<?php
require_once "../../../config/settings.inc.php";
require_once "../../../include/myview.php";
$t = new MyView();
$t->iem_resource = "MOSAIC";
$t->title = "About NEXRAD Mosaics";
$d = date("Y/m/d");
$t->content = <<<EOM

<h3>Documentation on IEM generated NEXRAD Mosaics</h3>

<div class="row">
<div class="col-md-6">

<img src="example_raster.png" class="img-fluid" />
<br />Example composite from 1 March 2007.

<h4>Quick Information:</h4>
<table class="table table-striped">
<thead><tr><td></td><th>N0R</th><th>N0Q</th></tr></thead>
<tbody>
<tr>
 <th>Product:</th>
 <td>4 bit Base Reflectivity 5dbz</td>
 <td>8 bit Base Reflectivity 0.5dbz</td>
 </tr>
 
<tr>
 <th>Format:</th>
 <td colspan="2">PNG image (GeoTiff available)</td></tr>

<tr>
 <th>Size:</th>
 <td>6000x2600 pixels</td>
 <td>12000x5200 pixels<br />12200x5400 after 8 Aug 2014</td>
 </tr>
 
<tr>
 <th>Time:</th>
 <td>Every 5 minutes since 1 Jan 1995</td>
 <td>Every 5 minutes since 13 Nov 2010 16:25 UTC</td>
 </tr>

<tr><th>Download:</th>
<td colspan="2"><a href="/data/gis/images/4326/USCOMP/">Current</a> 
and <a href="/archive/data/{$d}/GIS/uscomp/">Archive for today</a></td></tr>
</tbody>
</table>

</div>
<div class="col-md-6">

<table class="table table-bordered">
<thead>
<tr>
 <th colspan="4">Precipitation</th>
 <th colspan="2">N0R (4bit) Reflectivity</th>
 <th colspan="2">N0Q (8bit) Reflectivity</th>
</tr>
</thead>
<tr>
 <td>Ramp</td>
 <td colspan="3">Index values [inch]</td>
 <td>Ramp</td><td>Index values [dBZ]</td>
 <td>Ramp</td><td>Index values [dBZ]</td>
 </tr>
<tr>
<td><img src="precip_ramp.png" width="10" style="float: left;" /></td>
<td valign="top">
0
<br />0.25
<br />0.5
<br />0.75
<br />1.0
<br />1.25
<br />1.5
<br />1.75
<br />2.0
<br />2.25
<br />2.5
<br />2.75
<br />3.0
<br />3.25
<br />3.5
<br />3.75
<br />4
</td>
<td valign="top">
4.8
<br />5.6
<br />6.4
<br />7.2
<br />8.0
<br />8.8
<br />9.6
<br />10.4
<br />11.2
</td><td valign="top">
12
<br />13
<br />14
<br />15
<br />16
<br />17
<br />18
<br />19
<br />20
<br />21
<br />22
<br />23
<br />24+
</td>
<td><img src="reflect_ramp.png" width="20" style="float: left;" /></td>
<td>
NODATA
<br />-30
<br />-25
<br />-20
<br />-15
<br />-10
<br />-5
<br />0
<br />5
<br />10
<br />15
<br />20
<br />25
<br />30
<br />35
<br />40
<br />45
<br />50
<br />55
<br />60
<br />65
<br />70
<br />75
</td>
<td><img src="n0q_ramp.png" width="20" style="float: left;" /></td>
<td>
NODATA
<br />-32 dBZ
<br />through
<br />90 dBZ
<br />0.5 dBZ increment
</td>
</tr></table>

</div></div>

<p><strong>IEM Applications using this product</strong>
<ul>
 <li><a href="/current/mcview.phtml">Static Maps</a></li>
 <li><a href="/GIS/apps/rview/warnings.phtml">Interactive RADAR</a></li>
 <li><a href="/vtec/">VTEC Product Browser</a></li>
 <li><a href="/data/summary/max_n0r_0z0z_usrad.png">Max Reflectivity Mosaic 0z-0z</a></li>
 <li><a href="/data/summary/max_n0r_6z6z_usrad.png">Max Reflectivity Mosaic 6z-6z</a></li>
 <li><a href="/GIS/rad-by-year-fe.phtml">NEXRAD Mosiacs by Year</a></li>
</ul>

