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My geodataframe includes some points of unknown coordinate reference system, each point has address as well, so I am able to find coordinates for them in WGS84.

An example point is: POINT (472593.82615019 573557.105385679),I know the coordinate in WGS84 should be approximately POINT (20.9434625 52.208522).

So far I tried to bet proper origin CRS and get point in WGS84 closely to the POINT (20.9434625 52.208522).

from shapely.geometry import Point
import pyproj

origin_proj = pyproj.Proj(init='epsg:3395') #cartesian
wgs_proj = pyproj.Proj(proj='latlong', datum='WGS84')

x = 472593.82615019
y = 573557.105385679

new_lon, new_lat = pyproj.transform(origin_proj, wgs_proj, x, y)

I tried to use several origin projections, but I didn't get any of point of WGS84 that would be close to expected one.

Do you have any hints how to detect the origin crs?

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  • 1
    How do you know that that coordinate should be at that particular place in WGS84?
    – Erik
    Commented Jun 24 at 8:30
  • @Erik OP has addresses for the points so is using some sort of geocoder--maybe nothing better than Google maps.
    – mkennedy
    Commented Jun 25 at 21:54

1 Answer 1

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The only way really is to try all possible projection codes until you hit one that matches close enough. In python, you'd have to loop over a few thousand EPSG:abcde strings, and make sure you catch failures such as invalid coordinates in those projections.

There is a web site that does this if you have a small number of cases to find, projfinder.com, where you centre the map roughly where you think your point is, put the coordinates in the X and Y box, then it will find projections that hit locations near the map centre.

Trying it with your numbers, the map centre cross-hair is roughly on your WGS84 origin, and the numbers in the box are your coordinates, and it finds two projections that give locations somewhat north-west of your possible location (and a third we can ignore) marked by yellow dots. Are these close enough? Can you try other examples? Did I type all the numbers in correctly and did I get X-Y and lat-long the right way round?

enter image description here

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  • Tried the same on epsg.io, but the coordinates are off by about 200 km when converting to UTM34N
    – Erik
    Commented Jun 24 at 8:32
  • 1
    Yes, but when someone gives coordinates the nanometre I just accept there's no clue to the actual required precision :)
    – Spacedman
    Commented Jun 24 at 8:42

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