Friday, 20 March 2009

Building super fast, super portable mobile maps - Part One

I've spend the last couple of weeks building mapping into one of my projects. It is something I've resisted in the past as being too complicated, too difficult and not offering a lot of value. However, my client wants a location based messaging solution, so maps we're a must have.

My client (who shall remain nameless for now) said that it was easy. His previous partners had done it really quickly; just mash-up Google Maps. The problem is that this is a very web-oriented view of development. Whilst GM are easy to mash-up in a web environment, they aren't licenced for mobile application development. Their API is also Javascript-based, so I wasn't going to be able to use that either.

So the next stop is just to hack it. I found that many people have done this in the past. You just need to know how Google Maps for Mobile (GMM) converts co-ordinates into map tiles, and you can build URLs to get the correct tiles. I also discovered that everyone who had done this had quickly received 'cease-and-desist' letters from Google's lawyers.

So what are the alternatives? Yahoo! Maps are as rigidly licenced as Googles. Microsoft are much more relaxed about accessing their geodata, but they only make tiles for the web.

The issue here is the size of the tile. Let's assume for the sake of argument that the normal size of a mobile screen is 240x320 pixels. The tiles used on the websites are 256x256 pixels, which means that one tile will cover almost the whole screen. If you've only got a 128x128 screen, then you've got something which is way to big, giving the developer the additional headache of working out which bit of this tile needs to be on screen. The main problem here is that this is one download which means a big delay between hitting the button on the phone and seeing the map. GMM has mobile-friendly map tiles sized at 64x64 pixels. This means that I can convert my location to a single 64x64 tile, and centre my screen around this.

So a quick bit of research later brought me to the OpenStreetMaps initiative. This is crowd-sourced geo-data. You go out with your GPS and send data about all the streets in your neighbourhood. This becomes 'open sourced' data. Digging a bit more lead me to CloudMade, the extension of OSM to convert their raw data into useable map tiles.

CloudMade have fantastic support for mobile. Not only do they do their tiles in 256x256 and 64x64 pixel tiles, but they also do their mobile tiles with high-contrast colour schemes. Now they are extending this, so anyone can create custom cartography with their style editor.

Better news seemed to be that Jaak Laineste has developed a J2ME component from his compay Nutiteq. This wraps up all the functionality you need to make your own GMM-clone with maps from CloudMade. This would be a massive short-cut, except that I'm not writing in J2ME; I developing in MoSync.


The number one problem with mobile development is that every damn phone is a little bit different. The purpose of Java is that you write your code once, and it will run in an identical fashion on a different platform. The problem with this is that it has never quite been true, and for the Java you've got on your phone, this problem is magnified by a thousand times.

The problem is that you've got one body specifiying the language, and dozens of bodies implementing it. Just as no two people will interpret a book in the same way, no two implementers make J2ME work in exactly the same way.

The upshot of this is that even when you've got your J2ME application working on your phone, there is no guarantee that it will run on anyone else's. Or a Windows Mobile device, or in an S60 environment.

The guys at Mobile Sorcery have taken this pain away. They've written their own API which they've tested on the handsets. The difference with this approach is that it is one body who is managing implementation, massively improving compatibility. You write (or port) your code in C/C++ against their API, and it will build your application for hundreds of phones. Each of your target handsets gets a build specifically for it. On J2ME phones, it builds a J2ME application. On Windows Mobile devices, it builds a Windows application. On S60 devices it builds a Symbian application.


Still, even without being able to use Nutiteq's mapping component, I've got a supplier of map tiles.

Part Two >>>

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