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<div class="moz-cite-prefix">Hi Michael,<br>
<br>
Le 05/04/2014 21:25, Michael Judex a écrit :<br>
</div>
<blockquote cite="mid:534058C0.6070407@gmx.de" type="cite">
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Thanks for the answer! I've another related question/issue: There
is a systematic geometric shift between SPOT-6 images of task 489
(Guinée / Northern Liberia border area) and Pleiades-1A images of
task 471 (only for the town of Macenta, which is included
geographically in 489). I think that an offset of 10.44; 14.24 (in
JOSM) for the SPOT-6 images is good to have a proper fit to the
Pleiades images. <br>
<br>
So my questions are:<br>
- is the geometric accuracy of the Pleiades better than SPOT-6? (I
assume yes)<br>
</blockquote>
<br>
Yes, Pleiades has 6.5 m CE90 location accuracy, and SPOT-6 10 m CE90
location accuracy.<br>
<br>
<blockquote cite="mid:534058C0.6070407@gmx.de" type="cite"> - do we
then have a systematic geometeric distortion in task 489 for the
edits that relied only on the SPOT-6 imagery? If yes can we
correct this? (maybe the the only way to really fix offsets
between different images are GPS ground control points...)<br>
</blockquote>
<br>
The shift in Macenta doesn't mean that the same offset there would
be suitable for the whole SPOT-6 imagery. It is likely suitable only
for the area near Macenta. <br>
<br>
Geometric distortions are for example likely to depend on relief, in
a way more complex than a simple uniform offset could fix.<br>
<br>
<blockquote cite="mid:534058C0.6070407@gmx.de" type="cite"> <br>
I think it could be helpful to have an instant overview of ALL
available imagery for a specific area. If a mapper opens a task
only the dedicated imagery is listed in the task instructions. Is
there a simple way to achieve this?<br>
</blockquote>
<br>
You can simply overlay the Pleiades imagery for one of the Pleiades
jobs (469 or 471 for Guéckédou or Macenta - both contain the same
Pleiades layer, with Kissidougou too ; and the Pleiades imagery
layer for job <a class="moz-txt-link-freetext" href="http://tasks.hotosm.org/job/487">http://tasks.hotosm.org/job/487</a> for Foya contains the
4 Pleiades images) to the SPOT-6 imagery of job
<a class="moz-txt-link-freetext" href="http://tasks.hotosm.org/job/489">http://tasks.hotosm.org/job/489</a>. And switch them on and off to
compare (which is what you probably did, explaining here for the
others).<br>
<br>
<br>
A better answer to your question : on VISOV's Umap used to track
news about the Ebola outbreak, boundaries for high resolution
imagery layers can be switched on and off (in the layer menu, icon
is near top left) (grouped by when they where made available) :<br>
<br>
<a class="moz-txt-link-freetext" href="http://umap.openstreetmap.fr/fr/map/esov-suivi-epidemie-ebola_6356#10/8.5640/-9.7806">http://umap.openstreetmap.fr/fr/map/esov-suivi-epidemie-ebola_6356#10/8.5640/-9.7806</a><br>
<br>
<br>
<blockquote cite="mid:534058C0.6070407@gmx.de" type="cite"> <br>
Thanks for your support!<br>
<br>
Michael<br>
</blockquote>
<br>
<br>
Thanks for your questions, and for your mapping!<br>
<br>
Jean-Guilhem<br>
<br>
<br>
<blockquote cite="mid:534058C0.6070407@gmx.de" type="cite"> <br>
<br>
<br>
<div class="moz-cite-prefix">Am 05.04.2014 11:19, schrieb Pierre
Béland:<br>
</div>
<blockquote
cite="mid:1396689593.33373.YahooMailNeo@web171401.mail.ir2.yahoo.com"
type="cite">
<div>Great. Thanks both.</div>
<div> </div>
<div><span style="font-style:italic;color:rgb(0, 0,
191);font-weight:bold;">Pierre <br>
</span><br>
</div>
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<hr size="1"> <font size="2" face="Arial"> <b><span
style="font-weight:bold;">De :</span></b>
Jean-Guilhem Cailton <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:jgc@arkemie.com"><jgc@arkemie.com></a><br>
<b><span style="font-weight: bold;">À :</span></b>
Michael Judex <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:m.judex@gmx.de"><m.judex@gmx.de></a>;
<a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:hot@openstreetmap.org">hot@openstreetmap.org</a>
<br>
<b><span style="font-weight: bold;">Envoyé le :</span></b>
Vendredi 4 avril 2014 22h10<br>
<b><span style="font-weight: bold;">Objet :</span></b>
Re: [HOT] Spot-6 images of Guinée / Northern Liberia
available, job 489<br>
</font> </div>
<div class="y_msg_container"><br>
Hi Michael,<br clear="none">
<br clear="none">
The existing roads were probably based on Landsat, the
geometric<br clear="none">
accuracy of which is lower than Spot-6. So if you feel
that adjustment<br clear="none">
is needed, the pre-existing road should probably be
adjusted. This would<br clear="none">
also make it possible to have a consistent geometry for
tracing streets<br clear="none">
and buildings within villages and towns.<br clear="none">
<br clear="none">
Best wishes,<br clear="none">
<br clear="none">
Jean-Guilhem</div>
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