317 lines
10 KiB
C
317 lines
10 KiB
C
/***************************************************************************
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TITLE: ls_geodesy
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----------------------------------------------------------------------------
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FUNCTION: Converts geocentric coordinates to geodetic positions
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----------------------------------------------------------------------------
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MODULE STATUS: developmental
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----------------------------------------------------------------------------
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GENEALOGY: Written as part of LaRCSim project by E. B. Jackson
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----------------------------------------------------------------------------
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DESIGNED BY: E. B. Jackson
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CODED BY: E. B. Jackson
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MAINTAINED BY: E. B. Jackson
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----------------------------------------------------------------------------
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MODIFICATION HISTORY:
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DATE PURPOSE BY
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930208 Modified to avoid singularity near polar region. EBJ
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930602 Moved backwards calcs here from ls_step. EBJ
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931214 Changed erroneous Latitude and Altitude variables to
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*lat_geod and *alt in routine ls_geoc_to_geod. EBJ
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940111 Changed header files from old ls_eom.h style to ls_types,
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and ls_constants. Also replaced old DATA type with new
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SCALAR type. EBJ
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CURRENT RCS HEADER:
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$Header$
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$Log$
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Revision 1.3 2001/03/24 05:03:12 curt
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SG-ified logstream.
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Revision 1.2 2000/10/23 22:34:54 curt
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I tested:
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LaRCsim c172 on-ground and in-air starts, reset: all work
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UIUC Cessna172 on-ground and in-air starts work as expected, reset
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results in an aircraft that is upside down but does not crash FG. I
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don't know what it was like before, so it may well be no change.
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JSBSim c172 and X15 in-air starts work fine, resets now work (and are
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trimmed), on-ground starts do not -- the c172 ends up on its back. I
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suspect this is no worse than before.
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I did not test:
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Balloon (the weather code returns nan's for the atmosphere data --this
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is in the weather module and apparently is a linux only bug)
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ADA (don't know how)
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MagicCarpet (needs work yet)
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External (don't know how)
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known to be broken:
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LaRCsim c172 on-ground starts with a negative terrain altitude (this
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happens at KPAO when the scenery is not present). The FDM inits to
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about 50 feet AGL and the model falls to the ground. It does stay
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upright, however, and seems to be fine once it settles out, FWIW.
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To do:
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--implement set_Model on the bus
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--bring Christian's weather data into JSBSim
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-- add default method to bus for updating things like the sin and cos of
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latitude (for Balloon, MagicCarpet)
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-- lots of cleanup
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The files:
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src/FDM/flight.cxx
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src/FDM/flight.hxx
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-- all data members now declared protected instead of private.
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-- eliminated all but a small set of 'setters', no change to getters.
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-- that small set is declared virtual, the default implementation
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provided preserves the old behavior
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-- all of the vector data members are now initialized.
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-- added busdump() method -- SG_LOG's all the bus data when called,
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useful for diagnostics.
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src/FDM/ADA.cxx
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-- bus data members now directly assigned to
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src/FDM/Balloon.cxx
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-- bus data members now directly assigned to
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-- changed V_equiv_kts to V_calibrated_kts
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src/FDM/JSBSim.cxx
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src/FDM/JSBSim.hxx
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-- bus data members now directly assigned to
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-- implemented the FGInterface virtual setters with JSBSim specific
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logic
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-- changed the static FDMExec to a dynamic fdmex (needed so that the
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JSBSim object can be deleted when a model change is called for)
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-- implemented constructor and destructor, moved some of the logic
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formerly in init() to constructor
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-- added logic to bring up FGEngInterface objects and set the RPM and
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throttle values.
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src/FDM/LaRCsim.cxx
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src/FDM/LaRCsim.hxx
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-- bus data members now directly assigned to
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-- implemented the FGInterface virtual setters with LaRCsim specific
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logic, uses LaRCsimIC
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-- implemented constructor and destructor, moved some of the logic
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formerly in init() to constructor
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-- moved default inertias to here from fg_init.cxx
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-- eliminated the climb rate calculation. The equivalent, climb_rate =
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-1*vdown, is now in copy_from_LaRCsim().
