( ( Until recently ) ( , ( ( all ( of ( ( the techniques ) ( we ( used ( to ( ( measure ( volcano deformation ) ) ( -LRB- ( ( for ( ( ( ( ( ( ( example , ) ( electronic ( distance measurements ) ) ) , ) tiltmeters ) , ) and ) ( the ( Global ( Positioning System ) ) ) ) ) -RRB- ) ) ) ) ) ) ) ) ) ( ( were ( based ( on ( ( detecting changes ) ( at ( ( specific points ) ( on ( the ( ground surface ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Until) (ADVP (RB recently))) (, ,) (NP (NP (DT all)) (PP (IN of) (NP (NP (DT the) (NNS techniques)) (SBAR (S (NP (PRP we)) (VP (VBD used) (S (VP (TO to) (VP (VB measure) (NP (NN volcano) (NN deformation)) (PRN (-LRB- -LRB-) (PP (IN for) (NP (NP (NN example)) (, ,) (NP (JJ electronic) (NN distance) (NNS measurements)) (, ,) (NP (NNS tiltmeters)) (, ,) (CC and) (NP (DT the) (NNP Global) (NNP Positioning) (NNP System)))) (-RRB- -RRB-))))))))))) (VP (VBD were) (VP (VBN based) (PP (IN on) (S (VP (VBG detecting) (NP (NNS changes)) (PP (IN at) (NP (NP (JJ specific) (NNS points)) (PP (IN on) (NP (DT the) (NN ground) (NN surface)))))))))) (. .)))
Until recently, all of the techniques we used to measure volcano deformation (for example, electronic distance measurements, tiltmeters, and the Global Positioning System) were based on detecting changes at specific points on the ground surface.
(ROOT (S (NP (NNS Tiltmeters)) (VP (VBP are) (VP (VBN used) (S (VP (TO to) (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))))))))))) (. .)))