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 |