Use haversine formula for great-circle distance#90
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The spherical law of cosines loses numerical precision for short distances, since acos operates near 1.0 (the min(1, cos_val) clamp was a symptom of this). Adjacent OSM nodes are typically metres apart, so this is the dominant case for the tool. Switch to the haversine formula, which is numerically stable for short distances. The Earth radius constant (6373000 m) is unchanged so edge lengths stay comparable to previous output. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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The spherical law of cosines loses numerical precision for short distances, since acos operates near 1.0 (the min(1, cos_val) clamp was a symptom of this). Adjacent OSM nodes are typically metres apart, so this is the dominant case for the tool.
Switch to the haversine formula, which is numerically stable for short distances. The Earth radius constant (6373000 m) is unchanged so edge lengths stay comparable to previous output.