PolygonM

A PolygonM consists of a number of rings. A ring is a closed, non-self-intersecting loop. Note that intersections are calculated in XY space, not in XYM space. A PolygonM may contain multiple outer rings. The rings of a PolygonM are referred to as its parts.

The following fields are for a PolygonM:

Box: The bounding box for the PolygonM, stored in the order Xmin, Ymin, Xmax, Yma
NumParts: The number of rings in the PolygonM
NumPoints: The total number of points for all rings
Parts: An array of length NumParts
Stores, for each ring, the index of its first point in the points array. Array indexes are numbered with respect to 0.
Points: An array of length NumPoints
The points for each ring in the PolygonM are stored end to end. The points for Ring 2 follow the points for Ring 1, and so on. The parts array holds the array index of the starting point for each ring. There is no delimiter in the points array between rings.
M Range: The minimum and maximum measures for the PolygonM stored in the order Mmin, Mmax
M Array: An array of length NumPoints
The measures for each ring in the PolygonM are stored end to end. The measures for Ring 2 follow the measures for Ring 1, and so on. The parts array holds the array index of the starting measure for each ring. There is no delimiter in the measure array between rings.

The following are important notes about PolygonM shapes:

The rings are closed (the first and last vertex of a ring must be the same).
The order of rings in the points array is not significant.

The following table shows PolygonM byte stream contents.


Position	Field	Value	Type	Number	Byte order
Byte 0	Shape Type	15	Integer	1	Little endian
Byte 4	Box	Box	Double	4	Little endian
Byte 36	NumParts	NumParts	Integer	1	Little endian
Byte 40	NumPoints	NumPoints	Integer	1	Little endian
Byte 44	Parts	Parts	Integer	NumParts	Little endian
Byte X	Points	Points	Point	NumPoints	Little endian
Byte Y	Mmin	Mmin	Double	1	Little endian
Byte Y+8	Mmax	Mmax	Double	1	Little endian
Byte Y+16	M Array	M Array	Double	NumPoints	Little endian

Tip: X = 44 + (4 * NumParts), Y = X + (16 * NumPoints)