<div dir="ltr"><span style="font-family:arial,sans-serif;font-size:13px">Dear Mikael Rittri</span><br><div><span style="font-family:arial,sans-serif;font-size:13px"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:13px">Thank you very much for your well-explained answer.</span></div><div><span style="font-family:arial,sans-serif;font-size:13px">I have adopted it.</span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Oct 24, 2014 at 9:45 PM, Mikael Rittri <span dir="ltr"><<a href="mailto:Mikael.Rittri@carmenta.com" target="_blank">Mikael.Rittri@carmenta.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<u></u><u></u><u></u><u></u>
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<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">Artur,<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">The reason why the geodetic datum is not documented for your dataset,<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">can be that it is not very important. The resolution of the dataset was 1 km,
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">but the usual mismatch between two geodetic datums would seldom be
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">more than 500 m.
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">For example, let’s assume that your data was given in Pulkovo 1942.
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">If I am not mistaken, one way to transform your coordinates would in<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">that case be to use cs2cs like this:<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">>cs2cs +proj=longlat +ellips=krass +towgs84=23.57,-140.95,-79.8,0,0.35,0.79,0.22 +to +proj=longlat +datum=WGS84 -f "%.5f"<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">117.69043 50.89524<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">117.69118 50.89578 -146.13626<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">where I used the datum shift EPSG:5044, “Pulkovo 1942 to WGS 84 (20)”,
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">valid in
<u></u><u></u>Russia<u></u><u></u> with 3 m accuracy.
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">If this was the correct transformation, but you forgot to do it, the difference
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">would be only 80 meters, which could be insignificant when the data resolution
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">is 1 km. <u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">But of course, that would depend on the usage of the dataset.
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">Well – if this is a NASA product, I would bet that they use WGS84.
<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">Regards,<u></u><u></u></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"> Mikael
<u></u><u></u></span></font></p>
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<p class="MsoNormal"><b><font face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma;font-weight:bold">From:</span></font></b><font face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma"> <a href="mailto:proj-bounces@lists.maptools.org" target="_blank">proj-bounces@lists.maptools.org</a>
[mailto:<a href="mailto:proj-bounces@lists.maptools.org" target="_blank">proj-bounces@lists.maptools.org</a>] <b><span style="font-weight:bold">On Behalf Of
</span></b>Artur Bercik<br>
<b><span style="font-weight:bold">Sent:</span></b> Friday, October 24, 2014 12:48 PM<br>
<b><span style="font-weight:bold">To:</span></b> <u></u>PROJ.4 and general Projections Discussions<u></u><br>
<b><span style="font-weight:bold">Subject:</span></b> Re: [Proj] Converting to WGS84 Latitude/Longitude</span></font><span lang="EN-US"><u></u><u></u></span></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"><u></u> <u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"><u></u> <u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"><u></u> <u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">On Fri, Oct 24, 2014 at 7:30 PM, Charles Clercq <<a href="mailto:charles.clercq@gmail.com" target="_blank">charles.clercq@gmail.com</a>> wrote:<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Dear all,<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">I found a pdf document: <a href="http://www.yale.edu/ceo/Documentation/MODIS_data.pdf" target="_blank">http://www.yale.edu/ceo/Documentation/MODIS_data.pdf</a><u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"><u></u> <u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">which state: "The data are provided in the HDF-EOS format. MODIS data at version 4 and above use <u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">the Sinusoidal projection with the WGS84 datum. A very small sample of common <u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">products are listed below."<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Hope it helps<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Thank you Charles. However, the statement you have found is for land products, and I am using atmospheric products. In this case, the data are provided in geographic
coordinate system. The pair of lats and lons I have read are in geographic coordinate system, but do not know the datum.<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">2014-10-24 9:30 GMT+02:00 Artur Bercik <<a href="mailto:vbubbly21@gmail.com" target="_blank">vbubbly21@gmail.com</a>>:<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"><u></u> <u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"><u></u> <u></u></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">On Fri, Oct 24, 2014 at 3:50 PM, Mikael Rittri <<a href="mailto:Mikael.Rittri@carmenta.com" target="_blank">Mikael.Rittri@carmenta.com</a>> wrote:<u></u><u></u></span></font></p>
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<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy">Hi Artur.</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">It could be the same thing. “Geodetic” latitude is the same as
ordinary, </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">everyday latitude. There are some other flavours of latitude
as well, </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">auxiliary latitudes that are mainly used to simplify some kinds
of </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">computations, but “geodetic” is the ordinary kind.
</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">For longitudes, there is only one flavour, but the zero meridian
is </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">not always
<u></u><u></u>Greenwich<u></u><u></u>. </span>
</font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">So the coordinates you mention could be in WGS84 Lat/Long already.</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">But it is not certain, since they could be expressed in some
other </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">geodetic datum that uses a different ellipsoid.</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">Do you have any documentation about the geodetic datum of your<br>
coordinates (like Pulkovo 1942, Pulkovo 1995, PZ 1990, or WGS84), </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">or about the ellipsoid used?</span></font><u></u><u></u></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Dear Mikael Rittri
<br>
<br>
Thanks for your answer.<br>
Actually, I could not understand which datum or ellepsoid was used. The following documents says only geodetic latitude and longitude:<br>
<br>
<a href="http://modaps.nascom.nasa.gov/services/about/products/MOD03.html" target="_blank">http://modaps.nascom.nasa.gov/services/about/products/MOD03.html</a><br>
<br>
I have read the above data product; and retrieved the pairs of geodetic lats and lons as the document says, but could not figure out if I should convert them into WGS84 or not. I have to compare the data using above product with other data which are in WGS84
lats and lons. <u></u><u></u></span></font></p>
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<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy">Best regards,</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span lang="EN-US" style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy">Mikael Rittri</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy">Carmenta</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy">Sweden</span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy"><a href="http://www.carmenta.com" target="_blank">http://www.carmenta.com</a></span></font><u></u><u></u></p>
<p class="MsoNormal"><font color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy"> </span></font><u></u><u></u></p>
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<p class="MsoNormal"><b><font face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma;font-weight:bold">From:</span></font></b><font face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma">
<a href="mailto:proj-bounces@lists.maptools.org" target="_blank">proj-bounces@lists.maptools.org</a> [mailto:<a href="mailto:proj-bounces@lists.maptools.org" target="_blank">proj-bounces@lists.maptools.org</a>]
<b><span style="font-weight:bold">On Behalf Of </span></b>Artur Bercik<br>
<b><span style="font-weight:bold">Sent:</span></b> Friday, October 24, 2014 8:27 AM<br>
<b><span style="font-weight:bold">To:</span></b> <a href="mailto:proj@lists.maptools.org" target="_blank">
proj@lists.maptools.org</a><br>
<b><span style="font-weight:bold">Subject:</span></b> [Proj] (no subject)</span></font><u></u><u></u></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Dear Proj list members:<br>
<br>
Being a very new in this field, could someone answer me about the following problem:<br>
<br>
I have a pair of Geodetic Latitude and Geodetic Longitude (50.89524, 117.69043).<br>
How can I convert it into Latitude and Longitude with WGS84 Ellepsoid?<br>
<br>
Thanks in the advance.<br>
<br>
Artur<u></u><u></u></span></font></p>
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