program tt
c
c compare 2 routines to convert
c altitude setting to  surface pressure
c
	 do elev=0,5000,1000
	   palt=29.5
	   do i=1,10
	     call pa2sp(palt,elev,sfcp)
	     sfcp2=alt2prs(palt,elev)
	     write(*,*)palt,elev,sfcp,sfcp2
	     palt=palt+.05
	   enddo
	 enddo
	 end
	 subroutine pa2sp(palt,elev,sfcp)
c
c convert pressure altitude in inches (palt) and
c station elevation in feet to sfcp in mb .
c
	 parameter(xn=0.190284,xk=8.4288e-05)
	 parameter(xni=1./xn)
	 pmb=palt*33.8639
	 em=elev*.3048
	 p22=pmb**xn
	 p23=xk*em
	 sfcp=(p22-p23)**xni + 0.3
	 return
	 end
	function alt2prs(alti,elevf)
c
c convert altimeter setting (inches) and elevation (feet)
c  to station pressure (mb).
c
	parameter (ts=288.,slap=.0065,gasc=287.04,g=9.80616,c1=g/(slap*gasc))
c convert altimeter setting from inches to mb
	alt=alti*33.8639
c convert elevation from feet to meters
	elev=elevf*.3048
c
	alt2prs=alt*(1.-(elev*slap/ts)) ** c1
	return
	end