Unit conversion

New 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 +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> or <conversion_factor>

Horizontal input 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.

+xy_out=<unit> or <conversion_factor>

Horizontal 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.

+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

New 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.

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