Describe EXTRACT_DATA_PIC here.

      SUBROUTINE EXTRACT_DATA_PIC(NTMP,QSZ,SCALE,PICNM,IPL,
     .                     V,UX,UY,UZ,HUSE,HT,CP,SP,EUSE,ETOL,
     .                     FINV,DPIC_DLOC,DIDH,DJDH,Z0,KK,ESZ,DN, DNX)

* INTEGER NTMP

• NTMP is a global compile parameter that defines the maximum size of maplets (it allocates memory) Standard value is 128

* INTEGER QSZ

• QSZ is the half size of maplet. width = QSZ * 2 + 1

  It is derived from READ_MAP

* DOUBLE PRECISION SCALE

• The scale (both horizontally x and y, as well as verticlally). The values in the MAPLET should be multiplied by this value to get its actual value. Units are in km. It is derived from READ_MAP

* CHARACTER*12 PICNM

• The name of the image that you want to use. The file is read in (again) in this program)

* DOUBLE PRECISION IPL(2)

• IPL = Image Pixel Line. Scaling factor to translate from physical to image frame.

  Comes from V2IMGPLV

* DOUBLE PRECISION V(3)

• Central vector of the maplet

  It is derived from READ_MAP

* DOUBLE PRECISION UX(3)

* DOUBLE PRECISION UY(3)

* DOUBLE PRECISION UZ(3)

• Normal plane of the maplet in X, Y and Z space

  It is derived from READ_MAP

  • LOGICAL HUSE(-NTMP:NTMP,-NTMP:NTMP)

  Tracks each pixel of the maplet to define if its value should be considered

  Defined in HGT2SLP

  • REAL*4 HT(-NTMP:NTMP,-NTMP:NTMP)

* DOUBLE PRECISION CP(3)

• Camera vector Calculated in EXTRACT_DATA_PIC

* DOUBLE PRECISION SP(3)

• Sun vector Calculated in EXTRACT_DATA_PIC

* LOGICAL EUSE

• "Expanded T1" Flag for when to use the expanded threshold for DN.

  Is a flag set within lithos or lithosp using the 'x' option Uses the ETOL variable

* DOUBLE PRECISION ETOL

• Expanded T1 flag variable.

  Is a flag set within lithos or lithosp using the 'x' option Typically set to .025 (standard within the scripts for LITHOSP)

* DOUBLE PRECISION FINV

• Reports the fraction of invisible pixels within the maplet/image intersection

* DOUBLE PRECISION DPIC_DLOC(2,3)

• This subroutine computes the change in the image-space location (p,l) of a point (x,y,z) on a maplet as the point is moved in the maplet frame

  Called from LOC2PIX

* DOUBLE PRECISION DIDH

* DOUBLE PRECISION DJDH

• Rate of change for the position I and J in the picture Calcualted in this routine and reported back to who called it

* INTEGER Z0(2)

• Center point to extract the data from the image.

  Defined in lithos and derived from IPL. Used in PICINPT and BRT1

* INTEGER KK, ESZ

• KK is a spacing parameter, which I think is based upon the maplet. ESZ is the size of the array.

  Defined in lithos. Used in PICINPT and BRT1

* INTEGER DN(-1300:1300,-1300:1300)

• The workspace of displayed DN for both the image and the maplet (template) Set in this subroutine.

* REAL*4 DNX(-NTMP:NTMP,-NTMP:NTMP)

• The filled out data that we really want. Set in this routine.