[pd]: This a binding to the [https://trac.osgeo.org/proj/%|%proj4%|%] projection library. See [http://trac.osgeo.org/proj/wiki/ProjAPI#EXAMPLE%|% Proj API reference Example %|%] 
 
This implementation requires [http://andreas-kupries.github.io/critcl/%|%critcl%|%]

<<discussion>> proj4tcl.tcl
======
# proj4tcl.tcl
#

package require critcl 3.1
package require critcl::class
critcl::tcl 8.5

critcl::clibraries -lproj

critcl::ccode {
    #include <proj_api.h>
}

critcl::class::define proj4 {
    
    type projPJ

    constructor {
        if (objc != 1) {
            Tcl_WrongNumArgs (interp, objcskip, objv-objcskip,
                               "initstring");
            goto error;
        }

        char *defn = Tcl_GetString(objv[0]);
        instance = pj_init_plus(defn);

        if (instance == NULL) {
            Tcl_AppendResult(interp, "proj definition error: ",
                                pj_strerrno(pj_errno), NULL);
            goto error;
        }
    }

    destructor {
        pj_free(instance);
    }

    method to proc {
        char* dest
        Tcl_Obj* point
    } ok {
        int n;
        double x,y,z;
        Tcl_Obj **d,*l;
        Tcl_CmdInfo destinfo;
        projPJ dest_cs;

        if (Tcl_GetCommandInfo(interp, dest, &destinfo) == 0) {
            Tcl_AppendResult(interp,"Command not found: ",
                              dest, NULL);
            return TCL_ERROR;
        }

        dest_cs = (projPJ) destinfo.objClientData;

        if (Tcl_ListObjGetElements(interp, point, &n, &d) != TCL_OK) {
            return TCL_ERROR;
        }
       
        if (n != 3) {
            Tcl_AppendResult(interp,"not 3D point: ", NULL);
            return TCL_ERROR;
        }

        if (Tcl_GetDoubleFromObj(interp, d[0], &x) != TCL_OK
            || Tcl_GetDoubleFromObj(interp, d[1], &y) != TCL_OK 
            || Tcl_GetDoubleFromObj(interp, d[2], &z) != TCL_OK) {
                return TCL_ERROR;
        }

        if (pj_is_latlong(instance)) {
            x *= DEG_TO_RAD;
            y *= DEG_TO_RAD;
        }

        if (pj_transform(instance,dest_cs,1,1,&x,&y,&z)) {
            Tcl_AppendResult(interp, "proj error: ",
                                pj_strerrno(pj_errno), NULL);
            return TCL_ERROR;
        }

        if (pj_is_latlong(dest_cs)) {
            x *= RAD_TO_DEG;
            y *= RAD_TO_DEG;
        }

        l = Tcl_NewListObj(0, NULL);
        Tcl_ListObjAppendElement(interp, l, Tcl_NewDoubleObj(x));
        Tcl_ListObjAppendElement(interp, l, Tcl_NewDoubleObj(y));
        Tcl_ListObjAppendElement(interp, l, Tcl_NewDoubleObj(z));
        Tcl_SetObjResult(interp, l);
        return TCL_OK;
    }
}

package provide proj4tcl 1

#end 
======

<<discussion>>

**Compile**

======
critcl -pkg proj4tcl.tcl
======


**Use**


======
lappend auto_path [pwd]/lib
package require proj4tcl

# Create coordinate systems 
proj4 create mga56  "+proj=utm +zone=56 +south +ellps=GRS80 "
proj4 create gda94  "+proj=latlon +axis=neu +ellps=GRS80"

# A 3d point is just a 3-item list
# order is defined by the proj.4 +axis option
set pos [list 502810 6964520 0]

# Convert the point
set result [mga56 to gda94 $pos]

puts [format "%.5f %.5f %.2f" {*}$result]
# lats and lons are in decimal degrees.
# output -> -27.44279 153.02843 0.00
======

**Using Vertical Datums **

See [https://trac.osgeo.org/proj/wiki/VerticalDatums%|%Vertical Datums%|%]


======
set env(PROJ_LIB) [pwd]
# need to make/get .gtx file
proj4 create mga56ag09 "+proj=utm +zone=56 +south +ellps=GRS80  +geoidgrids=ausgeoid09.gtx"
set result [mga56ag09 to gda94 $pos]
puts [format "%.5f %.5f %.3f" {*}$result]
# output -> -27.44279 153.02843 41.901

======

**Windows**
Place proj_api.h and libproj-0.dll in the same directory as proj4tcl.tcl.<<br>>  libproj-0.dll becomes part of the package using the preload command.


======
package require critcl 3.1
package require critcl::class
critcl::tcl 8.5

set dir [pwd]
critcl::cheaders -I$dir
critcl::include proj_api.h
critcl::clibraries -L$dir
critcl::clibraries $dir/libproj-0.dll
critcl::preload $dir/libproj-0



======
Compiling with mingw32
======
critcl -target mingw32 -pkg proj4tcl
======

<<categories>>Geography | Critcl