1 // atmosphere.hxx -- routines to model the air column
3 // Written by David Megginson, started February 2002.
4 // Modified by John Denker to correct physics errors in 2007
6 // Copyright (C) 2002 David Megginson - david@megginson.com
8 // This program is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU General Public License as
10 // published by the Free Software Foundation; either version 2 of the
11 // License, or (at your option) any later version.
13 // This program is distributed in the hope that it will be useful, but
14 // WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 // General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
25 #ifndef _ATMOSPHERE_HXX
26 #define _ATMOSPHERE_HXX
28 #include <simgear/compiler.h>
29 #include <simgear/math/interpolater.hxx>
36 * Model the atmosphere in a way consistent with the laws
39 * Each instance of this class models a particular air mass.
40 * You may freely move up, down, or sideways in the air mass.
41 * In contrast, if you want to compare different air masses,
42 * you should use a separate instance for each one.
44 * See also ./environment.hxx
47 #define SCD(name,val) const double name(val)
49 SCD(g, 9.80665); // [m/s/s] acceleration of gravity
50 SCD(mm, .0289644); // [kg/mole] molar mass of air (dry?)
51 SCD(Rgas, 8.31432); // [J/K/mole] gas constant
52 SCD(inch, 0.0254); // [m] definition of inch
53 SCD(foot, 12 * inch); // [m]
54 SCD(inHg, 101325.0 / 760 * 1000 * inch); // [Pa] definition of inHg
55 SCD(freezing, 273.15); // [K] centigrade - kelvin offset
56 SCD(nm, 1852); // [m] nautical mile (NIST)
57 SCD(sm, 5280*foot); // [m] nautical mile (NIST)
60 SCD(P0, 101325.0); // [pascals] ISA sea-level pressure
61 SCD(T0, 15. + freezing); // [K] ISA sea-level temperature
62 SCD(lam0, .0065); // [K/m] ISA troposphere lapse rate
69 // The base class is little more than a namespace.
70 // It has no constructor, no destructor, and no variables.
73 double p_vs_a(const double height);
74 double a_vs_p(const double press, const double qnh = atmodel::ISA::P0);
75 double fake_t_vs_a_us(const double h_ft);
76 double fake_dp_vs_a_us(const double dpsl, const double h_ft);
77 double P_layer(const double height, const double href,
78 const double Pref, const double Tref,
80 void check_one(const double height);
81 double qnh(const double field_ft, const double press_in);
86 class FGAtmoCache : FGAtmo {
87 friend class FGAltimeter;
88 SGInterpTable * a_tvs_p; // _tvs_ means "tabulated versus"
95 void check_model(); // debug
100 class FGAltimeter : public FGAtmoCache {
106 double reading_ft(const double p_inHg,
107 const double set_inHg = atmodel::ISA::P0/atmodel::inHg);
108 inline double press_alt_ft(const double p_inHg) {
109 return a_tvs_p->interpolate(p_inHg);
111 inline double kollsman_ft(const double set_inHg) {
112 return a_tvs_p->interpolate(set_inHg);
117 void dump_stack1(const double Tref);
120 #endif // _ATMOSPHERE_HXX