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src/FDM/LaRCsimIC.cxx
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src/FDM/LaRCsimIC.hxx
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-- similar to FGInitialCondition, this class has all the logic needed to
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turn data like Vc and Mach into the more fundamental quantities LaRCsim
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needs to initialize.
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-- put it in src/FDM since it is a class
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src/FDM/MagicCarpet.cxx
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-- bus data members now directly assigned to
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src/FDM/Makefile.am
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-- adds LaRCsimIC.hxx and cxx
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src/FDM/JSBSim/FGAtmosphere.h
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src/FDM/JSBSim/FGDefs.h
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src/FDM/JSBSim/FGInitialCondition.cpp
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src/FDM/JSBSim/FGInitialCondition.h
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src/FDM/JSBSim/JSBSim.cpp
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-- changes to accomodate the new bus
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src/FDM/LaRCsim/atmos_62.h
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src/FDM/LaRCsim/ls_geodesy.h
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-- surrounded prototypes with #ifdef __cplusplus ... #endif , functions
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here are needed in LaRCsimIC
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src/FDM/LaRCsim/c172_main.c
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src/FDM/LaRCsim/cherokee_aero.c
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src/FDM/LaRCsim/ls_aux.c
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src/FDM/LaRCsim/ls_constants.h
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src/FDM/LaRCsim/ls_geodesy.c
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src/FDM/LaRCsim/ls_geodesy.h
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src/FDM/LaRCsim/ls_step.c
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src/FDM/UIUCModel/uiuc_betaprobe.cpp
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-- changed PI to LS_PI, eliminates preprocessor naming conflict with
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weather module
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src/FDM/LaRCsim/ls_interface.c
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src/FDM/LaRCsim/ls_interface.h
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-- added function ls_set_model_dt()
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src/Main/bfi.cxx
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-- eliminated calls that set the NED speeds to body components. They
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are no longer needed and confuse the new bus.
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src/Main/fg_init.cxx
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-- eliminated calls that just brought the bus data up-to-date (e.g.
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set_sin_cos_latitude). or set default values. The bus now handles the
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defaults and updates itself when the setters are called (for LaRCsim and
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JSBSim). A default method for doing this needs to be added to the bus.
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-- added fgVelocityInit() to set the speed the user asked for. Both
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JSBSim and LaRCsim can now be initialized using any of:
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vc,mach, NED components, UVW components.
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src/Main/main.cxx
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--eliminated call to fgFDMSetGroundElevation, this data is now 'pulled'
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onto the bus every update()
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src/Main/options.cxx
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src/Main/options.hxx
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-- added enum to keep track of the speed requested by the user
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-- eliminated calls to set NED velocity properties to body speeds, they
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are no longer needed.
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-- added options for the NED components.
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src/Network/garmin.cxx
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src/Network/nmea.cxx
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--eliminated calls that just brought the bus data up-to-date (e.g.
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set_sin_cos_latitude). The bus now updates itself when the setters are
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called (for LaRCsim and JSBSim). A default method for doing this needs
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to be added to the bus.
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-- changed set_V_equiv_kts to set_V_calibrated_kts. set_V_equiv_kts no
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longer exists ( get_V_equiv_kts still does, though)
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src/WeatherCM/FGLocalWeatherDatabase.cpp
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-- commented out the code to put the weather data on the bus, a
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different scheme for this is needed.
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Revision 1.1.1.1 1999/06/17 18:07:34 curt
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Start of 0.7.x branch
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Revision 1.1.1.1 1999/04/05 21:32:45 curt
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Start of 0.6.x branch.
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Revision 1.3 1998/07/08 14:41:37 curt
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.
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Revision 1.2 1998/01/19 18:40:25 curt
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Tons of little changes to clean up the code and to remove fatal errors
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when building with the c++ compiler.
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Revision 1.1 1997/05/29 00:09:56 curt
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Initial Flight Gear revision.
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* Revision 1.5 1994/01/11 18:47:05 bjax
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* Changed include files to use types and constants, not ls_eom.h
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* Also changed DATA type to SCALAR type.
