Grid Data Files for the United States
Concept Procedure

AutoCAD Map 3D uses North American Datum Conversion (NADCON) grid data files from the National Geodetic Survey to obtain latitude and longitude shift information for converting between coordinate systems within the United States. A pair of grid data files is required for each area or state covered: a .las file is required for latitude shift values (latitude seconds) and a .los file for longitude shift values (longitude seconds).

The NADCON files include grid data files for transformations between NAD83 and state readjustments to HARN (High Accuracy Resolution Network) projects.

The .las and .los files are in the public domain and are distributed with AutoCAD Map 3D. The files are stored in the Autodesk shared coordinate system folder, by default C:\Documents and Settings\All Users\Application Data\Autodesk\Geospatial Coordinate Systems\Usa\Nadcon.

The following is a list of NADCON grid data files.

Files (.las and .los) NADCON (North American Datum Conversion) Area/State
conus NAD27 to NAD83 United States (USA) - lower 48 states including EEZ
alaska Alaska to NAD83 Alaska
hawaii Old Hawaiian to NAD83 Hawaii
prvi Puerto Rico to NAD83 Puerto Rico, Virgin Islands
stlrnc St. Lawrence Island to NAD83 St Lawrence: off the coast of Alaska
stpaul St. Paul Island to NAD83 St Paul: Pribiloff Islands off the coast of Alaska
stgeorge St. George Island to NAD83 St George: Pribiloff Islands off the coast of Alaska
HARN Readjustments    
alhpgn NAD83 to NAD83 (HARN) Alabama
azhpgn NAD83 to NAD83 (HARN) Arizona
cahpgn NAD83 to NAD83 (HARN) California, south of 38 degrees North
cnhpgn NAD83 to NAD83 (HARN) California, north of 38 degrees North
cohpgn NAD83 to NAD83 (HARN) Colorado
emhpgn NAD83 to NAD83 (HARN) Idaho and Montana, east of 113 degrees West
ethpgn NAD83 to NAD83 (HARN) Texas, east of 100 degrees West
flhpgn NAD83 to NAD83 (HARN) Florida
gahpgn NAD83 to NAD83 (HARN) Georgia
kyhpgn NAD83 to NAD83 (HARN) Kentucky
lahpgn NAD83 to NAD83 (HARN) Louisiana
mdhpgn NAD83 to NAD83 (HARN) Maryland and Delaware
mehpgn NAD83 to NAD83 (HARN) Maine
mihpgn NAD83 to NAD83 (HARN) Michigan
mshpgn NAD83 to NAD83 (HARN) Mississippi
nbhpgn NAD83 to NAD83 (HARN) Nebraska
ndhpgn NAD83 to NAD83 (HARN) North Dakota
nehpgn NAD83 to NAD83 (HARN) New England (Connecticut, Massachusetts, New Hampshire, Rhode Island, and Vermont)
nmhpgn NAD83 to NAD83 (HARN) New Mexico
nyhpgn NAD83 to NAD83 (HARN) New York
okhpgn NAD83 to NAD83 (HARN) Oklahoma
pvhpgn NAD83 to NAD83 (HARN) Puerto Rico, Virgin Islands
sdhpgn NAD83 to NAD83 (HARN) South Dakota
tnhpgn NAD83 to NAD83 (HARN) Tennessee
vahpgn NAD83 to NAD83 (HARN) Virginia, excluding West Virginia
wihpgn NAD83 to NAD83 (HARN) Wisconsin
wmhpgn NAD83 to NAD83 (HARN) Idaho and Montana, west of 113 degrees West
wohpgn NAD83 to NAD83 (HARN) Washington and Oregon
wthpgn NAD83 to NAD83 (HARN) Texas, west of 100 degrees West
wyhpgn NAD83 to NAD83 (HARN) Wyoming

For more information about NADCON grid data files, refer to the National Geodetic Survey web site.

See Also