Pyramid

A "pyramid" of square tiles. Each level of the pyramid on the way down has four times as many tiles as the previous level.

When SIS draws an Index Overlay with a Pyramid namer, only one level of the pyramid will be drawn. For example, suppose that the bottom level of the pyramid has tiles of 1000m at 1:10000 scale, then the second level of the pyramid will have tiles of 2000m at 1:20000 scale. Now if you zoom in to an effective scale of 1:10000 then SIS will only draw tiles from the bottom level, but when you zoom out to 1:20000 then SIS will only draw tiles from the second level.

The properties of the Pyramid correspond to tiles on its bottom level (e.g. the smallest tiles).

Typical tile name: 0qNNNNNN.ext, where N is between 0 and 3 and specifies a pyramid level quadrant.

namer$ argument to CreateIndexOverlay and CreateIndexCoverage

• APyramidNamer(bCartesian%,width#,height#,projection$,nDigit%)
  
  bCartesian%
  

  True	The tiles are in a cartesian Coordinate Reference System.
  False	The tiles are in a spherical Coordinate Reference System.

  
  width#, height#
  The width and height of each tile, in metres or degrees for cartesian and spherical tiles respectively.
  
  projection$
  A named Coordinate Reference System stored in a Named Object Library (without quote characters).
  
  nDigit%
  The maximum number of digits in a file name, in the range 1 to 24 inclusive. This value also controls the depth of the pyramid.
  
  

Properties

• Cartesian tiles
  
• Number of digits in tile name
  
• Projection
  
• Scale
  
• Tile height (degrees)
  
• Tile height (metres)
  
• Tile span
  
• Tile width (degrees)
  
• Tile width (metres)
  

---

Properties

• Cartesian tiles: _bCartesian&
  Are the tiles in a cartesian coordinate reference system?
  
  
• Number of digits in tile name: _nDigit&
  The number of digits in the tile name.
  
  
• Projection: _projection$
  The tile naming convention Coordinate Reference System.
  
  
• Scale: _scale#
  The tile scale.
  
  
• Tile height (degrees): _degree_height#
  The tile height, in degrees.
  
  
• Tile height (metres): _metre_height#
  The tile height, in metres.
  
  
• Tile span: _span#
  The tile span, in metres.
  
  
• Tile width (degrees): _degree_width#
  The tile width, in degrees.
  
  
• Tile width (metres): _metre_width#
  The tile width, in metres.

---