Notes from Intro to OSM!

by Camille

I made my first edits to OSM a few weeks ago at our OSM 101 Maptime!  I’ve had an account since SOTM (June 2013), and while I’ve been actively evangelizing OSM to friends and family (e.g. telling my young cousins that there’s a new map ‘game’ where you can map your neighborhood, like Sim City), I hadn’t yet made any edits or contributed anything. There’s now been a cosmic shift. Watch out world, you’re going to get mapped.

Here, in note form, is some of what we learned (this a mashup of Beth’s notes and mine):

Save your edits!

A Tale of Two Editors:

  • iD - a new editor that runs in the browser. Easy to use, and full of features. The editor we were using.

  • JOSM - runs in Java, not JS. JOSM is editor of choice for ‘power-users’ because of the many plugins task oriented workflows that are optimized for JOSM (but do not exist yet for iD). For example, the Humanitarian Open Street Map Team Tasking Manager ( uses JOSM for sharing the grueling work of mapping disaster zones and other areas of humanitarian focus.

Best Practices:

  • When tracing buildings, trace the footprint of the building (where the building hits the ground), as opposed to the shape of the roof. Sometimes, the aerial imagery is a little tilted.

Copyright, Public Domain, and Licensing:

  • Since OSM uses an open license, and any data that is put into OSM falls under that license. If you do not hold the license to the data, or it’s not in the public domain, you shouldn’t add it to OSM!

  • Examples of off-limits copyrighted data: Google Map data, Bing Map data (their satellite imagery is OK)

  • The guaranteed way to go (as far as public domain and copyright) is to walk down a street with your editor open (mobile, anyone?) and add things you can see! Can you kick that cornerstone? Read that sign? You can add it.

  • Copyright Easter Eggs are a thing! Don’t even try!

    • E.g.: a Trap Street is fictitious entry on a map. If it appears on another map, then the mapmaker knows whether someone has copied data that they should not have.

Did you remember to save your edits?

Make a note!

  • Notes are on the map as the red points with white X’s

  • A note is a way to get things edited/added/deleted/noticed if you are unable to edit or feel like an expert is required. If this is the case, make a note!

What happens when you load a map?

  • Serving Tiles: The map tiles are ‘rendered,’ or compressed into .pngs when you are load a region within the bounding box in the browser. What is rendered is determined by the zoom level. Some objects are ‘thrown out’ at certain zoom levels for clarity’s sake. For example, minor streets may be tossed in favor of major roads and freeways at low zoom levels.

  • Rendering to raster: When you load a region, the map turns the data from vector to raster and compresses that data into .png files. In previously unviewed regions/zoom levels, this happens on the fly, however, popular locations may be pre-rendered and cached. The whole world at zoom level 10 is practically all pre-rendered, however, higher zoom levels may not be.

  • Seeing edits rendered: Beth noticed that when she added a building, she could see it at one zoom but not another. This is because the tile servers render at different times for different zooms sometimes.


Are your edits saved? Better be! :)

09.05.13 // Just back! + Glossary fill-in time

Tonight was the first night at Maptime after a 2-week break, following some Burning Man adventures (which involved no mapmaking, unless you count marking friends’ camps on a pre-made maps). We planned for it to be a chill one, which it delightfully was. Five new visitors showed up, and we all worked on Github entering new words and definitions for the ABCs of Cartography project

We also learned some fun new facts, including but not limited to:

Next week!

  • OSM 101! More cartographic term defining!
  • IMPORTANT! We’re moving to Wednesdays!
    …so that we can all go to more Geo meetups and any of the other things happening on Thursdays.

Want to help us define cartographic terms? Fill some out on Github, and don’t forget to save your work!

Maptime SF upcoming schedule!

Ahoy! If you haven’t already seen it on Twitter, then hear it here! Maptime SF is on break until Sept. 5, when we’ll reconvene and chack our progress on the ABCs glossary. After that, we’ll be starting up our workshops! Here’s the breakdown:

Sept. 5 - Glossary checkin. ALSO…do we like Thursdays? Let’s tawk :)

Sept. 12 - OSM 101

Sept. 19 - Leaflet tutorial walkthrough

Sept. 26 - CartoDB + Tilemill

October = making month! Pick some terms to illustrate and then let’s work on it together!

More soon…likely after Camille and I are back from the Burning Man. Cheers!

Thanks to everyone who came out last week for OSM’s Birthday!

It never ceases to amaze me how many people get excited about OSM! We had about 40 people show up to celebrate, so many that we ran out of seats!

Nevertheless, Alan (@mappingmashups) still managed to do an OSM 101 tutorial in Stamen’s conference room. Some people in there made their very first edits!

Outside of the conference room, well, it kind of turned into a big party. That’s cool, we can take a night off from learning for beers and a mapcake…

…or two…

Again, happy birthday OSM! And to sweet Stephanie (@mizmay), of Urban Mapping fame.

8.1.13: California Water Atlas workshop time

Tonight we tried a little something new – a participatory workshop by our friends working on the New California Water Atlas. The organizers, Chacha Sikes (@chachasikes) and Laci Videmsky (@videmsky), brought many maps of water in the state – including well location and groundwater – for the group to discuss and ask questions about.



After learning more about the project and the complexity of mapping water (coastlines shift, some water is underground, lots of it isn’t reported correctly if at all), we were asked to think of questions that we had about our water in California. Where is fracking happening? and Where is groundwater? were two of many questions that were asked during the course of the evening. All were documented on Post-It notes. Chach is the queen of the Post-its! (and also Sharpies).


Now documented, these questions have become part of Chach and Laci’s ongoing conversation with the public and policymakers, and they will inform the design in some way. Can’t wait to see what they make!

Another activity that happened during this MapTime was reviewing an in-progress project by Ryan Orban (@ryanorban) and Jonathan Dinu (@clearspandex). In their map (which I need a link to I realize…hmmm….) is all about mapping health department scores across San Francisco. Not only was it great to see their work (although kind of mortifying to realize that a score of 92 is the mean and that much of Chinatown is well below it) I also realized that feedback is an important part of the learning process, and therefore important to Maptime.  More of that in the months to come!

Celebrate OSM’s Birthday at MapTime!


This week, Open Street Map celebrates its 9th birthday, and we’ll be joining the festivities at MapTime with all kinds of OSM activities, including OSM 101 and the OSM #birthdaySprint! The studio will be set up so that people can either work on their #birthdaySprint projects or partake in learning and project sharing. 

Here’s the schedule for the evening:

6:30 Doors open, c’mon down! 
6:45 OSM 101
7:00 Project show and tell! Share what you’re working on and get feedback
7:30 Everybody work on OSM stuff! 
8:30 Wrap up

So come out and join the mapnerdery! Just be sure to sign up on Meetup

Things to come! …also more blog posts. Also! This Thursday we celebrate OSM’s birthday! More soon!

Things to come! …also more blog posts. Also! This Thursday we celebrate OSM’s birthday! More soon!