Distance and location units set as project default units appear on editing tools. The values you type in dialog boxes are automatically converted to map units. Similarly, you can add other units to a project and use them to create or modify features in maps assigned a projected coordinate system.

The following sections explain the distance and location unit settings that are available on the project Options dialog box.

For steps to add or change unit settings, see Configure unit settings for editing.

##### Note:

When ground to grid correction is turned on, an offset angle is applied to directions, and a distance factor multiplies distances. This occurs in real time as you create geometry using construction tools and type bearing and distance values.

To learn more, see Turn ground to grid corrections on or off.

## Metric units

Distance units | Abbreviation | Meters per unit | Description |
---|---|---|---|

Millimeter | mm | 0.001 | 1/1000 meters exactly |

Centimeter | cm | .01 | 1/100 meters exactly |

Meter | m | 1 | International meter |

Kilometer | km | 1,000 | 1,000 meters exactly |

## International and imperial units

Distance units | Abbreviation | Meters per unit | Description |
---|---|---|---|

Inch | in | 0.0254 | 1/12 international feet |

Foot | ft | 0.3048 | Known as the international foot |

Yard | yd | 0.9144 | 3 international feet |

Mile | mi | 1,609.344 | Also referred to as a statute mile, equal to 5,280 international feet |

Nautical mile | nm | 1,853.248 | The nautical mile is a unit of distance used primarily in sea travel and aviation. The nautical mile is defined as the average distance on the earth's surface represented by one minute of latitude. In ArcGIS Desktop the United States nautical mile is used, which is 1,853.248 meters. |

Link | lk | 0.201168 | 1/100 international chain, or 66/100 international feet |

Rod | rd | 5.0292 | 1/4 chain, or 16.5 international feet |

Chain | ch | 20.1168 | 66 international feet |

## U.S. survey units

Distance units | Abbreviation | Meters per unit | Description |
---|---|---|---|

Survey foot | ftUS | 0.3048006096 | Used in the state plane coordinate systems. To convert to meters, multiply U.S. survey feet by the fraction 1200/3937. |

Survey mile | miUS | 1,609.3472186944 | 5,280 survey feet. |

Survey chain | chUS | 20.1168402337 | 66 survey feet. |

Survey rod | rdUS | 5.0292100584 | 1/4 survey chain. |

Survey link | lkUS | 0.2011684023 | 1/100 survey chain. |

Survey yard | ydUS | 0.9144018288 | 3 survey feet. |

##### Dive-in:

In 1959, the National Bureau of Standards and the United States Coast and Geodetic Survey changed the definition of the yard to bring the U.S. yard and the yard used in other countries into agreement. This change redefined 1 foot as equal to 0.3048 meters exactly. The name of this new foot is international foot.

It was also decided that any data expressed in feet derived from geodetic surveys within the United States would continue to bear the relationship as defined in 1893 as 1 US Survey foot = (1200/3937) meters. The name of this foot is U.S. survey foot. The two are related to each other through the expression 1 international foot = 0.999 998 U.S. survey foot exactly.

The difference between these two values for the foot is very small, two parts per million, which is hardly measurable, but not trivial when computational consistency is desired. Fundamental survey units, such as rods, chains, statute miles, acres, sections, and townships, all depend on the relationship of 1 meter equaling 39.37 inches exactly.