exponentialvg<-function(ps,hs){
  c0<-ps[1]
  ce<-ps[2]
  ae<-ps[3]
  gs<-c0+ce*(1-exp(-1*hs/ae))
  return(gs)
}
#---------------------------------------------------
sphericalvg<-function(ps,hs){
  c0<-ps[1]
  cs<-ps[2]
  as<-ps[3]
  hs1<-hs[hs<=as]
  hs2<-hs[hs>as]
  gs1<-c0+cs*(1.5*(hs/as)-0.5*(hs/as)^3)
  gs1<-gs1*(hs<=as)
  gs2<-(c0+cs)*(hs>as)
  gs<-gs1+gs2
  return(gs)
 }
#---------------------------------------------------
wavevg<-function(ps,hs){
  c0<-ps[1]
  cw<-ps[2]
  aw<-ps[3]
  gs<-c0+cw*(1-aw*sin(hs/aw)/hs)
  return(gs)
 }