項16.5.2. 「Geometry
Functions」, discusses
several functions that construct new geometries from existing
ones. See that section for descriptions of these functions:
Envelope(
g
)
StartPoint(
ls
)
EndPoint(
ls
)
PointN(
ls
,N
)
ExteriorRing(
poly
)
InteriorRingN(
poly
,N
)
GeometryN(
gc
,N
)