Aloha. You might want to consider simply using Great Circle distances and then refining that if you need something better. J.
On 10/22/20 12:50, Peter Borissow wrote: > I agree with Hernán, that you are probably better off using > ellipsoidal (geodetic) distances rather than projected distances for > such large tracks. > > 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. > > > On Thursday, October 22, 2020, 3:14:34 PM EDT, Charles Dixon-Paver > <[email protected]> wrote: > > > 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. > > 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? > > This is pure conjecture on my part, so I'd appreciate the correction > if I'm missing the plot... > > > On Thu, 22 Oct 2020 at 19:35, Falk Huettmann <[email protected] > <mailto:[email protected]>> wrote: > > Hi there, Mike et al, > > thanks, > 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 - > there is sufficient literature on the topic for years re. > projections, e.g. this one for starters. > > https://www.researchgate.net/publication/12122402_Migration_Along_Orthodromic_Sun_Compass_Routes_by_Arctic_Birds > > <https://urldefense.com/v3/__https://www.researchgate.net/publication/12122402_Migration_Along_Orthodromic_Sun_Compass_Routes_by_Arctic_Birds__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv29mkBPrc$> > > Some others are found with the navigation sciences, with sea > turtle math work (former Ram Myers) and then rocket and missile > targeting of course. > 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). > > Overall, for birds these days, the public resource question should > sit on CONSERVATION and sustainable management, > not ivory-tower questions. The latter have been done for centuries > without relevant outcome and progress. > 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. > Other problems are more relevant these days. > > A nice question why after 100 years of research on bird migration, > state-funded with $Mio's, and with MPI and Movebank, ICARUS etc > no readily available solution or answer exist in R or GIS etc. > > That's my opinion and answer on your question. Feel free to follow > up as needed. > > Best regards > Falk Huettmann PhD, Professor > Uni of Alaska Fairbanks > > > On Wed, Oct 21, 2020 at 11:53 PM MIKE MCGRADY > <[email protected] <mailto:[email protected]>> wrote: > > 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? > > M > > M. J. McGrady > Am Rosenhugel 59 > A-3500 Krems > Austria > > > ------------------------------------------------------------------------ > *From:* Qgis-user <[email protected] > <mailto:[email protected]>> on behalf of > Hernán De Angelis <[email protected] > <mailto:[email protected]>> > *Sent:* Thursday, October 22, 2020 6:57 AM > *To:* [email protected] > <mailto:[email protected]> <[email protected] > <mailto:[email protected]>> > *Subject:* Re: [Qgis-user] Projections > > > Mike > > > 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). > > > If measuring areas is important consider an equal area > projection, like Albers for example, not a conformal one like > Lambert. > > > Hope this helps. > > > /H. > > > > > On 2020-10-22 07:43, MIKE MCGRADY wrote: >> 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. >> >> M. J. McGrady >> Am Rosenhugel 59 >> A-3500 Krems >> Austria >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] <mailto:[email protected]> >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > _______________________________________________ > Qgis-user mailing list > [email protected] <mailto:[email protected]> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > > <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > Unsubscribe: > https://lists.osgeo.org/mailman/listinfo/qgis-user > > <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > > _______________________________________________ > Qgis-user mailing list > [email protected] <mailto:[email protected]> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > > <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > > <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > > _______________________________________________ > Qgis-user mailing list > [email protected] <mailto:[email protected]> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > <https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$> > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: > https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$ > > Unsubscribe: > https://urldefense.com/v3/__https://lists.osgeo.org/mailman/listinfo/qgis-user__;!!Mih3wA!RyMpbAKaWAmYgznMW5fozhrNvNNW3iiURGcMTtYC4nYC8sSDMHP23tv2KFPyQ8s$ > -- John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile / http://www.sdsc.edu/~hellyj ORCID ID: orcid.org/0000-0002-3779-0603
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