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Lunch APRS Track 4/25/08

Sam Buchanan

been here awhile
An invitation to lunch at MSL has been graciously extended by fellow RVer Billy Baggett, so N399SB should be launching for the brief flight from DCU about 11:30am CST.

If you haven't had a chance to see an APRS track develop in real time, use this link to watch N399SB drop little red breadcrumbs on the DCU-MSL-DCU flight:

http://aprs.fi/?call=N399SB&mt=m&z=10&timerange=3600

If you are not familiar with Google maps, here are a few pointers:

The map can be panned by holding down the left mouse button and dragging the map. Don't use the mouse wheel unless you want to see the map be rapidly zoomed.

When the cursor is over the map, zoom controls appear in the upper left corner.

You can switch views to satellite or terrain by using the buttons at the top of the map.

The current flight data will appear in the bubble pointing to the latest beacon dot, but you can click on any dot to get data.

On the return flight, if you want to also see the first leg of the flight, you may need to change "Show Last" to "3 hours".

Have a nice flight!
 
Shoot

We lost Sam's crumbs at 1280 at 142mph.... most likely down already but can't tell from here.
 
An invitation to lunch at MSL has been graciously extended by fellow RVer Billy Baggett, so N399SB should be launching for the brief flight from DCU about 11:30am CST.

For some reason the process of getting packets from digipeaters to the aprs.fi server today was really sloppy. Lots of error messages, duplicate packets, etc, not sure where the problem lives, but I suspect most of it resides on the aprs server.

But...the good side of this is that in spite of the network issues, the ground track was still usable. Even though I am accustomed to seeing better tracking, guess it is some reassurance that APRS seems to work pretty well even when it is having a bad day.

Update: After checking over the raw data, it seems there is one particular digi in my area that is the troublemaker. For some reason it is posting position errors and the aprs.fi server tosses them out as unusable packets.
 
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For some reason the process of getting packets from digipeaters to the aprs.fi server today was really sloppy. Lots of error messages, duplicate packets, etc, not sure where the problem lives, but I suspect most of it resides on the aprs server.

I was wondering if you guys who are having good luck with APRS would be kind enough to post your latest TinyTrak3Config here.

I copied Pete's config but I was having errors today:
http://aprs.fi/?call=N714D

If you look at the raw packets, they came in duplicate, out of order, etc. I left my computer polling an APRS-IS server while I flew, and I can clearly see the dups and the out-of-order issues.

Any advice would be much appreciated for this total newb.
 
I was wondering if you guys who are having good luck with APRS would be kind enough to post your latest TinyTrak3Config here.

I copied Pete's config but I was having errors today:
http://aprs.fi/?call=N714D

If you look at the raw packets, they came in duplicate, out of order, etc. I left my computer polling an APRS-IS server while I flew, and I can clearly see the dups and the out-of-order issues.

Any advice would be much appreciated for this total newb.

Dan, I know of what you speak. Fortunately, even when the system has the occasional hiccup, we usually get a very good track. Sometimes my flights have very clean tracks, and sometimes there are dropped packets due to the server errors.

Here is an explanation of the packet parsing protocol from the guy who owns aprs.fi:

http://oh7lzb.blogspot.com/2008/03/on-duplicate-and-delayed-packets.html

It seems the filters are set pretty tight and that is why we see dropped packets. I have also run into the occasional digipeater that mispositions the plane due to not handling MIC-E compression correctly. This can result in conflicts with the parsing on the pars.fi system.

Both Pete and I get these errors sometimes, but I've never seen an instance where they were more than a slight aggravation. Even if 3-4 packets in a row get dropped, we still have a good track of the flight.

However.........your flight was pretty messy and I don't have an answer for why so many errors. You have far deeper software background than I so maybe you can figure out how the errors are created. If you have ideas, I'm sure OH7LZB would be interested in your insight. Of course if the errors are due to problems with your local digi population, I'm not sure how we address that. This is Amateur Radio after all. :)

Maybe APRS was just having a bad day?? Guess if you see similar results over the course of several flights you can assume a definite pattern of problems. I wonder if a large number of digipeaters in the same area and getting hit by an airborne tracker with the resulting server traffic jam would create this scenario?

To address your inquiry, here is one of the configs I've used with success:

tracker_config.jpg


Here is another site that compiles APRS packets showing your flight:

http://www.findu.com/cgi-bin/track.cgi?call=N714D

Unfortunately the map is far inferior to aprs.fi, but you can examine the raw APRS packet data if you want to delve into this a bit deeper. Might be interesting to compare that data to the data on aprs.fi.
 
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One More

Dan,

Here is my latest.

trackerconfigmg8.jpg



If you were yankin and bankin hard, you might have had some issues. When I fly tight circles, I get the kind of errors I see in your data
 
Thanks. After looking at the raw packets, I guess I just flooded the system with too many packets. I was pretty much constantly turning, so I suppose SmartBeacon went a little nuts. Then there were some sequence issues. Duplicate packets got into the system at different times, interlacing with other duplicates, causing the track to look all wacky.

I need to read that link you sent about APRS parsing & sequencing...thanks for that.

BTW...FWIW, my antenna setup was the Byonics VHF Antenna V1 duct taped to the inside of my canopy. Actually, the whole contraption, 9V and all, was duct taped in there. Just a hack setup for testing.

Eventually once I steal everybody's good ideas I'll have a working system. ;-)
 
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