Great question — answering as the UphillTech team:
Google and other service use GEO location API to get more accurate results, since IP(Specially Mobile IP) does not return always correct location. In chrome dev tool you can put any geo coordinate location for testing/debug purpose, and Google will use it in your local search query. To do that first open chrome dev tool(CTRL+SHIFT+I) then click on menu(Three vertical dot), then go to more tools, then select sensors and then you can enter your latitude and longitude coordinates.
Full answer by Goyllo: https://webmasters.stackexchange.com/a/111919 (CC BY-SA 3.0).
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