Binders Full Of TIGER Deserts


The U.S. has binders full of TIGER deserts.

Let me explain. Back in 2007, we imported TIGER/Line data from the U.S. Census into OpenStreetMap. TIGER/Line was and is pretty crappy geodata, never meant to make pretty maps with, let alone do frivolous things like routing. But we did it anyway, because it gave us more or less complete base data for the U.S. to work with. And so we worked. And worked and worked. Fixing spaghetti highways. Reclassifying and arguing about reclassifying. Connecting and disconnecting. And now, four years and change later, we have pretty maps!

Eat that, TIGER! (check it out)

But we don’t all live in Epcot Center (actually, I don’t think any of us do really) and there’s lots of places where we haven’t been taking as good care of the data. Vast expanses of U.S. territory where the majority of the data in OSM is still TIGER as it was imported all those years ago.

The TIGER deserts.

I want those all to go away, but there’s only so many folks mapping here in the U.S., so we may want to prioritize a little bit. So I wanted to look at the TIGER desert phenomenon a little closer. In particular, I wanted to look a the parts of TIGER deserts that cover towns, and even cities. That’s where people actually do live, and that’s where OSM data is most valuable.

So I set out to identify those the only way I know how: using ArcGIS. The thing is: this kind of job has ‘raster analysis’ plastered all over it, and I just don’t know how to do that using FOSS4G tools. So maybe I’ll just explain what I did in ArcGIS, and then you all can chime in with smart comments about how to do this in PostGIS, R, GRASS, QGIS or whatever free software can do this magic. If you don’t care for all that, just scroll to the bottom for the results.

I created a shapefile first with all OSM highways with TIGER tags in Florida using C++ and osmium. (There’s some good example code to get you started if you’re interested.)

Then, with that loaded into ArcMap, I first created a 5km grid with the predominant (in terms of way length) version number as the cell value.

A second grid for the neighborhood way density:

I reclassified the version grid generously – all cells with 1 or 2 a the predominant TIGER way version got true / 1, the rest false / 0. For distinguishing between built-up and boondock cells, a threshold of 1.8 looked good after some tweaking.

And finally some simple map algebra to combine the two variables into the final result grid:

So there we are folks – TIGER deserts and TIGER ghost towns in Florida:

TIGER deserts in Florida

TIGER ghost towns in Florida

Hmm. I hope we can figure out a way to improve this analysis so the situation does not look quite so bleak. GIS does not lie though – these are the 5km cells that have a reasonably high way density and TIGER way versions that are predominantly 1 or 2.

So let me know folks – 1) Is this a good approach for identifying TIGER ghost towns and if not, what is? and 2) how do you do this using FOSS4G tools?

Un-Zorro-Tron – The 90 Second Video


Folks tell me that the Un-Zorro-Tron is less intuitive than its predecessor the Remap-A-Tron. So here is a 90 second video that shows you what a Zorro way is and what to do about them.

UN-ZORRO-TRON 90 sec instructions from rhodes on Vimeo.

If you don’t have 90 seconds, here’s a 60 second video:

If you don’t have 60 seconds, a picture may tell you more than 1,000 words:

Remap-A-Tron SOTM US Talk Slides


Here are my slides from my Remap-A-Tron talk at the amazing State Of The Map US conference from which I just returned. Without any context this is going to make very little sense, but for those of you who have seen Pulp Fiction more than a couple of times, it may still be worth a few minutes of your time. I will follow up with a more insightful post about this and SOTM soon.

The OpenStreetMap US Chapter – My Outlook For Next Year


It’s been almost a year since I was elected board member to the OpenStreetMap US Chapter. That means the next elections are just around the corner – actually, they are happening this weekend at State Of The Map US. If you’re a Chapter Member, vote! If not, it’s not too late to join.

I decided to run for re-election, and I want to take a moment to briefly reflect on the past year of serving on the board, as well as give my personal outlook for next year.

Reflection

My first year in the US community, and on the US Chapter Board, taught me a few important lessons. First, the US is a big place and for that reason, ‘community’ has a different meaning here than in the Netherlands where I come from. If you want to focus on things like ‘community support’ and ‘community development’, you need to define those things very differently here. More on that later.

Another important lesson I draw from my first year is that big plans are OK, but they need to be broken down into baby steps. The average board member doesn’t have a huge amount of time to invest, and as a result we don’t have the manpower to implement Big Things ourselves.

Finally, I feel that serving on the Chapter board comes without much of the public scrutiny and political constraints that the Foundation board has to deal with. I don’t know how I feel about this – on the one hand, it gives you more freedom to set your own agenda as a board, while on the other hand our mandate as a Chapter board is so flimsy (I was elected with something like a dozen votes) that it makes you think twice about what having a local Chapter actually means.

