The BBC is conducting a major survey into the state of mobile phone coverage in the UK. Over the course of the next month, the project will attempt to chart the availability of 3G and 2G services up and down the country.
Mobile operators offer their own coverage maps but no independent survey has yet been carried out.
Measurements will be made using an app developed by network analysis firm Epitiro. The software can be downloaded by anyone with an Android handset and will record street level coverage across Britain.
There is no iPhone app at present, because of the difficulty in making Apple devices collect such information in the background while other programmes are running.
At the end of the test period, the BBC aims to display the results on a clickable map.