Archive for July, 2009

OSM and Tucson

I noticed that various cities and counties/states have pages in the OpenStreetMap (OSM) wiki, but Tucson didn’t. I’ve now fixed that with a page for Tucson that provides a list of projects with percentage of completion. I hope that will encourage people to contribute by giving them ideas of where to start.

Personal Open Street Map Goals

I’ve decided to write down my goals. These are long-term; if I can get them done in six months that would be great.

1. Large Scale Features

Adding national forests, parks and preserves, wilderness areas and the trails inside those areas for Arizona. I am perhaps 70% done with this goal. The benefit is vastly improved recreation maps for the six million people in the state. The area is huge (larger than the UK) and the total number of nodes is probably in the 100,000s.

2. Medium Scale Features

Adding key features in the city of Tucson. This includes major rivers and washes, large buildings such as hospitals, malls and big box stores, realigning primary and secondary roads. To date I have added at least one of each of these features. The benefit is a good overall map for the one million people who live in the Tucson area.

3. Small Scale Features

I plan to completely map in as much detail as possible the nine square miles or so around my home. This includes realigning all the streets, adding buildings which are not houses, adding recreation areas, ensuring all streets are named, etc. Of the three goals this is probably the most work. The number of people living in the area isn’t that much, but I intend this to be an example for future Tucson mappers.

A Wash in OSM

Adding Rivers To Open Street Map

Some rivers are small enough that they can be added with just a line. But how are wider rivers added? They are polygons that can stretch hundreds of miles. How do you stop and start editing or does the entire river somehow have to be added at once?

The answer is to use the tag waterway:riverbank and build the river up from polygons that are next to each other. This diagram shows:

Ways in a river

Seems simple enough. But what about bridges. The bridge:yes page explained. Just cut up the road and mark the section on the bridge with bridge:yes. The layer option was a bit ambiguous so to be sure I added layer:1 for the bridge.

So I tried added a section of the Pantano Wash in Tucson. After waiting 15 minutes or so the result was added to the map:

A Wash in OSM

Looking good. Now to add some more.

Open Street Map Tags

Finding out which tags to use when can be difficult. JOSM includes a presets menu that helps, but what is the difference between landuse:retail and landuse:commercial?

I had an idea of the difference but before using these tags for the first time I needed confirmation. After some digging I found the Map Features page in the OSM wiki. It confirmed my thoughts. Retail = shops, commercial = offices.

Summerhaven Before Mapping

Preparing to Map Summerhaven

The village of Summerhaven is in the Santa Catalina mountains just north of Tucson. The US Tiger data imported into Open Street Map is a mess, and needs to be fixed. Unfortunately the satellite images from Yahoo are not much help for that place.

At the weekend we plan to undertake our first mapping trip. This will involve driving around all the roads in the village with the GPS unit turned on and taking pictures of street signs and points of interest.

Back home JOSM can be used to load in the track log and match up the timestamps of the pictures with where the GPS unit was at the time. Hopefully that will give me all the data I need to rip out Summerhaven and draw it from scratch, but in the correct place and with more detail.

Here is a picture of what Summerhaven current looks like.

Summerhaven Before Mapping

Open Street Map

Open Street Map (OSM) is a world map that anyone can edit, just like a wiki. I used the data in a few projects but seeing as the US road system was generated from a mass import of US Government data, I thought that it was largely complete and not much to do. This was, of course, wrong.

Back in May I was in East Yorkshire, England and I added a trail to the map.  A local OSM mapper contacted me about it. When I got back to Tucson, Ariz. I was inspired to look more closely at the local data to see what was missing.

I found that most of the streets were not aligned correctly. Also the National Forests were missing, plus a nearby National Park. There is a lot to do in the US, that’s for sure.

I started off by realigning the streets in my area and completed four square miles. But what really interested me was the forests. A bonus is that US Government data is in the public domain and can be freely used for OSM.

I’ve now spent the last month, off and on, working on this. So far I have added all the National Forest boundaries in Arizona and New Mexico, some grasslands in New Mexico and Oklahoma and a Nature Preserve in New Mexico. I’ve also added Saguaro National Park East and the trails in the park. Currently I am working on adding the Wilderness Areas for Arizona and New Mexico and the forest trails.

I encourage you to take a look at the map in your area and see what you can do!