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/* -*- Last-Edit: Fri Jan 29 11:13:27 1993 by Tarak S. Goradia; -*- */
/* $Log: tcas_v23_523.c,v $
/* Revision 1.1 2006-04-04 08:38:22 kroening
/* more
/*
* Revision 1.2 1993/03/12 19:29:50 foster
* Correct logic bug which didn't allow output of 2 - hf
* */
#include <stdio.h>
#define OLEV 600 /* in feets/minute */
#define MAXALTDIFF 600 /* max altitude difference in feet */
#define MINSEP 300 /* min separation in feet */
#define NOZCROSS 100 /* in feet */
/* variables */
typedef int bool;
int Cur_Vertical_Sep;
bool High_Confidence;
bool Two_of_Three_Reports_Valid;
int Own_Tracked_Alt;
int Own_Tracked_Alt_Rate;
int Other_Tracked_Alt;
int Alt_Layer_Value; /* 0, 1, 2, 3 */
int Positive_RA_Alt_Thresh[4];
int Up_Separation;
int Down_Separation;
/* state variables */
int Other_RAC; /* NO_INTENT, DO_NOT_CLIMB, DO_NOT_DESCEND */
#define NO_INTENT 0
#define DO_NOT_CLIMB 1
#define DO_NOT_DESCEND 2
int Other_Capability; /* TCAS_TA, OTHER */
#define TCAS_TA 1
#define OTHER 2
int Climb_Inhibit; /* true/false */
#define UNRESOLVED 0
#define UPWARD_RA 1
#define DOWNWARD_RA 2
int ALIM();
int Inhibit_Biased_Climb();
bool Non_Crossing_Biased_Climb();
bool Non_Crossing_Biased_Descend();
bool Own_Below_Threat();
bool Own_Above_Threat();
int alt_sep_test();
void initialize()
{
Positive_RA_Alt_Thresh[0] = 400;
Positive_RA_Alt_Thresh[1] = 500;
Positive_RA_Alt_Thresh[2] = 640;
Positive_RA_Alt_Thresh[3] = 740;
}
int ALIM ()
{
return Positive_RA_Alt_Thresh[Alt_Layer_Value];
}
int Inhibit_Biased_Climb ()
{
return (Climb_Inhibit ? Up_Separation + NOZCROSS : Up_Separation);
}
bool Non_Crossing_Biased_Climb()
{
int upward_preferred;
int upward_crossing_situation;
bool result;
upward_preferred = Inhibit_Biased_Climb() > Down_Separation;
if (upward_preferred)
{
result = !(Own_Below_Threat()) || ((Own_Below_Threat()) && (!(Down_Separation >= ALIM())));
}
else
{
result = Own_Above_Threat() && (Cur_Vertical_Sep >= MINSEP) && (Up_Separation >= ALIM());
}
return result;
}
bool Non_Crossing_Biased_Descend()
{
int upward_preferred;
int upward_crossing_situation;
bool result;
upward_preferred = (Up_Separation + NOZCROSS) > Down_Separation;
if (upward_preferred)
{
result = Own_Below_Threat() && (Cur_Vertical_Sep >= MINSEP) && (Down_Separation >= ALIM());
}
else
{
result = !(Own_Above_Threat()) || ((Own_Above_Threat()) && (Up_Separation >= ALIM()));
}
return result;
}
bool Own_Below_Threat()
{
return (Own_Tracked_Alt < Other_Tracked_Alt);
}
bool Own_Above_Threat()
{
return (Other_Tracked_Alt < Own_Tracked_Alt);
}
int alt_sep_test()
{
bool enabled, tcas_equipped, intent_not_known;
bool need_upward_RA, need_downward_RA;
int alt_sep;
enabled = High_Confidence && (Own_Tracked_Alt_Rate <= OLEV) && (Cur_Vertical_Sep > MAXALTDIFF);
tcas_equipped = Other_Capability == TCAS_TA;
intent_not_known = Two_of_Three_Reports_Valid && Other_RAC == NO_INTENT;
alt_sep = UNRESOLVED;
if (enabled && ((tcas_equipped && intent_not_known) || !tcas_equipped))
{
need_upward_RA = Non_Crossing_Biased_Climb() && Own_Below_Threat();
need_downward_RA = Non_Crossing_Biased_Descend() && Own_Above_Threat();
if (need_upward_RA && need_downward_RA)
/* unreachable: requires Own_Below_Threat and Own_Above_Threat
to both be true - that requires Own_Tracked_Alt < Other_Tracked_Alt
and Other_Tracked_Alt < Own_Tracked_Alt, which isn't possible */
alt_sep = UNRESOLVED;
else if (need_upward_RA)
alt_sep = UPWARD_RA;
else if (need_downward_RA)
alt_sep = DOWNWARD_RA;
else
alt_sep = UNRESOLVED;
}
return alt_sep;
}
main(int argc, char*argv[])
{
initialize();
Cur_Vertical_Sep = 860;
High_Confidence = 1;
Two_of_Three_Reports_Valid = 1;
Own_Tracked_Alt = 618;
Own_Tracked_Alt_Rate = 329;
Other_Tracked_Alt = 574;
Alt_Layer_Value = 4;
Up_Separation = 893;
Down_Separation = 914;
Other_RAC = 0;
Other_Capability = 2;
Climb_Inhibit = 0;
assert(alt_sep_test()==0);
}
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