locar-tiler is a tiled download system for geodata, particularly useful for augmented reality applications.

Introduction

In many geographically-aware applications, including (but not limited to) location-based augmented reality applications, it is useful to be able to download new data as we move around and then store it on the device for later use.

locar-tiler's approach is to download data by tiles. It works out which tile corresponds to your current latitude and longitude, and then downloads all data for that tile. The tiling system is the Spherical Mercator-based system used by many web maps, such as Google Maps or OpenStreetMap (see OGC). Each tile has an x (west-east), y (north-south) and z (zoom) coordinate.

This tiling system is normally used for rendered 2D maps but can also be used for pure data tiles. locar-tiler uses it, with a default zoom level of 13 (though this can be changed).

Consequently locar-tiler needs to be provided with a server URL which accepts x, y and z parameters and serves data fro that tile.

Note that locar-tiler does not include any mechanism to cache the tiled data - this is up to the developer to do. It merely downloads the tiled data when needed (i.e. the user moves into a new area) and holds it in memory so the data for that tile isn't downloaded if the user revisits that tile in the same session.

API Documentation

Available on GitHub Pages.

Based on

locar-tiler is based on jsfreemaplib, converted to TypeScript and with some API changes made. As author of jsfreemaplib I have re-licensed locar-tiler under the MIT License to be consistent with other AR.js code.