Tracing buildings from OS OpenData Stree View for Openstreetmap

First, it needs to be said. Automatic tracing and dumping data into Openstreetmap is not a good idea. This page is something I have been playing with as an aid to manual edits.

This is a simple summary of the steps I used. If you need more information, then you probably should not be doing this.

Source Data

Grab some data for the area of interest from Ordnance Survey.

The Gimp

Find the tile required and open in The Gimp. The following steps should isolate the buildings.

• Select by colour, threshold set to 26, pick the centre of a building, avoiding the antialiased edges.
• Sharpen selection.
• Fill whole selection with black
• Invert Selection
• Fill whole selection with white.
• Save image in bmp format.

Potrace

Make sure that you have the latest potrace that does geojson. With the required tif image from the OS data, run to following command:
potrace -b geojson -L XXXXXX -B YYYYYY -O 1 -a 0 tile.bmp
Replace XXXXXX and YYYYYY with the appropriate offsets for the tile being worked on. The required data is in the package downloaded from OS.

Quantum GIS

• Create a new project with CRS OSGB 1936 / British National Grid. EPSG:27700.
• Load a new vector layer, select the json file from potrace and make sure the CRS is as above. Make sure that the scale is making sense. It would be possible to load another layer of known good data as a check. Be sure to allow on the fly CRS transforms if the data you check against is not OSGB 1936.
• Save the layer as a shapefile. Use the same CRS as the layer for the shapefile.

JOSM

The shapefile can now be loaded into JOSM. The polygons should line up well with the OS OpenData StreetView background images. However, there will still be a lot of manual cleaning up required. Extra nodes need to be deleted and squaring up done.

I am not sure if this actually makes much improvement over simply clicking over the background imagery by hand. Maybe someone else can improve this process a bit more. This is really written as a reminder to myself incase I come back to this later.

All this is done with free software. The initial idea came from the openstreetmap wiki. There is also a python program that can do this called Mapseg, but it is not very fast on my little computer.

Ubuntu Touch pre-Alpha on Nexus 10

First Boot

Curiosity got the better of me. Having seen a few YouTube demos of the new Ubuntu touch interface on the phone, I was excited to learn that the developer preview was going to be released for the Nexus 10. Not that I am a developer though.

First thing I needed to do was decide that there was nothing on my tablet that I needed. Once I was happy about that, I went ahead and followed the instructions. The only problem I had was after unlocking the boot-loader  the tablet would not boot up. It was stuck at the boot animation. As I needed to be in Android to complete the next step, I had to reinstall Android first.

After that little hiccup, it all went fine. Then I was presented with the image above.

There is still allot that does not work. Most of what does work, works well. There are many rough edges, and a few little quirks that no doubt will be adjusted over the next few months. The one thing that did strike me was the lack of a back button. That was probably the most unintuitive aspect to the interface.

It seemed that allot of what was working were internet apps. Gmail, Maps, Twitter, Facebook etc. And they all thought they were running on an iPad.

So far it seems like a good effort. Not sure I fully grasp the point though. It seems to be trying to do what Android does, but differently. What I was hoping for was something more like the Ubuntu Desktop. For that I would need at least a terminal, ssh, vim, LaTeX, apt-get etc. If proper user access control is implemented, that could be a real advantage.

In the meantime, I will be running Android on my tablet, as I only have the one. It would be nice to have a spare that I could keep on Ubuntu so that the development can be tracked. In a few months time, it may be worth trying again.

It is going to be interesting to see where this goes.

Openstreetmap Zoom

I have played around with this before. Having recently set up Mapnik again to render Openstreetmap data. Currently it is using the standard Openstreetmap osm.xml file so should look like the mad used on the main website.

This animation is created by rendering each frame with Mapnik. The script is based on a hack of the standard generate_image.py script that comes with Mapnik. It simply loops, and for each loop a new bounds is calculated to provide the zoom effect.

A seperate script is used that adds the watermarks in the bottom corners of each frame. This was done with the help of ImageMagick. Finally, avconv was used to convert the frames into an mp4 file.

The next step is to make an animation based on a GPX file. That will take a GPX file as input and provide a zooming animation that shows the start, and an overview of the whole GPX track.

Garmin Vista HCx

Some time ago, I purchased a Garmin etrex Vista HCx. Certainly not the most sophisticated GPS system available, but still good fun. It works well in the car, the pocket and on the bike. The only real downside was that the maps that come with it are fairly limited, and it would work out expensive to purchase all the maps I may want to use with it.

