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List: postgis-users
Subject: [postgis-users] Re: Projection...
From: Wacek <wacek () adams ! szczecin ! pl>
Date: 2005-09-23 7:04:56
Message-ID: 4333A918.4070800 () adams ! szczecin ! pl
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On Thu, Sep 22, 2005 at 04:36:22PM +0200, Nicolas Ribot wrote:
> > > > Hi,
> > > >
> > > > I have some data from USA in 'NAD83 Nevada East' fromat (EPSG:32107 -
> > > > ?). I want to change it to WGS84 (EPSG:4326) using PostGIS. When I use:
> > > >
> > > > "select updategeometrysrid('table', 'the_geom', 4326);" resulting values
> > > > are'nt correct. What am I doing wrong?
> > > >
> > > > Thanks in advance for your replies.
> > > >
> > > > Best regards
> > > > Wacek
> > > >
> >
> >
> >
> > Hi Wacek,
> >
> > calling updategeometrysrid only changes the internal geometries SRID.
> > It does not reproject them.
> > You have to explicitly transform the geometries from the source
> > coordinates system to the target one, using the tranform() function.
> >
> > select transform(the_geom, 4326) from table;
> >
> > You can either create a new table containing the transformed
> > geometries, or drop SRID constraint on your table, transform the
> > geometries and re-add the SRID constraint adapted to the new
> > geometries' SRID
>
>
Or:
SELECT updateGeometrySRID('mytable', 'the_geom', 4326);
UPDATE mytable set the_geom =
transform(SetSRID(the_geom, 32107), 4326);
--strk;
----------------------------------
Hi, again.
This works but values after reprojection aren't quite correct (every point has the \
same coordinates). I have checked reprojecting my own points between these two SRIDs \
and it is correct. I am wondering if the source data SRID is really 32107 ('NAD83 \
Nevada East'). Vendor does not provide such information. To check this I use UDIG \
('User-friendly Desktop Internet GIS') and his layer information feature. After \
adding a layer from file the visualisation is OK, but after exporting it to DB and \
trying to visualize it from there no features are rendered. That's why I am asking \
about reprojecting this data to SRID:4326. I am using source file \
http://gisgate.co.clark.nv.us/gismo/downloads/scl_l.zip containing streets in Clark \
County in USA. How can I check what SRID is my source data? Maybe someone can try \
reprojecting source data I have mentioned to 4326 and tell me about the results.
Thanks a lot for your previous posts and looking forward for some new :)
Wacek
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On Thu, Sep 22, 2005 at 04:36:22PM +0200, Nicolas Ribot wrote:
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">> > </span>Hi,
<span class="moz-txt-citetags">> ></span>
<span class="moz-txt-citetags">> > </span>I have some data from USA in 'NAD83 \
Nevada East' fromat (EPSG:32107 - <span class="moz-txt-citetags">> > </span>?). \
I want to change it to WGS84 (EPSG:4326) using PostGIS. When I use: <span \
class="moz-txt-citetags">> ></span> <span class="moz-txt-citetags">> > \
</span>"select updategeometrysrid('table', 'the_geom', 4326);" resulting values <span \
class="moz-txt-citetags">> > </span>are'nt correct. What am I doing wrong? \
<span class="moz-txt-citetags">> ></span> <span class="moz-txt-citetags">> \
> </span>Thanks in advance for your replies. <span class="moz-txt-citetags">> \
></span> <span class="moz-txt-citetags">> > </span>Best regards
<span class="moz-txt-citetags">> > </span>Wacek
<span class="moz-txt-citetags">> ></span>
</pre>
</blockquote>
<pre wrap=""><span class="moz-txt-citetags">> </span>
<span class="moz-txt-citetags">> </span>Hi Wacek,
<span class="moz-txt-citetags">> </span>
<span class="moz-txt-citetags">> </span>calling updategeometrysrid only changes \
the internal geometries SRID. <span class="moz-txt-citetags">> </span>It does not \
reproject them. <span class="moz-txt-citetags">> </span>You have to explicitly \
transform the geometries from the source <span class="moz-txt-citetags">> \
</span>coordinates system to the target one, using the tranform() function. <span \
class="moz-txt-citetags">> </span> <span class="moz-txt-citetags">> \
</span>select transform(the_geom, 4326) from table; <span \
class="moz-txt-citetags">> </span> <span class="moz-txt-citetags">> </span>You \
can either create a new table containing the transformed <span \
class="moz-txt-citetags">> </span>geometries, or drop SRID constraint on your \
table, transform the <span class="moz-txt-citetags">> </span>geometries and re-add \
the SRID constraint adapted to the new <span class="moz-txt-citetags">> \
</span>geometries' SRID </pre>
</blockquote>
<pre wrap=""><!---->
Or:
SELECT updateGeometrySRID('mytable', 'the_geom', 4326);
UPDATE mytable set the_geom =
transform(SetSRID(the_geom, 32107), 4326);
--strk;
----------------------------------
Hi, again.
This works but values after reprojection aren't quite correct (every point has the \
same coordinates). I have checked reprojecting my own points between these two SRIDs \
and it is correct. I am wondering if the source data SRID is really 32107 ('NAD83 \
Nevada East'). Vendor does not provide such information. To check this I use UDIG \
('User-friendly Desktop Internet GIS') and his layer information feature. After \
adding a layer from file the visualisation is OK, but after exporting it to DB and \
trying to visualize it from there no features are rendered. That's why I am asking \
about reprojecting this data to SRID:4326. I am using source file <a \
class="moz-txt-link-freetext" \
href="http://gisgate.co.clark.nv.us/gismo/downloads/scl_l.zip">http://gisgate.co.clark.nv.us/gismo/downloads/scl_l.zip</a> \
containing streets in Clark County in USA. How can I check what SRID is my source \
data? Maybe someone can try reprojecting source data I have mentioned to 4326 and \
tell me about the results.
Thanks a lot for your previous posts and looking forward for some new :)
Wacek
</pre>
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