.:twodc:home

Format

 *.2dc - 2-DC data structure with format:
 twodc = REPLICATE({ $                     ; Byte      Description
          FRONT:161UL,                   $ ; 00-03     CONSTANT Y'10100001'
          IMAGE:BYTARR(4096),            $ ; 04-4099   2-D Image Slices
          STTIME:0UL,                    $ ; 4100-4103 Image Start (Seconds from midnight*10000)
          NDTIME:0UL,                    $ ; 4104-4107 Image End (Seconds from midnight*10000)
          STTAS:0U,                      $ ; 4108-4109 Image Start TAS *100
          NDTAS:0U,                      $ ; 4110-4111 Image End TAS *100
          SPARE:0UL,                     $ ; 4112-4115 Space               
          DATE:0UL,                      $ ; 4116-4119 Date (MMDDYY)
          Spare1:0UL,                    $ ; 4120-4123 Total Air Temperature Multiplied by 100 in Kelvin
          Spare2:0UL},                   $ ; 4124-4127 Spare
          4)                               ; 4 element Array

 *.cip - Cloud Imaging Probe (CIP) image data stored in the 2-DC data structure.  Format is:
 cip   = REPLICATE({ $                     ; Byte      Description
          FRONT:161UL,                   $ ; 00-03     CONSTANT Y'10100001'
          IMAGE:BYTARR(4096),            $ ; 04-4099   CIP compressed image slices
          STTIME:0UL,                    $ ; 4100-4103 Image Start (Seconds from midnight*10000)
          NDTIME:0UL,                    $ ; 4104-4107 Image End (Seconds from midnight*10000)
          STTAS:0U,                      $ ; 4108-4109 Image Start TAS *100
          NDTAS:0U,                      $ ; 4110-4111 Image End TAS *100
          SPARE:0UL,                     $ ; 4112-4115 Space               
          DATE:0UL,                      $ ; 4116-4119 Date (MMDDYY)
          Spare1:0UL,                    $ ; 4120-4123 Total Air Temperature Multiplied by 100 in Kelvin
          Spare2:0UL},                   $ ; 4124-4127 Spare
          4)                               ; 4 element Array

 *.pip - Precipitation Imaging Probe (PIP) image data stored in the 2-DC data structure.  Format is:
 pip   = REPLICATE({ $                     ; Byte      Description
          FRONT:161UL,                   $ ; 00-03     CONSTANT Y'10100001'
          IMAGE:BYTARR(4096),            $ ; 04-4099   PIP compressed image slices
          STTIME:0UL,                    $ ; 4100-4103 Image Start (Seconds from midnight*10000)
          NDTIME:0UL,                    $ ; 4104-4107 Image End (Seconds from midnight*10000)
          STTAS:0U,                      $ ; 4108-4109 Image Start TAS *100
          NDTAS:0U,                      $ ; 4110-4111 Image End TAS *100
          SPARE:0UL,                     $ ; 4112-4115 Space               
          DATE:0UL,                      $ ; 4116-4119 Date (MMDDYY)
          Spare1:0UL,                    $ ; 4120-4123 Total Air Temperature Multiplied by 100 in Kelvin
          Spare2:0UL},                   $ ; 4124-4127 Spare
          4)                               ; 4 element Array

Note: The 2-DC image data slices are stored in a 12-bit array while the CIP and PIP image data are compressed binary data that are stored within a 12-byte array. Therefore a decompression routine is required to extract the CIP and PIP images from this format.

Conversion from Total Air Temperature (TAT) to Static Air Temperature (SAT)

The difference between TAT and SAT is called ram rise (RR) and is caused by compressibility and friction of the air at high velocities.

<math>RRtotal=TAT-SAT</math>

where

<math>RRtotal=V^2/87^2</math>

V is the air speed in knot