At the heart of the system is the process by which the location data is used to deliver or create artwork. As outlined above in Aesthetics One, the system will make a correspondence between a geographic coordinate and a file name. Thus a database will hold details of a file (its name and other unique qualities such as date created), plus a geographic coordinate or coordinates with which it is ‘tagged’. The objective is to connect this ‘tag’ to the coordinate returned for the user.

All of the mobile networks and aggregators will return a standard Ordnance Survey X,Y grid reference, and so we have used this as the basis for all of our calculations. World Geodetic data (WSG 84) is available but would add a level of complexity to the data processing that we though inappropriate at this stage of the project. In order to be useful to artists, the system needs to be able to use location data to do three things:

• Record the location of a mobile user - very simple. We record the grid reference returned by the location request in a database.
• Return a list of artworks within distance x from the mobile user - Step One diagram. To achieve this, we run a search on the database to return all artwork which is within n squares of the user. This is a fast but not accurate, could be up to ~40% out if user and art work are at opposite corners of the square. In effect it is a pre-processing stage, quickly reducing the data set to enable the next, algorithm to work effectively.
• Find the nearest artwork to the mobile user - Stage Two diagram. This is done by using Pythagoras’ theorem (which states that for a right-angle triangle with short sides of length a and b and long side of length c, a²+b²=c²). A and B are calculated by subtracting the X and Y co-ordinates of the user’s location from the X and Y co- ordinates of the artworks’ location (which is stored in the database), and the distance C is calculated from these values. This is processor intensive.

Step One

• In example above, to find artwork within approx. 10km, select pieces where X is between 2 & 5, and Y is between 1 & 4.

Step Two

• Art works returned in Step One are processed individually.
• Use Pythagoras' theorem to find distances - a²+b²=c²
• In the diagram, A is 12.1km away, B is 11.7km away.