The US Air Force Space Command has said that garbled information transmitted by its global positioning system (GPS) satellites was the result of a software error.

Reuters reported on 22 March that the bug was related to ground-based software used to sort (i.e index) messages transmitted by GPS satellites. Space Command spokesman Andy Roake said that the error appeared to have gone unnoticed since 2013, but that it had not degraded the accuracy of the GPS signals received by users.

The report suggested that the contractor responsible for the software was Lockheed Martin Corp. A Lockheed spokesperson said that the company had put a “workaround” in place to prevent further errors and was working with the US Air Force on a full software update.

Lockheed’s competitor Boeing, the prime contractor for the GPS satellites, did not comment on the issue. The ninth Boeing-built GPS satellite is due to be launched on 25 March, the first of three to be launched this year.

In total, there are currently 30 satellites orbiting earth in the American GPS constellation, but many have surpassed their operational lifespan. Lockheed is developing the next generation of satellites. It claims that these will deliver signals three times more accurate that current GPS spacecraft (up to eight time for military users) and much better connectivity for civilian users.

The US will hope this keeps its GPS abilities ahead of the competition. The People’s Republic of China is rapidly rolling out its own GPS system, BeiDou, while Russia continues to invest in its GLONASS equivalent.