This is a super interesting paper that uses mobile phone locational data to assess the use levels of informal trails in parks and protected areas. As far as I've been able to find, this is the first paper to incorporate this data into its methods and as such is incredibly relevant to my study, which also aims to use phone data to approximate use levels. My mentor and I have reached out to Ms. Spernbauer with questions, and her knowledge have been very helpful when designing our own study.