maplate :: a demonstration and skeleton project for today's common opensource mapping client libraries
In a simple HTML file, link to leaflet.js and associated libraries wax.leaflet and cartodb.leaflet. This will allow us to display map tiles (show a map in the browser) from various tile servers and also draw arbitrary points and shapes on the map based on geo data stored in a geospatial db (like cartodb).
Tile Server - This is a host computer that holds the map tiles that make up the map you want to render. Various organizations host tile servers like Stamen, OSM, MapQuest, MapBox, etc..
leaflet.js - javascript library that renders map tiles from a tile server in the browser
wax.leaflet.js - javascript library from MapBox that essentially adds functionality to leaflet so that MapBox tiles and Interactivity are available
cartodb.leaflet.js - javascript library from CartoDB that adds functionality to leaflet so that points and shapes from cartodb can be displayed on a leaflet rendered map
Tile URL - This is a scheme for communicating from the client to the tile server which tiles you want. The OSM standard is: http://[abc].tile.openstreetmap.org/zoom/x/y.png Several organizations use this format including Stamen and Mapnik This wiki page explains more details about the URL schemes and how tile servers work. Note that MapBox uses a different scheme, it looks like this: http://a.tiles.mapbox.com/v3/user.tilesetname.jsonp
The template.html file has javascript with 4 recipes. At the top of the file you can uncomment one function (recipe) at a time and refresh this template.html file in your browser to see how they look. Here is an explanation of each recipe:
Recipe 1: This function simply displays tiles from MapQuest using leafet. You can change the tile server url to show tiles from other places (make sure to give proper attribution!). For example, let's use Stamen's watercolor map tiles:
$ var baseUrl = 'http://{s}.tile.stamen.com/watercolor/{z}/{x}/{y}.jpg', $ attrib = 'Map tiles by Stamen Design, ' + $ 'under CC BY 3.0. ' + $ 'Data by OpenStreetMap, ' + $ 'under CC BY SA.'
Note: you can find the url for Stamen and other tile servers here at geocommons
This first recipe uses leaflet with the "typical" tileserver format. Typical in this case is really the Open Streetmap tile format with server/{z}/{x}/{y}.jpg. The z / x / y describe zoom, lat, and lon and are substituted out automatically for you by the leaflet library when you load the map, when you scroll around, and when you zoom. Basically, every time you manipulate the map, leaflet goes back to the tile server and requests new tiles based on the lat / lon you are viewing and the zoom level. Next, we'll look at an example using MapBox tiles.
Recipe 2: This uses wax to grab tiles from mapbox. The mechanics work similarly but, because mapbox does not use the exact same algorithm and url scheme for serving tiles, wax is used to handle tile interaction like mapbox likes and normailze it for leaflet so leaflet can work like it normally does.
Recipe 3: This is similar to Recipe 2, except now we are using wax to grab not just the basemap tiles but also transparent (except for points) tiles that overlay on top of the basemap - points on a map! This is interesting because we are not using leaflet to insert individual markers in the layer. The cartodb/wax stack is actually rendering speical tiles that live on top of our base map layer. We could theoretically show many thousands of points in just a few seconds because the the dots are coming as tiles (not individual geojson).
Recipe 4: This is just like Recipe 3, except that we are not using wax to load the base layer tiles - we are using leaflet instead. This let's us grab tiles from a non-mapbox tile server (like Stamen in this case).