anchor.diff:        A=ZHM/(XMM-XM)
         IF(DM.GT.0.AND.DD.GT.0) GOTO 5
           WRITE(6,*) 'DNET LOG ERROR',DM,DD,XM
  +        error stop
           IF(DD.EQ.0.AND.DM.EQ.0) DD=1.
           IF(DM.EQ.0) GOTO 10
           IF(DD.EQ.0) GOTO 20
  
positive.code: C        T(2) - TEMPERATURE AT ALT
  C
  C     NOTES ON OUTPUT VARIABLES:
  C        TO GET OUTPUT IN M-3 and KG/M3:   CALL METERS(.TRUE.) 
  C
  C        O, H, and N are set to zero below 72.5 km
  C
  
negative.code:       PLG(7,3)=(11.*C*PLG(6,3)-7.*PLG(5,3))/4.
        PLG(8,3)=(13.*C*PLG(7,3)-8.*PLG(6,3))/5.
        PLG(4,4) = 15.*S2*S
        PLG(5,4) = 105.*S2*S*C
        PLG(6,4)=(9.*C*PLG(5,4)-7.*PLG(4,4))/2.
        PLG(7,4)=(11.*C*PLG(6,4)-8.*PLG(5,4))/3.
        XL=LAT
  