(form "00049" (size 66 16)
  (heading "EXTRACT CONTOURS FROM A DTM")
  (label (position 15  3) (text "DTM from which contours will be extracted"))
  (label (position 15  4) (text "Location"))
  (label (position 15  5) (text "ID number"))
  (label (position 50  7) (text "Contour value"))
  (label (position  2  8) (text "Minimum"))
  (label (position  2  9) (text "Maximum"))
  (label (position  2 11) (text "Define contours by (I)nterval or (R)ange"))
  (label (position 33 12) (text "Contour range"))
  (label (position  2 12) (text "Minimum contour"))
  (label (position  2 13) (text "Maximum contour"))
  (label (position  2 14) (text "Contour interval"))
  (field "dtmloc" (position 26  4) (display_length 26) (input disallowed)
     (file (link "dtmid") (extension "*.dtm")))
  (field "dtmid" (position 26  5) (display_length 16) (input disallowed))
  (field "xmin" (position 29  8) (display_length 16) (input disallowed))
  (field "ymin" (position 11  8) (display_length 16) (input disallowed))
  (field "zmin" (position 47  8) (display_length 16) (input disallowed))
  (field "xmax" (position 29  9) (display_length 16) (input disallowed))
  (field "ymax" (position 11  9) (display_length 16) (input disallowed))
  (field "zmax" (position 47  9) (display_length 16) (input disallowed))
  (field "reflabel" (position 11  7) (display_length 10)
    (background) (input disallowed))
  (field "nonreflabel" (position 29  7) (display_length 10)
    (background) (input disallowed))
  (field "deftype" (position 38 11) (display_length  1) (input allowed)
    (value_in "I" "R")
    (translate upper) (null allowed) (max_length 1)
    )
  (field "conmin" (position 19 12) (display_length 10) (input allowed)
    (dependency (value "deftype") == "I")
    (translate upper) (format real_8) (null disallowed) (max_length 10)
    )
  (field "conmax" (position 19 13) (display_length 10) (input allowed)
    (dependency (value "deftype") == "I")
    (translate upper) (format real_8) (null disallowed) (max_length 10)
    (help (field "conmin")))
  (field "ci" (position 19 14) (display_length 10) (input allowed)
    (dependency (value "deftype") == "I")
    (translate upper) (format real_8) (null disallowed) (max_length 10)
    (help (field "conmin")))
  (field "conrng" (position 47 12) (display_length 16) (input allowed)
    (dependency (value "deftype") == "R")
    (max_length 32)
    (translate lower) (null allowed)
    )
  (default_buttons)
)