( ( This speed ) ( ( is ( ( called ( the ( radial ( Doppler velocity ) ) ) ) ( because ( it ( gives ( ( only ( the ( radial variation ) ) ) ( of ( distance ( versus ( time ( between ( ( ( the radar ) and ) ( the target ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This) (NN speed)) (VP (VBZ is) (VP (VBN called) (NP (DT the) (JJ radial) (NNP Doppler) (NN velocity)) (SBAR (IN because) (S (NP (PRP it)) (VP (VBZ gives) (NP (NP (RB only) (DT the) (JJ radial) (NN variation)) (PP (IN of) (NP (NP (NN distance)) (PP (IN versus) (NP (NP (NN time)) (PP (IN between) (NP (NP (DT the) (NN radar)) (CC and) (NP (DT the) (NN target)))))))))))))) (. .)))
This speed is called the radial Doppler velocity because it gives only the radial variation of distance versus time between the radar and the target.
(ROOT (S (NP (NP (NNP Distance)) (PP (IN over) (NP (NP (NN time)) (PP (IN in) (NP (DT a) (VBN given) (NN direction)))))) (VP (VBZ determines) (NP (NN velocity))) (. .)))