} = lists:keyfind(pitch_roll_heading, 1, GroupsNamed),
```
-Data format references
-----------------------
+Packet structure
+----------------
+```erlang
+<<"DATA", PacketIndex:8/integer, Groups/binary>>,
+<< GroupIndex:32/little-integer
+ , GroupValue1:32/little-float
+ , GroupValue2:32/little-float
+ , GroupValue3:32/little-float
+ , GroupValue4:32/little-float
+ , GroupValue5:32/little-float
+ , GroupValue6:32/little-float
+ , GroupValue7:32/little-float
+ , GroupValue8:32/little-float
+ , GroupsRest/binary
+>> = Groups,
+```
+
+Where `PacketIndex` indicates something like a schema version, i.e. what each
+of the numbered groups means. For example, in X-Plane 10, packet index is 64
+(character `"@"`) and group 3 contains speed data, in which the 8 group values
+are:
+
+| Location | Label | Description |
+|----------|---------------|-------------|
+| 1 | `vind_kias` | Velocity indicated, in knots indicated airspeed. |
+| 2 | `vind_keas` | Velocity indicated, in knots equivalent airspeed (the calibrated airspeed corrected for adiabatic compressible flow at the craft's current altitude). |
+| 3 | `vtrue_ktas` | Velocity true (the speed of the craft relative to undisturbed air), in knots true airspeed. |
+| 4 | `vtrue_ktgs` | Velocity true, in knots true ground speed. |
+| 5 | | Unused. Contains a dummy value. |
+| 6 | `vind_mph` | Velocity indicated, in miles per hour. |
+| 7 | `vtrue_mphas` | Velocity true, in miles per hour airspeed. |
+| 8 | `vtrue_mphgs` | Velocity true, in miles per hour ground speed. |
+
+
+References
+----------
+
+- `X-Plane_10_manual.pdf` (distributed with X-Plane 10)
- http://b58.svglobe.com/data.html
- http://www.nuclearprojects.com/xplane/xplaneref.html
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