<p>Since 2003, the IEM has been generating and archiving nationwide mosaics 
of NEXRAD base reflectivity every 5 minutes.  These mosaics are generated 
by combining the 130+ individual RADARs that comprise the NEXRAD network. This
page provides background information on this dataset and highlights various
ways this dataset can be and is used.  <b>Please note:</b>  Errors can and do
occur during the automated generation of these images, please use them with 
care.

<h3>Important changes to this product.</h3>
<ul>
 <li><b>1 August 2003:</b> 5 minute interval archive begins.  The initial
  pixel resolution is roughly ~2 km.</li>
 <li><b>14 November 2005:</b> The pixel resolution is increased to ~1 km
  thanks to the support of a <a href="/docs/unidata2006/">Unidata Equipment grant</a>.</li>
 <li><b>10 May 2007:</b> Implemented a clutter suppression algorithm to 
  remove most anomalous propogation during the summertime.</li>
 <li><b>11 Nov 2008:</b> Implemented a crude check against RUC model
surface temperature analysis for near freezing areas to stop the clutter
suppression algorithm from removing areas of winter precipitation.</li>
 <li><b>14 May 2009:</b> Completed a 7 month process of backfilling the
mosaics back to 1 Jan 1995. Also regenerated mosaics prior to 2006 to
produce them on a ~1 km grid as well.  Big thanks to Steve Ansari at NCEI 
for providing the level3 archive.</li>
 <li><b>25 Aug 2010:</b> Reprocessed 2005 + 2006 data to improve product
quality and to backfill the archive with clutter suppression enabled during
the summer months (Apr-Sep).</li>
    <li><strong>16 July 2014:</strong> Modified the clutter removal routine
    to use the higher resolution EET level III product.  Previously NET was
    used.</li>
    <li><strong>8 Aug 2014:</strong> The spatial domain of the N0Q composite
    was expanded 1 degree east and south.  The reason is that the clipping was
    occurring on the eastern and southern borders of the domain.</li>
<li><strong>7 Sep 2016 1940 UTC</strong>: The original intent of the N0Q
mosaics was to provide imagery at a resolution of 0.5 dBZ.  After some
investigation, it was discovered that the N0Q mosaics only contained data
at values of whole integer values of dBZ. After some debugging of GEMPAK, the
issue was <a href="https://github.com/Unidata/gempak/pull/11">hopefully fixed within GEMPAK</a>.  The good news is that this bug did
not impact any processing of the file.  The conversion of color index and
RGB colors to dBZ was OK.  There just was not any data at those 0.5 dBZ, non-int
values.</li>
<li><strong>5 May 2021</strong>: The NWS discontinued the dissemination of the
N0R product.  The IEM is now generating a <a href="/onsite/news.phtml?id=1419">pseudo composite</a>
derived from the N0Q composite.</li>
<li><strong>18 April 2022</strong>: The NWS discontinued the dissemination of the
N0Q product.  The IEM is now using <a href="/onsite/news.phtml?id=1431">the N0B product</a>
as the source for N0Q.</li>

<li><strong>28 September 2023</strong>: The NWS discontinued the dissemination of
N1P (1 Hour Precip) and NTP (Storm Total Precip) products.  The IEM is now producing
composites of DAA and DTA instead with no plans of creating a psuedo composite.</li>

