Does Ping need cellular service to transmit my location?
Yes. Ping uses four different cell networks to attempt to transmit the location of its device. GPS is only used to obtain the location of the device, not as a method of transmitting data. If you do not have cell coverage in an area, Ping will continue to try to connect on a regular basis for up to 24 hours to transmit its location or receive any requests for its location.
Please note, roaming in and out of cell coverage can definitely impact the battery life. The battery will still last longer than more other devices, but there will be some impact.