The great circle distance calculation was taking up too much code space and time, so it's just calculating the Euclidean distance and fudging the X distance by a factor that depends on the latitude. I think I figured that it was accurate to a few percent at normal APRS distances.
Scott Dan zubey wrote: > > > Hey Scott, > > Do the calculations take into account the curvature of the earth? > > A straight line from here to 100 mi from here goes through some dirt. > Driving there is a little bit farther than 100mi. > > Just occured to me while sitting here. > > -Dan > ___ > Sent with SnapperMail > www.snappermail.com > > ...... Original Message ....... > On Thu, 17 Sep 2009 19:57:04 -0700 "Scott Miller" <[email protected] > <mailto:scott%40opentrac.org>> > wrote: > >But the very close position (~30 ft) was correct, right? > > > >I'm not sure what's going on here. The calculation itself is fairly > >simple. Seems more likely that it's a decoding problem. > > > >Scott > > > >Fred Hillhouse wrote: > >> > >> > >> Hi Scott, > >> > >> I will see what I can capture. It will take a few days to get it. At > the > >> moment, PNRDVL is off the air for some testing on another system. It > >> will return on Friday evening. > >> > >> The distance on the GPS always appears correct. And the waypoint is > >> always where it should be. > >> > >> On the LCD, the distance appears to be consistently much longer when > the > >> distance is short. How short I don't know. I will have to do some more > >> data gathering and forward it. > >> > >> Best regards, > >> Fred > >> > >> > >> > >> > >> > ---------------------------------------------------------- > >> *From:* [email protected] <mailto:tracker2%40yahoogroups.com> > [mailto:[email protected] <mailto:tracker2%40yahoogroups.com>] > >> *On Behalf Of *Scott Miller > >> *Sent:* Tuesday, September 15, 2009 21:36 > >> *To:* [email protected] <mailto:tracker2%40yahoogroups.com> > >> *Subject:* Re: [tracker2] Distance calculations > >> > >> > >> > >> Hmmm. Is the reported distance consistent? Can you send me an example > >> of a raw packet that it's reporting incorrectly? > >> > >> Scott > >> > >> Fred Hillhouse wrote: > >> > > >> > > >> > HI Scott, > >> > > >> > That is correct. > >> > > >> > Best regards, > >> > Fred > >> > > >> > ---------------------------------------------------------- > >> > *From:* [email protected] <mailto:tracker2%40yahoogroups.com> > >> <mailto:tracker2%40yahoogroups.com> [mailto:[email protected] > <mailto:tracker2%40yahoogroups.com> > >> <mailto:tracker2%40yahoogroups.com>] > >> > *On Behalf Of *Scott Miller > >> > *Sent:* Tuesday, September 15, 2009 00:24 > >> > *To:* [email protected] <mailto:tracker2%40yahoogroups.com> > <mailto:tracker2%40yahoogroups.com> > >> > *Subject:* Re: [tracker2] Distance calculations > >> > > >> > > >> > > >> > Is that showing 4 miles on the LCD and 0.27 miles on the GPS? > >> > > >> > Scott > >> > > >> > Fred Hillhouse wrote: > >> > > > >> > > [Attachment(s) <#TopText> from Fred Hillhouse included below] > >> > > > >> > > Hi Scott, > >> > > > >> > > I noticed a slight distance discrepancy the other day and > >> > captured a photo. > >> > > Or I have a incorrect setting. I am good with either option. It > >> > looks like > >> > > the range calculations are okay when the distance is close but > >> > not when it > >> > > is further way. I have seen this several times. > >> > > > >> > > Thanks! > >> > > > >> > > Best regards, > >> > > Fred > >> > > > >> > > > >> > > >> > > >> > >> > > > > > > > >------------------------------------ > > > >Yahoo! Groups Links > > > > > > > >
