Cross-Country Soaring 2004
User Guide 
10. Using Scenery Lift
Scenery lift is lift produced by a Flight Simulator scenery file (BGL extension). There are various third-party sources of free scenery lift and programs to create scenery lift. The primary distinction between scenery lift and Cross-Country Soaring (CCS) lift is that scenery lift is typically stationary (fixed position) and eternal (except thermal lift, which will at least wax and wane with the time of day). With or without scenery lift, CCS can create dynamic thermals, slope lift, and sink throughout your flight. You may, however, use CCS in conjunction with scenery lift (e.g., to add wave lift downwind of a mountain).
CCS is as likely to place lift or sink in scenery lift as anywhere else. The cooperation of CCS and scenery lift/sink is dependent on the Enable Scenery (BGL) Lift/Sink setting in the CCS Control Panel. The following describes the behavior given the chosen setting. CCS defaults to the “disabled” setting. Note that this setting only affects the overlap of CCS and BGL lift/sink. Setting this to “disabled” only disables BGL lift/sink when it and CCS lift/sink overlap. Where there is no overlap, any BGL lift/sink present will always be enabled. To fully disable BGL lift/sink, remove the BGL files from your FS scenery library.
Enabled: CCS will use any scenery (BGL) lift in a cumulative fashion with CCS lift/sink. For example, 20 fpm CCS widespread sink will cause a 20 fpm reduction in climb rate in a scenery (BGL) lift area. CCS lift/sink modeling is slightly more “choppy” with scenery lift enabled, so enable it only when needed.
Disabled: CCS lift/sink will override scenery (BGL) lift. For example, if you’re flying in scenery slope (ridge) lift giving you a climb rate of 200 fpm and you enter a CCS thermal, you will quit climbing and will quickly go to a still air sink rate. You will then experience the CCS thermal as if no scenery lift were present, flying through sink, then lift, then sink. Once out of the CCS thermal, if you’re still in the scenery lift, your climb rate will jump quickly back to 200 fpm. In reality, the effect of a thermal existing in an area of ridge lift would be more additive (thermal lift plus ridge lift) than exclusive (only thermal lift, no ridge lift). In the previous example, if widespread sink were enabled, you would never experience the scenery ridge lift at all, as the widespread sink would override the scenery lift.