I got a question about pinpointing devices on one WiFi network. Let's say for example I sit at my home and I bought that big beefy WiFi antena and use it to connect to local cafe 100m down the street. And let's say someone is looking for me, when they track my location will my address or the address of local cafe show up ?
If somebody is looking for you, he could find out your public IP address (by for example sending you a link to a web page on a server that he hosts, or even a known public forum post with an embedded image that is hosting on his server). In your case that IP address is actually the IP of your Cafe. That would bring him close to you, but too close you.
Your computer has just a private IP address assigned by the Cafe to which you connect, but that IP address would not tell anything about your location.
But based on the strength of the WiFi signal that is being sent from your computer, it would be possible to identify your location, in case someone has the right tools and has identified your appriximate location or the locatinf of the Cafe to which you connect.
I assume that you do not share your GPS data of course.
If you would use TOR, it would be much harder to find you or the IP of the Cafe you are connecting to.
If you were to use a directional antenna then an attacker would need to be located close enough to the directional signal in order to physically locate you. Even then, they would only get the direction. By moving upstream, they would be able to see the signal strength increase - maybe - there are quite a few variables involved including your height above street level and how many residences there are in the locality.
An attacker would, of course, know that you are within signal reach of the cafe assuming they could track your IP address back to that particular spot. Something that would normally be possible, at least to a national-level organisation with government ties.
Without significant investment in time and manpower, they would only know your IP address and maybe some other information leaked from your PC depending on what you are doing online.
Some of the info that would be leaked from your PC is the MAC address that would potentially identify the network card you are using and maybe the PC. Also browser parameters that again may reveal the PC type in use.
As the previous replies has pointed out, your public IP would be traceable to the cafe, without any issues. Beyond that the network administrator could probably trace your more exact location with help of the access point(s), because most access points today have the ability to register in which direction a connected client is and the approximate distance to said client.
However, there are a few more unique identifiers on your machine, like your mac-address, and if you're very unlucky, the net-bios name of your PC gets registered as well outside of the cafe network. There are ways to use a website to "spoof" the net-bios name, OS version, web browser and etc, of any connected client. But the net-bios name (and other info) is really only as traceable in this situation as your mac-address, so I wouldn't worry too much about it.
This does give someone the opportunity to trace your movements over time, by cross-referencing your mac-address and net-bios name. If another client appears, let's say at your home network with said network's public IP, with the same net-bios name and mac-address, one can assume it's most likely you. Thus you can technically be traced around if someone is interested in you.