# Unit conversion¶

New in version 5.0.0.

Convert between various distance 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=0.999964286 +x_0=500000.00001016 +y_0=0
+step +proj=unitconvert +xy_in=m +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=gpsweek +t_out=decimalyear
+step +proj=helmert +epoch=2000.0 +t_obs=2017.5 ...


## Parameters¶

+xy_in=<unit>

Horizontal input units. See Distance units for a list of available units.

+xy_out=<unit>

Horizontal output units. See Distance units for a list of available units.

+z_in=<unit>

Vertical output units. See Distance units for a list of available units.

+z_out=<unit>

Vertical output units. See Distance units for a list of available 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 is 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

## Time units¶

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

 label Name mjd Modified Julian date decimalyear Decimal year gps_week GPS Week yyyymmdd Date in yyyymmdd format