4.3 Spatial schema (ISO 19107)
149
transform
The operation "transform" shaB return a new GM _ Object that is the coordinate
transformation of this GM_Object into the passed Coordinate Reference System
within the accuracy of the transformation.
Fig. 4.29. Operation transform
enve/ope
The operation "envelope" returns the minImUm bounding box for this
GM_Object. The minimum bounding rectangle is the 2-dimensional case. This is the
coordinate region spanning the minimum and maximum value for each ordinate
taken on by DirectPositions in this GM_Object. The simplest representation for an
envelope consists of two DirectPositions, the first one containing aB the minimums
for each ordinate and second one containing a11 the maximums.
Fig. 4.30. Operation envelope
centroid
The operation "centroid" sha11 return the mathematical centroid for this
GM _ Object. The result is not guaranteed to be on the object. For heterogeneous collections of primitives, the centroid only takes into account those of the largest dimension. For example, when calculating the centroid of surfaces, an average is taken
weighted by area. Since curves have no area they do not contribute to the average.