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General BYU SIR file naming scheme:

A long, but human-readable, standard file naming scheme is used for .SIR files produced by BYU. This scheme can be expressed as

SENS-T-REGYR-DY1-DY2.RCN (24 characters + possible additional extensions)

where SENS = Sensor* and polarization name (4 chars):

  • nscv = NSCAT V pol
  • nsch = NSCAT H pol
  • ers1 = ERS1
  • ers2 = ERS2
  • sash = SASS H pol
  • sasv = SASS V pol
  • quev = QuikScat egg outer beam (v-pol)
  • queh = QuikScat egg inner beam (h-pol)
  • qusv = QuikScat slice outer beam (v-pol)
  • qush = QuikScat slice inner beam (h-pol)
  • swev = SeaWinds egg outer beam (v-pol)
  • sweh = SeaWinds egg inner beam (h-pol)
  • swsv = SeaWinds slice outer beam (v-pol)
  • swsh = SeaWinds slice inner beam (h-pol)
  • sqev = Tandem SeaWinds and QuikSCAT egg outer beam (v-pol)
  • sqeh = Tandem SeaWinds and QuikSCAT egg inner beam (h-pol)
  • sqsv = Tandem SeaWinds and QuikSCAT slice outer beam (v-pol)
  • sqsh = Tandem SeaWinds and QuikSCAT slice inner beam (h-pol)
  • FXXY = SSM/I where XX=SSM/I number (e.g., 13, 14), Y=channel index
    • 19V (channel index Y=1)
    • 19H (channel index Y=2)
    • 22V (channel index Y=3)
    • 37V (channel index Y=4)
    • 37H (channel index Y=5)
    • 85V (channel index Y=6)
    • 85H (channel index Y=7)
  • topo = topography map
  • ???? = other sensor type

* Note: In general, SIR images are made from multiple orbit passes of the study area. For some specialized images, the ascending (north-bound) orbit passes and descending (south-bound) orbit passes are processed separately. In these cases, the second letter of the sensor name may be replaced with an "a" or "d" as appropriate. The full sensor name then indicates that both types of passes are combined.

and T = image type code (1 char) (the file header itype code value in shown in the parenthesis)

  • a (1) = A image (sigma-0 in dB, typically at 40 deg incidence)
  • b (2) = B image (slope of sigma-0 in dB/deg)
  • c (4) = C image (2nd order curvature of sigma-0 in dB/deg**2)
  • C (8) = counts or hits (measurements) per pixel
  • d (5) = D image (3rd order curvature of sigma-0 in dB/deg**3)
  • E (21) = Sigma-0 error image (dB)
  • h (19) = height (in m)
  • I (7) = incidence angle standard deviation (in deg)
  • J (9) = average incidence angle (in deg)
  • m (0) = mask image
  • N (6) = counts of negative sigma-0 values
  • p (11) = pixel time estimate (in min from start of image interval)
  • q (32) = magnitude of 1st harmonic of azimuth modulation (dB)
  • Q (32) = magnitude of 3rd harmonic of azimuth modulation (dB)
  • r (33) = phase angle of 1st harmonic of azimuth modulation (deg)
  • R (36) = phase angle of 3rd harmonic of azimuth modulation (deg)
  • s (34) = magnitude of 2nd harmonic of azimuth modulation (dB)
  • S (37) = magnitude of 4th harmonic of azimuth modulation (dB)
  • S (12) = counts of small sigma-0 values
  • t (35) = phase angle of 2nd harmonic of azimuth modulation (deg)
  • T (38) = phase angle of 4th harmonic of azimuth modulation (deg)
  • T (3) = Tb brightness temperature (in K)
  • u (36) = Sigma-0 standard deviation image w/Az mod removed (dB)
  • U (39) = Sigma-0 standard deviation image w/Az fourth mod removed (dB)
  • v (10) = vegetation index
  • V (22) = Sigma-0 standard deviation image (dB)
  • w (46) = wind direction image (deg)
  • W (16) = mean wind speed image (m/s)
  • x (30) = longitude image (deg)
  • y (31) = latitude image (deg)
  • Y (17) = wind speed standard deviation image (m/s)
  • X (?) = misc.
  • z (45) = angle of image grid w/respect to north (deg)
  • Z (44) = area of image grid elements (pixels) (km**2)
and REG = Region Id code (3 chars). The following is a partial list of the regions and their corresponding numerical codes:
  • Ama = (1) Amazon
  • Con = (2) Congo
  • Ant = (100) Antarctica
  • Arc = (110) Artic
  • Grn = (202) Greenland
  • Ala = (203) Alaska
  • CAm = (204) Central America
  • NAm = (205) North America
  • SAm = (206) South America
  • NAf = (207) North Africa
  • NHe = (111) Northern Hemisphere
  • SAf = (208) South Africa
  • Sib = (209) Siberia
  • Eur = (210) Europe
  • SAs = (211) South Asia
  • ChJ = (212) China-Japan
  • Ind = (213) Indonesia
  • Aus = (214) Australia
  • Bor = (254) Borneo
  • Con = (255) Congo
  • Ber = (256) Bering Sea
  • Ice = (257) Iceland
  • Wil = (259) Wilkes Land
  • Glb = (500) Globe
  • Cus = (?) custom region
  • xxx = (?) custom region
and YR = year (2 chars) eg. - 78, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, etc.

and DY1 = 1st day of data used to make image (3 chars) (Julian Day of year) eg. - 001, 034, 267, 354

and DY2 = End day of data used in image (3 chars) (Julian Day of year) if imaging time crosses year boundary, DY2 < DY1

and RCN = Reconstruction technique (3 chars):

  • sir = sir or sirf algorithm
  • ave = ave image algorithm
  • non = nonenhanced enlarged grd image
  • grd = gridded data image
  • lis = list information file

Special file Extensions

The following common file extensions may be optionally added to the end of the filename to identify specially processed and/or stored images:

  • lmsk = Land masked data image (ocean set to no data value)
  • lmask = Land mask image (0=ocean, 1=land)
  • mask = general mask image
  • imsk = Ice masked image (non-ice covered ocean set to no data value)
  • omsk = Ocean masked image (land set to no data value)
  • dif = Difference image
  • gz = gzipped file
  • diff = Difference image
  • sr = Subregion extracted image
  • ie = ASCII sea ice extent file
  • ed = Manually edited image

Further information is available on line from the BYU MERS web site or the NASA Scatterometer Climate Record Pathfinder web site


Note: All BYU-produced data products and associated documentation and software are copyright BYU. BYU-produced data products may not be used for commercial purposes without written authorization by Dr. David G. Long (further authorization may be required from NASA). Appropriate acknowledgement for BYU MERS and the JPL PO.DAAC should be given when using data products in published works, with a copy of the publication sent to Dr. David G. Long and to the JPL PO.DAAC.