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Fix wrong annotation/gridline alignment for decimal-degree geographic annotations #9091

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Fix wrong annotation/gridline alignment for decimal-degree geographic annotations #9091

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6b65810
Fix geo annotation rounding mismatch
Esteban82 Jul 7, 2026
528b9cd
Fix geo annotation rounding mismatch
Esteban82 Jul 7, 2026
d2a0c9c
Remove patch
Esteban82 Jul 7, 2026
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20 changes: 18 additions & 2 deletions src/gmt_map.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7085,8 +7085,24 @@ void gmt_auto_frame_interval (struct GMT_CTRL *GMT, unsigned int axis, unsigned
d *= MAX (0.05, MIN (5.0 * GMT->current.setting.font_annot[item].size / f, 0.2));

/* Now determine 'round' major and minor tick intervals */
if (gmt_M_axis_is_geo (GMT, axis)) /* Geographical coordinate */
p = (d < GMT_MIN2DEG) ? GMT_SEC2DEG : (d < 1.0) ? GMT_MIN2DEG : 1.0;
if (gmt_M_axis_is_geo (GMT, axis)) { /* Geographical coordinate */
struct GMT_GEO_IO *S = &GMT->current.plot.calclock.geo;
if (S->order[1] == GMT_NOTSET && S->n_sec_decimals > 0) {
/* FORMAT_GEO_MAP is a plain decimal-degree template with a fixed number
* of decimals (e.g., ddd.xxF or ddd.xxxF). If we let the interval be
* picked in arcsec/arcmin/degree "nice" units as usual it may end up as
* a value (e.g., 25" = 0.006944...9 degrees) that cannot be represented
* exactly at the requested decimal precision. The annotation label is
* then rounded for display while the tick/gridline is still placed at
* the true (unrounded) coordinate, so the label and its position visibly
* disagree -- see GMT issue #8490. To avoid this we pick the interval
* directly in units of the smallest displayable decimal step so that any
* "nice" multiple of it is exactly representable in the chosen format. */
p = pow (10.0, -(double)S->n_sec_decimals);
}
else
p = (d < GMT_MIN2DEG) ? GMT_SEC2DEG : (d < 1.0) ? GMT_MIN2DEG : 1.0;
}
else if (GMT->current.io.cycle_col == axis && GMT->current.io.cycle_operator != GMT_CYCLE_CUSTOM) {
switch (GMT->current.io.cycle_operator) {
case GMT_CYCLE_MIN: case GMT_CYCLE_HOUR: /* With a range of 60 it behaves like geo */
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