( ( ( Tilt ( the instrument ) ) ( to ( the ( normal ( viewing angle ) ) ) ) ) . )
(ROOT (S (VP (VB Tilt) (NP (DT the) (NN instrument)) (PP (TO to) (NP (DT the) (JJ normal) (NN viewing) (NN angle)))) (. .)))
Tilt the instrument to the normal viewing angle.
(ROOT (S (NP (NP (NNP Instruments)) (SBAR (WHNP (WDT that)) (S (VP (VB measure) (NP (NP (DT the) (NN angle)) (PP (IN of) (NP (NP (DT the) (NN slope)) (PP (IN of) (NP (DT a) (NN volcano)))))))))) (VP (VBP are) (VP (VBN called) (NP (NN tilt) (NNS meters)))) (. .)))