OpenStreetMap
I’ve been having a great time recently using Osmium to write my own analysis code in C++ to look for anomalies in the PBF extracts. Today it found this very strange coastline in South Africa:
Perhaps, i thought, this is some rare geological formation, that makes an amazing wavy line? So let’s look at the data over aerial:
The recent #MissingMaps project added to the Tasking Manager is a great way to work together on specific places!
However, some of the maps are sadly neglected. The “high priority” HOT places (like for ebola and cyclones) get a lot of contributors. But, other #MissingMaps have little work.
For example, #793 - Missing Maps: Bukavu, Democratic Republic of Congo was added 5 days ago and nobody contributed at all. I have begun, but it’s kinda lonely. Come join me! The imagery is good, the infrastructure is easy to see, and the DRC has tons of unmapped detail. Come join the fun and MAP THE PLANET!
Some recent work i’m proud of:
Fixed the tags (and in some cases the boundaries) of all of Ethiopia’s national parks, including Gambella, Bale Mountains, Awash, etc. I even added the Alatish National Park which was entirely missing.
Nearby on the Ethiopia/Sudan border, improved the area where they are building the Grand Ethiopian Renaissance Dam on the Blue Nile.
In Ethiopia’s Afar province, added the newly-built Tendaho Irrigation Dam with its huge reservoir.
In Sudan, improved the massive Khashm el-Girba Reservoir and nearby city of Al-Qadarif which needed lots of work.
A large number of waterways in the wild eastern parts of Nicaragua (like here) and Honduras (around here), although sadly most of the streams aren’t visible until zoom level 13.
Just now, a complex relation for the Las Trampas Regional Wilderness, near San Ramon, CA, USA
User interfaces are very much a matter of taste, so with the caveat that this is all really subjective…
In any graphical program, I find that I am most fast and fluid when I have my left hand on the keyboard (e.g. on ASDF) and my right on a mouse. It’s best if all the key combinations I need are easily pressed with my left hand. If i have to move my left hand away, or take my right off the mouse, everything slows down.
So, with JOSM. The first thing I do is open the Preferences, under Keyboard Shortcuts and re-map Delete from the Delete key to ‘D’. Now, for shortcuts for all the other common tags (highway=service, building=yes…), it’s not simple, but it’s possible. JOSM lets you map keys to presets, but those presets still open a dialog (extra steps). To program my own shortcuts, I dug into the scripting plugin (Javascript API). It’s very nice, well-supported (thank you “Gubear”!) and I’ve only begun to explore what it can do.
Here is my script (install_custom_menus.js)
To use it, first enable the Scripting plugin in JOSM’s plugin preferences. (You’ll need the very latest JOSM, 6891 or later, and up-to-date plugins). Now, from the Scripting menu, open the “console”, load the js file, and run it. If it works, you will then see 4 new items on your “Edit” menu.
You can now use Preferences: Keyboard Shortcuts to map keys onto them. I use:
With only basic familiarity with Javascript, you can easily modify the script to add your own commands, and then maps keys to them. You will need to run the script once, each time you restart JOSM, to add the menu items, but the shortcuts are persistent so you only need to set them once.
The first Scout-Telenav 30-day OSM Mapping Challenge just ended. Let me share some of the story.
When it was announce February 11, I was excited. At that time I was already an “addicted mapper”, and fairly sure of my fast-accurate JOSM editing skills, so I figured I could win it. The challenge was for the USA. I usually trace Bing in remote parts of the world, but I did know of a lot of roads in Hawaii that could be quickly cleaned up, so I figured that would give me a quick start.
My Hawaii edits did produce a good number of points, but experienced Canadian mapper ingalls was in the lead! He was cleaning Tiger in Texas at an impressive rate. I was slowly catching up, but he remained ahead.
Suddenly, when ingalls and I were both at ~30k points, he stopped mapping. I breathed a sigh of relief and took the lead. I found myself doing too many steps in JOSM while editing, and started wondering if I could set up keyboard shortcuts that would let me go faster…
Just when I seemed safely in the lead, a user ada_s appeared in the rankings and rapidly went up to second place. All their edits had the same comment, “Add address information + split way when exiting the city border” That seemed like an odd thing to do, but it sure racked a lot of points. I struggled to find enough time to stay ahead (I do have a full-time job and girlfriend) and ada_s continued to gain. At this point, my exploration of the JOSM scripting engine produced some results - I was able to create a lot of single-key shortcuts (like Shift+S, set highway=service) that let me go faster (more about those scripts in my next diary entry). I was working faster now, but ada_s was still gaining on me.
