Discussing how to control the Internet and the big data companies like Google, Amazon and Facebook is import. https://d3-media.blogspot.com/2018/07/take-back-control-over-internet.html However finding out what these companies know about you is an other question. This is about YOUR data and thus on a personal level. I found out that it is pretty scary how much Google for examples knows about the details of my whereabouts.
First I downloaded my Google data using Take Out: https://takeout.google.com/settings/takeout. Unzipped the file was 363 GB. To show the amount of detail and to produce an interesting visualization I took out the location history file, 273 MB. The file is in JSON. There is in interesting site that visualize your location history in a heat map - https://locationhistoryvisualizer.com/heatmap/ , and by zooming in you get much details.
Last year I worked for a month at Cape Town, the three pictures below zoom in step by step, and in the end I can find the restaurant at Bree Straat where I had lunch last year. This time traveling.
NOW it is time to scrutinize all my data at Google and Facebook!