Hi John,
Atlas is
- Handy for visual navigation, as maps show terrain and airport locations
- A good reference for data: VOR frequencies, NDB frequencies, airport elevations, waypoint locations
It merges two major datasets: scenery and navigational data. However I wouldn't call it a flight planner: it doesn't allow you to choose points and the corresponding headings.
It is really a separate program from flightgear. I launch both flightgear and Atlas, and tell Atlas to synchronize its position with that of flightgear. This is done by telling flightgear to output its position to some internet socket (e.g. start fgfs with --nmea=socket,out,2,localhost,5504,udp ); and tell Atlas to get its position from this socket (e.g. start Atlas with --udp=5504).
There are typically other options that need to be specified on the command line, but not knowing about Macs or your setup, I can't comment.
If you remain within the Bay area, that is all you need to know. But venturing further afield you may encounter (what I consider to be) bigger challenges. These are to do with downloading new scenery - a chore whenever flying somewhere for the first time. There are three rather obscure steps needed before FlightGear and Atlas will show scenery outside the Bay area. Unless you go through the following process, anywhere away from the Bay Area will look like a bleak salt-plain or else water.
First, the extra scenery needs to be downloaded. As of FlightGear 2.6 this can be done by enabling downloading via the Environment -> Automatic Scenery Download dialog. (Before 2.6, another program 'terrasync' needed to be called explicitly.) The dialog shows the progress of each download. 'Scenery' refers to topography, landcover, buildings, and other structures. This is needed by both the flight simulator program and the Atlas program.
Second the new scenery has to be processed to generate map images. This is done with a program called 'Map'.
Thirdly, you need to restart both fgfs and Atlas before the new scenery is visible.
Hope this explains what Atlas can and can't do.
Chris