subroutine splitpoly0(npts,mcause0,iseq0,jcause,
     x	mpts,mcause,iseq,iotmsg)

c	split a polygon (with causeways) into two subpolygons

c	input:
c	number of segments in input polygon 1
	integer npts
c	causeway id of segment ii
	integer mcause0(1)
c	input array  - segment positions of polygon including causeways
	integer iseq0(1)
c	id of causeway to remove (normally 1)
	integer jcause

c	no of pts in subpolygons 1 and 2
	integer mpts(1)
c	output array - causeway ids of subpolygons
	integer mcause(900,1)
c	output array - segment positions of subpolygons
	integer iseq(900,1)
c	logical unit of output
	integer iotmsg

c	following statement merely avoids annoying message in compilation
	ijunk=iotmsg

c	detach polygon associated with causeway jcause

c	first causeway segment not yet found
	ifound=0
c	second causeway segment not yet found
	ifinish=0
c	pts in subpolygon 1
	iused=0
c	pts in subpolygon 2
	iremain=0

c	initially ii=npts,...1
 	do 1722 ii=1,npts

c	collect consecutive segments between the two
c	segments of causeway jcause, provided a different
c	causeway does not intervene

	if ((ifound.eq.0.or.ifinish.ne.0)
     x	.and.mcause0(ii).ne.jcause) then
c	ordinary segment not in subpolygon 1
c	add to subpolygon 2
		iremain=iremain+1
		mpts(2)=iremain
		iseq(iremain,2)=iseq0(ii)
		mcause(iremain,2)=mcause0(ii)

	else if (mcause0(ii).eq.jcause.and.ifound.eq.0) then
c	0th segment of subpolygon 1
		ifound=1
		mpts(1)=0

	else if (ifound.ne.0.and.ifinish.eq.0
     x	.and.mcause0(ii).ne.jcause) then
c	ordinary segment in subpolygon 1
		iused=iused+1
		mpts(1)=iused
		iseq(iused,1)=iseq0(ii)
		mcause(iused,1)=mcause0(ii)

	else if (mcause0(ii).eq.jcause.and.ifound.ne.0
     x	.and.ifinish.eq.0) then
c	last+1 segment of subpolygon 1
		ifinish=1

	else
c		should never happen
	endif

c	end of point loop ii
1722	continue

c	write(iotmsg,200)
c	write(iotmsg,200) npts
c	write(iotmsg,200) (iseq0(kk),kk=1,npts)
c	write(iotmsg,200) (mcause0(kk),kk=1,npts)
c	write(iotmsg,200) (iseq(kk,1),	kk=1,iused)
c	write(iotmsg,200) (mcause(kk,1),kk=1,iused)
c	write(iotmsg,200) (iseq(kk,2),	kk=1,iremain)
c	write(iotmsg,200) (mcause(kk,2),kk=1,iremain)
200	format (1x,'0',25i3)

	return
	end