What is gs-loc.apple.com?
Yep, it’s Location Services. The location is updated on a regular interval, or when an app requests it.

I worked it out while using Little Snitch, just like you. As there was a loc in the domain name, I figured it would be Location Services. 

To confirm, I turned off Location Services, and sure enough, locationd shut down and no connections to gs-loc were made. To confirm again, I blocked gs-loc, and Location Services stopped working.

From: discussions.apple.com


  Locationd is a daemon that provides location services for OS X's "Core Location". This uses skyhook technology to figure out your mac's location (using WiFi). It's the same system used by the iPod Touch, and is also used by the iPhone (The iPhone also uses cell tower triangulation and GPS)