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Dear QGis Developpers and Users <br>
<br>
First of all many thanks to the Developpers of Qgis for this wonderful
and user friendly Sofwaret. I'm sure that Qgis will become more and
more a "standard" in the next few years<br>
<br>
So, just a small point (and I hope to be wrong with this, but if it
is the case i don't see where) : as i needed to find quite exactly some
ellipsoïdal distances, I'm afraid to have also found that in some
cases the ellipsoïdal distance could have some problem in QGIS 1.7.4
(tested versions Windows and Debian). This could depend on the
algorithm used and the geographical position of the points.<br>
<br>
The following table suggests for few studied points that the
ellipsoïdal distances computed in Qgis 1.7.4 was overestimated and
quite different than ellipsoïdal distances computed with the help of
two geodesic estimations<br>
<br>
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<table cellspacing="0" cols="11" rules="NONE" border="0" frame="VOID">
<colgroup><col width="86"><col width="89"><col width="89"><col
width="102"><col width="102"><col width="74"><col width="84"><col
width="141"><col width="167"><col width="96"><col width="84"></colgroup>
<tbody>
<tr>
<td valign="MIDDLE" width="86" align="LEFT" height="131"><b>point
name in the study</b></td>
<td valign="MIDDLE" width="89" align="CENTER"><b><font
color="#0000ff">East EPSG:27572<br>
(m)<br>
</font></b></td>
<td valign="MIDDLE" width="89" align="CENTER"><b><font
color="#0000ff">North EPSG:27572<br>
(m)<br>
</font></b></td>
<td valign="MIDDLE" width="102" align="CENTER"><b><font
color="#800080">Lat WGS84 (obtained from deprojection in latlon WGS 84
in QGIS 1.7.4)<br>
deg. dec.<br>
</font></b></td>
<td valign="MIDDLE" width="102" align="CENTER"><b><font
color="#800080">Long WGS84 (obtained from deprojection in latlon WGS
84 in QGIS 1.7.4)<br>
deg. dec.<br>
</font></b></td>
<td valign="MIDDLE" width="74" align="CENTER" bgcolor="#94bd5e"><b><font
color="#ffffff">Simple Pythagore dist<br>
(m)<br>
</font></b></td>
<td valign="MIDDLE" width="84" align="CENTER" bgcolor="#94bd5e"><b><font
color="#ffffff">Simple Pythagore dist QGIS 1.7.4<br>
(m)<br>
</font></b></td>
<td valign="MIDDLE" width="141" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">dist ellips Clarke 1880 estimated from linear
alteration given by geodesic soft 1 (IGN Circé v4)<br>
(m)<br>
</font></td>
<td valign="MIDDLE" width="167" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">dist ellips WGS84 from geodesic Vincenty formula
recommanded by proj4 (found in soft 2 at
<a class="moz-txt-link-freetext" href="http://www.movable-type.co.uk/scripts/latlong-vincenty.html">http://www.movable-type.co.uk/scripts/latlong-vincenty.html</a><br>
(m)<br>
</font></td>
<td valign="MIDDLE" width="96" align="CENTER" bgcolor="#ff950e"><b><font
color="#ffff00">dist ellips QGIS 1.7.4 Clarke 1880<br>
(m)<br>
</font></b></td>
<td valign="MIDDLE" width="84" align="CENTER" bgcolor="#ff950e"><b><font
color="#ffff00">dist ellips QGIS 1.7.4 WGS84<br>
(m)<br>
</font></b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><br>
</td>
<td valign="TOP" align="CENTER"><b><font color="#0000ff"><br>
</font></b></td>
<td valign="TOP" align="CENTER"><b><font color="#0000ff"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td align="CENTER"><font color="#00ff00"><br>
</font></td>
<td align="LEFT"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">B (-)9</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733080.2641</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1847716.595</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.61880918</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.983106135</font></b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">540.795</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">540.795</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">540.048</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">540.045</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>541.016</b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>541.000</b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">AC (-)9</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">732806.9273</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1848183.228</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62305376</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.979845905</font></b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000"><br>
</font></b></td>
<td valign="MIDDLE" align="LEFT"><font color="#800000"><br>
</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000"><br>
</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">A 0</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733245.932</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1847790.425</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.61944142</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.985174410</font></b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">560.824</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">560.824</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">560.049</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">560.046</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>561.054</b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>561.038</b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">AC 0</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">732962.4713</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1848274.34</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62384326</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.981793539</font></b></td>
</tr>
<tr>
<td align="LEFT" height="17"><br>
</td>
<td align="LEFT"><br>
</td>
<td align="LEFT"><br>
