Function SpatialObjectToGeoHash

pkg/geo/encode.go:195–232

SpatialObjectToGeoHash transforms a given SpatialObject to a GeoHash.

(so geopb.SpatialObject, p int)

// SpatialObjectToGeoHash transforms a given SpatialObject to a GeoHash.
func SpatialObjectToGeoHash(so geopb.SpatialObject, p int) (string, error) {
	if so.BoundingBox == nil {
		return "", nil
	}
	bbox := so.BoundingBox
	if so.Type == geopb.SpatialObjectType_GeographyType {
		// Convert bounding box back to degrees.
		bbox = &geopb.BoundingBox{
			LoX: s1.Angle(bbox.LoX).Degrees(),
			HiX: s1.Angle(bbox.HiX).Degrees(),
			LoY: s1.Angle(bbox.LoY).Degrees(),
			HiY: s1.Angle(bbox.HiY).Degrees(),
		}
	}
	if bbox.LoX < -180 || bbox.HiX > 180 || bbox.LoY < -90 || bbox.HiY > 90 {
		return "", pgerror.Newf(
			pgcode.InvalidParameterValue,
			"object has bounds greater than the bounds of lat/lng, got (%f %f, %f %f)",
			bbox.LoX, bbox.LoY,
			bbox.HiX, bbox.HiY,
		)
	}

	// Get precision using the bounding box if required.
	if p <= GeoHashAutoPrecision {
		p = getPrecisionForBBox(bbox)
	}

	// Support up to 20, which is the same as PostGIS.
	if p > GeoHashMaxPrecision {
		p = GeoHashMaxPrecision
	}

	bbCenterLng := bbox.LoX + (bbox.HiX-bbox.LoX)/2.0
	bbCenterLat := bbox.LoY + (bbox.HiY-bbox.LoY)/2.0

	return geohash.Encode(bbCenterLat, bbCenterLng, p), nil
}

// getPrecisionForBBox is a function imitating PostGIS's ability to go from
// a world bounding box and truncating a GeoHash to fit the given bounding box.