VICAR2: Summary from the Encyclopedia of Graphics File Formats

VICAR2 File Format Summary

Also Known As: Planetary File Format


Type Bitmap
Colors Unlimited
Compression Uncompressed
Maximum Image Size Unlimited
Multiple Images Per File No
Numerical Format Little-endian
Originator NASA
Platform VAX/VMS
Supporting Applications Many
See Also FITS, PDS

Usage
Storage of bitmap data.

Comments
You are unlikely to see the VICAR2 format unless you deal with planetary data from NASA or JPL.

Vendor specifications are available for this format.

Code fragments are available for this format.

Sample images are available for this format.


The VICAR2 image file format is used primarily for storing planetary image data collected by both interplanetary spacecraft and Earth-based stations. Many astronomical and astrophysical organizations use and support the VICAR2 format.

Contents:
File Organization
File Details
For Further Information

File Organization

VICAR2 is very similar in construction to the FITS and PDS image file formats. A VICAR2 image file is divided into an ASCII header (called a label) and a collection of binary image data.

File Details

This section contains information on the label and image data in a VICAR2 file.

Labels

A VICAR2 label contains system label items and may contain history label items as well. History label items are added to the label during software processing, and it is possible for history label items not to be present in a VICAR2 label at all. If history label items do exist, they always occur following the last system label item.

The history label section may also contain other, software-specific keywords called user labels. They are for informational purposes for any software application that knows how to interpret them. If a VICAR2 reader does not recognize them, then they are ignored and always preserved whenever the file is written or read.

The label is always located at the beginning of the file, starting on the first byte, and is always arranged in system-/history-/user-section order.

All label sections contain one or more fixed-length records in the form of ASCII character strings. Because all records in the label must be the same length, the last record must be padded out to the proper size with NULL (ASCII 00h) characters if it is too short.

All records in the label use the standard keyword=value format for storing information about the image. Keywords are written in uppercase and have a maximum of eight characters. The value may be one of four data types:

  • INTEGER (fixed-point)

  • REAL (floating-point)

  • DOUBLE (double-precision REAL)

  • STRING

STRING data is delimited by single quotation marks (') containing any printable ASCII characters and spaces except for single quotation mark characters. Strings may be from 1 to 512 characters in length.

A keyword=value pair is always separated by an equals sign (=). There are never any spaces between the equal sign and the keyword/value data. Each keyword=value pair is separated from the next pair by one more spaces.

The following is a list of valid VICAR2 label keywords. Refer to the VICAR2 specification on the CD-ROM for an explanation of each keyword and the data format of its associated value:

BUFSIZE N4
LBLSIZE NB
DAT_TIM NBB
DIM NL
EOL NLB
FORMAT NS
HOST ORG
INTFMT REALFMT
N1 RECSIZE
N2 TASK
N3 USER

The first keyword of the system section of the label is always LBLSIZE, which specifies the total number of bytes in the label, including any NULL bytes used for padding out the last record. LBLSIZE is always a multiple of the file record size.

A system label may end with the keyword TASK, which marks the beginning of the history section of the label. If no history section exists, then the label ends with an ASCII NULL value, or simply after the number of characters specified by LBLSIZE.

If the EOL KEYWORD is present in the label and has a VALUE of 1, then an additional label record appears at the end of the file following the image data. Your guess is as good as ours as to the use of this End-Of-File trailing record.

Image Data

The image data begins on the next record boundary following the label. The image data contains one record per scan line in the image. The size of each record is a number of bytes equal to the number of bytes in one scan line.

The image data is represented by one of the following data types, indicated by the FORMAT keyword in the image label:

BYTE 8 bits
HALF 16 bits
FULL 32 bits
REAL 32 bits
DOUB 64 bits
COMPLEX 64 bits

The following is a typical VICAR2 label section, including history and user records. Note that in this example, carriage returns have been inserted for clarity; none actually exist in a real label.

LBLSIZE=1680 FORMAT='BYTE'  TYPE='IMAGE'  BUFSIZ=20480  DIM=3  EOL=0
RECSIZE=840  ORG='BSQ'  NL=738  NS=840  NB=1  N1=840  N2=738  N3=1
N4=0  NBB=0  NLB=0  HOST='VAX-VMS'  INTFMT='LOW'  REALFMT='VAX'
TASK='LOGMOS'  USER='HXS343'  DAT_TIM='Fri Nov  2 17:41:32 1990'
SPECSAMP=493943  PROJSAMP=4096  PROJ_L ON=350.7789496599263
PRODTYPE='F-MIDR'  PIXSIZ=75  SEAM='CORRECTED'  MAP_PROJ='SINUSOIDAL'
SEAMLOC='NO'  IMAGE='RADAR CROSS SECTION POWER'  DN_UNITS='DECI BELS'
SPECLINE=38724  LAT_UR=27.5  LAT_UL=27.5  LAT_LR=22.4102769981245
LAT_LL =22.4102769981245  LON_UL=347.5  LON_UR=354.0578993198525
LON_LL=347.6328878639 307  LON_LR=353.9250114559218
M_SPDN_1='MISSING DATA'  LOW_REP=-20.0  HI_REP=30 .0  LOW_DN=1
HI_DN=250  N_SPDN=1  SPDN_1=0  REV_STRT=460 REV_END=4 93
PRODUCT='F-MIDR.25N351;1'  TASK='COPY'  USER='DNJ345'
DAT_TIM='Sat Apr 20 12:29:24 1991'  TASK='STRETCH'  USER='DNJ345'
DAT_TIM='Sat Apr 20 12:29: 39 1991'  PARMS=' LINEAR STRETCH:
71 TO      0 AND  155 TO    255'

For Further Information

For further information about VICAR2, see the documentation included on the CD-ROM that accompanies this book. You can also contact:

National Aeronautics and Space Administration (NASA)
Attn: Bob Deen
Image Processing Laboratory
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109
Email: [email protected]
WWW: http://stardust.jpl.nasa.gov/pds_home.html

You can also obtain VICAR2 images from the FTP archive:

ftp://ames.arc.nasa.gov/pub/SPACE/VICAR/


This page is taken from the Encyclopedia of Graphics File Formats and is licensed by O'Reilly under the Creative Common/Attribution license.

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