170
4 Geometry standards
CV _ ContinuousQuadrilateralGridCoverage
The quadrilateral grid coverage (class CV _ ContinuousQuadrilateralGridCoverage) employs a systematic tessellation of the spatiotemporal domain. The principle
advantage of such tessellations is that they support a sequential enumeration of
elements that makes data storage and access more efficient.
A quadrilateral grid coverage may be a rectified grid or a referenceable grid. A
rectified grid can be transformed into a Coordinate Reference System using an affine
transformation. An affine transformation has six parameters: two translations (x, y),
two rotations (one for each axis), and two scales (one for each axis). A referenceable
grid requires a formula with a higher order that transforms into a Coordinate Reference System. An example is the perspective transformation with 8 parameters.
Fig. 4.67. Rectified grid (affine transformation)
Fig. 4.68. Referenceable grid (non-affine transformation)
CV_HexagonalGridCoverage
A hexagonal grid coverage (class CV _ HexagonalGridCoverage) is based on regular hexagons. That grid can be described as a rectified grid in which the two offset
vectors are of equallength but differ in direction by 60°.
4 Geometry standards
CV _ ContinuousQuadrilateralGridCoverage
The quadrilateral grid coverage (class CV _ ContinuousQuadrilateralGridCoverage) employs a systematic tessellation of the spatiotemporal domain. The principle
advantage of such tessellations is that they support a sequential enumeration of
elements that makes data storage and access more efficient.
A quadrilateral grid coverage may be a rectified grid or a referenceable grid. A
rectified grid can be transformed into a Coordinate Reference System using an affine
transformation. An affine transformation has six parameters: two translations (x, y),
two rotations (one for each axis), and two scales (one for each axis). A referenceable
grid requires a formula with a higher order that transforms into a Coordinate Reference System. An example is the perspective transformation with 8 parameters.
Fig. 4.67. Rectified grid (affine transformation)
Fig. 4.68. Referenceable grid (non-affine transformation)
CV_HexagonalGridCoverage
A hexagonal grid coverage (class CV _ HexagonalGridCoverage) is based on regular hexagons. That grid can be described as a rectified grid in which the two offset
vectors are of equallength but differ in direction by 60°.