Convert coordinates from St. George Island (EPSG:4138) to NAD83 (EPSG:4269) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.
The EPSG Geodetic Parameter Dataset defines 2 transformations between St. George Island (EPSG:4138) and NAD83 (EPSG:4269). Each applies to a specific area — pick the one whose area of use covers your data.
Grid files: nadcon5.sg1952.nad83_1986.stgeorge.lat.trn.20160901.bnadcon5.sg1952.nad83_1986.stgeorge.lon.trn.20160901.b
Uses NADCON5 method which expects longitudes positive east in range 0-360°; EPSG source and target CRSs have longitudes positive east in range -180° to +180°.
Grid files: stgeorge.lasstgeorge.los
Accuracy 0.5m at 67% confidence level. Uses NADCON method which expects longitudes positive west; source and target CRSs have longitudes positive east. NADCON converts from St. George Datum but makes the transformation appear to be from NAD27.
The same transformation with common GIS tools and libraries:
from pyproj import Transformer
transformer = Transformer.from_crs("EPSG:4138", "EPSG:4269", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)geographic system using latitude and longitude on an ellipsoid · Area of use: USA - Alaska - St. George Island
+proj=longlat +ellps=clrk66 +no_defs +type=crsMore about EPSG:4138 →
geographic system using latitude and longitude on an ellipsoid · Area of use: North America - NAD83
+proj=longlat +datum=NAD83 +no_defs +type=crsMore about EPSG:4269 →