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20020730: Nexrad Level II Data

>From: Alan Bruno <address@hidden>
>Organization: ?
>Keywords: 200207302203.g6UM3K914425 NEXRAD

Alan,

I apologize for not being able to respond to your inquiry earlier.

>I am working on a project to determine, as accurately as I can, the
>location of a flight path of an aircraft relative to a cell.  (My
>background is engineering and piloting, so Nexrad is somewhat foreign to
>me).  I have determined the flight path quite accurately.  And I have
>Nexrad II and III images in the vicinity, but would prefer to be working
>with discrete data.
>
>I have received archived Nexrad data for the period I am interested in
>and have been trying to determine if the data can provide me with
>discrete information such as:time, range, azimuth, db level.  In
>reviewing the FMH handbook, I know that a lot more is recorded.  I have
>downloaded and run the NCDC Iras software, but the results have been
>problematic.
>
>Is the Nexrad image the most basic form of the data from the results of
>a sweep of the radar?

The image data you are referring to is the most commonly available form
of the NEXRAD data.  The images are products produced at the radar PUPs
and distributed to end users by the NOAAPORT broadcast in near realtime.
These products are referred to as Level III data.

>In other words, the data is never archived as
>discrete data but is archived as a image only?

There is a new initiative at NCDC to archive the full volume scan data
from the NEXRADS.  This data is referred to as Level II data.  It
would be best to contact NCDC for the status of this project.

>If it is not an image, is there extraction software available to look at
>the underlying data listing? (Operating on a Windows OS)

There are software packages designed to display and analyze Level II
data.  One such package is the OpenRPG package developed by NSSL.
This is most easily found by doing a web search on ORPG.

>Or, if it is an image, is it readily possible for me to extract the
>image file in a manner in which I can readily look at the reflectivity
>on a pixel by pixel basis by perhaps using the proper decompression
>algorithm to view the image?

The NEXRAD Level III images are sent either in radial or raster format
(both are compressed, however).  The raster formatted ones are most
easy to read out things like reflectivity on a pixel-by-pixel basis.
The radial ones can be rasterized so that you can do the same, but
there is extra work involved.  We provide software to our sites that
use the data in packages we support, but we do not have generic
software that will extract pixel data out of the products for use
by generic software.

>Thank you,
>Alan Bruno

Tom Yoksas