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Aloha.<br>
You might want to consider simply using Great Circle distances and
then refining that if you need something better.<br>
J.<br>
<br>
<div class="moz-cite-prefix">On 10/22/20 12:50, Peter Borissow
wrote:<br>
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<blockquote type="cite"
cite="mid:1532527642.1931908.1603396215329@mail.yahoo.com">
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<div dir="ltr" data-setdir="false"><span>I agree with Hernán,
that you are probably better off using ellipsoidal
(geodetic) distances rather than projected distances for
such large tracks. <br>
</span>
<div><br>
</div>
<div dir="ltr" data-setdir="false"><span>Of course, you can
use whatever projection you want to RENDER the routes. For
example you can use a conic projection to render the bird
tracks or a orthographic map projection. It all depends on
what message you are trying to convey to your audience. <br>
</span>
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<div id="ydp836de6ecyahoo_quoted_3427699017"
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<div style="font-family:'Helvetica Neue', Helvetica, Arial,
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<div> On Thursday, October 22, 2020, 3:14:34 PM EDT, Charles
Dixon-Paver <a class="moz-txt-link-rfc2396E" href="mailto:charles@kartoza.com"><charles@kartoza.com></a> wrote: </div>
<div><br>
</div>
<div><br>
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<div>
<div id="ydp836de6ecyiv6357707573">
<div>
<div dir="ltr">Pardon my ignorance, but my brain is
burning a bit with this topic... Is there a particular
reason nobody is suggesting the utilisation of an
equidistant projection? I thought this was what they
are optimised for. Albers conic equal area is for the
preservation of area, not distance as far as I'm
aware.
<div><br clear="none">
</div>
<div>I know pretty much nothing of Two Point
Equidistant projections, but considering the field
of interest is migration I feel like this is
probably the most accurate method (depending on
implementation)? I would think an Azimuthal
Equidistant projection centered on the area of
interest would be more accurate than albers at
least... And if the maps look way too funny then use
something like the equidistant conic?</div>
<div><br clear="none">
</div>
<div>This is pure conjecture on my part, so I'd
appreciate the correction if I'm missing the plot...</div>
<div><br clear="none">
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<div class="ydp836de6ecyiv6357707573gmail_quote">
<div class="ydp836de6ecyiv6357707573yqt9759778791"
id="ydp836de6ecyiv6357707573yqtfd89088">
<div class="ydp836de6ecyiv6357707573gmail_attr"
dir="ltr">On Thu, 22 Oct 2020 at 19:35, Falk
Huettmann <<a shape="rect"
href="mailto:fhuettmann@alaska.edu"
rel="nofollow" target="_blank"
moz-do-not-send="true">fhuettmann@alaska.edu</a>>
wrote:<br clear="none">
</div>
<blockquote
class="ydp836de6ecyiv6357707573gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px
solid rgb(204,204,204);padding-left:1ex;">
<div dir="ltr">Hi there, Mike et al,
<div><br clear="none">
</div>
<div>thanks,</div>
<div>but if you check up with Thomas Alerstam
from Sweden - as a bird tracking migration
person you really ought to know those things
and his entire books/papers -</div>
<div>there is sufficient literature on the topic
for years re. projections, e.g. this one for
starters. </div>
<div><a shape="rect"
href="https://urldefense.com/v3/__https://www.researchgate.net/publication/12122402_Migration_Along_Orthodromic_Sun_Compass_Routes_by_Arctic_Birds__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv29mkBPrc$"
rel="nofollow" target="_blank"
moz-do-not-send="true">https://www.researchgate.net/publication/12122402_Migration_Along_Orthodromic_Sun_Compass_Routes_by_Arctic_Birds</a><br
clear="none">
</div>
<div><br clear="none">
</div>
<div>Some others are found with the navigation
sciences, with sea turtle math work (former
Ram Myers) and then rocket and missile
targeting of course.</div>
<div>It's usually not written though by
geography or GIS experts. The Google Earth
maps boldly ignore the projection issue (as
they are just a shiny commercial PR tool).</div>
<div><br clear="none">
</div>
<div>Overall, for birds these days, the public
resource question should sit on CONSERVATION
and sustainable management,</div>
<div>not ivory-tower questions. The latter have
been done for centuries without relevant
outcome and progress.</div>
<div>Yes, the earth is round and an optimal
route exist, but now what ? Birds know and
used that for millennia and their presences
show it no other.. Data exist to that degree.</div>
<div>Other problems are more relevant these
days.</div>
<div><br clear="none">
</div>
<div>A nice question why after 100 years of
research on bird migration, state-funded with
$Mio's, and with MPI and Movebank, ICARUS etc</div>
<div>no readily available solution or answer
exist in R or GIS etc.</div>
<div><br clear="none">
</div>
<div>That's my opinion and answer on your
question. Feel free to follow up as needed.</div>
<div><br clear="none">
</div>
<div>Best regards</div>
<div> Falk Huettmann PhD, Professor</div>
<div> Uni of Alaska Fairbanks</div>
<div><br clear="none">
</div>
</div>
