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# How do I pinpoint GPS coordinates with Conic Projection

Unfortunately I'm not very strong in Math, maybe somebody can help.

I need to pinpoint GPS Coordinates on given 2D Maps of a Street Atlas (Pages of a Map of Europe) Especially at the Edges of the map, the distortion is strong (the circles of latitude are curved and tilted up to -17°), so I cannot simply transfer to x/y but need more math...

I have:

-GPS Coordinates of the target (longitude/latitude)

-GPS Cornerpoints of the Graphic(longitude/latitude)

-Size of the 2D Map (but relative Values 0-1 would suffice)

Even though I have no Infos about the Projection, I presume conic projection (y is tilted but linear, x is curved)

I measured the angles at some longitudes and they can be described by this function:

Angle(degrees) = longitude*0,7272727272-9.7

From this I derived a function to describe the curve of the circles of latitude:

y=x*(4545453265*x-121249965856)/12499996480

This seems correct so far, but whatever I try the results are too imprecise. How do I continue from here? Thanks in Advance!

Knowing the projection is a good start, but not sufficient information - to reproject from one spatial reference system into another you also need to know the datum (the length of the semi-major and semi-minor axis of the ellipsoid model), and the prime meridian. Or, do you know the EPSG reference of the projection? That would make it a lot simpler.

Thank you so much for your quick answer! With no experience in projection maths this gave me some pointers where to look. Even though my customer has no idea what I'm talking about I'm trying to make him get the information. For now, I would assume that we're facing a projection similar to EPSG 3035 (equal area seems to make sense of a street atlas), but the center latitude seems to be at around 13.35°East instead of 9° East. How do I continue from here? Are there API's around I can use to speed up the process (I need to solve this rather quickly)?

Ok, here we go. These are the actual Values. What do I do with it ?

System:Lambert Conformal Conic

Geodetic Datum: MGI (=Austria-Datum)

Parameter for Projection System:

2 Standard Parallels/Schnittbreiten

Standard Parallel 1: 46:00:00 d:m:s

Standard Parallel 2: 49:00:00 d:m:s

Central Point/Zentralpunkt

Longitude of Origin: 13:20:00 d:m:s

Latitude of Origin: 47:30:00 d:m:s

False Easting/Korrektur Hochwert: 400000.000 m

False Northing/ Korrektur Rechtswert: 400000.000 m

Parameter for MGI Geodetic Datum

Ellipsoid: Bessel 1841

Equatorial Radius: 6377397.155 m

Polar Radius: 6356078.963 m

Flattening Inverse: 299.152812800001

Bursa-Wolfe Umrechnungsparameter von MGI nach WGS84

Delta X 575

Delta Y 93

Delta Z 466

Rot X (sec) -5,1

Rot Y (sec) -1,6

Rot Z (sec) -5,2

BW Scale 2,5

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