If you are using apps for weather, news or local information ( finding petrol station or ATM) the data is available to anyone willing to pay a price and then analyse your daily habits, over days, accurate location recorded as frequently as every 15-20 minutes providing a detailed snapshot of everything you do.
If you think this is fiction, read this report in The New York Times researched and written by Jennifer Valentino-DeVries, Natasha Singer, Michael H. Keller and Aaron Krolik . Times reviewed data from 2017 was held by one company and it ..”reveals people’s travels in startling detail, accurate to within a few years and in some cases updated more than 14,000 times a day.”
Connecting the dots with available information, though claimed to be anonymized , can pinpoint a person, doctors she sees and the person she spent the night with. Data examined by Times, showed phones potentially belonging to school going children and traceable to nearby homes.
The app companies sell raw data or derivatives to advertisers making up the $21 Bn industry delivering location specific advertisements.
So next time you think your location usage is private matter, think again.