1 // gsdi.cxx - Ground Speed Drift Angle Indicator (known as GSDI or GSDA)
2 // Written by Melchior FRANZ, started 2006.
4 // Copyright (C) 2006 Melchior FRANZ - mfranz#aon:at
6 // This program is free software; you can redistribute it and/or
7 // modify it under the terms of the GNU General Public License as
8 // published by the Free Software Foundation; either version 2 of the
9 // License, or (at your option) any later version.
11 // This program is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
16 // You should have received a copy of the GNU General Public License
17 // along with this program; if not, write to the Free Software
18 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
24 #include <simgear/sg_inlines.h>
25 #include <simgear/constants.h>
27 #include <Main/fg_props.hxx>
32 * Failures or inaccuracies are currently not modeled due to lack of data.
33 * The Doppler based GSDI should output unreliable data with increasing
34 * pitch, roll, vertical acceleration and altitude-agl.
38 GSDI::GSDI(SGPropertyNode *node) :
39 _name(node->getStringValue("name", "gsdi")),
40 _num(node->getIntValue("number", 0))
53 branch = "/instrumentation/" + _name;
54 SGPropertyNode *n = fgGetNode(branch.c_str(), _num, true);
55 _serviceableN = n->getNode("serviceable", true);
58 _headingN = fgGetNode("/orientation/heading-deg", true);
59 _ubodyN = fgGetNode("/velocities/uBody-fps", true);
60 _vbodyN = fgGetNode("/velocities/vBody-fps", true);
61 _wind_dirN = fgGetNode("/environment/wind-from-heading-deg", true);
62 _wind_speedN = fgGetNode("/environment/wind-speed-kt", true);
65 _drift_uN = n->getNode("drift-u-kt", true);
66 _drift_vN = n->getNode("drift-v-kt", true);
67 _drift_speedN = n->getNode("drift-speed-kt", true);
68 _drift_angleN = n->getNode("drift-angle-deg", true);
72 void GSDI::update(double /*delta_time_sec*/)
74 if (!_serviceableN->getBoolValue())
77 double wind_speed = _wind_speedN->getDoubleValue();
78 double rel_wind_dir = (_headingN->getDoubleValue() - _wind_dirN->getDoubleValue())
79 * SGD_DEGREES_TO_RADIANS;
80 double wind_u = wind_speed * cos(rel_wind_dir);
81 double wind_v = wind_speed * sin(rel_wind_dir);
83 double u = _ubodyN->getDoubleValue() * SG_FPS_TO_KT - wind_u;
84 double v = _vbodyN->getDoubleValue() * SG_FPS_TO_KT + wind_v;
86 double speed = sqrt(u * u + v * v);
87 double angle = atan2(v, u) * SGD_RADIANS_TO_DEGREES;
89 _drift_uN->setDoubleValue(u);
90 _drift_vN->setDoubleValue(v);
91 _drift_speedN->setDoubleValue(speed);
92 _drift_angleN->setDoubleValue(angle);