Converting cartesian coordinates to geographical gps

Hi everybody,
I need to convert cartesian coordinates to geographical gps. Knowing
X,Y coordinates how can I calculate Latitude and Longitude?

A friend of mine give me this formula:

/*gps coordinates of zero local point*/
X0POL =3D 38.4758676627;                # 1=B0 ZERO POINT POLAR
Y0POL =3D 15.9189614895;                # 2=B0 ZERO POINT POLAR

/*convert zero point from DD coordinate to DDM*/
B5 =3D (60 * X0POL) - (38 * 60) + 3800;#3828.5521         # 1=B0 ZERO POINT
B6 =3D (60 * Y0POL) - (15 * 60) + 1500;#1555.1377        # 2=B0 ZERO POINT

G5 =3D 4.12841392;                                # TERRESTRIAL ROTATION RADIANS DEGREE

COEFFX =3D 1849.94;
COEFFY =3D 1454.88;

VALORE1 =3D (X * SIN(G5) + B5 * COEFFX + Y * COS(G5)) / COEFFX;
VALORE2 =3D (VALORE1 * COEFFX * COT(G5) - Y * (SIN(G5) + COS(G5) * COT
(G5)) - B5 * COEFFX * COT(G5) + B6 * COEFFY) / COEFFY;

/*transform from DDM to DD*/
LatGPS =3D (VALORE1+38*60-3800)/60;
LongGPS =3D (VALORE2+15*60-1500)/60;


But he doesn't remember how he got COEFFX and COEFFY.
Using these formula the gps coordinates I get are enough precise, they
correspond "enough" to what they should be considering the position of
some points about which I know the correct Lat/Lon coordinates.

But I need a better precision, therefore I hope you can help me
finding some formulas to convert cartesian coordinates to geographical
gps.

Thank you very much in advance
Carmelo

wrote:


There isn't enough information to do this, I am afraid. There is no
single way of converting X,.Y coordinates to Latitude and Longitude or
the other way round; there are millions! And without knowing which
method (known as a "projection") was used, you simply can't do it.

Paul Cooper

I have got X,Y coordinates in a local metric system, of which I know:
- origin (0,0) gps coordinates
- angle between the Y axis and the North


For a given point with X,Y coordinates I need to know its GPS Lat/Lon
coordinates... Do you know any algorithm to calculate them? Or do you
need more info?

I hope you can help me

You can refer to a couple of websites to get it done , some C
source codes are also posted that can do the job . But it really
depends on the location of the co-ordinates , datum , projection
because the method of conversion varies depending on each of them.




carmelo wrote:
T

some C


I have got X,Y coordinates in a local metric system, of which I know:
- origin (0,0) gps coordinates
- angle between the Y axis and the North

Can you give me any web site about which you're talking that can help
me solving this problem?