I’ve now spent a LOT of time using JOSM, and it is one of the best applications i have ever used, of any kind. With left hand on the keyboard, right on the mouse, you can do quality editing with great speed and accuracy. Advice for newbies: Install the “utilsplugin2” right now, then “buildings_tools” for buildings, and “FastDraw” for streams and ponds.
Eventually, though, you find yourself doing a lot of the same steps over again. One thing JOSM does NOT have is a “macro” ability to record and play back commands. It does, however, have a scripting plugin! (Thank you “Gubaer”, author of the plugin!) I have just begun to work with its Javascript API, which has decent docs but very few examples. I will give some examples here in my diary of of scripts i’ve written, in case they are useful!
As a first example, renaming streets. The JOSM validator will warn you about abbreviated English street names (“Main St”) but it won’t automatically fix them for you. I wrote a script which does that. Just install the scripting plugin, open the scripting console, paste in this script and press “Run”.
Note that this not a shining example of great code, just a rough script. As an exercise for the reader, you could extend it to also handle “Blvd” for “Boulevard”.
I was mapping in rural Darfur today and discovered an entire city which was completely unknown/unmapped. It did not appear in Google, Bing, OSM or anywhere else, not even as a village dot. It’s 90 km SSE of Nyala, Sudan (latlon: 11.28, 25.14, i.e. osm.org/#map=14/11.28/25.14) with an airstrip, two large markets, and large street grid. I’ve mapped it now, anyone care to find a name for the city?
In order to keep my road follower in the middle of the road, I tried switching from an incremental similarity (compare each point to the next) to absolute (compare each point to the starting point). Since the starting point is given in the middle of road, it happily follows the road center, until this happens:
With incremental similarity, we were largely immune to disruptions along the side of the road, because we came upon them gradually. Now, a large shadow is sufficiently unlike our starting point that it scares the algorithm into swerving away from the shadow and running off the road. (I can sympathize with the algorithm. I did the same thing in a car once :-)
So, it just solves one problem, and exposes another.
I also tried the idea of, each step, taking a cross-section and look for symmetry to find where the “middle” of the road is. It didn’t work; the RGB is just too noisy to find a clear center of symmetry.
By reducing the step size, I can actually get my naive road-follower to do a better-than-expected job of following curves:
I’m guessing that this is because roads are more self-similar than what surrounds them, so looking for linear self-similarity stays on the road.
What it does NOT do, however, is find the middle of the road. Look closely and you’ll see that the path drifts over to one edge of the road and stay there, then wanders back again.
My naive thought was, many roads are clear and self-similar, how hard could it be to write an algorithm which simply walks along a step at a time, moving in the direction which is most similar to the previous spot in the image?
It turns out the catch is in “similar”. There are apparently countless academic papers on how to evaluate when two images are “similar”. I naively went ahead and tried a dumb algorithm: the summed difference of the RGB values.
Amazingly, it actually works in a lot of cases. Behold:
The first two points are given, the rest moving downward follow the road based on naive image similarly. Now, it’s not hard to find cases where it fails and drifts off the road - in particular it struggles if the road gets a few pixels wider, as many do - but this is just a first test.
After so many hours manually tracing roads, one naturally begins to wonder if there’s some software for automatically detecting them. Google turns up only a research project, the “Microsoft Road Detect” at http://magicshop.cloudapp.net/
There’s some discussion among OSM people about whether this would be a good thing or not. I think the point’s moot because it doesn’t work.
First thing I tried was the JOSM experimental plugin “MagicShop”; it hadn’t been touched in 2 years which is a bad sign. Current JOSM refused to accept the jar, not a huge surprise.
I’d consider it worthwhile to fix the plugin if it would give useful results, so I went directly to magicshop.cloudapp.net and gave it some test coordinates: a nice clear straight section of road in India I happened to be tracing recently.
And this is what it did:
Yeah. Well, maybe I could write my own algorithm/plugin.
It seems I have two OSM accounts, one with >800 edits, one with 70 edits: osm.org/user/bdiscoe osm.org/user/Ben%20Discoe But regardless of which one use to log into OSM.org, it takes me to the second URL. Baffling. If only there was a way to merge them…