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<html><head><title>L1B -- NOAA Polar Orbiter Level 1b Data Set (AVHRR)</title></head><body bgcolor="#ffffff"><h1>L1B -- NOAA Polar Orbiter Level 1b Data Set (AVHRR)</h1>GDAL supports NOAA Polar Orbiter Level 1b Data Set format for reading. Now it canread NOAA-9(F) --- NOAA-17(M) datasets. NOTE: only AVHRR instrument supportednow, if you want read data from other instruments, write to me (Andrey Kiselev, <a href=mailto:dron@ak4719.spb.edu>dron@ak4719.spb.edu</a>). AVHRRLAC/HRPT (1 km resolution) and GAC (4 km resolution) should be processedcorrectly.<h2>Georeference</h2>Note, that GDAL simple affine georeference model completely unsuitable forthe NOAA data. So you should not rely on it. It is recommended to use thethin plate spline warper (tps). Automatic image rectification can be done withground control points (GCPs) from the input file.NOAA stores 51 GCPs per scanline both in the LAC and GAC datasets. In factyou may get less than 51 GCPs, especially at end of scanlines. Another approachto rectification is manual selection of the GCPs using external source ofgeoreference information.<br>Precision of the GCPs determination depends from the satellite type. In theNOAA-9 -- NOAA-14 datasets geographic coordinates of the GCPs stored ininteger values as a 128th of a degree. So we can't determine positions moreprecise than 1/128=0.0078125 of degree (~28"). In NOAA-15 -- NOAA-17 datasetswe have much more precise positions, they are stored as 10000th of degree.<br>Image will be always returned with most northern scanline located at the top ofimage. If you want determine actual direction of the satellite moving youshould look at <b>LOCATION</b> metadata record.<h2>Data</h2>In case of NOAA-10 in channel 5 you will get repeated channel 4 data.<br>AVHRR/3 instrument (NOAA-15 -- NOAA-17) is a six channel radiometer, but onlyfive channels are transmitted to the ground at any given time. Channels 3A and3B cannot operate simultaneously. Look at channel description field reportedby <tt>gdalinfo</tt> to determine what kind of channel contained in processed file.<h2>Metadata</h2>Several parameters, obtained from the dataset stored as metadata records. <p>Metadata records:<p><ul><li> <b>SATELLITE</b>: Satellite name<p><li> <b>DATA_TYPE</b>: Type of the data, stored in the Level 1b dataset (AVHRRHRPT/LAC/GAC). <p><li> <b>REVOLUTION</b>: Orbit number. Note that it can be 1 to 2 off thecorrect orbit number (according to documentation).<p><li> <b>SOURCE</b>: Receiving station name.<p><li> <b>PROCESSING_CENTER</b>: Name of data processing center.<p><li> <b>START</b>: Time of first scanline acquisition (year, day of year,millisecond of day).<p><li> <b>STOP</b>: Time of last scanline acquisition (year, day of year,millisecond of day).<p><li> <b>LOCATION</b>: AVHRR Earth location indication. Will be <b>Ascending</b>when satellite moves from low latitudes to high latitudes and <b>Descending</b>in other case.<p></ul><h2>See Also:</h2><ul><li> Implemented as <tt>gdal/frmts/l1b/l1bdataset.cpp</tt>.<p><li> NOAA Polar Orbiter Level 1b Data Set documented in the ``POD User'sGuide'' (TIROS-N -- NOAA-14 satellites) and in the ``NOAA KLM User's Guide''(NOAA-15 -- NOAA-16 satellites). You can find this manuals at<a href="http://www2.ncdc.noaa.gov/docs/intro.htm">NOAA Technical Documentation Introduction Page</a><p><li> Excellent and complete review contained in the printed book ``TheAdvanced Very High Resolution Radiometer (AVHRR)'' by Arthur P. Cracknell,Taylor and Francis Ltd., 1997, ISBN 0-7484-0209-8.</a><p><li> NOAA data can be downloaded from the <a href="http://www.class.noaa.gov/">Comprehensive Large Array-data Stewardship System (CLASS)</a>(former SAA). Actually it is only source of Level 1b datasets for me, so my implementationtested with that files only. <p><li> <a href="http://www.oso.noaa.gov/poesstatus/">NOAA spacecrafts status page</a></ul></body></html>⌨️ 快捷键说明
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