NOAA KLM User's GuideSection 9.2.1 |
The mapped GAC (polar stereographic) data are organized as daytime and nighttime for the northern and southern hemispheres. The daytime data contain both visible (Channel 1) and IR (Channel 4) data while the nighttime data contain only the IR data. The data are reported in pairs of files. The first file of each file pair consists of a documentation record for that variable, immediately followed by an EOF and a second file containing the data records for the same variable. All records are 16,384 bytes in length. Both documentation and data records are in binary format and have the same length. A value of zero indicates missing data.
Every day a 3480 cartridge is created which contains one day of data in the polar stereographic projection. Table 9.2.1-1 contains the general file structure of this daily KLM Master map cartridge. Each cartridge contains 12 files arranged as shown in Table 9.2.1-1.
The variables reported in the documentation record are all INTEGER*2 with the exception of the satellite type in the first two bytes of the record, which is CHARACTER*2. Table 9.2.1-2 defines the basic documentation record format.
Each data record (16,384 bytes) consists of four mapped rows, each containing 4096 pixels of data. Each pixel is represented by one byte of data.
| File, record # | Contents |
|---|---|
| DAYTIME NORTHERN HEMISPHERE | |
| Visible Channels | |
| F1, rec. 1 | Channel 1 documentation record. See Table 9.2.1-2 for format |
| F2, rec. 1-1024 | Channel 1 data records. Consists of 16,384 bytes of data or 4 mapped rows of data. Each row contains 4096 pixels of data. Each pixel is one byte. A value of 0 indicates missing data |
| IR Channels | |
| F3, rec. 1 | Channel 4 documentation record. See Table 9.2.1-2 for format |
| F4, rec. 1-1024 | Channel 4 data records. Same as F2 data records |
| DAYTIME SOUTHERN HEMISPHERE | |
| Visible Channels | |
| F5, rec. 1 | Channel 1 documentation record. See Table 9.2.1-2 for format. |
| F6, rec. 1-1024 | Channel 1 data records. Same as F2 data records |
| IR Channels | |
| F7, rec. 1 | Channel 4 documentation record. See Table 9.2.1-2 for format. |
| F8, rec. 1-1024 | Channel 4 data records. Same as F2 data records. |
| NIGHTTIME NORTHERN HEMISPHERE | |
| IR Channels | |
| F9, rec. 1 | Channel 4 documentation record. See Table 9.2.1-2 for format. |
| F10, rec. 1-1024 | Channel 4 data records. Same as F2 data records |
| NIGHTTIME SOUTHERN HEMISPHERE | |
| IR Channels | |
| F11, rec. 1 | Channel 4 documentation record. See Table 9.2.1-2 for format. |
| F12, rec. 1-1024 | Channel 4 data records. Same as F2 data records. |
| Byte #s | Contents |
|---|---|
| 1-2 | Satellite type, e.g., NH=NOAA-H (CHARACTER*2) |
| 3-4 | Satellite ID: 0=morning satellite; 1=afternoon sat. |
| 5-6 | Data set type: 1=LAC; 2=GAC; 3=HRPT |
| 7-8 | Projection type: 0=unmapped; 1=Mercator; 2=Polar; 3=linear lat/lon |
| IMAGE BOUNDARIES | |
| 9-10 | Beginning latitude x 128; North>0; South<0 |
| 11-12 | Ending latitude x 128 |
| 13-14 | Beginning longitude x 128; East>0; West<0 |
| 15-16 | Ending longitude x 128 |
| 17-18 | Mapped resolution x 100; km for polar and mercator projections; degree/pixel for linear lat/lon projections; sampling interval for unmapped projection |
| 19-22 | Spares |
| POLAR PROJECTION DATA | |
| 23-24 | Polar grid mesh size (grid size that corresponds to resolution, e.g., 64 = 1/64 grid) |
