Matching coordinates

Let’s say we know the x and y coordinates in an unknown unit of a location, but its projection information is somehow missing. We have a general idea about where the location is and can find its approximate latitude and longitude with a tolerable error in distance in an unknown unit. What is the projection of the x and y coordinates?

In this example, we have a point at 432697.24 and 1363705.31 in xy in our data with missing projection information and know it’s the location of Georgia State Governor’s Office (33.7490 and -84.3880 in latlon). Let’s find out what projection our data is in. Our error tolerance for distance matching is 200 xy units.


# matching is slow
projpicker postfix match_tol=200 33.7490,-84.3880 xy 432697.24,1363705.31 match

# to speed up, let's just return the first match only
projpicker postfix match_max=1 match_tol=200 33.7490,-84.3880 xy 432697.24,1363705.31 match

Using geometry variables:

projpicker <<EOT
match_max=1 match_tol=200

A: 33.7490,-84.3880
B: 432697.24,1363705.31

:A :B match


import projpicker as ppik

ppik.query_mixed_geoms(["postfix", "match_tol=200",
                        [33.7490, -84.3880],
                        "xy", [432697.24, 1363705.31],

# return just the first match
ppik.query_mixed_geoms(["postfix", "match_max=1", "match_tol=200",
                        [33.7490, -84.3880],
                        "xy", [432697.24, 1363705.31],