Col de la Croix 1988 autumn survey radar tracking data

Individual tracks of free flying nocturnal migrants recorded by a military tracking radar (see Bruderer 1997):
Bruderer, B. The Study of Bird Migration by Radar Part 1: The Technical Basis*. Naturwissenschaften 84, 1–8 (1997). https://doi.org/10.1007/s001140050338 

Description of variables 
Code     site code (C88: Col de la Croix)
FNr        Track number starting each day at 00:00 with 1
Z             mean flight altitude (m above radar)
Rg           mean flight direction (°)
Ra           mean heading (°, body axis)
Vg          mean ground speed (cm/s)
Va          mean airspeed (cm/s)
Vz           mean climb rate (cm/s)
FieldClass            Echo class 1-9 based on wingbeat pattern, see description below

description of variable FieldClass            
Code     description
1             wader-type large (continuous wingbeats)
2             wader-type small (continuous wingbeats)
3             passerine-type large (regular phases of wingbeats and pauses => bounding flight)
4             passerine-type small (regular phases of wingbeats and pauses => bounding flight)
5             swift-type (irregular phases of wingbeats and pauses => flap-gliding flight)
6             raptor (visually identified)
7             single bird large (partly visually identified)
8             flock of unidentified birds
9             unknown bird