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Working Units

As NHDOT transitions from drawings with working units of International Feet to drawings with U.S. Survey Feet, there is bound to be some confusion. This page will clarify some of the issues associated with this transition.

International Feet vs. U.S. Survey Feet

When MicroStation was implemented in 1999, seed files were created with working units set to International Feet. At the time, a custom unit needed to be defined to use U.S. Survey feet.

What's the difference?

  • One standard or international foot = 0.3048 meters.
  • One U.S. Survey foot = 1200/3937 meters.

With the advent of the Geographic Coordinate System within Bentley products and increased interaction with organizations outside the DOT, it is now imperative that we change our practice to match the units of measure used by survey and construction personnel. All future projects should be set up with U.S. Survey Foot drawings.

Checking the Project Configuration File

If you are not familiar with the project, check the working units specified in the Project Configuration File (PCF). Look for the variable MS_DESIGNSEED. International Foot projects will have a seed file set to nhseedf2.dgn while U.S. Survey Foot projects will have this variable set to nhseedf2-ussf.dgn.

Checking the Current Drawing

There are multiple ways to confirm the working units of a drawing. The drawing's working units should match the drawing seed file specified in the project's PCF.

Option 1

From the CAD Menu select Settings > Design File and click on Working Units in the left column.

Design file working units

Design File Working Units

drawing scale toolbox

Drawing Scale

Option 2

From the CAD Menu select Settings > Drawing Scale. This will display the Drawing Scale toolbar. It can be docked with other toolbars so the drawing units are displayed when a drawing is opened. To save some space, right click on the toolbar and uncheck ACS and ACS scale.

OpenRoads Seed File

A typical MX DGN file has 3 models in it; a 2D Default model, a 3D Default-3D model and an MX model. Work should be done in the Default model unless otherwise stated. All MX models and strings will be displayed in the MX model.

Previously, there was a single seed file for OpenRoads drawings - NHDOTMX_seed_i_3d+2d.dgn. That file is now called nhseed-or-intf.dgn ("or" = OpenRoads, "intf" = International Feet). All future projects should be set up with U.S. Survey Foot drawings using the seed file nhseed-or-ussf.dgn ("ussf" = US Survey Feet) when working in OpenRoads. There are other seed files for special purposes. For a complete list see NHDOT Seed Files.

New Hampshire Department of Transportation
PO Box 483  |  7 Hazen Drive  |  
Concord, NH  |  03302-0483
Tel: 603.271.3734  |  Fax: 603.271.3914