According to BIA/Kelsey, location data will be used in upwards of $38bn of mobile ad spend in the US this year, but unfortunately for marketers paying to reach consumers in specific locations, the evidence suggests that much of the location data being used in location-based ad targeting is not only inaccurate but totally fraudulent.

Somewhere between 30% to 80% of location data used is believed by experts to be illegitimate and if this belief is accurate, this means that marketers are spending potentially tens of billions of dollars on ads that don't have the characteristics they're paying for.

Needless to say, this is a huge problem and it's only likely to get worse as location data becomes more important. For example, with cookie tracking dying a slow death, alternative ways of measuring digital marketing activities will become more prominent and some of these, such as geo-testing, rely on the use of location-based ad targeting.

So what can marketers do? Here are six ways they can fight the scourge of bad location data in the digital ad ecosystem.