A reasonable compass app, but use with great care!!
The good things:
You can get Compass readings, National Grid coordinates, and altitude. One of the more interesting features is the excellent tutorial on Navigation (Help with map reading)..
The compass needs calibration from time to time. The app does not tell you when - many other apps tell you when the accuracy degrades. There are no instructions on how to do this. So here is the answer - you twist your phone in a number of eight fashion a few times, then tilt it back and forth, then twist it left and right.
I have been trying to work out why the live compass has a camera on when the Silva compass is showing - Answer: You can orient your map (align it with North) if you place the map under your phone. Again no instructions on this. The altitude is out as well - my location is 92m on the OS maps but the app tells me I am at 141. Thats quite an error. Its not too difficult for the OS to look at their map since they know my location and tell me what my altitude is...
I have included the app because of the excellent Navigation tutorial - again would it not be good if the links worked in the document...