Big

First things first: What is Maptime all about?

A time for learning about maps
Hands-on
Beginner-focused
Emphasis on open source, programming and web-mapping

Stolen from Lyzi Diamond

There are Maptime resources all over

Our mission is to open the doors of cartographic possibility to anyone interested

Maptime exists because community, inclusivity, and accessibility are important components of positive learning experiences.

First of all: A web map is a map that lives on the web.

Even an embedded image in a page is a web map. (But download this PDF does not a web map make.)

But when we think of web maps, we think about interactivity. We think about...

We want interactivity. We want people to engage with our web maps.

But let's step back and talk about how web maps work.

These slides are adapted from awesome presentations by Lyzi Diamond, Alan McConchie, and Beth Schechter of Maptime fame!

Lyzi also wrote a great blog post that explains more about this stuff.

Raster tiles, anyway. Vector tiles some other time.

"... web maps are made up of many small, square images called tiles."

"These tiles are typically 256x256 pixels and are placed side-by-side in order to create the illusion of a very large seamless image."

All these little tiles load way faster than one big map.

This kind of map is colloquially called a slippy map.

With each additional zoom level, the number of tiles increases exponentially.

Map tiles only render when you're looking at them in that moment, so tiles make maps hella fast.

As you can see, map tiles are static images on the web.

Cool. But what does this have to do with Leaflet?

These tiles need to live somewhere on the web page. They need to know when to load and they need to react when you click or drag.

Leaflet is a JavaScript library that allows us to do just that.

Think of leaflet as one part of a web map's anatomy.

Including JavaScript libraries in our code is like copying and pasting someone else's code into yours.

You have access to everything in that library. In our case, it's a bunch of cool tools to make web maps and give them familiar functionality.

(You can read more about Leaflet at leafletjs.com.)

TECHNOLOGY BREAK
If you don't already have a text editor on your computer, let's get you set up.

I will be using Sublime Text, which should work great on any operating system. Head to that link and install the proper version.

If you are using a work computer and don't have install rights, that's okay!

Notepad on Windows or TextEdit on Mac will work fine for today.

If you're on Linux, you've probably already got this figured out.

Once you've got your text editor situation sorted, head to this URL, which is a bit of HTML to get you started.

Copy and paste the contents into your text editor and save it as somthing like map.html.

The first awesome thing we can do with Leaflet is make ourselves a map container.

var map = L.map('leaflet-map');

The

'leaflet-map'

in that tag refers to the div on the page where the map is going to live.

But it's empty. We haven't added any tiles. Let's do that.

There are many free tilesets on the web. Let's use some from Stamen.

var map = L.map('leaflet-map').
setView([41.8947, -87.6105], 13);

L.tileLayer('http://{s}.tile.stamen.com/watercolor/{z}/{x}/{y}.jpg').
addTo(map);

We added some tiles, centered the map on The Loop, and gave it a zoom level.

As Stephanie May would point out, what we have here is a reference map.

A very pretty reference map with no labels, but a reference map nonetheless.

What if we want to show some data on the map? Maybe this building we're sitting in.

L.marker([41.885100, -87.621699]).addTo(map);

We added a map marker at the lat/lon of the hotel to the map.

Last part. Let's add a popup to the marker so when we click on it it'll tell us what it's identifying.

L.marker([41.885100, -87.621699])
.bindPopup("Maptime!").addTo(map);

We binded a popup to the marker that says Maptime!.

You can do this on your own! Go forth and make web maps!

Remember: You're a champion! Keep going! You can do it!

The tutorial in the previous slide will guide you through the process and the data here will make your rat map Chicago-specific.

My name is Dan! I am on Twitter at @danswick! Please come talk to me! I like talking to people!