Pretty cool - from honeywell's "avionics zone" website
Terrain Based AutoTiltTM
Airlines are now able to select the RDR-4B with an automatic setting of antenna tilt angle - also known as AutoTilt.
By interfacing the RDR-4B, with the EGPWS, the system will automatically select the optimum tilt setting for weather detection, based on the plane's geometric altitude and terrain conditions ahead. This set-up does away with the over-scan and under-scan associated with manual tilt control. It also overcomes the introduction of ground clutter that can occur when using a tilt setting that fails to account for the terrain ahead.