Really, all you can count on is being inside a 20' or 14' box.... my gps often tells me it's "accuracy" is 6', but I know the reality... garmin is usualy a little optimistic. As I write this, I see that Gerry is threating to turn on GPS lecture series (lol). Back when I first got into APRS, my GPS wandered in a 100' circle. APRS offered display within a 60' x 60' box. The width of that box varies based on your latitude. The weak link was the GPS.
Once SA was turned off, my GPS began to wander in a 20' circle. When WAAS came on, it wandered in a 14' circle. Now the weak link is the number of digits of precision in the APRS system. DAO adds the needed digits. Funny thing is, just where you want GPS to work good... let's say to mark a spot in the woods, the accuracy goes out the window with the heavy foilage. Even with WAAS. DAO format is a great improvement over the 60' square boxes now that GPS units resolve positions smaller than those boxes. However, if you call the random spot you could be at inside a 20' box a "lie" lol.... then all DAO does is tell a much more detailed / better lie. I'm not meaning to sound negative here at all, just being realistic. At least with DAO, the weak link is back in the court of the GPS, not the precision of the reporting system. While this may sound like a waste to some, another use for the increased precision is in placing objects manually on a map. Wes --- Our lives begin to end the day we become silent about things that matter On Sat, Aug 16, 2008 at 10:33 AM, Jim Tolbert <[EMAIL PROTECTED]>wrote: > Running back to the desire for DAO packets..... I am assuming that with > standard APRS packets having 2 decimal places and DAO having 3 decimal > places that I will be locating a particular GPS receiver to an area that is > an order of magnitude more precise. I am probably not saying this > correctly, but with the standard APRS packet, I have an area of uncertainty > of about 20' x 40' ( in northern Wisconsin, US ( N45,W92)). By moving to a > DAO packet, I will have an area of uncertainty of about 2' x 4'. > > If I have a bunch of GPS receivers of the same type, can I assume that the > relative location is pretty good, even if the absolute location may be off a > bit? I am really primarily interested in relative positioning. > > Since Xastir is really just plotting the data it receives, I am going to > post this query on the APRS group as well, but I wanted to be sure to catch > Gerry <grin>........... > > Many thanks, all................... jt > > -- > Jim Tolbert > RiverRidge Consulting, LLC > PO Box 536 > Webster, WI 54893 > > 715-866-4398 home office > > [EMAIL PROTECTED] > > _______________________________________________ > Xastir mailing list > [email protected] > http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir > _______________________________________________ Xastir mailing list [email protected] http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
