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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 Dec 8 '17 at 17:23
  • Good question. A survey monument perhaps? Is there a formula for locating it using that South/East number pair? – whandley Dec 8 '17 at 18:30
  • where's the bus terminal? – Elio Diaz Dec 8 '17 at 18:33
  • 1372 East Main St, Rochester, New York. The center of the facility is at 43.1621, -77.5731. – whandley Dec 8 '17 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 Dec 8 '17 at 21:15
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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.

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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 Dec 8 '17 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 Dec 8 '17 at 18:57

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