Geoprocessing considerations for length and area units
Many geoprocessing tools, including Spatial Join, Densify, and Generate Points Along Lines, have a parameter for specifying a linear distance and units. Several other tools, including Simplify Building and Subdivide Polygon, have a parameter for specifying an areal distance and units. These parameter types are commonly used for setting spatial tolerances and applying a linear or areal interval at which some spatial action is undertaken.
In the Geoprocessing pane, both the Linear Unit and Area Unit parameter data types are displayed as a text box for a numeric value and a choice list of valid unit types. In Python, values for both parameter data types are expressed as a string as a distance value and unit, for example, "3.5 Kilometers".
The tables below provide information about the units of measurement used in geoprocessing tools. Each row provides the unit type found in tools in the Geoprocessing pane and its corresponding keyword for use in Python, as well as a description.
Linear units
The following units are available for the measurement of length:
| Unit type | Python keyword | Description |
|---|---|---|
| Kilometers | Kilometers |
1,000 meters. |
| Meters | Meters |
Metric base unit of distance. |
| Decimeters | Decimeters |
0.1 of a meter. |
| Centimeters | Centimeters |
0.01 of a meter. |
| Millimeters | Millimeters |
0.001 of a meter. |
| International Nautical Miles | NauticalMilesInt |
1,852.0 meters. |
| Statute Miles | MilesInt |
1,609.344 meters. This unit is synonymous with international miles. |
| International Yards | YardsInt |
0.9144 meters. |
| International Feet | FeetInt |
0.3048 meters. This is required for new coordinate systems used by U.S. government agencies beginning in 2023. |
| International Inches | InchesInt |
0.0254 meters. |
| US Survey Nautical Miles | NauticalMiles |
1,853.248 meters. |
| US Survey Miles | Miles |
63,360.0/39.37 meters. |
| US Survey Yards | Yards |
36.0/39.37 meters. |
| US Survey Feet | Feet |
1,200/3937 meters or 0.3048006096012192. This is used in existing U.S. coordinate systems based on NAD27 and NAD83. Usage will be phased out starting in 2023. |
| US Survey Inches | Inches |
1.0/39.37 meters. |
| Decimal Degrees | DecimalDegrees |
Angular unit of measure based on 1/360 of a circle. The actual length of a degree depends on its location on the spherical or ellipsoidal model that is being used. |
Area units
The following units are available for the measurement of area:
| Unit type | Python keyword | Description |
|---|---|---|
| Square Kilometers | SquareKilometers |
Area of a square 1 kilometer per side |
| Hectares | Hectares |
Standard metric unit of land area as defined by a square 100 meters per side |
| Ares | Ares |
Area of a square 10 meters per side |
| Square Meters | SquareMeters |
Area of a square 1 meter per side |
| Square Decimeters | SquareDecimeters |
Area of a square 1 decimeter per side |
| Square Centimeters | SquareCentimeters |
Area of a square 1 centimeter per side |
| Square Millimeters | SquareMillimeters |
Area of a square 1 millimeter per side |
| Square Statute Miles | SquareMiles |
Area of a square 1 Statue mile per side |
| Square International Nautical Miles | SquareNauticalMilesInt |
Area of a square 1 international nautical mile per side |
| International Acres | Acres |
Area of 4046.8564224 square meters |
| Square International Yards | SquareYards |
Area of a square 1 international yard per side |
| Square International Feet | SquareFeet |
Area of a square 1 international foot per side |
| Square International Inches | SquareInches |
Area of a square 1 international inch per side |
| Square US Survey Miles | SquareMilesUS |
Area of a square 1 US Survey mile per side |
| Square US Survey Nautical Miles | SquareNauticalMiles |
Area of a square 1 US Survey nautical mile per side. |
| US Survey Acres | AcresUS |
Used when working with US Survey feet and equal to 43,560 square U.S. Survey Feet or 4,046.872 square meters |
| Square US Survey Yards | SquareYardsUS |
Area of a square 1 US Survey yard per side |
| Square US Survey Feet | SquareFeetUS |
Area of a square 1 US Survey foot per side |
| Square US Survey Inches | SquareInchesUS |
Area of a square 1 US Survey inch per side |