Outlook – My Manifesto

My most important personal objective in serving on the Chapter board was and remains supporting and growing the community, but I want to redefine that objective based on what I feel ‘community’ means here in the US. I am a strong believer in local communities that meet face to face, know each other, and get together and talk mapping over beers or coffee or shakes. I think there is far too little of that going on in the US, but I think the role of the Chapter Board in growing and building these local communities can only be fairly limited. You need active local mappers to build and sustain them, and we cannot conjure those up out of thin air. What we can do as a board is make these local communities more visible and give them a platform to present themselves and communicate. I want that platform to be our national web site: openstreetmap.us

The other dimension that defines us as the U.S. OpenStreetMap community is the map itself. We all strive to make it better, and this binds us together. I want to work actively to leverage the map, our data that we work together to improve and enhance, as a binding element for our community. The way to do that is to give the community projects to work on. That sounds mundane, but I want to take it beyond a ‘project of the week’. Taking inspiration from the Remap-a-tron that I built and ran, I want to provide the community with tools to work on specific problems. For example, the Remap-a-tron can be repurposed to work on things like connectivity errors, spaghetti ways, and TIGER deserts. I want openstreetmap.us to be the platform to organize these projects and report on their results. If you’re looking for something to map, head over to the web site!

In short, I want to transform openstreetmap.us into much more of a destination for mappers, both hardcore and casual. I want to be able to welcome new mappers by just saying: ‘hey, you want to start doing some useful mapping right away? Have a look at the web site!’.

Are we going to pull this off in the next  year? I don’t know, really. I would love to be able to say that we would, but I can’t even be sure of how much time I will be able to invest in it. There will also be State Of The Map US 2013 to organize, something I want to see happen as well. What I will commit to is investing at least 10 hours a month of my time on working towards these goals, and I believe this is a commitment that every candidate should be prepared to make for the board as a whole to be successful.

Google Maps and OpenStreetMap Data Views – Find The 10 Differences


Google Maps had The Atlantic over for a chat about how they work up their ‘deep map’ from various sources. It’s interesting to read about how Google invests incredible amounts of money and manpower to try and do the best job possible of capturing ground truth without people on the ground.

The article contains some ‘data views’ of Google Maps data in various stages of being worked up. I don’t know if it’s actual screenshots of an editing environment, but regardless, it’s an interesting peek behind the scenes that I had not had before.

This is from the article:

The Google Maps editing environment. Source: The Atlantic

This is about the same area loaded into the OpenStreetMap desktop editor JOSM:

The same area in the OpenStreetMap editor JOSM

Now you can look long and hard to try and make out ten or maybe a hundred differences in the data, but there’s one difference between these two views that reaches much deeper. The data behind Google Maps you will never get to see, let alone touch. The data in OpenStreetMap on the other hand is there for anyone to download, use, make great products out of and, most importantly, edit and improve. That difference marks a cardinal characteristic of the Google Maps platform that the article failed to raise. Consider that itch scratched.

Post-Redaction Repair Tools: Maps and the Remap-A-Tron


Although the OpenStreetMap data license change from CC-BY-SA to ODbL is not formally done, the redaction bot has done its thing. It was activated in mid-July after rigorous testing and months of development to go over the entire planet, square degree by square degree, and delete any tainted node, way and relation or revert it to a untainted state. (An object is tainted, simply put, when it was at some point edited by a contributor who did not agree to the license change and the new contributor terms.)

OpenStreetMap Redaction bot progress map screenshot taken on July 17th as the bot was just progressing to Switzerland and re-running London.

Although less than 1% of all data was removed in the redaction process, some areas are much more strongly affected than others, depending on the amount and previous activitiy of local ‘decliners’ as well as pre-emptive remapping of tainted features. This was made possible by tools that identified potentially tainted objects, such as Simon Poole’s Cleanmap and a JOSM plugin. (These tools have since been discontinued.)

Looking at the situation in the US, what we’re left with after the license change redaction is a map that has issues. Well, let’s say it has more issues now than it had before the redaction. Just looking at the street network, which is the one single most important dimension of OpenStreetMap if you ask me, we don’t have to look very hard to find missing  street segments, entire missing streets, and messy geometry. We had messy geometry before, because of the inherent messiness of TIGER/Line data off of which the US road network is based, but the redaction process left us with some really, ehm, interesting spaghetti in places.

Messy way geometries as a result of the redaction, near Los Angeles, CA.

Missing way segment as a result of the redaction, north of Honolulu, HI

And then there’s the invisible results of the redaction: lost attributes such as speed limits, lane count, direction of flow – but I would suggest we fix the road geometries and topological integrity of the main road network first, so the OpenStreetMap data is routable and the routes make sense. In order to do that effectively, the community needs tools. Fortunately, we have some available already. There’s Toby Murray’s map showing suspicious way segments last touched by the redaction bot. Kai Krueger provided a routing grid page that calculates route times and distances between major US cities, and compares those to reference data to expose potential routing issues. And there’s also the venerable OSM Inspector tool that provides a layer showing objects affected by the redaction process.

