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SwRI can revise these Terms at any time * without notice by updating this posting. * * Trademarks * * The SwRI logo is a trademark of SwRI in the United States and other countries. * */ #ident "@(#) find_pixel.c 1.19 05/08/19 SwRI" #include "libtrec_idfs.h" /**************************************************************************** * * * IR_FIND_PIXEL SUBROUTINE * * * * DESCRIPTION * * This routine determines which pixel a given time period is associated * * with. Since data is being accumulated for a given time period, and * * that time period represents one pixel's worth of information, it is * * possible to determine pixel location using the current time values, a * * base reference time and a base pixel location. * * * * INPUT VARIABLES * * SDDAS_SHORT new_year year component of the current time * * SDDAS_SHORT new_day day component of the current time * * SDDAS_SHORT index index to get to the timing structure for * * the sensor being processed * * SDDAS_SHORT *pix_yr, start time, in terms of the base time and* * *pix_day resolution, for the buffer's start pixel * * SDDAS_LONG time_sec seconds component of the current time * * SDDAS_LONG new_nano nsec component of the current time * * SDDAS_LONG *pix_sec, start time, in terms of the base time and* * *pix_nsec resolution, for the buffer's start pixel * * SDDAS_FLOAT *frac the fractional part of pixel covered by * * the current time value * * SDDAS_CHAR leading_edge pixel boundary flag * * treated as a leading or trailing edge: * * 0 - trailing edge * * 1 - leading edge * * * * USAGE * * x = ir_find_pixel (new_year, new_day, time_sec, new_nano, &frac, * * leading_edge, &pix_yr, &pix_day, &pix_sec, * * &pix_nsec, index) * * * * NECESSARY SUBPROGRAMS * * ir_pixel_forward () determines the pixel location for time * * samples that advance past the base time * * ir_pixel_backward () determines the pixel location for time * * samples that go backward from base time * * ir_extra_days () determines the number of extra days to * * be accounted for due to leap years * * * * EXTERNAL VARIABLES * * struct general_info structure holding information concerning * * ginfo the experiment that is being processed * * * * INTERNAL VARIABLES * * reg struct experiment_info a pointer to the structure that holds * * *ex specific experiment information * * reg struct timing *tptr a pointer to the structure that holds * * timing information * * register SDDAS_LONG *l1 ptr to elements in the timing structure * * SDDAS_FLOAT combo_diff the fractional amount of time converted * * to a common time base (seconds) * * SDDAS_LONG new_sec the corrected seconds component for the * * current time sample * * SDDAS_LONG cnt_sub the number of delta T's between the base * * time and the current time * * SDDAS_LONG pixel_loc the pixel location associated with the * * current time sample (returned value) * * SDDAS_LONG e_sec, e_nsec time of the trailing edge of base pixel * * SDDAS_LONG b_sec, b_nsec time of the leading edge of base pixel * * SDDAS_LONG add_bsec year and dayofyear time differential to * * add to seconds comparision * * SDDAS_SHORT extra_days no. of leap year days (day 366) found * * between current and base reference time * * * * SUBSYSTEM * * Display Level * * * ***************************************************************************/ SDDAS_LONG ir_find_pixel (SDDAS_SHORT new_year, SDDAS_SHORT new_day, SDDAS_LONG time_sec, SDDAS_LONG new_nano, SDDAS_FLOAT *frac, SDDAS_CHAR leading_edge, SDDAS_SHORT *pix_yr, SDDAS_SHORT *pix_day, SDDAS_LONG *pix_sec, SDDAS_LONG *pix_nsec, SDDAS_SHORT index) { extern struct general_info ginfo; register struct experiment_info *ex; register struct timing *tptr; register SDDAS_LONG *l1; SDDAS_FLOAT combo_diff; SDDAS_LONG new_sec, cnt_sub, pixel_loc, e_sec, e_nsec, b_sec, b_nsec; SDDAS_LONG add_bsec; SDDAS_SHORT extra_days; /*******************************************************************/ /* Set pointer to seconds component of leading edge of pixel */ /* The following is true */ /* */ /* *l1 = seconds of leading edge of current pixel */ /* *(l1+1) = nsec of leading edge of current pixel */ /* *(l1+2) = seconds of trailing edge of current pixel */ /* *(l1+3) = nsec of trailing edge of current pixel */ /*******************************************************************/ ex = ginfo.expt; tptr = ex->timing_ptr + index; l1 = &tptr->start_sec; /********************************************************************/ /* Determine how many leap years are contained within the */ /* specified duration. Get the current seconds of sample which */ /* necessitates bumping it up by the current seconds of year and */ /* day. Both are computed from the base year and day. */ /********************************************************************/ extra_days = ir_extra_days (new_year, ex->time_values.base_year); new_sec = (new_year - ex->time_values.base_year) * 31536000 + (new_day - ex->time_values.base_day) * 86400 + extra_days * 86400 + time_sec; /********************************************************************/ /* Since the resolution per pixel could cause a roll-over to the */ /* next day, the end second and nanosecond could be less than the */ /* start second and nanosecond, even though the year and day will */ /* be correct; therefore, adjust the end time for comparison since */ /* the year and day are not looked at. */ /********************************************************************/ e_sec = *(l1 + 2); e_nsec = *(l1 + 3); extra_days = ir_extra_days (tptr->end_yr, ex->time_values.base_year); e_sec += (tptr->end_yr - ex->time_values.base_year) * 31536000 + (tptr->end_day - ex->time_values.base_day) * 86400 + extra_days * 86400; /********************************************************************/ /* Determine if time advanced or went backwards from the base time. */ /* The first check is for time advancement. */ /********************************************************************/ if (new_sec > e_sec || (new_sec == e_sec && new_nano >= e_nsec)) ir_pixel_forward (new_sec, new_nano, frac, leading_edge, &cnt_sub, index); else { b_sec = *l1; b_nsec = *(l1 + 1); extra_days = ir_extra_days (tptr->start_yr, ex->time_values.base_year); add_bsec = (tptr->start_yr - ex->time_values.base_year) * 31536000 + (tptr->start_day - ex->time_values.base_day) * 86400 + extra_days * 86400; b_sec += add_bsec; if (new_sec < b_sec || (new_sec == b_sec && new_nano < b_nsec)) ir_pixel_backward (new_sec, new_nano, frac, leading_edge, &cnt_sub, index); else { combo_diff = (new_sec - b_sec) + 0.000000001 * (new_nano - b_nsec); *frac = combo_diff / ex->time_values.pix_width; } } /***********************************************************************/ /* Since pix_sec is always modified to avoid a roll-over in pix_nsec, */ /* and since pix_sec is a delta value off the base time, year and day */ /* can be computed using the delta value (pix_sec) and the base time. */ /***********************************************************************/ pixel_loc = *(l1-1); *pix_sec = *l1; *pix_nsec = *(l1+1); *pix_yr = tptr->start_yr; *pix_day = tptr->start_day; return (pixel_loc); }