Hello again. Thank you for clarifying.
I'm sorry to say that I do not have good news for you.
First, the employer absolutely has the right to track you via GPS if you're using a company car. It has the right to track wherever you take that car at any time (not just during working hours). Second, the grocery store owns the video, and has the right to release that video to anybody it chooses, including your employer or even the evening news. Accordingly, your privacy rights were not violated.
I am truly sorry that my answer is bad news, but please understand that it would be unfair to you (and unprofessional of me) to provide you with anything less than an honest response. However, if your concerns were not satisfactorily addressed, then please let me know, and I will be happy to clarify my answer.
Also, despite the bad news, I would certainly appreciate it if you remember to provide a positive rating via the stars, as it is the only way that I'll get credit for answering your question(s). Thank you. :)