# Units of Measure

## ERDAS IMAGINE Help

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16.5.1
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ERDAS IMAGINE
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Units of measure are expressed in numerous functions throughout ERDAS IMAGINE. For example, these units are expressed in places such as measuring a line drawn in an image in the View, recalculating elevation values, or if you are looking at the Rectangle Properties dialog of an AOI in an image. This document defines the units of measure used in ERDAS IMAGINE.

Units of measure are categorized into angle, distance, area, volume, and time. For a complete list of valid strings used in the tables below for <units1>, see the file <\$IMAGINE_HOME>/etc/units.dat. You can edit the units.dat text file to add a desired unit. See Add New Units of Measure.

Angle

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Radian is the standard internal unit used when measuring angles.

 Unit Symbol Conversion to radians Definition radian rad 1.0 decimal degrees dd combination of latitude/longitude degrees, minutes, and seconds converted into a decimal fraction, expressed as degrees decimal minutes dm In latitude/longitude, minutes value converted into a decimal decimal seconds ds In latitude/longitude, seconds value converted into a decimal degree deg, dg plane angular degree grad grad 100 grads in a 90 degree angle, 1 grad = 0.9 of a degree or of a radian. Measurement of an arc in metric system. gon gon Same as grad. The term gon is used in European countries where grad means degree.

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

<units1> is the expression in Unit column, <standardunits> is the expression derived after conversion.

Example: 2 degrees = 0.034906 radians (to 6 places)

Distance

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Meter is the standard internal unit used when measuring distance.

Metric Units

 Unit Symbol Conversion to meters Definition meter m 1.0 Basic SI* unit of length or distance centimeter cm * 0.01 100 centimeters = 1 meter millimeter mm * 0.001 1000 millimeters = 1 meter kilometer km * 1000.0 1 kilometer = 1000 meters nanometer nm * 0.000000001 1 meter = nanometers micron * 0.000001 1 meter = microns micrometer * 0.000001 1 meter = micrometers other 1.0 standard internal unit (meter) or if unit is unknown

* International System of Units (abbreviated SI from the French name Le Système International d'Unités)

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 25 kilometers = 25,000 meters

U.S. Survey Foot Units

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Meter is the standard internal unit used when measuring distance.

 Unit Symbol Conversion to meters Definition us survey feetus survey foot ft * 0.3048006096012192 1 meter = 3.2808333 U.S. survey feet feetfoot ft * 0.3048006096012192 1 meter = 3.2808333 U.S. survey feet

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 200 U.S. survey feet = 60.9601 meters (to 4 places)

International Foot Units

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Meter is the standard internal unit used when measuring distance.

 Unit Symbol Conversion to meters Definition international feetinternational foot * 0.3048 1 international foot = 0.3048 meters1 meter = 3.2808398 international feet inchesinch in * 0.3048006096012192 / 12.0 1 inch = 2.54 centimeters1 meter = 39.3700787 inches point pt * 0.3048 / 12 / 72.0 Intended for map compositions. A measurement unit for font sizes in paper units. device pixel * 0.3048 / 12 / 300.0 Intended for map compositions. A measurement unit for printer devices. Default assumes a device resolution of 300 dpi. yard yd * 3 * 0.3048 1 yard = 3 feet mile mi * 5280 * 0.3048 A unit of length defined to be exactly 5,280 feet.1 mile = 5,280 feet1 mile = 1609.3472 meters (to 4 places)

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 3 miles = 4828.032 meters

Variants

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Meter is the standard internal unit used when measuring distance.

 Unit Conversion to meters modified american foot * 0.3048122530 clarke foot * 0.3047972651 indian foot * 0.3047995142 link * 0.2011661950 benoit link * 0.2011678249 clarke link * 0.2011661949 sears link * 0.2011676512 benoit chain * 20.1167824944 sears foot * 0.30479947153867620 benoit chain 1895 a * 20.1167824 benoit chain 1895 b * 20.1167824944 sears chain * 20.1167651216 sears yard sears yd * 0.9143984146 indian yardindian yd * 0.9143985425 fathom * 1.8288000000 international nautical mile * 1852.0 gold coast foot * 0.3047997101815088

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 3 fathoms = 5.4864 meters

Area

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Hectare is the standard internal unit used when measuring area.

 Unit Symbol Conversion to hectares Definition hectare 1.0 1 hectare = 10,000 square meters.Equivalent to 2.471 acres in the English system. acre * 0.4046856 Defined as 10 square chains (1 chain = 4 rods or 66 feet)1 acre = 43,560 square feet1 acre = approximately 4047 square meters square milesqmile * 258.9988 Area of a plane surface enclosed by a square with each side 1 mile in length.1 sq mile = approximately 640 acres square nautical milesqnautical mile * 342.9904 Area of a plane surface enclosed by a square with each side 1 international nautical mile in length. square footsqfootsqfeet * 0.00000929030 Area of a plane surface enclosed by a square with each side 1 foot in length. square metersqmeter * 0.0001 Area of a plane surface enclosed by a square with each side 1 meter in length. square kilometersqkilometer * 100 Area of a plane surface enclosed by a square with each side 1 kilometer in length.

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 56 square meters = 0.0056 hectares

Volume

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Liter is the standard internal unit used when measuring volume.

 Unit Symbol Conversion to liters Definition liter lt 1.0 Metric unit of capacity equal to volume of 1 kilogram of water at  4 degrees C (39 degrees F) and at standard atmospheric pressure of 760 mm of mercury. milliliter ml * 0.001 1 liter = 1000 ml gallon gal * 3.7854118 Volume used in liquid measure equal to 4 quarts or approximately 3.785 liters. cubic foot * 28.3169 Volume occupied by a cube with each side 1 foot in length.1 cubic foot = 28,316.8 cubic centimeters cubic meter * 1000 Volume occupied by a cube with each side 1 meter in length.1 cubic meter = 1000 liters cubic kilometer * 1000000000000 Volume occupied by a cube with each side 1 kilometer in length.

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 4 gallons = 15.1416472 liters

Time

Conversion column lists the formula to convert a numeric value from your selected unit to the IMAGINE standard internal unit. Second is the standard internal unit used when measuring time.

 Unit Symbol Conversion to seconds Definition second sec 1.0 Basic SI* unit of time. 1/60 of a minute of time. minute * 60.0 1 minute = 60 seconds. 60 minutes = 1 hour. hour hr * 60.0 * 60.0 1 hour = 60 minutes. 24 hours = 1 day. day * 24.0 * 60.0 * 60.0 1 day = 24 hours. 365.25 days = 1 year. year yr * 365.25 * 24.0 * 60.0 * 60.0 1 year = 365.25 days.

* International System of Units (abbreviated SI from the French name Le Système International d'Unités)

Convert the value <value> from <units1> to the same amount expressed in <standardunits>.

Example: 4 days = 345,600 seconds