</td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td align="CENTER"><br>
</td>
<td align="CENTER"><br>
</td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">B 8</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733374.0699</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1847888.697</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62030034</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.986784862</font></b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">540.794</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">540.794</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">540.047</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">540.043</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>541.016</b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>541.001</b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">AC 8</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733100.7324</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1848355.328</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62454501</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.983524812</font></b></td>
</tr>
<tr>
<td align="LEFT" height="17"><br>
</td>
<td align="LEFT"><br>
</td>
<td align="LEFT"><br>
</td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td align="LEFT"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td align="CENTER"><br>
</td>
<td align="CENTER"><br>
</td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">C (-)9</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733070.1404</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1847733.878</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.61896639</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.982985394</font></b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">380.560</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">380.560</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">380.034</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">380.031</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>380.715</b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>380.692</b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">C 10</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733398.5116</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1847926.227</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62063297</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.987096932</font></b></td>
</tr>
<tr>
<td align="LEFT" height="17"><br>
</td>
<td align="LEFT"><br>
</td>
<td align="LEFT"><br>
</td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080"><br>
</font></b></td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td valign="MIDDLE" align="CENTER"><br>
</td>
<td align="CENTER"><br>
</td>
<td align="CENTER"><br>
</td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">AC (-)13</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">732737.7966</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1848142.733</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62270285</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.978980306</font></b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">420.617</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#94bd5e">420.617</td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">420.036</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#355e00"><font
color="#00ff00">420.034</font></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>420.790</b></td>
<td rowspan="2" valign="MIDDLE" align="CENTER" bgcolor="#ff950e"><b>420.765</b></td>
</tr>
<tr>
<td valign="MIDDLE" align="LEFT" height="17"><b><font
color="#800000">AC 8</font></b></td>
<td valign="MIDDLE" align="RIGHT"><font color="#800000">733100.7324</font></td>
<td valign="MIDDLE" align="CENTER"><font color="#800000">1848355.328</font></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">43.62454501</font></b></td>
<td valign="MIDDLE" align="CENTER"><b><font color="#800080">3.983524812</font></b></td>
</tr>
</tbody>
</table>
<br>
<br>
<br>
Best regards<br>
<br>
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<p style="margin-bottom: 0cm;"><font size="2">_______________________________________________________________________________________</font></p>
<p style="margin-bottom: 0cm;"><font color="#008000"><font size="2"><b>Didier
B</b><b>lavet</b> </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Institut
de
Recherche pour le Développement - IRD (<font color="#0000ff"><a class="moz-txt-link-freetext" href="http://www.ird.fr">http://www.ird.fr</a></font>)
</font></font></p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">UMR
Eco&Sols - Ecologie Fonctionnelle & Biogéochimie des Sols &
Agroécosystèmes </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">(Montpellier
SupAgro-CIRAD-INRA-IRD)
(<font color="#0000ff"><a class="moz-txt-link-freetext" href="http://www.montpellier.inra.fr/ecosols">http://www.montpellier.inra.fr/ecosols</a></font><span
style="font-style: normal;">)</span></font></font></p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Bâtiment
12,
2 place Viala, F-34060 Montpellier Cedex 2 , France </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Tel
bureau : +33 (0)4 99 61 21 33 </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Secrétariat
:
+33 (0)4 99 61 21 01 / Fax : +33 (0)4 99 61 21 19 </font></font>
</p>
<p style="margin-bottom: 0cm;"><font color="#000000"><font size="2">Courriel
:
<font color="#0000ff"><a class="moz-txt-link-abbreviated" href="mailto:didier.blavet@ird.fr">didier.blavet@ird.fr</a></font> </font></font>
</p>
<p style="margin-bottom: 0cm;"><font size="2">_______________________________________________________________________________________</font></p>
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