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Truncate, don't round. #15

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Jul 16, 2016
Merged

Truncate, don't round. #15

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39 changes: 2 additions & 37 deletions libmgrs/mgrs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -351,25 +351,6 @@ long Check_Zone(char* MGRS, long* zone_exists)
} /* Check_Zone */


long Round_MGRS (double value)
/*
* The function Round_MGRS rounds the input value to the
* nearest integer, using the standard engineering rule.
* The rounded integer value is then returned.
*
* value : Value to be rounded (input)
*/
{ /* Round_MGRS */
double ivalue;
long ival;
double fraction = modf (value, &ivalue);
ival = (long)(ivalue);
if ((fraction > 0.5) || ((fraction == 0.5) && (ival%2 == 1)))
ival++;
return (ival);
} /* Round_MGRS */


long Make_MGRS_String (char* MGRS,
long Zone,
int Letters[MGRS_LETTERS],
Expand Down Expand Up @@ -617,16 +598,12 @@ long UTM_To_MGRS (long Zone,
long ltr2_low_value; /* 2nd letter range - low number */
long ltr2_high_value; /* 2nd letter range - high number */
int letters[MGRS_LETTERS]; /* Number location of 3 letters in alphabet */
double divisor;
double rounded_easting;
long temp_error_code = MGRS_NO_ERROR;
long error_code = MGRS_NO_ERROR;

divisor = pow (10.0, (5 - Precision));
rounded_easting = Round_MGRS (Easting/divisor) * divisor;

/* Special check for rounding to (truncated) eastern edge of zone 31V */
if ((Zone == 31) && (((Latitude >= 56.0 * DEG_TO_RAD) && (Latitude < 64.0 * DEG_TO_RAD)) && ((Longitude >= 3.0 * DEG_TO_RAD) || (rounded_easting >= 500000.0))))
if ((Zone == 31) && (((Latitude >= 56.0 * DEG_TO_RAD) && (Latitude < 64.0 * DEG_TO_RAD)) && ((Longitude >= 3.0 * DEG_TO_RAD) || (Easting >= 500000.0))))
{ /* Reconvert to UTM zone 32 */
Set_UTM_Parameters (MGRS_a, MGRS_f, 32);
temp_error_code = Convert_Geodetic_To_UTM (Latitude, Longitude, &Zone, &Hemisphere, &Easting, &Northing);
Expand All @@ -645,15 +622,7 @@ long UTM_To_MGRS (long Zone,

return error_code;
}
else
/* Round easting value using new easting */
Easting = Round_MGRS (Easting/divisor) * divisor;
}
else
Easting = rounded_easting;

/* Round northing values */
Northing = Round_MGRS (Northing/divisor) * divisor;
}

if( Latitude <= 0.0 && Northing == 1.0e7)
{
Expand Down Expand Up @@ -1155,7 +1124,6 @@ long Convert_UPS_To_MGRS (char Hemisphere,
double grid_northing; /* Northing used to derive 3rd letter of MGRS */
long ltr2_low_value; /* 2nd letter range - low number */
int letters[MGRS_LETTERS]; /* Number location of 3 letters in alphabet */
double divisor;
int index = 0;
long error_code = MGRS_NO_ERROR;

Expand All @@ -1169,9 +1137,6 @@ long Convert_UPS_To_MGRS (char Hemisphere,
error_code |= MGRS_PRECISION_ERROR;
if (!error_code)
{
divisor = pow (10.0, (5 - Precision));
Easting = Round_MGRS (Easting/divisor) * divisor;
Northing = Round_MGRS (Northing/divisor) * divisor;

if (Hemisphere == 'N')
{
Expand Down
14 changes: 13 additions & 1 deletion tests/test.txt
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Expand Up @@ -41,4 +41,16 @@ Test basic import

>>> d, m, s = m.ddtodms(32.328414)
>>> (d, m,'%.6f' % s)
(32.0, 19.0, '42.290400')
(32.0, 19.0, '42.290400')

>>> m = mgrs.MGRS()
>>> washingtondc = (38.9072, -77.0369)
>>> c = m.toMGRS(*washingtondc)
>>> str(c.decode("ascii"))
'18SUJ2338308450'

>>> philadelphia = (39.9526, -75.1652)
>>> c = m.toMGRS(*philadelphia)
>>> str(c.decode("ascii"))
'18SVK8588822509'