GLA05 Records: Release 34

Follow the links in the table below to the GLAS Altimetry Data Dictionary for details of each record, including units and scaling factors. The GLAS science team created this dictionary. Units and scaling factors with a "d" indicate double-precision constants; for example, a value of "1.0d5" is equivalent to 100,000. Nearly all integers are signed; exceptions are noted below.

The following codes are used to denote data types throughout the remainder of this document.

i1b: 1-byte integer
i2b: 2-byte (short) integer
i4b: 4-byte (long) integer
r4b: 4-byte real
r8b: 8-byte real

Values in parentheses indicate the record size, for example:

i2b(39): 39 records of 2-byte integers
i1b(48,40): 48-record x 40-record array of 1-byte integers

When comparing data from different products, the record index is consistent as long as all products represent the same release of data. If you want to compare different products with different releases, you should update your oldest product to the latest release. For example, if you want to compare data from a GLA05 Release-12 file and GLA12 Release-18 file, you should order a new GLA05 Release-18 file to replace the older release. The ICESat/GLAS Data Releases page describes characteristics and temporal coverage of each version of data.

Table 1. GLA05 Main Record
Name Short Description Byte Offset Data Type Total Bytes
i_rec_ndx GLAS record index 0 i4b 4
i_UTCTime Transmit time of first shot in J2000 4 i4b(2) 8
i_transtime One-way transmit time 12 i2b 2
i_spare1 Spares 14 i1b(2) 2
i_deltagpstmcor Delta GPS time correction 16 i4b 4
i_dShotTime Laser shot time deltas (shots 2-40) 20 i4b(39) 156
i_lat Spot coordinate data - latitude (uncorrected) 176 i4b(40) 160
i_lon Spot coordinate data - longitude (uncorrected) 336 i4b(40) 160
i_elev Spot surface elevation with respect to ITRF ellipsoid (uncorrected) 496 i4b(40) 160
i_GmCns i_GmCns 656 i4b(40) 160
i_spare43 Spare 43 816 i4b(11,40) 1760
i_sigmaatt Attitude quality indicator 2576 i2b(40) 80
i_gval_rcv Gain value used for received pulse 2656 i2b(40) 80
i_wfnoiseOb1 1064-nm background noise (alternative) 2736 i2b(40) 80
i_wfnoiseOb2 1064 nm background noise (standard) 2816 i2b(40) 80
i_sDevNsOb1 Standard deviation of 1064-nm background noise (alternative) 2896 i2b(40) 80
i_sDevNsOb2 Standard deviation of 1064-nm background noise (standard) 2976 i2b(40) 80
i_refRngNs Reference Range 3056 i4b(40) 160
i_thRtkRngOff1 Threshold retracker range offset (alternative) 3216 i4b(40) 160
i_thRtkRngOff2 Threshold retracker range offset (standard) 3376 i4b(40) 160
i_minRngOff1 Minimum range offset (alternative) 3536 i4b(40) 160
i_minRngOff2 Minimum range offset (standard) 3696 i4b(40) 160
i_preRngOff1 Preliminary uncorrected range offset (alternative) 3856 i4b(40) 160
i_preRngOff2 Preliminary uncorrected range offset (standard) 4016 i4b(40) 160
i_centroid1 Centroid retracker offset (alternative) 4176 i4b(40) 160
i_centroid2 Centroid retracker offset (standard) 4336 i4b(40) 160
i_centroidInstr Centroid retracker offset using max peak 4496 i4b(40) 160
i_areaRecWF1 Area under received echo (alternative) 4656 i2b(40) 80
i_areaRecWF2 Area under received echo (standard) 4736 i2b(40) 80