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*
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* Revision 1.4 1993/12/14 21:06:47 bjax
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* Removed global variable references Altitude and Latitude. EBJ
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*
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* Revision 1.3 1993/06/02 15:03:40 bjax
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* Made new subroutine for calculating geodetic to geocentric; changed name
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* of forward conversion routine from ls_geodesy to ls_geoc_to_geod.
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*
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----------------------------------------------------------------------------
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REFERENCES:
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[ 1] Stevens, Brian L.; and Lewis, Frank L.: "Aircraft
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Control and Simulation", Wiley and Sons, 1992.
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ISBN 0-471-61397-5
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----------------------------------------------------------------------------
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CALLED BY: ls_aux
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----------------------------------------------------------------------------
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CALLS TO:
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----------------------------------------------------------------------------
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INPUTS:
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lat_geoc Geocentric latitude, radians, + = North
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radius C.G. radius to earth center, ft
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----------------------------------------------------------------------------
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OUTPUTS:
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lat_geod Geodetic latitude, radians, + = North
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alt C.G. altitude above mean sea level, ft
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sea_level_r radius from earth center to sea level at
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local vertical (surface normal) of C.G.
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--------------------------------------------------------------------------*/
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#include "ls_types.h"
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#include "ls_constants.h"
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#include "ls_geodesy.h"
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#include <math.h>
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/* ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator */
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#define ONE_SECOND 4.848136811E-6
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#define HALF_PI 0.5*LS_PI
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void ls_geoc_to_geod( SCALAR lat_geoc, SCALAR radius, SCALAR *lat_geod,
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SCALAR *alt, SCALAR *sea_level_r )
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{
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SCALAR t_lat, x_alpha, mu_alpha, delt_mu, r_alpha, l_point, rho_alpha;
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SCALAR sin_mu_a, denom,delt_lambda, lambda_sl, sin_lambda_sl;
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if( ( (HALF_PI - lat_geoc) < ONE_SECOND ) /* near North pole */
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|| ( (HALF_PI + lat_geoc) < ONE_SECOND ) ) /* near South pole */
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{
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*lat_geod = lat_geoc;
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*sea_level_r = EQUATORIAL_RADIUS*E;
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*alt = radius - *sea_level_r;
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}
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else
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{
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t_lat = tan(lat_geoc);
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x_alpha = E*EQUATORIAL_RADIUS/sqrt(t_lat*t_lat + E*E);
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mu_alpha = atan2(sqrt(RESQ - x_alpha*x_alpha),E*x_alpha);
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if (lat_geoc < 0) mu_alpha = - mu_alpha;
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sin_mu_a = sin(mu_alpha);
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delt_lambda = mu_alpha - lat_geoc;
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r_alpha = x_alpha/cos(lat_geoc);
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l_point = radius - r_alpha;
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*alt = l_point*cos(delt_lambda);
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denom = sqrt(1-EPS*EPS*sin_mu_a*sin_mu_a);
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rho_alpha = EQUATORIAL_RADIUS*(1-EPS)/
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(denom*denom*denom);
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delt_mu = atan2(l_point*sin(delt_lambda),rho_alpha + *alt);
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*lat_geod = mu_alpha - delt_mu;
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lambda_sl = atan( E*E * tan(*lat_geod) ); /* SL geoc. latitude */
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sin_lambda_sl = sin( lambda_sl );
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*sea_level_r = sqrt(RESQ
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/(1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
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}
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}
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void ls_geod_to_geoc( SCALAR lat_geod, SCALAR alt,
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SCALAR *sl_radius, SCALAR *lat_geoc )
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{
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SCALAR lambda_sl, sin_lambda_sl, cos_lambda_sl, sin_mu, cos_mu, px, py;
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lambda_sl = atan( E*E * tan(lat_geod) ); /* sea level geocentric latitude */
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sin_lambda_sl = sin( lambda_sl );
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cos_lambda_sl = cos( lambda_sl );
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sin_mu = sin(lat_geod); /* Geodetic (map makers') latitude */
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cos_mu = cos(lat_geod);
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*sl_radius = sqrt(RESQ
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/(1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
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py = *sl_radius*sin_lambda_sl + alt*sin_mu;
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px = *sl_radius*cos_lambda_sl + alt*cos_mu;
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*lat_geoc = atan2( py, px );
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}
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