QuadTiles. QuadTiles are a geo-data storage/indexing strategy - it's more commonly referred to as hierarchical binning. The idea is to store a geo-database such that data for a specific location can be retrieved quickly, by dividing the data up by location, partitioning the world into tiles. Note that we use the word tiles a lot in OpenStreetMap, and in fact we're normally talking about tiled map images, that's not really what this page is about although a QuadTile data indexing scheme has some similarities with Slippy map tilenames. Splitting the world into tiles If we split the world into 4 tiles, (level 1 of zoom) then we would need 2 bits to give a tile address (topleft, topright, bottomleft, bottomright). Each of those tiles would be about 20,000km in size. This is obviously too big to be practical, so we would need to split it into smaller tiles. Tile size tradeoffs The smaller tiles that you have, the more bits are required to address them.
Quadtile implementation And again: Tilespace users. Modest Maps. OpenLayerer. Aust-NZ Info Page. Giorgio.clavelli at gmail.com, Giorgio Clavelli membership configuration for Aust-NZ. SettingZoomLevels – OpenLayers. The OpenLayers Map is designed to display each of its layers at different levels of Scale or Resolution. The map object refers to these levels as ZoomLevels, and allows each layer to define its own ZoomLevels as it sees fit. To configure the ZoomLevels of any OpenLayers Layer, the user sets various properties in the options array on initialization. Normal Layers ¶ For normal layers which are based off of OpenLayers.Layer and are able to display at any resolution, there exist a multitude of different ways to configure the ZoomLevels and their respective scales and resolutions.
Resolutions Array: To translate ZoomLevels into Resolution, a resolutions array is populated, which is a list of the different supported resolutions for the layer. Example: If the layer's resolution is [a,b,c], then ZoomLevel 0 is a, ZoomLevel 1 is b, and so on. Ways to Configure the Resolutions Array ¶ Available Options: Example Declarations: Obviously all of the configuration options listed above can not be set at once.