NOAA KLM User's Guide

Section 9.2.1

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9.2.1 Mapped GAC (Polar Stereographic) Product

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.

Table 9.2.1-1. General structure of the polar stereographic KLM Master Map cartridge.
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.

9.2.1-2. Format of documentation record for polar stereographic KLM Master Map data.
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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