the syntax check preprocessor to warn the user
about potentially dangerous (or omitted) statements
etc.
This is not the first time we see these errors due to
small typos or misunderstandings which the scanner
just took in without arguing about them.
regards: Janne.
-------------------------------------------
Eric Miller [EMiller at dfg.ca.gov] kirjoitti:
> I think you want "x_0" and "y_0".
> --
>
> Eric G. Miller
> Software Developer
> CA Dept. of Fish & Game
>
>
> >>> On 4/9/2012 at 7:07 AM, Bob Fischer <robert.p.fischer-1 at nasa.gov> wrote:
> > Hello,
> >
> > I'm pretty new to Proj.4. I'm having a bit of trouble with false
> > easting and northing. See code below (using a simple C++ wrapper):
> >
> > const double D2R = M_PI / 180.0;
> >
> > double proj_lon_0 = -40;
> > double proj_lat_0 = 74;
> > char sproj[100];
> > sprintf(sproj, "+proj=laea +lon_0=%f +lat_0=%f +x0=1000000
> > +y0=1700000 +ellps=sphere",
> > proj_lon_0, proj_lat_0);
> > printf("Using projection: \"%s\"\n", sproj);
> > Proj proj(sproj);
> > printf("Using full projection: \"%s\"\n", proj.get_def().c_str());
> >
> > The output is:
> >
> > Using projection: "+proj=laea +lon_0=-40.000000 +lat_0=74.000000
> > +x0=1000000 +y0=1700000 +ellps=sphere"
> > Using full projection: " +proj=laea +lon_0=-40.000000 +lat_0=74.000000
> > +ellps=sphere"
> >
> > Note that my false easting/northing has been removed from my proj.4
> > string! The fact that no false easting/northing is being used is
> > confirmed when I try to transform a point:
> >
> > double lon00 = -40;
> > double lat00 = 74;
> > double xp,yp;
> > int err = transform(llproj, proj, lon00*D2R, lat00*D2R, xp, yp);
> > printf("Proj.4 transform 00 -> (%f, %f) (err = %d)\n", xp, yp, err);
> >
> > Output is:
> >
> > Proj.4 transform 00 -> (0.000000, -0.000000) (err = 0)
> >
> > Any ideas on why I'm not getting a false easting/northing here? I can
> > certainly work around the problem, but it would be nice if it could work.
> >
> > Thanks!
> > -- Bob
> >
> > (C++ wrapper is included below, for reference)
> >
> >
> >
> > /** C++ API for proj.4 Projection Library.
> > Copyright (c) 2012 by Robert Fischer: robert.fischer at nasa.gov
> > April 5, 2012
> >
> > Permission is hereby granted, free of charge, to any person obtaining a
> > copy of this software and associated documentation files (the "Software"),
> > to deal in the Software without restriction, including without limitation
> > the rights to use, copy, modify, merge, publish, distribute, sublicense,
> > and/or sell copies of the Software, and to permit persons to whom the
> > Software is furnished to do so, subject to the following conditions:
> >
> > The above copyright notice and this permission notice shall be included
> > in all copies or substantial portions of the Software.
> >
> > THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
> > OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> > MERCHANTABILITY,
> > FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> > THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> > FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> > DEALINGS IN THE SOFTWARE.
> > */
> >
> > #ifndef PROJPP_HPP
> > #define PROJPP_HPP
> >
> > #include <proj_api.h>
> >
> >
> > #if 0
> > class ProjContext;
> >
> > class ProjStatic {
> > public:
> > ProjContext const defaultContext;
> >
> > ProjStatic();
> > };
> > extern ProjStatic projStatic;
> >
> >
> > class ProjContext {
> > projCtx ctx;
> >
> > public :
> >
> >
> > };
> >
> > #endif
> >
> > namespace giss {
> >
> > class Proj {
> > projPJ pj;
> >
> > explicit Proj(projPJ _pj) : pj(_pj) {}
> >
> > public:
> > friend int transform(Proj const &src, Proj const &dest,
> > long point_count, int point_offset,
> > double *x, double *y, double *z);
> >
> >
> > // ------------------ Five Standard constructors/methods
> > // See: http://www2.research.att.com/~bs/C++0xFAQ.html
> >
> > explicit Proj(std::string const &definition)
> > {
> > pj = pj_init_plus(definition.c_str());
> > // pj_def = 0;
> > }
> >
> > explicit Proj(char const *definition)
> > {
> > pj = pj_init_plus(definition);
> > }
> >
> > ~Proj()
> > {
> > pj_free(pj);
> > // if (pj_def) pj_dalloc(pj_def);
> > }
> >
> > /** Transfer ownership */
> > Proj(Proj&& h) : pj{h.pj} //, pj_def{h.pj_def}
> > {
> > h.pj = 0;
> > // h.pj_def = 0;
> > }
> >
> > /** Transfer value */
> > Proj& operator=(Proj&& h) = delete;
> >
> > /** Copy constructor */
> > Proj(const Proj &h)
> > {
> > char *pj_def = pj_get_def(h.pj, 0);
> > pj = pj_init_plus(pj_def);
> > pj_dalloc(pj_def);
> > }
> >
> > // no copy with operator=()
> > Proj& operator=(const Proj&) = delete;
> >
> > // --------------------------- Other Stuff
> >
> >
> > /** Returns TRUE if the passed coordinate system is geographic
> > (proj=latlong). */
> > int is_latlong() const
> > { return pj_is_latlong(pj); }
> >
> >
> > /** Returns TRUE if the coordinate system is geocentric
> > (proj=geocent). */
> > int is_geocent() const
> > { return pj_is_geocent(pj); }
> >
> > /** Returns the PROJ.4 initialization string suitable for use with
> > pj_init_plus() that would produce this coordinate system, but with the
> > definition expanded as much as possible (for instance +init= and
> > +datum= definitions).
> > @param options Unused at this point
> > */
> > std::string get_def(int options=0) const
> > {
> > char *pj_def = 0;
> > pj_def = pj_get_def(pj, options);
> >
> > std::string ret = std::string(pj_def);
> > pj_dalloc(pj_def);
> > return ret;
> > }
> >
> >
> > /** Returns a new coordinate system definition which is the geographic
> > coordinate (lat/long) system underlying pj_in. */
> > Proj latlong_from_proj() const
> > {
> > return Proj(pj_latlong_from_proj(pj));
> > }
> >
> > };
> >
> >
> > inline int transform(Proj const &src, Proj const &dest,
> > long point_count, int point_offset, double *x, double *y, double *z=0)
> > {
> > return pj_transform(src.pj, dest.pj,
> > point_count, point_offset, x, y, z);
> > }
> >
> > inline int transform(Proj const &src, Proj const &dest,
> > double x0, double y0, double &x1, double &y1)
> > {
> > x1 = x0;
> > y1 = y0;
> > int ret = transform(src, dest, 1, 1, &x1, &y1);
> > return ret;
> > }
> >
> >
> > }
> >
> > #endif
> >
> > _______________________________________________
> > Proj mailing list
> > Proj at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/proj
>
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