Re: Odd patterns from a station

Lynn Deffenbaugh

Ok.  KJ6DZB-3 is a SainSonic AP510 which, IIRC, is tricky to set a symbol in.  This station managed to set a symbol to the secondary table (\) lower case L (l) which is an "Area Object" to APRS.  This is described in chapter 11 on page 60 of aprs101.pdf.  Basically, because of this symbol, the nnn/mmm in the station's packets are being interpreted as the type, color, and lat/lon offsets of an area object.  Here's the salient section from aprs101.pdf:

Area Objects
Using the \l symbol (i.e. the lower-case letter “L” symbol from the Alternate
Symbol Table) it is possible to define circle, line, ellipse, triangle and box
objects in all colors, either open or filled in, any size from 60 feet to 100

These Objects are useful for real-time events such as for a search-and-rescue,
or adding a special road or route for a special event.

The Object format is specified as a 7-character APRS Data Extension
Tyy/Cxx immediately following the l Symbol Code. For example:
;OBJECTVVV*ddmm.hhN\dddmm.hhW l Tyy/Cxx


T is the type of object shape.
/C is the color of the object.
yy is the square root of the latitude offset in 1/100ths of a degree.
xx is the square root of the longitude offset in 1/100ths of a degree.

The object type and color codes are as follows:

The latitude/longitude position is the upper left corner of the object, and the
offsets are relative to this position — the yy offset is down from this position
and the xx offset is to the right of this position. (An exception is the special
case of a Type 6 line which is drawn down and to the left).

and it goes on to provide some examples of this.

So, APRSIS32 is just displaying what the station is (inadvertently, most likely) asking it to display.  If you can contact this operator, have him set his symbol to something else and the visual effects should quit happening and the nnn/mmm will go back to being interpreted as speed and heading as s/he likely intends.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

On 4/7/2018 9:07 PM, Arnold Harding kq6di@... [aprsisce] wrote:

I’m seeing odd patterns of lines appear from a station, and I’m wondering why.  The station is KJ6DZB-3 in the San Francisco Bay Area (Berkeley to be more precise)..

I’ve seen multi-sided almost circles, vertical lines.  The lines might go 100 km, sometimes just North, other times North and South.  The “circle” is odd because it’s not round.


Insight would be appreciated.





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