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1997-06-22
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614 lines
NAME:
HEADER - Format specifications for EPIC standard image header
2 COMMENTS:
(1) This format is primarily intended for images stored on magnetic
tape (see (4) for disk). Each image is stored in a single unlabeled tape
file. Each file ends with a tape end-of-file mark. A double end-of-file
mark appears at the end of the last image file.
(2) Each image consists of a header followed by the image data itself.
The header consists of at least 1 physical record each of which is of
length 1024 bytes.
The image data consists of NL physical records of data each
(((NP*NBIT+7)/8+3)/4)*4 bytes long.
NL = Number of lines in image
NP = Number of pixels in each image line
NBIT = Number of bits/pixel
NH = Number of header records (1024 bytes each)
(3) At present NBIT may have the following values -
1 - Integer
8 - Unsigned integer (0-255)
16 - Signed integer (note that the most significant byte should be
first on the tape)
32 - VAX format real
64 - VAX format complex
64 - VAX format double precision real
128 - VAX format double precision complex
(Note that real and complex images are not normally transferred between
differing computer types).
(4) When the image is read to disk the header should be retained but
the actual format in which the data is stored on the disk may vary with
the computer and the operating system. For any given computer only 1
disk image data format should ever be used.
On the VAX the format is very similar to that used on the tape.
The number of bytes allocated to each line is the necessary number rounded
up to the nearest 4 byte boundary. The number of bytes set aside for header
records is the necessary number rounded up to the nearest multiple of
bytes_per_line. Using integer arithmetic
bytes_per_line = (4 * NP * NBIT + 31)/32
equivalent_header_lines = (NH * 1024 + bytes_per_line - 1)/bytes_per_line
The header records are then packed into the first NH*1024 bytes in the file.
To access a data line (numbered from 1) you start at the byte in the file
given by (line_number - 1) * bytes_per_line + equivalent_header_lines.
Note although the header records and data lines start at particular bytes in
the file as described above, the file is defined with a 512 byte record
structure for VMS.
(5) The header should contain only valid ascii characters.
(6) A header record should be initialised with blanks before its first use.
(7) Each header consists of a number of sets of header records each of
length 1024 bytes.
At present these are -
Fixed data - 1 or 2 records
Comments data - >= 0 records
The fixed data record must come first. The comments records must be
consecutive.
The number of fixed data header records can be increased as desired
by mutual agreement.
2 FIXED_DATA_RECORDS:
BYTES FORMAT NAME PURPOSE
1-6 I6 NL NO OF LINES
(6 Digits allows up to 999999)
(right justified as for all
integer data)
7-12 I6 NP PIXELS/LINE
(6 Digits allows up to 999999)
13-15 I3 NBIT BITS/PIXEL
Allowed values : see above
16-18 I3 NH Total no of header records
minimum 1
19-20 I2 NBLOCK If not 0,it is the number of
image lines/magtape block.
Used by programs BLOCKH and
UNBLKH.
21-22 I2 NRCOM Number of first comments
record. Usually 2.
0 If no comments data is
present.
23-27 I5 NFRAME If not 0, it is the number
of frames in a movie image.
Each frame has NL/NFRAME
lines.
28-30 I3 NPROJ Projection no of image
initially 0
only gets set after
rectification.
See TMNZS.FOR for the full
list of available projections.
Note that a projection may be
rotated.
31-36 I6 LENC Length of comments in bytes
initially 0
37-39 I3 NPROC Type of image compression used.
0= no compression.
40 (Unused)
41-70 30A1 E0FNAM Disk file name - inserted
when copying
image to tape
this can be used when loading
an image to disk, or when
doing a tape directory
71-150 80A1 E0HEAD Descriptive header for present
image. This can be written to
a display device as a title.
151-190 4F10.4 ATLL,ATLP,ABRL,
ABRP
top left and These are with respect to the
bottom right original image that was loaded
(line,pixel) or created, or with respect
to the last rectification or
extraction from a rectified
image.
(A rectified image is always treated as being a master image.
Note they must be reset on rectification,and updated when images are
extracted.)
(Note that coordinate (0.,0.) refers to the top left of the top left pixel
of the original image. This pixel is referred to as pixel (1,1) .
(NL,NP) refers to the bottom right of the bottom right pixel.)
191-194 4A1 ' PEL' Checkword for epic images
195-234 40A1 TYPESA(10), Description of satellite
TYPESE(30) and sensor type following
a standard format for each
satellite and sensor. EG-
Landsat 1 MSS
Landsat 3 RBV
Spot 1 HRV1
LRM A/S MSS
DIT Spect.
