When using the D7 with the Avmap, you need to have "waypoints" enabled, as described on page 5 of the Extended Operaitions manual for the D7(g), excerpted here:
When APRS data is received with a GPS receiver connected, included position data is sent to the receiver, using the NMEA-0183 $GPWPL format (or Magellan format). This data is registered in the Waypoint List of the receiver. Access Menu 2–3 (WAYPOINT) and select the number of characters to be input. You can select 6 to 9 digits for NMEA, 6 digits for Magellan, DGPS, or OFF (default) . With NMEA 6 digits selected, the right 6 characters of the call sign is used as a name (ex. for KJ6HC-3, J6HC-3).
Unfortunately, the $GPWPL statement doesn't really have all the info the AvMAP needs to show nice data: it will give you position and the ID (if you're a geek, Glenn Baddeley has an excellent breakdown of GPS sentences, including GPWPL, here:http://home.mira.net/~gnb/gps/nmea.html#gpwpl
Because the GPWPL statement is weak, the Avmap will show the position of the contacts picked up by the D7A as red triangles with a dot in them. The Identifier in the WPGPL sentence is the callsign of the sending station, so you'll eventually get a map covered in little red triangles.
To really get the full glory of the AvMap GPS, you need a source of the "proprietary" $PKWDWPL sentences. Fortunately, if you're really hardcore, this is available for the D7 radios too, here:http://www.kh-gps.de/codeconv.htm
Or, you can just do what I did and break open my piggy bank and buy the D710, which Just Works with the AvMap.