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16.5.2.5 Polygon Functions »
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16.5.2.4. MultiLineString Functions

These functions return properties of MultiLineString values.

  • GLength(mls)

    Returns as a double-precision number the length of the MultiLineString value mls. The length of mls is equal to the sum of the lengths of its elements. 

    mysql> SET @mls = 'MultiLineString((1 1,2 2,3 3),(4 4,5 5))';
mysql> SELECT GLength(GeomFromText(@mls));
+-----------------------------+
| GLength(GeomFromText(@mls)) |
+-----------------------------+
|             4.2426406871193 |
+-----------------------------+

    GLength() is a nonstandard name. It corresponds to the OpenGIS Length() function.

  • IsClosed(mls)

    Returns 1 if the MultiLineString value mls is closed (that is, the StartPoint() and EndPoint() values are the same for each LineString in mls). Returns 0 if mls is not closed, and –1 if it is NULL. 

    mysql> SET @mls = 'MultiLineString((1 1,2 2,3 3),(4 4,5 5))';
mysql> SELECT IsClosed(GeomFromText(@mls));
+------------------------------+
| IsClosed(GeomFromText(@mls)) |
+------------------------------+
|                            0 |
+------------------------------+

User Comments

Posted by Mircea LUTIC on May 25 2005 10:05am[Delete] [Edit]

The result of GLength() depends on the type of Spatial Reference (SRID).

The value above is based on euclidian geometry.
The length of a line (and hence of a LineString and MultiLineString) is given by
SQRT ( (x2-x1)^2 + (y2-y1)^2 )
only in planar (euclidian) geometry.

If x & y are spherical lattitude and longitude then the distance between 2 points of coordinates (lng1,lat1) and (lng2,lat2) is given by
distInRadians = acos ( sin(lat1)*sin(lat2) +cos(lat1)*cos(lat2)*cos(lng2-lng1) )
distInMeters = distInRadians * RadiusOfSphere

See also My comment on 19.5.2.6 MultiPolygon Functions

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