(left justified)
(the sensor position
always starts at byte 205)
235-238 I4 IBANDH Band number
default 0
239-278 40A1 FRAMID Frame id left justified
the format of this is
particular to each
satellite and may
include the orbit number.
(10 digits for Landsat,
8 for Spot)
279-280 I2 ICMPLX =0 Initially
=1 after 2-D FFT
=2 after 1-D FFT along lines
=3 after 1-D FFT along columns
Reset to 0 after 2-D inverse.
281-292 12A1 E0IDAT GMT date at start of
image capture.
'DD-MON-YY '
(MON is first 3 letters
of month)
293-304 12A1 E0ITIM GMT time at start of
image capture
'HH:MM:SSFFFF'
The last 4 digits are tenths
of milliseconds if present
305-317 F13.8 E0ALAT Image centre latitude
-90. TO 90.
(of the original full image
if not rectified)
(If the image is rectified
it is the coordinate of the
centre of the image as viewed
on the earth's sphere.)
318-330 F13.8 E0ALNG Image centre longitude
0.-360. Going east
(of the original full image
if not rectified)
331-334 I4 ISUNEL Sun elevation angle at image
centre 0-90 from horizontal
335-338 I4 ISUNAZ Sun azimuth angle at image
centre 0-360 from north going
east ie clockwise is positive.
339-442 8F13.8 4*(LAT,LONG) Top Left, Top Right, Bottom
Right, Bottom Left corner
BLAT(8) points of image. Range as
for centre points.
These refer to the full
original image if it has not
been rectified. Otherwise
they refer to the actual
image.
443-444 I2 IQUAL Band quality 0-9
445-448 I4 ICLOUD Percentage cloud cover. 0-100
449-452 I4 ISENSG Sensor gain
from 1-8 for Spot.
From 0-3 for CZCS.
453-454 I2 IRECT =1 for rectified image
=0 otherwise
455-486 2F16.6 RTLL,RTLP Top Left map coordinates
of full rectified image
in projection NPROJ.
these refer to the Top Left
of the Top Left pixel.
NB: note that all map coordinates throughout epic are always stored
in the order Line, Pixel or Lat, Long or Northing, Easting etc.
487-518 2F16.6 RBRL,RBRP Bottom Right map coordinates
of full rectified image.
These refer to the Bottom Right
of the Bottom Right pixel.
They are usually in yards,
meters or degrees as
appropriate to the projection.
519-530 F12.6 E0ASMP Sampling distance on map
(OR E12.5) of rectified image in
pixel direction.
Usually in yards, meters
or seconds as appropriate.
531-532 I2 E0IINT Interpolation technique
used in rectification.
=1 Cubic
=2 Bilinear
=3 Nearest neighbour
533-544 F12.4 SLITW DIT/PEL spectrometer slit
width (microns).
(just for spectrometer).
545-556 F12.4 STARTW Starting value for calibration
in pixel direction.
(EG wavelength (NM))
STARTW and DELTAW are used when
the pixel position is itself
a calibrated value.
in this case the image cannot
be rectified.
557-568 F12.4 DELTAW Step value in pixel direction.
(eg for wavelength sampling
increment (nm) /pixel)
569-574 I6 IBLACK DIT/PEL spectrometer black
level.
(just for spectrometer).
575-586 F12.4 E0TMIN Value corresponding to
data=0 for calibrated
data (eg temperature).
587-598 F12.4 E0TSTP Step in calibrated data
corresponding to data
step of 1.
Same units as E0TMIN.
599-638 40A1 CUNITS Calibration units for
pixel value. EG -
mw/sq cm/sr/micrometer
microwatts/cm2/st/micrometer
w/m2/sr
K
ALBEDO 0-1
TEMP DEGREES C
DEGREES
METRES
FEET
YARDS
CHLOROPHYLL CONCENTRATION MG/CUBIC M
The remainder of this field
may be used for comments.
639-668 30A1 PUNITS Calibration units
in the pixel direction.
669-678 F10.6 E0RANG Rotation angle in degrees
for projection NPROJS.
Clockwise is positive.
Range 0. to 360. .
The top of the map is rotated
clockwise from North.
679-688 F10.6 ALPHA First camera angle (roll) in
degrees. These are for
use in rectifying
aircraft images. X tilt.
Angle is from vertical.
For Spot images
this is the scanner tilt angle.
ie the angle between the camera
direction and the line to the
centre of the earth measured
at the satellite.
+=looking to left (ie east for
SPOT)
This look direction is at
right angles to the direction
of flight.
689-698 F10.6 BETA Second camera angle (pitch).
