NWS ftp radar product sn.xxxx

[Andy Jackson]

I'm writing a program that may solve a radar data problem when I am in CDMA data locations. I should be able to write this program with minimal issues except for translating the "sn.xxxx" file format to a graphical representation as JPG or PNG. I was wondering if anyone knows of a specification for this file format (whatever they call it). I have sent the NWS an email for this particular issue but haven't received a response. If you know of a publication on this subject or all of the NWS products that would be helpful too.

 

[Skip Talbot]

Which product does the sn.xxxx file represent? I've been writing my own decoder and viewer, but can't remember the naming conventions off the top of my head. I did look at the documentation for those file specifications, but it was pretty grisly. I could dig it up again if I looked. An easier approach that I found was to follow an existing implementation in the open source, Java based NCDC Weather and Climate Toolkit:
http://www.ncdc.noaa.gov/oa/wct/source.php

The level 3 radar products are not that complex once you know where stuff is... just a few properties in the header, and then a couple loops to iterate through the pixel data gets you everything. The documentation makes it look a lot more complicated.

Here's some documentation, not sure if these are the right ones:
http://www.ncdc.noaa.gov/doclib/?choice=complete&searchstring=&submitted=1&submit_form=Search

I'm moving this out of B&G since writing software to decode radar is on topic and it will get more exposure.

 

[Andy Jackson]

sn.xxxx is for a radar product, here's a sample directory for koax: ftp://tgftp.nws.noaa.gov/SL.us008001/DF.of/DC.radar/DS.p38cr/SI.koax/. There are many other products as well and from previous binary file experience some sort of specification is always helpful to avoid guessing what the fields represent. I threw it out here to see if anyone has any experience with these files.

 

[rdale]

Those are the exact files that every radar viewing program in existence uses... I'm not sure the authors will be giving away their algorithms anytime soon

The format is spelled out in the ICDs available from NWS. http://www.roc.noaa.gov/WSR88D/Program/ICDs.aspx

 

[Skip Talbot]

You can download Eclipse for free and launch WCT from the debugger and break in the code where that file gets opened. It reads the header and then decodes the bins (the pixel data). The variable names are pretty easy to understand if you're familiar with the radar products and how they work (like the tilt, elevation, scan angle). It made a lot more sense to me than trying to read the specifications at least. I can probably fire up my project and help if you run into any specific snags figuring stuff out.

 

[Andy Jackson]

Those are the exact files that every radar viewing program in existence uses... I'm not sure the authors will be giving away their algorithms anytime soon

The format is spelled out in the ICDs available from NWS. http://www.roc.noaa.gov/WSR88D/Program/ICDs.aspx

I'm not looking for any algorithms, but thanks for the link that should be all I need.