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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 "@(#) check_bound.c 1.7 05/08/19 SwRI" #include "libtrec_idfs.h" /******************************************************************************* * * * IR_CHECK_BOUNDARY SUBROUTINE * * * * DESCRIPTION * * This routine is called to determine if a boundary has been crossed for * * discontinuous data sets. This routine only works for a discontinuous * * range of -180 to 180. The algorithm is as follows: the data is monitored * * to see when a boundary is crossed. Once a boundary has been crossed, the * * values are adjusted to their opposite pole values. For example, if the * * data is increasing, all values less than 0 are converted such that the * * values go from 181 to 360, thus ending up with a range of values from 0 to * * 360. If the values are decreasing, all values greater than or equal to * * zero are converted such that the values go from -360 to -181, thus ending * * up with a range of values from -360 to 0. This conversion continues until * * increasing data returns positive or until decreasing data returns negative.* * * * INPUT VARIABLES * * SDDAS_CHAR *cross_bound flag that indicates if a boundary has been * * crossed * * SDDAS_FLOAT *new_val the value that is to be added to the data * * buffers filled by FILL_DATA * * SDDAS_FLOAT data_value the data value being checked * * SDDAS_FLOAT old_value the previous value for comparison purposes * * to see if a boundary has been crossed * * * * USAGE * * ir_check_boundary (&cross_bound, &new_val, data_value, old_value) * * * * NECESSARY SUBPROGRAMS * * None * * * * EXTERNAL VARIABLES * * None * * * * INTERNAL VARIABLES * * None * * * * SUBSYSTEM * * Display Level * * * ******************************************************************************/ void ir_check_boundary (SDDAS_CHAR *cross_bound, SDDAS_FLOAT *new_val, SDDAS_FLOAT data_value, SDDAS_FLOAT old_value) { /*****************************************************************/ /* Did previous data cross a boundary? */ /*****************************************************************/ if (*cross_bound != 0) { /***************************************************************/ /* Data is increasing; stop correcting once positive values */ /* are re-established. */ /***************************************************************/ if (*cross_bound == 1 && data_value >= 0.0) { *cross_bound = 0; *new_val = data_value; } /***************************************************************/ /* Data less than the midpoint is taken to the opposite pole. */ /***************************************************************/ else if (*cross_bound == 1) *new_val = 360.0 + data_value; /***************************************************************/ /* Data is decreasing; stop correcting once negative values */ /* are re-established. */ /***************************************************************/ else if (*cross_bound == -1 && data_value < 0.0) { *cross_bound = 0; *new_val = data_value; } /******************************************************************/ /* Data greater than the midpoint is taken to the opposite pole. */ /******************************************************************/ else if (*cross_bound == -1) *new_val = data_value - 360.0; } /*******************************************************************/ /* Check the data for a possible boundary crossing. */ /*******************************************************************/ else { /****************************************************************/ /* Make sure old value is a good comparison value (data is */ /* initialized to OUTSIDE_MIN, in which case, no comparison). */ /****************************************************************/ if (old_value < -180.0) *new_val = data_value; /****************************************************************/ /* A boundary is crossed if the following happens: */ /* a) old_value is > 90.0 & new_value is < -90.0 */ /* b) old_value is < -90.0 & new_value is > 90.0 */ /* Restriction to these quadrants is necessary so that false */ /* boundary crossings aren't registered (e.g. -1 and 1). May */ /* need to move more toward ends. */ /****************************************************************/ else if (old_value > 90.0 && data_value < -90.0) { *cross_bound = 1; *new_val = 360.0 + data_value; } else if (old_value < -90.0 && data_value > 90.0) { *cross_bound = -1; *new_val = data_value - 360.0; } else *new_val = data_value; } }