Below is a map of reported "rodent activity" in Boston from the Mayor's Hotline. This is Maptime Boston, so obviously we're going to make a #ratmap for this example. Points (e.g., the locations of restaurants).Generally these data will be displayed as vector features, in contrast to the raster base map. Sometimes base tiles are all you need, but usually your web map will show some specific data besides general reference features. As we'll see later, other types of layers are added in a very similar manner. Just pile on additional layers the same way as the first one. The map above adds MAPC's bike lane layer, which looks like vector data but is actually made up of PNG images with transparency. Sometimes maps use multiple tile layers at once. Used the addTo() method to add this tile layer to the map we just created.These options prevent the user from zooming beyond that range and seeing a blank map. Some tile sets such as this one only cover a certain zoom range. Attribution text to appear in the corner.is a template that Leaflet uses to find tiles at the correct zoom, x, and y coordinates. In this case we're using MAPC's basemap, but there are many options out there. Used L.tileLayer() to create a base layer of map tiles, specifying a URL template for the tile images.Used the setView() method to center the initial map view on Boston (latitude 42.35, longitude -71.08, and zoom level 13).Used L.map() to initialize the map object, passing it the id of the div where we want the map to go.Let's focus on the code in that tag near the end. Want to follow along? Download this starter file. Var map = L.map('map').setView(, 13) Īttribution: 'Tiles by MAPC, Data by MassGIS', A short script to create the map in that.A height style specified for the map div.The simple map above requires only a few things: View this example on its own Let's make a map! Easy ways of doing this include running Python's SimpleHTTPServer in your map directory, installing MAMP (for Mac), or installing WampServer (for Windows). If you want to follow along on your own computer, your maps will need be on a local web server.For thorough documentation, see the Leaflet site. Click the "View this example on its own" link underneath a map to see complete code. Many code blocks show only a snippet of code, highlighting the changes over previous examples. It won't explain every little object or array, but will contain plenty of links. It assumes a basic knowledge of HTML and JavaScript, or at the very least assumes the will to tinker with the code to better understand what it does-and how to use it for your own work. ![]() How this tutorial works: It's structured around examples that progressively build upon one another, starting from scratch and ending with slightly advanced techniques. If you need total freedom of form, interaction, transitions, and map projections, consider working with something like D3. Leaflet is also not GIS, although it can be combined with tools like CartoDB for GIS-like capabilities. ![]() ![]() What Leaflet does not do: Provide any data for you! Leaflet is a framework for showing and interacting with map data, but it's up to you to provide that data, including a basemap. See Anatomy of a Web Map for an introduction to the most common kinds of web maps, which is what Leaflet is good for. It will also work well across most types of devices. It handles various basic tasks like converting data to map layers and mouse interactions, and it's easy to extend with plugins. What Leaflet does: "Slippy" maps with tiled base layers, panning and zooming, and feature layers that you supply. Leaflet is developed by Vladimir Agafonkin (currently of MapBox) and other contributors. It's lightweight, simple, and flexible, and is probably the most popular open-source mapping library at the moment. Leaflet is an open-source JavaScript library for interactive web maps. It was written by Andy Woodruff, Ryan Mullins and Cristen Jones for Maptime Boston, but you don't need to be with us to follow along. Don't worry it's easy! This is an introduction to web maps using Leaflet.
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