Thank you all for your helpful links and information. Two follow-up questions:
1) Is the following statement accurate: "The aircraft GPS only finds locations such as my RTH location at launch and the compass helps the aircraft navigate to that GPS location"?
2) The last few times I have launched my aircraft, before receiving this helpful hints, I calibrated my compass since I launched from several different locations. After calibration, or maybe it occurred during calibration, I received a notice on my DJI GO app that asked me to turn off my GPS since it had identified magnetic/electronic fields or sources nearby. I was launching from a rural park in which there were no cell towers, buildings, telephone/electric power lines, etc nearby. The only magnetic or electronic sources nearby that I could identify were my iPhone attached to my controller and the gold crucifix I was wearing around my neck. In response to this nag notice, I held the aircraft at arm's length away from my body while calibrating and the warning message disappeared and the GPS icon on the DJI Go app indicated I was ready for flight. In light of the horror stories I have read on this forum concerning crashes, fly-a-ways, and loss of control what was the significance of the process described above and what could have been causing the warning message? Thanks again to all of you who have provided suggestions.