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Position Ambiguity [was] Re: [aprssig] findu.com Location off by 100 miles.

Robert Bruninga bruninga at usna.edu
Tue Jun 6 20:24:40 UTC 2006


>>Until *all* the applications that use GoogleMaps, NavTeq maps, 
>>TIGER databases, and other sources of imprecise online mapping 
>>stop using "pinpoints" and start using "blobs"...
>
>I've been the topic of some of your public criticsm on this list. 
>So I'd like to respond by asking you to provide me, pubically, 
>with a nice algorithm for the above and help me implement it 
>for APRS World's maps. 

Although that question was not directed at me, I'd like to kibitz
if I could...  APRSworld is a fantastic resource and please
do not take these comments as criticism, but as suggestions
for improving the human interface more in keeping with the original
intent of APRS.  

1) RANGE SCALE.  THis lets all viewers see in a consistent manner
the approximate range that a given zoom covers.  Range is the 
approximate distance from the center of the map to the edge.  
Range is a common term in HAM radio as well as most tactical 
display systems.  If I am looking at an "8 mile" map on WinAPRS 
zoomed in on Washington DC, I  should see approximately the same 
thing as an "8  mile" map on UIview.    THe software should 
calculate and display the Range Scale on all displays so that 
when people are communicating what they are seeing, they are 
both referring to the same "apples", not oranges.

APRSworld approximates this description of map view by using a scale 
of  Street, Town, County and Regional.  But those terms are kind of 
ambiguous and do not have the consistancy of the original APRS 
standard of RANGE SCALE.  I'd like to see the selection be based
on Range scale.  Most people know what size they want to look at
and could easily select a map based on the APRS standard of 
Range.

2)  Position ambiguity.  My preferences for displaying the various
transmitted precisions are:
a) do nothing if the size of the "icon" is larger than the area of 
    ambiguity on the presently zoomed map.
b) If the size of the ICON is significantly smaller than the area of 
    ambiguity either draw a circle or rectangle instead, showing the 
    approximate area of ambiguity...
c) or if you cannot draw these areas, then do not show the
    ICON at all, and somehow convey to the viewer (maybe by text)
    that the requested zoom scale is inappropriate for viewing the
    transmitted resolution of the given object.  This works well when
    looking at one object.

d) If someone is zoomed into say the 16 mile range scale and one of
the stations on the map is a manual position with 10 mile ambiguity,
then I would suggest a little list off to the side that implies this meaning:
"The following stations with 10 mile ambiguity are somewhere in this 
map view, but their precise position is not being sent by the originator."

Because in many areas, a 10 mile circle on a map with 50 other
stations is not very user friendly either.

e) Or invent some other method that is unimstakeably communicated
    to the viewer.

Just some ideas.  I hope you can think of some
clever ways to implement them.

thanks
Bob, WB4APR






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