major changes. should still work without circle fit. using ixmin etc. and doing necessary reshaping in an if block. I haven't written any interpolation code, except for determining water depth patch.
 added interpolation code but interpolation for streamer mask doesn't work. need some trick. haven't looked at plots yet
ok. errors fixed but everything looks like crap. must check interpolation
fixed interpolation along streamer. looks reasonable. maybe should plot different fields. yesterday's interpolation error was because xumat was in m and xin was in kn. Doh