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8657Re: [tracker2] Distance calculations

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  • Scott Miller
    Sep 18, 2009
    • 0 Attachment
      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" <scott@...
      > <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:* tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>
      > [mailto:tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>]
      > >> *On Behalf Of *Scott Miller
      > >> *Sent:* Tuesday, September 15, 2009 21:36
      > >> *To:* tracker2@yahoogroups.com <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:* tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>
      > >> <mailto:tracker2%40yahoogroups.com> [mailto:tracker2@yahoogroups.com
      > <mailto:tracker2%40yahoogroups.com>
      > >> <mailto:tracker2%40yahoogroups.com>]
      > >> > *On Behalf Of *Scott Miller
      > >> > *Sent:* Tuesday, September 15, 2009 00:24
      > >> > *To:* tracker2@yahoogroups.com <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
      > >
      > >
      > >
      >
      >
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