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: http://www.stsci.edu/~sontag/spicedocs/cspice/convrt_c.html
Дата изменения: Sat Dec 17 06:08:38 2005 Дата индексирования: Sun Apr 10 23:58:27 2016 Кодировка: |
Take a measurement X, the units associated with X, and units to which X should be converted; return Y --- the value of the measurement in the output units.
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VARIABLE I/O DESCRIPTION -------- --- ------------------------------------------------- x I Number representing a measurement in some units. in I The units in which x is measured. out I Desired units for the measurement. y O The measurment in the desired units.
x is a number representing a measurement in the units specified by in. in represents the units associated with a measurement x. Acceptable units are: Angles: "RADIANS" "DEGREES" "ARCMINUTES" "ARCSECONDS" "HOURANGLE" "MINUTEANGLE" "SECONDANGLE" Metric Distances: "METERS" "KM" "CM" "MM" English Distances: "FEET" "INCHES" "YARDS" "STATUTE_MILES" "NAUTICAL_MILES" Astrometric Distances: "AU" "PARSECS" "LIGHTSECS" "LIGHTYEARS" julian lightyears Time: "SECONDS" "MINUTES" "HOURS" "DAYS" "JULIAN_YEARS" "TROPICAL_YEARS" "YEARS" (same as julian years) The case of the string in is not significant. out represents the units desired for the measurement x. See the description of in. The case of the string out is not significant.
y is the input measurement converted to the desired units.
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This routine converts a measurement x given in units specified by in to the equivalent value y in units specified by out. If a unit is not recognized, an error message is produced that indicates which one was not recognized. If input and output units are incompatible (for example angle and distance units) and error message will be produced stating the requested units and associated types.
To convert 1 meter to statute miles and feet you could make the calls convrt_c ( 1.0, "meters", "statute_miles", &miles ); convrt_c ( miles, "statute_miles", "feet", &feet ); or convrt_c ( 1.0, "METERS", "STATUTE_MILES", &miles ); convrt_c ( 1.0, "METERS", "FEET", &feet );
You should make sure that your units are appropriate for the measurement. This routine does not do any checking for over- flow. Something like convrt_c ( 10.0e302, "LIGHTYEARS", "MM", &y ); will cause a floating point overflow. Some of the units are not "defined" quantities. In such a case a best estimate is provided as of the date of the current version of this routine. Those estimated quantities are: 1 AU --- the astronomical unit is taken from the JPL ephemeris DE125. It is believed to be accurate to about 40 meters. The tropical year is the time from equinox to equinox. This varies slightly with time. 1 PARSEC --- is dependent upon the value of the astronomical unit.
1) If the input units, output units, or both input and output units are not recognized, the error SPICE(UNITSNOTREC) is signaled. 2) If the units being converted between are incompatible, the error SPICE(INCOMPATIBLEUNITS) is signaled.
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N.J. Bachman (JPL) C.A. Curzon (JPL) H.A. Neilan (JPL) W.M. Owen (JPL) W.L. Taber (JPL) I.M. Underwood (JPL)
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-CSPICE Version 1.0.0, 17-MAY-1999 (NJB)(CAC)(HAN)(WMO)(WLT)(IMU)
convert units