Y tilt.
With no roll the angle is from
the vertical.
For CZCS images
this is the scanner tilt angle.
ie the angle between the camera
direction and the line to the
centre of the earth measured
at the satellite.
+=looking forward (or North for
CZCS in ascending orbit)
This look direction is in
the direction of flight.
Note that these axes are right
handed.The Z direction is away
from the earth. The right hand
rule along the axis gives the
positive rotation direction.
699-708 F10.6 GAMMA Third camera angle (yaw).
Z tilt.
These correspond to omega,
psi, kappa in 3rd ed. Manual
of Photogrammetry (asp)
(VOL 1 page 47)
709-718 F10.5 RFOCAL Focal length in
millimeters of camera lens.
719-734 F16.6 SENNOR Sensor northing or
equivalent coordinate
735-750 F16.6 SENEAS Sensor easting
751-766 F16.6 SENEL Sensor height in m for aircraft
or satellite.
767-768 I2 IMONIS Units of image coordinate
system and focal length.
0 - mm
1 - meters
2 - pixels (for nonfocussing
sensors).
769-771 I3 NPROJS Projection no for sensor
easting and northing.
This projection uses the default
associated parameters for this
projection.
772-783 F12.4 STARTL Starting value for calibration
in line direction. (Corresponds
to line 0). For use when image
is not rectified.
For storing projections this is the initial projection angle in degrees
starting from 0 as North or up and moving clockwise. This is the angle for
the first projection stored as line 1.
784-795 F12.4 DELTAL Step value in line direction.
For storing projections this is the angle increment in degrees
( += clockwise, -=anticlockwise) for each new projection.
796-835 40A1 LUNITS Calibration units in line
direction
836-839 I4 IROTAN Rotation angle of projection
nproj 0-360 to east from north.
Clockwise is positive.
840-842 I3 E0PATH World reference path number
for this satellite
(eg for landsat mss or spot)
843-846 I4 E0ROW World reference row number
for this satellite
847-848 I2 E0RTHE =0 normally
=1 for r-theta transformation
=2 for theta-r transformation
(order is lines-pixels)
=3 if each image line is a
projection.
849-854 I6 E0NLRT Image line size before r-theta
transformation
855-860 I6 E0NPRT Image pixel size before r-theta
transformation
861-870 F10.3 E0LCEN Line coordinate of centre before
r-theta transformation
871-880 F10.3 E0PCEN Pixel coordinate of centre
before r-theta transformation
Current orbital elements -
881-892 I12 E0ORBN Orbit number,from 0, incremented
at perigee
893-902 F10.4 E0SMA Semi major axis (km)
903-912 F10.6 E0ECCE Eccentricity X 10**3
913-922 F10.4 E0INCL Inclination from equatorial
plane (degrees)
923-932 F10.4 E0MA Mean anomaly at epoch (degrees)
933-942 F10.4 E0AOP Argument of the perigee(degrees)
943-952 F10.4 E0RAD Right ascension ,ascending node
(degrees)
Current epoch data -
953-964 12A1 E0DATE GMT 'DD-MON-YY '
(MON is first 3 letters
of month)
965-976 12A1 E0TIME 'HH:MM:SSFFFF'
977 A1 E0ELEM Element form, B = Brouwer (Def)
O = Ocsulating
978-994 17A1 E0XXXX SPARE
995-997 I3 E0ICYC Cycle number for satellite
from 0
998-1009 12A1 E0LDAT Launch date GMT
'DD-MON-YY '
1010-1021 F12.6 E0SAML Sampling distance on map
(OR E12.5) of rectified image in
line direction.
Usually in yards, meters
or seconds as appropriate.
The default for E0ASAML is
E0ASAMP.
1022-1024 I3 E0FORM Image form
=0 for normal EPIC image
receiving station information -
1025-1044 20A1 E0RSTN Name
1045-1054 F10.6 E0RSLA Latitude deg
1055-1064 F10.6 E0RSLO Longitude deg
1065-1074 F10.6 E0WAVL Centre wavelength of band
in nm
1075-1084 F10.6 E0BW Width of wavelength band
in nm
1085-1088 4I1 E0CLQ(4) Cloud in quadrant from
0-9 (as provided by Spot).
quadrants -
1 2
3 4
1089-1092 A4 E0SNCH Sensor characteristics.
Byte 1 - x=multispectral
p=panchromatic
Byte 2 - d=double
t=twin
Byte 3 - c=compressed
l=linear
1093-1095 I3 E0MPOS Mirror position number
(as provided by Spot)
1096-1099 A4 E0SPRO Sensor problems.