That said, it still works very well for recording tracks. When I first had the device, Openstreetmap was still fairly incomplete in my area, so it was good fun uploading GPX traces to help add detail to the map.

Eventually, I found out how to create a map from the Openstreetmap data that can be loaded into the Garmin etrex Vista HCX device. It requires a number of steps, but these are easy in Linux.

Grab the data

The data that is used to build the Openstreetmap map is freely available. There are a number sources for the data, but it would not be normal to want the entire world database. The people at Geofabrik provide a usefull service where they maintain a selection of extracts. Please remember this is provided as a service, so be kind to their servers. The extract I get is the one for Great Britain.

wget http://download.geofabrik.de/openstreetmap/europe/great_britain.osm.pbf

Get the tools

A number of tools are required to process the data to make it useful for the Garmin. Following is a list of tools that I have found work for me.

Splitter

Used to split the map into manageable pieces.

Mkgmap

Converts the OSM data into format suitable for Garmin device

Use the tools

These tools can be used as follows. This is not a definitive guide. Best refer to the relevant sites for the tools, but this is how I am using the commands.

splitter

java -Xmx1536m -jar splitter.jar \
   --max-nodes=1000000 \
   --mapid=63240001 \
   great_britain.osm.pbf

This will generate a series of files from the input.

mkgmap

CMD="java -Xmx1024m -jar mkgmap.jar \
   --route --remove-short-arcs \
   --add-pois-to-areas --index \
   --location-autofill=bounds \
   --generate-sea"
for f in 6324*.osm.pbf
do
    echo $f
    $CMD $f
done

After this is run, we should have a number of .img files. At this point, it may be possible to use these tiles with the Garmin map tool for the PC. But why bother. Let us just bundle these all up into one large file.

java -Xmx1024m -jar mkgmap.jar \
   --gmapsupp --family-id=50 --product-id=1 63*.img

This should result in a single map file named gmapsupp.img. All we need to do now is copy this to the Garmin directory on the SD card used by the Etrex Vista HCx.

Results

Windows 7 use NTP when in domain

Having recently had to reload windows, one of the little things to irritate me was the clock being wrong. It would seem logical that any computer with a reliable web connection should have the correct time. Well the default situation for Windows 7, when in a domain is to not allow the user to select a NTP server to sync with. Sensibly, it will sync with the domain controller.

Unfortunately our domain controller does not have the correct time. So my clock was wrong, and there was no 'point and click' way to fix it.

After some searching around a solution was found.

• Click 'Start' and type cmd in the search box
• Right click cmd.exe in the results, and select 'Run as administrator'
• At the command prompt, run the following:

c:\>w32tm /config /update /manualpeerlist:"uk.pool.ntp.org" /syncfromflags:manual
c:\>net stop w32time
c:\>net start w32time

It would be good to change the URL in the first command to a suitable pool from this list based on your location.

Windows 8 Preview

The hard drive failed on my computer. Just went phut! No warning or anything. So that required a new hard disk. With a new blank disk in the machine, it seemed like an ideal opportunity to give Windows 8  preview a spin, before putting the system back.
The install was painless. Probably as it is not released yet, there was not the endless list of updates required with an older version of Windows.
The first impression is it feels a little mixed up. The new Metro interface looks clean and works well, but feels out of place on a desktop machine with a large monitor. If the screen was touch enabled, or it was a tablet, then great, but on a desktop, not so sure. Behind that, there is the more familiar windows interface, but without a Start button. This feels more natural for a desktop, but again, elements from the Metro interface pop up when the mouse hits a corner.
Maybe it still needs some polish, and the final release version will be more coherent. One thing is for sure, it will get noticed. Some are going to love it, but there will be lots of noise from those that hate it.
The big thing that struck me was how it compares with my recent experience with Linux. For some time now I have been using Ubuntu. The Unity interface for Ubuntu at first felt like a simplified interface for small screens. Once familiar with it, it works very well, but in a different way to the sort of desktops we are used to. With Windows 8, it feels like they are hedging their bets, and using two styles of interface.
Whatever the design goal is, and the direction it takes, it does feel like Windows is now following Linux. That was the weirdest thing about my experience of the Windows 8 preview.

Alternative Window Managers

For sometime I have been using Ubuntu, and been very happy with it. More recently I have started to be less satisfied. Not sure why. Since upgrading to 12.04 things have not been so good. It is probably about time that the machine was installed fresh as that last happened at 10.04.

Before doing something that drastic, I decided to have a look at some alternative Window Managers. This is what I found.