When using Python anad fiona package to read a shapefile of Boston, I am getting very large values in the tens of thousands. Why is this?

# Import Boston shapefile
shapefilename = 'ZIPCODES_NT_POLY'
shp = fiona.open(shapefilename + '.shp')
coords = shp.bounds

Then running coords gives the output

(33869.92130000144, 777617.2998000011, 330800.31099999696, 959741.1853)

1 Answer 1


On the page you linked to (that describes the data you converted), it says:

MassGIS also projected the data into the Massachusetts State Plane Mainland coordinate system.

Consequently, values in the range that you are observing, are to be expected.

I am assuming that you were expecting latitude and longitude values but this data has been projected.

  • It is EPSG:26986 — NAD83 / Massachusetts Mainland
    – Mike T
    Commented Aug 9, 2015 at 20:20

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