L1B -- NOAA Polar Orbiter Level 1b Data Set (AVHRR)
GDAL supports NOAA Polar Orbiter Level 1b Data Set format for reading. Now it can
read NOAA-9(F) --- NOAA-17(M) datasets. NOTE: only AVHRR instrument supported
now, if you want read data from other instruments, write to me (Andrey Kiselev,
dron@ak4719.spb.edu). AVHRR
LAC/HRPT (1 km resolution) and GAC (4 km resolution) should be processed
correctly.
Georeference
Note, that GDAL simple affine georeference model completely unsuitable for
the NOAA data. So you should not rely on it. It is recommended to use the
thin plate spline warper (tps). Automatic image rectification can be done with
ground control points (GCPs) from the input file.
NOAA stores 51 GCPs per scanline both in the LAC and GAC datasets. In fact
you may get less than 51 GCPs, especially at end of scanlines. Another approach
to rectification is manual selection of the GCPs using external source of
georeference information.
Precision of the GCPs determination depends from the satellite type. In the
NOAA-9 -- NOAA-14 datasets geographic coordinates of the GCPs stored in
integer values as a 128th of a degree. So we can't determine positions more
precise than 1/128=0.0078125 of degree (~28"). In NOAA-15 -- NOAA-17 datasets
we have much more precise positions, they are stored as 10000th of degree.
Image will be always returned with most northern scanline located at the top of
image. If you want determine actual direction of the satellite moving you
should look at LOCATION metadata record.
Data
In case of NOAA-10 in channel 5 you will get repeated channel 4 data.
AVHRR/3 instrument (NOAA-15 -- NOAA-17) is a six channel radiometer, but only
five channels are transmitted to the ground at any given time. Channels 3A and
3B cannot operate simultaneously. Look at channel description field reported
by gdalinfo to determine what kind of channel contained in processed file.
Metadata
Several parameters, obtained from the dataset stored as metadata records.
Metadata records:
- SATELLITE: Satellite name
- DATA_TYPE: Type of the data, stored in the Level 1b dataset (AVHRR
HRPT/LAC/GAC).
- REVOLUTION: Orbit number. Note that it can be 1 to 2 off the
correct orbit number (according to documentation).
- SOURCE: Receiving station name.
- PROCESSING_CENTER: Name of data processing center.
- START: Time of first scanline acquisition (year, day of year,
millisecond of day).
- STOP: Time of last scanline acquisition (year, day of year,
millisecond of day).
- LOCATION: AVHRR Earth location indication. Will be Ascending
when satellite moves from low latitudes to high latitudes and Descending
in other case.
See Also:
- Implemented as gdal/frmts/l1b/l1bdataset.cpp.
- NOAA Polar Orbiter Level 1b Data Set documented in the ``POD User's
Guide'' (TIROS-N -- NOAA-14 satellites) and in the ``NOAA KLM User's Guide''
(NOAA-15 -- NOAA-16 satellites). You can find this manuals at
NOAA Technical Documentation Introduction Page
- Excellent and complete review contained in the printed book ``The
Advanced Very High Resolution Radiometer (AVHRR)'' by Arthur P. Cracknell,
Taylor and Francis Ltd., 1997, ISBN 0-7484-0209-8.
- NOAA data can be downloaded from the
Comprehensive Large Array-data Stewardship System (CLASS)
(former SAA). Actually it is only source of Level 1b datasets for me, so my implementation
tested with that files only.
- NOAA spacecrafts status page