<div dir="ltr"><div dir="ltr"><div dir="ltr"><div><div class="gmail-aju"><div class="gmail-aCi"><img id="gmail-:0_5-e" name=":0" src="https://ssl.gstatic.com/ui/v1/icons/mail/profile_mask2.png" class="gmail-ajn" style="background-color: rgb(137, 211, 178);"></div></div> Hi Luís,</div><div> Thank you for your answer. The <a href="https://en.m.wikipedia.org/wiki/Equirectangular_projection">linked article</a> says the Marinus of Tyre's projection is also called the equidistant cylindrical projection. It implies, that the 'lonlat' and 'latlong' are just aliases for 'eqc'. Right? In that case I would expect to get this information after I enter<br></div><div>$ proj -l=lonlat</div><div>IMHO the output</div><div>lonlat : Lat/long (Geodetic) <br></div><div>does not say much.<br><br>I am just a beginner, so I might be wrong, but a note saying it's an alias for 'eqc' could improve the description listing.</div><div><br></div><div>Best wishes,<br></div><div> Pavel<br></div></div></div></div><br><div class="gmail_quote"><div dir="ltr">so 17. 11. 2018 v 23:52 odesílatel Luís Moreira de Sousa <<a href="mailto:luis.de.sousa@protonmail.ch">luis.de.sousa@protonmail.ch</a>> napsal:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Pavel,<br><br>that equates to Marinus of Tyre's projection [0]. Even though PROJ itself takes it as a geodetical coordinate system, pretty much all other software (Qgis, GRASS, etc) treats it as cartographic. You should keep this in mind when computing distances or areas in this system.<br><br>Regards.<br><br>[0] <a href="https://en.m.wikipedia.org/wiki/Plate_carr%C3%A9e_projection" target="_blank">https://en.m.wikipedia.org/wiki/Plate_carr%C3%A9e_projection</a><br><br><br>Sent from ProtonMail mobile<br><br><br><br>-------- Original Message --------<br>On 17 Nov 2018, 21:03, Pavel Hančar < <a href="mailto:pavel.hancar@gmail.com" target="_blank">pavel.hancar@gmail.com</a>> wrote:<blockquote class="m_-9114605361177031736protonmail_quote"><br><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div> Hello,</div><div>I
am trying to understand some basic concepts of map rendering, but I've
got really confused by the fact, that "longlat" or "lonlat" are often
mentioned as a name of a projection. For example:<br></div><div>+proj=longlat +datum=WGS84 +no_defs</div><div><br></div><div>AFAIK
longitude and latitude stay for a coordination system, not for a map projection. Thus I
thought it was a kind of simplification and the actual projection must have been
the Equidistant Cylindrical. But I found the Equidistant Cylindrical
being determined by "eqc" not "longlat". So what is the "longlat"? I ended up running
`proj -lP`, but found just this:</div><div><br> </div><div>lonlat : Lat/long (Geodetic)<br>latlon : Lat/long (Geodetic alias)<br> <br></div><div>The
only explanation is, that it is geodetic. But to me it seems it is not
any explanation, but a further specification saying it is not
geocentric, but the angles are taken from normals of the ellipsoid.</div><div><br></div><div>So, what projection is the "lonlat"? Or how are longitude and latitude projected to the flat map when nothing else is specified?</div><div><br></div><div> Thank you very much.</div><div><br></div><div> Best wishes,</div><div> Pavel Hančar<div class="m_-9114605361177031736gmail-adL"><br> </div></div></div></div></div></div>
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