Homemade gps plot of London

One of the limitations of www.gpsvisualizer.com is that it has an upper limit on the filesize of the raw GPS traces of 3mb. The log of treks across London reached this data limit at the start of last week, and whilst there were some measures I could take to reduce the size, it was unsatisfying and a better solution was required.

Using my bare ninja skillz I wrote a script in perl that processed the raw gps data from a txt file and then generated a png image file from scratch.

perl script
Larger version of map
AllTraces file

Writing the script myself allowed me to more finely control what was being plotted. One of the first things I added to the plot was a grid. This was simply done by creating a txt file with the coordinates and then drawing them as lines rather than points.
grid file

As well as gps traces of my walking routes across London I'm also tracking routes that I travelled on public transport and by car. These are plotted in red.
vehicle log file

One of the problems I've encountered and not satisfactorily addressed is that the gps coordinates are latitude and longitude, which because the world isn't flat, don't have a consistent aspect ratio. As you go further north from the equator the latitude ought to get closer together. This is why the grid squares are rectangular. If I lived in sunnier climes they would be more square.

As I'm mostly wandering round one city on the surface of the earth I can approximate a fixed aspect ratio. Although I could really do with getting my head round a better formula, something to do with the radians and the cosines.

London Walking GPS Trace

At weekends, odd days off work and occasionally in the evenings, I have spent the past three years wandering and running round London.

London walks 2011 to 2013

To make this trace image I use an Android app called Endomondo to track my position and speed when I'm out strolling, and to log my fitness stats online. From the Endomondo website I can download the GPS traces of individual routes as GPX files.

Then I use a website called GPSVisualizer to merge all my GPX files into a single plain text .txt file, this format keeps the filesize small. Then I can use GPSVisualizer to create the trace image from the txt file. This big image which is essentially my walking map of London.

GPSVisualizer limits the image size to 4000pix in its smallest dimension, and the input GPS files are limited to 3 megabytes.

To the north has me following the River Lea to Waltham Abbey and the M25. To the west is my old place of work, Merit House on Edgware Road, Colindale, and in the south west of the map is my current place of work, in Harlesden, reached by way of the Grand Union Canal.

At the bottom of the map you will probably recognise the shape of the Thames. The big cross like structure in the middle of the map is Dalston junction.

Pretty neat, huh?

30Km walk to Rough Trade

My 2013 exercise regime has now taken me on a 30 km walk.

I wandered up my usual route up to Tottenham Hale, then a Veronica Falls song came on my ipod, so I figured I ought to walk down to Rough Trade in Brick Lane and get the new album, so I strolled down the A10 through Stoke Newington and Hoxton.

It got there in good time, almost persuaded myself to buy a Korg Monotron, but chickened out.

On the way back I went via Victoria Park then back up the River Lea by the Olympic park. There was a dead fox floating. When I went to get a photo, two swans swam up and started showing off, so I ran away.

So 30 km (18.6 miles) in 4:54:20