</ul>

<h3>Product Generation:</h3>
<div style="float: right; padding: 5px; border: 2px solid #000; margin: 5px;">
<a href="https://mesonet.agron.iastate.edu/archive/data/2007/10/19/usrad/max_n0r_0z0z_20071019.png"><img src="https://mesonet.agron.iastate.edu/archive/data/2007/10/19/usrad/max_n0r_0z0z_20071019.png" width="480"></a>
<br />Composite of mosaics for 18 Oct 2007. Click image for regular size.
</div>
<p>The IEM receives a feed of NEXRAD Level III products from the <a href="http://www.unidata.ucar.edu/software/idd/">Unidata Internet Data Distribution</a>. 
This feed includes the Base Reflectivity (N0R) and Net Echo Top (NET) products
which are saved to disk for later processing.  Every 5 minutes, a script runs
a <a href="http://www.unidata.ucar.edu/software/gempak/">GEMPAK</a> program 
called <a href="http://www.unidata.ucar.edu/cgi-bin/gempak/manual/programs_index?nex2img">nex2img</a>.  nex2img searches the on-disk data for current (within
15 minutes of runtime) products and then mosaics them into a large image.</p>


<p>The result of the nex2img process is a simple raster image with size of 6000
pixels in width by 2600 pixels in height.  This raster image is then compared
with a similiar raster of NET to remove any suspected false echos.  In the
wintertime, this comparison is skipped for most of the country. The final result
is a PNG formatted image looking much like the example image shown above.

<p>The final image is shipped to the IEM webfarm for archival and use. You can
always find the 10 most recently generated rasters <a href="https://mesonet.agron.iastate.edu/data/gis/images/4326/USCOMP/">here</a> (n0r_0* is the newest). 
You can also find current and historical images in the archive.  The format 
for the URL is:
<br /><code style="margin: 20px;">
https://mesonet.agron.iastate.edu/archive/data/YYYY/mm/dd/GIS/uscomp/
</code>
<br />For example, here are the images generated for today:
<code style="margin: 20px;">
https://mesonet.agron.iastate.edu/archive/data/{$d}/GIS/uscomp/
</code>
<br />All dates in the archive are in UTC time.

<h3>Product Format:</h3>

<p>The images are stored in PNG format.  They have a 4-bit colormap and are
non-interlaced.  Images for the past 50 minutes are also available in TIFF, 
GeoTIFF, and gzipped GeoTIFF format.  Most people want to use these images
in a GIS, so world files (.wld or .tfw) are available in the same current and
archive folders.  The projection of these images is in EPSG:4326 (WGS84 longlat).

<p>For some people, the PNG format is not readable by their GIS, so the 
IEM provides a server-side conversion of the PNG files for delivery of a 
GeoTIFF.  This application is called like so:
<br /><code style="margin: 20px;">
https://mesonet.agron.iastate.edu/request/gis/n0r2gtiff.php?dstr=200711010025
</code>
<br />where <i>dstr</i> specifies the {year}{month}{day}{hour}{minute} in UTC
of the requested raster.  Rasters are only available at minutes modulo 5.

<h3>Colormap Information:</h3>

<img src="color_ramp.gif" style="float: left; margin: 10px; border: 1px;">

<p>The raster image has a colormap associated with it. The raw pixel values 
increase monotonically from -30 dbz to 75 dbz every 5 dbz.  All values below
0 dbz are assigned black (rgb 0 0 0).  We have tried to match the commonly
used NEXRAD display as what you see on <a href="http://radar.weather.gov">National Weather Service</a> page. <b>Please note:</b> We do not include a concept
of missing data or "no-data".  So spots with beem blockage in the mountains
or out away from the CONUS are just "black".

<h3>Web Map Service (WMS)</h3>

<p>A special way you can interface with this data archive is via the Web 
Map Service that also supports time based retrieval (<a href="http://www.opengeospatial.org/standards/wms">WMS-T</a>).  Point your WMS-T aware app at:
<br /><code style="margin: 20px;">
https://mesonet.agron.iastate.edu/cgi-bin/wms/nexrad/n0r-t.cgi?
</code>
<br />The <i>nexrad-n0r-wmst</i> layer is time aware!

<h3>Example WMS-T Application</h3>

<p>Here is an <a href="wmst.html">example interface</a> utilizing the WMS-T NEXRAD service. 
        The interface code is a part of the 
        <a href="http://www.openlayers.org/">OpenLayers toolkit</a>. 
        The default time display shows Hurricane Katrina making landfall.
<br />
<iframe src="wmst.html" style="width: 550px; height: 450px;"></iframe>

EOM;
$t->render('single.phtml');
