Due to the size of the data, the data set for North America was split into a series of tiles.
Two similar, but slightly different, tiling schemes were developed: one for the US and one for
Canada.
- As a general rule, tiles are limited to 150,000 two-way links (or 300,000 one-way links).
However, some of the very large counties and areas violate this rule in order to make the tiles useful.
- Tiles include a 3 km (2 mile) buffer area that is in addition to the defined tile area
US
- Tiles are aggregations of counties
- Tiles do not cross state boundaries or state plane projection zones.
There are two exceptions though - Washington state and Colorado.
In both cases state plane zones are not consistent with county boundaries.
In these cases the county boundaries are respected
- Tiles generally respect MPO boundaries
- Tiles are projected in feet in their state plane zone with the NAD83 datum
- The projection field contains the state plane zone name
- Tiles are named as follows: State Abbreviation_State Plane Zone_Tile Number.
For example: FL_E_3, or Florida East Zone Tile 3
- In States with only one zone (such as Vermont) the name of the tile is:
VT_1_1, which is Vermont, Zone One (unstated in state plane zone definition), Tile 1
- Within state plane zones, tiled are numbered from 1 to n, in the North -> South
and/or West -> East direction
Canada
- The tiles are aggregations of regional municipalities
- Tiles do not cross Provincial boundaries or regional municipality boundaries
- Tiles generally respect city boundaries
- Tiles are projected in meters in the East -> West central-most North UTM zone with the NAD83 datum
- The projection column field contains the UTM zone number
- Tiles are named as follows: Province Abbreviation_Tile Number. For example: ON_1, or Ontario Tile 1
- Within Provinces, tiled are numbered from 1 to n, in the North -> South and/or West -> East direction
Weight Points
Each tile has a "weight" corresponding to the number of links and the population of that area.
The number of weight points (WP) per VISUM license is calculated as follows:
- VISUM Base - 3 WP
- VISUM Medium - 5 WP
- VISUM Large - 8 WP
- VISUM XL - 10 WP
Multiple licence discounts are also applied to WPs. For example. a customer licences VISUM Medium
+ 4 extra licences. The resulting WPs is calculated as 5 + (5 * 65% * 4) = 18 WPs.
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