I have architectural drawings of a bus terminal in Rochester, NY done in 1974 that lists the coordinates of the corners of each building. But I don't recognize the system of these coordinates. For example, instead of the usual "North" and "West," the first number is identified as "South," the second as "East." A full example is 49,876.06 South, 41,834.17 East. I need to convert these to lat/longs (degrees, mins, seconds) to relate to coordinates reported by the on-board GPS system of buses moving about the terminal. I thought these might be State Plane Coordinates, but I've found those have a different format. Can anyone identify the system these coordinates belong to?

  • if values were feet, or meters, where would the 0,0 be?
    – Elio Diaz
    Commented Dec 8, 2017 at 17:23
  • Good question. A survey monument perhaps? Is there a formula for locating it using that South/East number pair?
    – whandley
    Commented Dec 8, 2017 at 18:30
  • where's the bus terminal?
    – Elio Diaz
    Commented Dec 8, 2017 at 18:33
  • 1372 East Main St, Rochester, New York. The center of the facility is at 43.1621, -77.5731.
    – whandley
    Commented Dec 8, 2017 at 18:44
  • Lazy idea: Could you skip the identification-part and go on to "I'll simply digitize the corners anew myself" or "oh look, OSM is coming around the corner and hands me the desired values"?
    – Erik
    Commented Dec 8, 2017 at 21:15

2 Answers 2


From the information you have, you can set up a custom local CRS like this:

+proj=sterea +lat_0=43.1621 +lon_0=-77.5731 +x_0=41834.17 +y_0=-49876.06 +datum=NAD27 +units=m +no_defs

lat0 and lon_0 are the degree coordinates of your reference point, and x_0 and y_0 the projected ones (south coordinates negative). I assume they are in meters, and based on the NAD27 ellipsoid.

With that, you can create a vector grid like this:

enter image description here

The origin is somewhere in Lake Ontario, but placed to get only positive East and South values for data inside the county.


Most likely New York State Plane, a lot of time they originate from the state capital thus you are getting your East and South designations

  • I don't think so in this case, but i could be wrong. I used an online map tool provided by New York and selected State Plane Coordinates and hovered over the facility, and it displayed a pair of coordinates in the format "E: 1410975, N: 1157705."
    – whandley
    Commented Dec 8, 2017 at 18:38
  • Did you have the opportunity to change the units in the State Plane Viewer (i.e. Survey foot to international feet)? Might change your result
    – user17260
    Commented Dec 8, 2017 at 18:57

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