When using the lowest data rate (SF12; for long distances to the nearest gateway, or for any moving node?), sending 6 bytes for two 24 bit coordinates would need 1.3 seconds air time. So the 1% duty cycle would already limit to sending one coordinate every 131.9 seconds, not every 15 seconds. And along with the 30 seconds/day Fair Access Policy one could, on average, send fewer than one GPS coordinate per hour on The Things Network.
However, location by triangulation also needs the node to send some data to trigger the calculation? Even an empty packet, only sending the 13 bytes LoRaWAN header, needs 1.16 seconds air time on SF12, hence at most 26 such packets a day?