I also took a stab at a small set of tools that I hope will be helpful in identifying the remaining issues in the road network for the US: a Redacted / Deleted Ways map, and the Remap-A-Tron.

Redacted / Deleted Ways Map

Not unlike the redaction layer in OSM Inspector, this map duo exposes features affected by the redaction process, with a few notable differences. The main difference is that it has a clear focus on the US road network data. The Redacted Ways Map differentiates between Motorway, Trunk, Primary, Secondary and lower class roads, in an attempt to make it easier for remappers to seek out and prioritize the more important roads.

The Redacted Ways Map showing different road classes in appropriate coloring for easy prioritization of remapping efforts

The Deleted Ways map complements the Redacted Ways map. It only shows the way segments that were completely obliterated by the redaction bot. The focus on the road network means that only ways with a highway tag are visualized here.

The Deleted Ways map differentiates between ways that are likely to already have been remapped, and those that still need to be remapped.

If you look at this map, you will notice that there are two different classes of deleted ways, displaued in red and green respectively. The difference is in remapping status. The red ways are probably not remapped yet, while the green ways are likely to have been remapped already. I make this distinction by periodically comparing the deleted way geometries with newly mapped way geometries in the database. Using the Hausdorff distance algorithm as the main component, I devised an algorithm that reasonably accurately predicts whether a way has already been remapped.

Remap-A-Tron

I came up with another way to leverage the knowledge of remappedness of the OpenStreetMap street network. Building on an idea I already had semi-developed a while ago, I built a web application that serves up one deleted way geometry overlaid onto a current OpenStreetMap basemap. Using a simple menu or handy keyboard shortcuts, you can flag the segment as already remapped, skip it for whatever reason, or load that area into JOSM or Potlatch right away to remap it.

The Remap-A-Tron serves up one non-remapped important way segment at a time for remappers to work on.

The data backend is refreshed every (US) night, so there should not be too much of a lag. Currently, the app serves up only non-remapped important segments: motorways down to tertiary class roads. There are about 1900 segments in this category as of the time of writing. If a handful of people spend an evening with the Remap-A-Tron, this should be down to zero in a matter of days. Once we complete the repairs on the important roads, I can tweak the app to include all other highways (~15K segments not remapped) and ultimately all ways (~52K segments not remapped).

I built this tool with versatility in mind. After the street remapping is done, it could easily be repurposed to identify other issues in OSM that are identifiable on the Mapnik map: self-intersecting ways, road connectivity issues, missing bridge tags, maybe even missing traffic lights? I would love to hear your ideas.

If this turns out to be useful and used, I will try and increase the coverage to the entire world. For that to happen, the Remap-A-Tron will need to find a home that is not the server next to my desk, though..

Happy remapping!

Life After Redaction: Detecting Remapped Ways


There are some pretty awesome tools out there to help with the remapping effort after the redaction bot made its sweep across the OpenStreetMap database. (Does this sound like Latin to you? Read up on the license change and the redaction process here.) Geofabrik’s OSM Inspektor shows all the objects affected by the redaction. It is likely the most comprehensive view of the result of the license change redaction. Numerous other tools are listed on the Remapping wiki page. Most of these tools will show you, in some shape or form, the effects of the redaction process: which nodes, ways and relations have been deleted or reverted to a previous, ‘ODbL Clean’ version of the object.

I want to see if we can take it a step further and determine whether an object has already been remapped. This is useful for monitoring remapping progress as well as determining where to focus efforts when you want to contribute to the remapping effort.

For now, I am going to stick with ways. I think maintaining, or reinstating, a good quality routable road network is an important objective for OSM anyway, and especially at this point in time, when many roads are broken due to redaction.

Let’s start by locating a deleted way here in the US using my own Redaction Affected / Deleted Ways Map. That’s easy enough around severely affected Austin, TX:

 

I am going to use three comparison parameters to determine whether this way is likely to already have been remapped:

  1. The Hausdorff distance between the deleted geometry and any new geometries in that area
  2. The highway type of the deleted and any new geometries in that area
  3. The length of the deleted and any new geometries in that area

For this to work, I will need a table with all the ways deleted by the redaction bot. This is easy enough to compile by looking at the changesets created by the redaction account, but Frederik Ramm was kind enough to send the list of OSM IDs to me, so all I had to do is extract the deleted ways by ID from a pre-redaction database. The comparison can then be run on that table and a ways table from a current planet:

 

It is immediately clear that this way is very likely already remapped if we look at the top candidate, with object ID 172171755. It has a very small Hausdorff distance compared to the deleted way 30760760, it is tagged with the same highway= type, and the lengths are almost identical.

Sure enough, when fire up JOSM and load this area, it is clear that this area has been remapped:

 

(Selected objects are version 1 and created after July 18, 2012).

I need to do some more testing and tweaking on the query, but I will soon integrate this in the Redaction Affected / Deleted Ways Map.