As long suspected by consumers, 3G coverage in the UK has turned to be less impressive than the claims made for it by mobile operators, an independent survey sponsored by the BBC has found.

The BBC launched the effort in July using an Android app developed by consultant Epitiro, which was downloaded by nearly 45,000 smartphone users who used it to check on coverage levels in their locality.

With 1.7 million hours of data now in from 42 million locations around the country, the first coverage map shows that 3G is available roughly 75 percent of the time, somewhat less than the 90 percent confidently predicted by UK networks.

When 3G coverage stalls, users are forced back on to much slower 2G connections.

Although urban coverage is generally good and rural coverage considerably less so, unexpected local not-spots are common enough that consumers need to run a postcode check to work out whether they will be affected by signal issues.

Even in central London, the occasional not-spot was found on the coverage map where 3G data connections gave way to 2G.

"We're not making huge claims for our mobile map - it is after all just a snapshot - but it may provide consumers and the mobile networks themselves with a better picture of the real state of coverage," said BBC journalist Rory Cellan-Jones, who travelled from London to Cardiff by train to test the varying coverage sugegsted by the survey.

A separate map coverage project run by OpenSignalMaps has gathered it own data and found 3G to be available for 58 percent of locations tested. The coverage levels are drawn from fewer users that the BBC - around 30,000 - but are broken down by network, which provides some interesting variations in coverage for different locations.

The days of adequate 3G coverage being a luxury are drawing to a close because Smartphones depend on these connections to function according to their advertised abilities. Anyone regularly sent back to 2G to make a data connection on a smartphone is probably wasting their money buying into the technology.

The BBC Android 'UK 3G Survey' crowdsourcing app can be downloaded from the Google Market but it is not advised for anyone running an under-powered smartphone. Techworld found that this software bogged down anything other than a recent or high-end model running above 600MHz.

The BBC initiative is starting to give consumers some idea of 3G coverage one thing important measurement missing from its tests is throughput. Getting a signal is only half the battle; getting usable bandwidth could be a bigger and still hidden issue.

OpenSignalMaps (also available on Google's Market) does measure throughput and so far the average was found to be a respectable 1.65Mbit/s download, albeit with a mediocre latency of 282 milliseconds.