i_maxRecAmp Max amplitude of received echo 4816 i2b(40) 80
i_maxSmAmp Peak amplitude of smoothed received echo 4896 i2b(40) 80
i_reflctUncorr Reflectivity not corrected for atmospheric effects 4976 i4b(40) 160
i_reflctuncmxpk Reflectivity not corrected for atmospheric effects from max peak 5136 i4b(40) 160
i_tpCentX LPA Centroid X 5296 i2b(40) 80
i_tpCentY LPA Centroid Y 5376 i2b(40) 80
i_nPeaks1 Initial number of peaks in received echo (alternative) 5456 i1b(40) 40
i_nPeaks2 Initial number of peaks in received echo (standard) 5496 i1b(40) 40
i_parm1 Parameters from the Gaussian fit to the received echo (alternative) 5536 i4b(19,40) 3040
i_parm2 Parameters from the Gaussian fit to the received echo (standard) 8576 i4b(19,40) 3040
i_solnSigmas1 Sigmas of fit parameters (alternative) 11616 i2b(19,40) 1520
i_solnSigmas2 Sigmas of fit parameters (standard) 13136 i2b(19,40) 1520
i_wfFitSDev_1 Received echo fit standard deviation (alternative) 14656 i2b(40) 80
i_wfFitSDev_2 Received echo fit standard deviation (standard) 14736 i2b(40) 80
i_tpintensity Transmit pulse intensity 14816 i4b(40) 160
i_tpazimuth Transmit pulse azimuth 14976 i2b(40) 80
i_tpeccentricity Transmit pulse eccentricity 15056 i2b(40) 80
i_tpmajoraxis Transmit pulse major axis 15136 i2b(40) 80
i_skew1 Skewness of received echo (alternative) 15216 i2b(40) 80
i_kurt1 Kurtosis of received echo (alternative) 15296 i2b(40) 80
i_skew2 Skewness 15376 i2b(40) 80
i_kurt2 Kurtosis of received echo (standard) 15456 i2b(40) 80
i_WFqual Received echo quality flag (view byte structure) 15536 i4b(40) 160
i_TxNrg 1064 nm laser transmit energy 15696 i2b(40) 80
i_tpOrX Pulse orientation 15776 i2b(40) 80
i_locTr Centroid of transmitted pulse in time relative to gate 1 of transmitted waveform 15856 i4b(40) 160
i_parmTr Parameters of the Gaussian fit to the transmitted pulse 16016 i4b(4,40) 640
i_sDevFitTr Standard deviation of fit of transmitted pulse 16656 i2b(40) 80
i_skewTr Skewness of transmitted pulse 16736 i4b(40) 160
i_maxTrAmp Maximum amp of transmitted pulse 16896 i2b(40) 80
i_gval_tx Gain value used for transmitted pulse - uncalibrated 16976 i2b 2
i_compRatio Compression ratios 16978 i2b(2) 4
i_N_val Value of N 16982 i2b 2
i_r_val Value of r 16984 i2b 2
i_ElvuseFlg Elevation use flag 16986 i1b(5) 5
i_spare3 Spares 16991 i1b 1
i_ElvFlg Elevation definition flag 16992 i1b(40) 40
i_spare49 Spare 49 17032 i1b(10) 10
i_timecorflg Time correction flag 17042 i2b 2
i_APID_AvFlg APID data availability flag 17044 i1b(8) 8
i_AttFlg2 Attitude flag 2 17052 i1b(20) 20
i_spare4 Spares 17072 i1b 1
i_FrameQF Altimeter frame quality flag 17073 i1b 1
i_OrbFlg POD flag (orbit flag) 17074 i1b(2) 2
i_rngCorrFlg Range correction flag 17076 i1b(2) 2
i_spare5 Spares 17078 i1b(2) 2
i_beam_coelev Co-elevation 17080 i4b 4
i_beam_azimuth Azimuth 17084 i4b 4
i_AttFlg1 Attitude flag 1 17088 i2b 2
i_RMSpulseWd RMS pulse width 17090 i2b(40) 80
i_satNdx Saturation index 17170 i1b(40) 40
i_RecNrgAll Received Energy signal begin to signal end 17210 i2b (40) 80
i_numIters Number of iterations performed during fit 17290 i1b (40) 40
i_Spare6 Spare 6 17330 i1b(70) 70

Page last updated: 01/11/13