| 25-26 | Number of grid points (that correspond to grid size, e.g., 1/64 grid corresponds to 4096 points) |
| 27-28 | Hemisphere: 1=Northern; -1=Southern |
| 29-30 | Prime longitude; East>0; West<0 |
| GRID OFFSETS | |
| 31-32 | IOFF; grid coordinates of top left corner of the image. (not applicable for unmapped projections) |
| 33-34 | JOFF |
| IMAGE SIZE | |
| 35-36 | Number of rows |
| 37-38 | Number of Columns |
| 39-42 | Spares |
| 43-44 | Composite flag: 0=no composite; 1=composite based on minimum nadir angle; 2=retain average value; 3=retain later value; 4=retain warmer value; 5=retain colder value |
| 45-46 | Calibration flag: 0=raw counts; 1=radiances; 2=calibrated to albedos and BTs; 3=calibrated to albedos and GOES counts |
| 47-48 | Fill-up options: 0=no fill-up; 1=fill-up using averages; 2=fill-up using adjacent pixel values |
| 49-50 | Channel number: 1-5=channel number; 101 = scan angle; 102 = satellite zenith angle; 103 = solar zenith angle; 104 = relative azimuth angle; 105 = scan time; 201 = SST split window; 202 = SST dual window; 203 = SST Triple window |
| 51-52 | Data ID: 0=visible; 1=infrared; 2=ancillary |
| DATA CORRECTION FLAGS | |
| 53-54 | Sun normalization: 0=not performed; 1=performed |
| 55-56 | Limb correction: 0=not performed; 1=performed |
| 57-58 | Nonlinearity correction: 0=not performed; 1=performed |
| 59-60 | Number of orbits processed |
| CHANNEL IMAGES | |
| 61-62 | Number of channels produced |
| 63-64 | Pixel size: 1=1 byte; 2=2 bytes |
| 65-66 | Starting block number |
| 67-68 | Ending block number |
| ANCILLARY DATA | |
| 69-70 | Number of ancillary parameters produced |
| 71-72 | Pixel size: 1=1 byte; 2=2bytes |
| 73-74 | Starting block number |
| 75-76 | Ending block number |
| 77-78 | Block size of image files |
| 79-80 | Compression flag |
| 81-100 | Spares |
| ORBIT 1 INFORMATION | |
| 101-102 | Orbital node over region: -1=asc; 1=desc; 2=both |
| 103-104 | Day/night flag: 0=day; 1=night |
| IMAGE DATA BOUNDARIES | |
| 105-106 | Start row |
| 107-108 | Start column |
| 109-110 | End row |
| 111-112 | End column |
| ORBIT START TIME | |
| 113-114 | Year of century |
| 115-116 | Day of year |
| 117-118 | Month and day of month (month x 100) + day |
| 119-120 | Hours and minutes (hours x 100) + minutes |
| 121-122 | Seconds |
| 123-124 | Milliseconds |
| ORBIT END TIME | |
| 125-126 | Year of century |
| 127-128 | Day of year |
| 129-130 | Month and day of month (month x 100) + day |
| 131-132 | Hours and minutes (hours x 100) + minutes |
| 133-134 | Seconds |
| 135-136 | Milliseconds |
| 137-138 | Processing block ID (orbit number) |
| QUALITY FLAGS | |
| 139-140 | Ramp/auto calibration flag |
| 141-142 | Number of data gaps |
| 143-144 | Sync errors |
| 145-146 | TIP parity errors |
| 147-148 | Auxiliary errors |
| 149-150 | Calibration parameter ID |
| 151-152 | DACS status |
| CALIBRATION COEFFICIENTS | |
| 153-154 | Channel 1 slope x 10,000 |
| 155-156 | Channel 1 intercept x 1,000 |
| 157-158 | Channel 2 slope x 10,000 |
| 159-160 | Channel 2 intercept x 1,000 |
| 161-166 | Spares |
| ORBIT 2 INFORMATION | |
| 167-232 | Same as bytes 102-166 |
| ORBIT 3 INFORMATION | |
| 233-298 | Same as bytes 102-166 |
| ... | ... |
| ... | ... |
| ORBIT n INFORMATION | |
| ((n-1) x 66+102) -((n-1)x 66+166) | Same as bytes 102-166 |
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