L=line start anomaly
1100-1109 F10.6 E0LOOK Look angle from vertical
at centre of image.
+=satellite is looking from
east or right
-=looking from west or left
this is measured on the ground
not at the satellite.
1110 A1 E0DBLE =' ' for single precision
='D' for double precision
( eg for 64 bit double precision
real data).
1111-1120 f10.6 E0SCAN angle in milliradians subtended
by each original image pixel
in scan direction.
1121-1123 i3 E0ICUB warping method used in
rectification.
0=quadrilateral mapping
1=cubic
2=second order
3=affine
AUXILLIARY MAP PROJECTION INFORMATION -
1124-1126 i3 E0IZON UTM zone number (1-60)
1127-1129 i3 E0INOR hemisphere =1 for north,
-1 for south
USED FOR UTM.
1130-1132 i3 E0ISPH earth spheroid
1 = International 1924(default)
2 = Clarke 1866 (north america)
3 = Clarke 1880 (africa)
4 = Everest 1830
5 = Bessel 1841
6 = Australian national 1965
7 = IUGG 1967
8 = IUGG 1980
etc as in setmap.for
1133-1138 f6.1 E0CLAT centre latitude of defined map
projection
1139-1144 f6.1 E0CLON centre longitude of defined map
projection
1145-1154 f10.1 E0CNOR northing at defined map centre
1155-1164 f10.1 E0CEAS easting at defined map centre
1165-1170 f6.1 E0PLL1 first standard latitude (deg)
parallel for use with eg
lamberts conformal map
projection.
For Polar stereographic
projection it is the orientation
of Greenwich clockwise from
the vertical meridian.
1171-1176 f6.1 E0PLL2 second optional standard
latitude parallel
1177-1184 f8.5 E0CSCA scale of map at defined centre
(default =1.)
1185-1196 12A1 E0JDAT GMT date at end of
image capture.
'DD-MON-YY '
(MON is first 3 letters
of month)
1197-1208 12A1 E0JTIM GMT time at end of
image capture
'HH:MM:SSFFFF'
The last 4 digits are tenths
of milliseconds if present
Additional data for Current orbital elements -
1209-1221 f13.7 e0tan anomalous period (minutes)
1222-1231 e10.3 e0drg secular drag (only if e0drad
to e0d3ta zero)
1232-1244 e13.6 e0drad 1st derivative of e0rad
(degrees/day)
1245-1244 e13.6 e0decc 1st derivative of e0ecce
(degrees/day)
1258-1270 e13.6 e0daop 1st derivative of e0aop
(degrees/day)
1271-1283 e13.6 e0dtan 1st derivative of e0tan
(minutess/day)
1284-1296 e13.6 e0d2a0 2nd derivative of e0aop
(degrees/day**2)
1297-1309 e13.6 e0d2ra 2nd derivative of e0rad
(degrees/day**2)
1310-1322 e13.6 e0d2ec 2nd derivative of e0ecce
(degrees/day**2)
1323-1335 e13.6 e0d2ta 2nd derivative of e0tan
(minutes/day**2)
1336-1348 e13.6 e0d3ta 3rd derivative of e0tan
(minutes/day**3)
1349-1356 I8 E0LSAV saved number of lines in
image before it was blocked.
If zero assume exact multiple
of blocking number.
1357-1358 I2 VFIELD Image is a vector field
if VFIELD <> 0
1359-1364 I6 WSIZE Extent of square search window
(in pixels) in original window.
1365-1370 I6 TSIZE Extent of square template
(in pixels) in original
template image.
1371-1376 I6 TUPPER Upper and lower thresholds for
1377-1382 I6 TLOWER validating window template data.
A pixel value is set to zero if
f<=TLOWER or f>= TUPPER
1383-1388 f6.2 TDIST Maximum allowed percentage of
total contaninated area in both
window and template.
If actual > TDIST the vector
is not evaluated.
2 COMMENTS_FIELD:
Ascii string containing variable length records each terminated by a
carriage return and a line feed character.
See NRCOM and LENC above.
2 COMMON_BLOCK:
Common block EPIC in FORTRAN gives direct access to all of the above
header parameters except for NL, NP, NBIT and text blocks (eg calibration
units) which are written to the header buffer directly.
2 RECORD DEFINITION:
A record has been defined, for use in PASCAL, which gives access to all
of the above fields. See the file called "DPDEF.DEF" for its definition.
2 AUTHOR:
M.J.McDonnell in coordination with D.Pairman, P.J.Ellis, P.J.Bruin,
S J McNeill and J.Dymond.
LAST MODIFIED 23-FEB-1990.
