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20010405: NIDS Data Format



>From:  "charles h. murphy" <address@hidden>
>Organization:  Kean University
>Keywords:  200104051732.f35HWHL25802 NEXRAD Level III format

Charlie,

>       Hope you are well, it acutally feels as if
>spring will arrive here in the east finally.

It really feels like spring here.  It has been up to the lower 70s a
few times already, and this week has been hovering in the upper 60s
consistently.

>       I was wondering if you know where I can find
>the format of the Level III radar data files. I wanted
>to try someting with the data and need the format.
>
>       If you can point me in the right direction
>I would really appreciated it.

There are a couple of documents you will need:  the first is the
document that describes the unzlib-compressed format, and the second is
a description of the zlib compression that gets applied to the original
format.  If you are looking for documentation of the WSI NIDS format,
then you don't have to worry about the zlib-compressed bit.  If, like I
suspect, you are looking for the format of the images now being freely
distributed in NOAAPORT, then you have to worry about both of the
things above.

The document that describes the unzlibed compressed data formats that we
have used here for quite some time is labled:

CDRL 221
Communications Interface Users Guide (Part IV)
For Class IV Users

Document Number 1213304-4B
Code Identification 56232
1 December 1992

This document describes more than you would ever want to know about the
unzlib-compressed NEXRAD Level III products.  Unfortunately, I don't know
where to get this.

I _think_ that all of the documentation you will need is accessible from:

NOAAPORT User's Page
http://www.nws.noaa.gov/noaaport/html/noaaport.shtml

I went to it and trapsed down the following path that I think leads to
most of the documents you need:

What's New
http://www.nws.noaa.gov/noaaport/html/whats_nw.shtml

From there, check out:

Radar Product Compression Approach
 
and

RPCCDS

Under the RPCCDS link, you will find:

"Radar Product Compression Approach" is a link to a pdf docuemnt.

Data Formats of radar products are supposedly found in the NEXRAD ICDs 
http://www.osf.noaa.gov/ssb/cm/icd_downloads.asp

The last page appears to be some kind of an order form for getting all of
the Interface Control Documents (ICDs).  The information you need is mostly
in them.

As you can see, there is not _one_ document that describes everything.
Such is the way of the government :-(

The other option you have is to read either/or the McIDAS or GEMPAK
source code that does the unpacking and reading of the image products.
I can give you the help you need to understand the McIDAS side, and
Chiz can most likely give you some help understanding the GEMPAK side.
Please let me know if you would like to pursue this.

>Thanks,

What exactly is it that you want to do?

Tom
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