pg2pc
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Contents: Description, Arguments, Usage, Examples, Sub-Functions, Related Functions, Source Supported Under Version: > 1.15
Description Converts planetographic latitude to planetocentric latitude
Arguments and Return Values Parameters: Numeric array specifying the planetographic latitudes, and an optional second input specifying the body's axial ratio Return Value: A single-precision (float) numeric array specifying the corresponding set of planetocentric latitudes
Usage Syntax: pg2pc(lat_pg, r) Planetocentric latitude of a point on the surface of a spheroidal body is just the angle between the equator and the point, with the vertex at the body's center. (Most planets and moons can be well approximated as oblate spheroids.) Planetographic latitude is the angle between the equator and the normal vector to the surface at the point, with the vertex not generally at the body's center (except for a spherical body, or at any spheroidal body's equator or poles). The axial ratio, r, is the body's polar radius divided by its equatorial radius (for an oblate spheroid). If r is omitted, the function defaults to a value of 0.994111, the value for Mars from the GSFC NSSDC Mars fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html). However, it is advisable to check whether you are using a system with a different value. This function does not account for the effect of latitude shift due to elevation. When pg2pc() is entered without any arguments, it prints its description, as shown below.
Examples dv> pg2pc() Converts planetographic latitude to planetocentric latitude pc2pg(latitude, axial ratio) Enter ONLY latitudes (not longitudes!), in degrees Axial ratio, r = (semiminor axis)/(semimajor axis) = (polar radius)/(equatorial radius), is optional; if omitted, this function will use 0.994111, the value for Mars from NSSDC. However, you may want to check whether you are using a system with a different ellipticity value. The NSSDC Mars fact sheet has Re = 3396.2 km and Rp = 3376.2 km, yielding r = Rp/Re = 0.994111 r is related to oblateness/flattening, f, by f = 1 - r Mars24 uses f = 0.0064763 Works for array inputs S.Marshall 04-17-2009 0 dv> pg2pc(0//45//90) 3x1x1 array of float, bsq format [12 bytes] 0.00000000000000 44.6615943908691 90.0000000000000 |
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Recent Library Changes Created On: 11-18-2009 |