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<div class="ydp836de6ecyiv6357707573gmail_quote">
<div class="ydp836de6ecyiv6357707573gmail_attr"
dir="ltr">On Wed, Oct 21, 2020 at 11:53 PM
MIKE MCGRADY <<a shape="rect"
href="mailto:mikemcgrady@hotmail.com"
rel="nofollow" target="_blank"
moz-do-not-send="true">mikemcgrady@hotmail.com</a>>
wrote:<br clear="none">
</div>
<blockquote
class="ydp836de6ecyiv6357707573gmail_quote"
style="margin:0px 0px 0px
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<div dir="ltr">
<div style="font-family:Calibri, Helvetica,
sans-serif;font-size:12pt;color:rgb(0,0,0);">
As far as I can recall, few studies of
long-distance migratory species state what
projections are used. Is there any
published study of the effect of
projections on analyses of animal
movement?</div>
<div style="font-family:Calibri, Helvetica,
sans-serif;font-size:12pt;color:rgb(0,0,0);">
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<div style="font-family:Calibri, Helvetica,
sans-serif;font-size:12pt;color:rgb(0,0,0);">
M</div>
<div>
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Helvetica,
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<div
id="ydp836de6ecyiv6357707573gmail-m_-4270035359120948779gmail-m_2330862348964759604gmail-m_201484568261164539Signature">
<div>
<div>M. J. McGrady </div>
<div>Am Rosenhugel 59</div>
<div>A-3500 Krems</div>
<div>Austria</div>
</div>
</div>
</div>
<div>
<div style="font-family:Calibri,
Helvetica,
sans-serif;font-size:12pt;color:rgb(0,0,0);">
<br clear="none">
</div>
<hr
style="display:inline-block;width:98%;">
<div dir="ltr"
id="ydp836de6ecyiv6357707573gmail-m_-4270035359120948779gmail-m_2330862348964759604gmail-m_201484568261164539divRplyFwdMsg"><font
style="font-size:11pt;" face="Calibri,
sans-serif" color="#000000"><b>From:</b>
Qgis-user <<a shape="rect"
href="mailto:qgis-user-bounces@lists.osgeo.org"
rel="nofollow" target="_blank"
moz-do-not-send="true">qgis-user-bounces@lists.osgeo.org</a>>
on behalf of Hernán De Angelis <<a
shape="rect"
href="mailto:variablestarlight@gmail.com"
rel="nofollow" target="_blank"
moz-do-not-send="true">variablestarlight@gmail.com</a>><br
clear="none">
<b>Sent:</b> Thursday, October 22,
2020 6:57 AM<br clear="none">
<b>To:</b> <a shape="rect"
href="mailto:qgis-user@lists.osgeo.org"
rel="nofollow" target="_blank"
moz-do-not-send="true">qgis-user@lists.osgeo.org</a>
<<a shape="rect"
href="mailto:qgis-user@lists.osgeo.org"
rel="nofollow" target="_blank"
moz-do-not-send="true">qgis-user@lists.osgeo.org</a>><br
clear="none">
<b>Subject:</b> Re: [Qgis-user]
Projections</font>
<div> </div>
</div>
<div>
<p
style="margin-top:0px;margin-bottom:0px;">Mike</p>
<p
style="margin-top:0px;margin-bottom:0px;"><br
clear="none">
</p>
<p
style="margin-top:0px;margin-bottom:0px;">For
measuring the kind of distances you
are mentioning I would suggest using
ellipsoidal (geodetic) distances
rather than projected distances. This
is because projected distances can
become very inaccurate over large
regions (depending on the particular
projection of course).<br clear="none">
</p>
<p
style="margin-top:0px;margin-bottom:0px;"><br
clear="none">
</p>
<p
style="margin-top:0px;margin-bottom:0px;">If
measuring areas is important consider
an equal area projection, like Albers
for example, not a conformal one like
Lambert.</p>
<p
style="margin-top:0px;margin-bottom:0px;"><br
clear="none">
</p>
<p
style="margin-top:0px;margin-bottom:0px;">Hope
this helps.<br clear="none">
</p>
<p
style="margin-top:0px;margin-bottom:0px;"><br
clear="none">
</p>
<p
style="margin-top:0px;margin-bottom:0px;">/H.<br
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</p>
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style="margin-top:0px;margin-bottom:0px;"><br
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</p>
<p
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</p>
<p
style="margin-top:0px;margin-bottom:0px;"><br
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</p>
<div>On 2020-10-22 07:43, MIKE MCGRADY
wrote:<br clear="none">
</div>
<blockquote type="cite">
<div style="font-family:Calibri,
Helvetica,
sans-serif;font-size:12pt;color:rgb(0,0,0);">
I have data on tracked migratory
birds, and want accurate measures of
distance travelled during migration
and areas of summering and wintering
ranges. These birds are summering
in central Asia (mostly Kazakhstan
and southern Russia), and wintering
in Arabia. Any advice on which
projection to use? My guess is
Lambert conformal conic. I'd really
like to avoid using different
projections for different phases of
the birds' annual cycle, unless
absolutely necessary. </div>
<div>
<div style="font-family:Calibri,
Helvetica,
sans-serif;font-size:12pt;color:rgb(0,0,0);">
<br clear="none">
</div>
<div
id="ydp836de6ecyiv6357707573gmail-m_-4270035359120948779gmail-m_2330862348964759604gmail-m_201484568261164539x_Signature">
<div>
<div>M. J. McGrady </div>
<div>Am Rosenhugel 59</div>
<div>A-3500 Krems</div>
<div>Austria</div>
</div>
</div>
</div>
<br clear="none">
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<pre class="moz-signature" cols="72">--
John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile / <a class="moz-txt-link-freetext" href="http://www.sdsc.edu/~hellyj">http://www.sdsc.edu/~hellyj</a>
ORCID ID: orcid.org/0000-0002-3779-0603</pre>
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