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The Department of Transportation's Survey Section collects spatial data and provides the basic framework used to map, build, and maintain New Hampshires transportation systems.

The NHCO Base Station is currently down.



About Our GNSS Base Station Site …

The geodetic component of the Survey Section makes extensive use of Global Navigation Satellite System technology to establish a highly accurate control network and supply geodetic coordinates for all projects undertaken by the Department.

We operate a full-time GNSS base station for the benefit of mapping activities within the Department as well as for outside governmental and private sector mapping and surveying groups.

NHDOT GNSS Site Detailsgps


Datum: NAD83 (2011)
Latitude: 43 12' 46.19587" N
Longitude: 71 31' 11.47551" W
Ellipsoid height: 89.430 m
Elevation Mask: 5
Logging Interval: 5 s
Rollover period: 1 hour
Antenna height: 0.000 m (ARP)

Data collected with Trimble NETR5 GNSS receiver with a Trimble Zephyr antenna (TRM57971.00) and GPSBase software.

The following links have been disabled pending the acceptance of this station into NGS's National CORS Network:

Site Coordinates | Station Log | Antenna Calibration Data Sheet

Note regarding our old base station , NHDT

On July 13, 2009, the DOT's previous GPS base station, NHDT, suffered a major crash. Data from the period before the crash is available online at the National Geodetic Survey's CORS Web site or by contacting the DOT's Survey Section.

Downloading GNSS Files:

  • DAT Files- Trimble format GNSS data, including pseudoprange, carrier phase, and ephemeris information as well as differential corrections.
  • RINEX Files (Receiver Independent Exchange Format) - developed by the Astronomical Institute of the University of Berne for easy exchange of GPS data.
  • TGD Files
  • T02 Files

The protocol to set up a Pathfinder Connection has changed, please stay tuned for an update to the following section:

Setting Up A Pathfinder Connection …

Below are instructions in setting up a connection in Pathfinder Office 2.51 (and later versions) to download base files automatically.

  1. Pull down the "Utilities" menu and select "Differential Correction."
  2. In "Rover Files," select a file to correct.
  3. In "Base Files," click "Internet Search" box and select "New."
  4. In "New Provider," check "Enter the details yourself."
  5. In "Provider Properties" many entries are optional, the required entries include:
    1. "General" tab: "Organization" type: "NHDOT"
    2. "Internet Server" tab: "Address Format" type: and "Base Server Type" select: "Other, GPS Time (UTC)"
  6. Select "OK" and complete the set up to return to the Differential Correction screen and proceed with the corrections as usual.

Note: The "Address Format" will need to be updated every year. The "9" in "s9" reflects the last digit of the current year, i.e. 2009. This will be s0 in 2010. Substituting rinex/09 or dat/d9 for ssf/s9 will link to the RINEX or DAT directories if desired.

For More Information …

National Geodetic Survey - National CORS
The National Geodetc Survey coordinates a network of continuously operating reference stations (CORS) that provide GPS measurements in support of 3-dimensional positioning activities throughout the United States and its territories.

NHDOT Geodetic Control Online
Geodetic Control data is available online at New Hampshire's Statewide Geographic Information System (GIS) Clearinghouse, NH GRANIT. Complete coordinate data and location information can be accessed through the site’s GRANIT Data Mapper

We'd like to thank The New Hampshire Geographically Referenced Analysis and Information Transfer System (NH GRANIT) and the University of New Hampshire for their continued support and assistance.

Do you have a question or comment about this information? Contact:
Brian Easler
New Hampshire Department of Transportation
PO Box 483,
Concord, NH 03302.
Tel: (603) 271-1600 Fax: (603) 271-7025

New Hampshire Department of Transportation
PO Box 483 | 7 Hazen Drive | Concord, NH | 03302-0483
Tel: 603.271-3734 | Fax: 603.271.3914

copyright 2015. State of New Hampshire