> How do they know where my SSID is? Is my phone sharing that info with them? Did they grab it with Street View cars?

It's crowdsourced from android devices (apple does the same with iOS devices). AFAIK google also grabs it with street view cars.

>Is their advertising now using the SSIDs I pass by to track me even when I explicitly turn off GPS?

>If I turn off location history in Google, does this prevent that information being shared with others in the ad industry chain?

Yes, but AFAIK on android grabbing SSIDs require the "location" permission for this exact reason.

>Do I need to track all them down and find how to opt out of them having a database of my frequent locations?

That's on them, not google.

> How do they know where my SSID is? Is my phone sharing that info with them?

Yes if you have it turned on and you're signed into Google.

> Is their advertising now using the SSIDs I pass by to track me even when I explicitly turn off GPS?

Turning off GPS stops GPS, not SSID tracking. Modern Android doesn't have a GPS toggle though. It has a "Location" toggle which stops the OS from sending the data to Google. However it does not turn off the location feature in Google Chrome (or other web browsers).

> If I turn off location history in Google, does this prevent that information being shared with others in the ad industry chain?

Google doesn't share their data with 3rd parties.

> Do I need to track all them down and find how to opt out of them having a database of my frequent locations?

No.

> Google doesn't share their data with 3rd parties.

I used to work for one of those third parties, here's google's public docs detailing how they provide that information: https://developers.google.com/authorized-buyers/rtb/realtime... (note: "geo", "geo_criteria_id", "postal_code", etc.)

>If I turn off location history in Google, does this prevent that information being shared with others in the ad industry chain?

I don't know. But in countries without strong privacy laws the carrier can sell something similar as triangulated by the cell network.

https://www.zdnet.com/article/us-cell-carriers-selling-acces...