Unit conversion

Added in version 5.0.0.

Convert between various distance, angular and time units.

Alias

unitconvert

Domain

2D, 3D or 4D

Input type

Any

Output type

Any

There are many examples of coordinate reference systems that are expressed in other units than the meter. There are also many cases where temporal data has to be translated to different units. The unitconvert operation takes care of that.

Many North American systems are defined with coordinates in feet. For example in Vermont:

+proj=pipeline \
+step +proj=tmerc +lat_0=42.5 +lon_0=-72.5 +k_0=0.999964286 +x_0=500000.00001016 \
+step +proj=unitconvert +xy_out=us-ft

Often when working with GNSS data the timestamps are presented in GPS-weeks, but when the data transformed with the helmert operation timestamps are expected to be in units of decimalyears. This can be fixed with unitconvert:

+proj=pipeline \
+step +proj=unitconvert +t_in=gps_week +t_out=decimalyear \
+step +proj=helmert +epoch=2000.0 +t_obs=2017.5 ...

Parameters

+xy_in=<unit> or <conversion_factor>

Horizontal input units. See Distance units and Angular units for a list of available units. Default: meter. <conversion_factor> is the conversion factor from the input unit to metre for linear units, or to radian for angular units. Default if not given: meters.

+xy_out=<unit> or <conversion_factor>

Horizontal output units. See Distance units and Angular units for a list of available units. Deault: meter. <conversion_factor> is the conversion factor from the output unit to metre for linear units, or to radian for angular units. Default if not given: meters.

+z_in=<unit> or <conversion_factor>

Vertical output units. See Distance units and Angular units for a list of available units. <conversion_factor> is the conversion factor from the input unit to metre for linear units, or to radian for angular units.

+z_out=<unit> or <conversion_factor>

Vertical output units. See Distance units and Angular units for a list of available units. <conversion_factor> is the conversion factor from the output unit to metre for linear units, or to radian for angular units.

+t_in=<unit>

Temporal input units. See Time units for a list of available units.

+t_out=<unit>

Temporal output units. See Time units for a list of available units.

Distance units

In the table below all distance units supported by PROJ are listed. The same list can also be produced on the command line with proj or cs2cs, by adding the -lu flag when calling the utility.

Label

Name

km

Kilometer

m

Meter

dm

Decimeter

cm

Centimeter

mm

Millimeter

kmi

International Nautical Mile

in

International Inch

ft

International Foot

yd

International Yard

mi

International Statute Mile

fath

International Fathom

ch

International Chain

link

International Link

us-in

U.S. Surveyor's Inch

us-ft

U.S. Surveyor's Foot

us-yd

U.S. Surveyor's Yard

us-ch

U.S. Surveyor's Chain

us-mi

U.S. Surveyor's Statute Mile

ind-yd

Indian Yard

ind-ft

Indian Foot

ind-ch

Indian Chain

Angular units

Added in version 5.2.0.

In the table below all angular units supported by PROJ unitconvert are listed.

Label

Name

deg

Degree

grad

Grad

rad

Radian

Time units

In the table below all time units supported by PROJ are listed.

Note

When converting time units from a date-only format (yyyymmdd), PROJ assumes a time value of 00:00 midnight. When converting time units to a date-only format, PROJ rounds to the nearest date at 00:00 midnight. That is, any time values less than 12:00 noon will round to 00:00 on the same day. Time values greater than or equal to 12:00 noon will round to 00:00 on the following day.

Label

Name

mjd

Modified Julian date

decimalyear

Decimal year

gps_week

GPS Week

yyyymmdd

Date in yyyymmdd format