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<div class="moz-cite-prefix">Le 01/07/2022 à 19:16, Javier Jimenez
Shaw a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CADRrdKuQF9500z84NJ2uGnveGjBG+czgr5G4vYY8Oc6yzP+pwQ@mail.gmail.com">
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<div dir="ltr">
<div>Hi</div>
<div><br>
</div>
<div>I am a bit confused with "--identify" option in projinfo. I
looked at the documentation of the method "identify" of CRS
classes in C++ trying to understand.<br>
</div>
<div><br>
</div>
<div>Running</div>
<div><span style="font-family:monospace">projinfo "$(projinfo
ESRI:102654 -o WKT1:GDAL -q)" --identify -o WKT1:GDAL</span></div>
<div>Produces <br>
</div>
<div><span style="font-family:monospace">PROJCS["NAD_1983_StatePlane_Colorado_Central_FIPS_0502_Feet
(deprecated)",<br>
....</span></div>
<div><span style="font-family:monospace">Identification match
count: 1<br>
ESRI:102654: 100 %</span></div>
<div><br>
</div>
<div>so far so good.</div>
</div>
</blockquote>
<span style="font-family:monospace">"projinfo ESRI:102654 -o
WKT1:GDAL -q" generates a WKT with the ESRI:102654 authority node,
hence it is used for identification<br>
</span>
<blockquote type="cite"
cite="mid:CADRrdKuQF9500z84NJ2uGnveGjBG+czgr5G4vYY8Oc6yzP+pwQ@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>Running (I just changed the wkt1 dialect in the inner call)<br>
</div>
<div><span style="font-family:monospace">projinfo "$(projinfo
ESRI:102654 -o WKT1:ESRI -q)" --identify -o WKT1:GDAL</span></div>
<div>Produces</div>
<div><span style="font-family:monospace">PROJCS["NAD83 /
Colorado Central (ftUS)",</span></div>
<div><span style="font-family:monospace">....</span></div>
<div><span style="font-family:monospace">Identification match
count: 1<br>
EPSG:2232: 100 %</span></div>
<div><br>
</div>
<div>Looking at the C++ documentation I think that a confidence
of 100% means that the names are the same (I do not really
know which names it refers to. Only the CRS name? geographic
crs? datum? units? anything else? all?) <br>
</div>
</div>
</blockquote>
<p><span style="font-family:monospace">"projinfo ESRI:102654 -o
WKT1:ESRI -q" strips the authority node (this is canonical for
ESRI WKT), so for identification PROJ relies on the CRS name (to
start with). The reason to match EPSG:2232 here is this entry in
the database:<br>
<br>
../data/sql/esri.sql:INSERT INTO alias_name
VALUES('projected_crs','EPSG','2232','NAD_1983_StatePlane_Colorado_Central_FIPS_0502_Feet','ESRI');<br>
<br>
which is added when importing the ESRI database where they link
their deprecated code to the EPSG entry</span></p>
<p><span style="font-family:monospace">I'm not sure to remember why
it chooses the entry corresponding to the alias rather than
ESRI:102654. Probably the fact that ESRI:102654 is deprecated.<br>
</span></p>
<br>
<blockquote type="cite"
cite="mid:CADRrdKuQF9500z84NJ2uGnveGjBG+czgr5G4vYY8Oc6yzP+pwQ@mail.gmail.com">
<div dir="ltr">
<div>If I use this WKT string (the ESRI one, but adding the
authority at the end -I found it somewhere-)<br>
</div>
<div><br>
</div>
<div><span style="font-family:monospace">PROJCS["NAD_1983_StatePlane_Colorado_Central_FIPS_0502_Feet",</span></div>
<div><span style="font-family:monospace">
GEOGCS["GCS_North_American_1983",</span></div>
<div><span style="font-family:monospace">
DATUM["D_North_American_1983",</span></div>
<div><span style="font-family:monospace">
SPHEROID["GRS_1980",6378137.0,298.257222101]],</span></div>
<div><span style="font-family:monospace">
PRIMEM["Greenwich",0.0],</span></div>
<div><span style="font-family:monospace">
UNIT["Degree",0.0174532925199433]],</span></div>
<div><span style="font-family:monospace">
PROJECTION["Lambert_Conformal_Conic"],</span></div>
<div><span style="font-family:monospace">
PARAMETER["False_Easting",3000000.00031608],</span></div>
<div><span style="font-family:monospace">
PARAMETER["False_Northing",999999.999996],</span></div>
<div><span style="font-family:monospace">
PARAMETER["Central_Meridian",-105.5],</span></div>
<div><span style="font-family:monospace">
PARAMETER["Standard_Parallel_1",38.45],</span></div>
<div><span style="font-family:monospace">
PARAMETER["Standard_Parallel_2",39.75],</span></div>
<div><span style="font-family:monospace">
PARAMETER["Latitude_Of_Origin",37.8333333333333],</span></div>
<div><span style="font-family:monospace"> UNIT["US survey
foot",0.304800609601219],</span></div>
<div><span style="font-family:monospace">
AUTHORITY["ESRI","102654"]]</span></div>
<div><span style="font-family:monospace"><br>
</span></div>
<div>Produces</div>
<div><span style="font-family:monospace">PROJCS["NAD83 /
Colorado Central (ftUS)",</span></div>
<div><span style="font-family:monospace">...</span></div>
<div><span style="font-family:monospace">Identification match
count: 1<br>
ESRI:102654: 100 %</span></div>
<div><br>
</div>
<div>It is also changing the name to the one in EPSG, returning
the ESRI code, and with a confidence of 100%</div>
</div>
</blockquote>
<p>When there's a code and the provided CRS is equivalent to the one
built from the code, the code is trusted.</p>
<p>Regarding the change of name to the one of EPSG, that's due to
the morphing done by PROJ when importing ESRI WKT to use EPSG
CRS/datum/projection method/projection parameter names. The
reverse morphing is done when exporting to ESRI WKT.<br>
</p>
<blockquote type="cite"
cite="mid:CADRrdKuQF9500z84NJ2uGnveGjBG+czgr5G4vYY8Oc6yzP+pwQ@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>Is all that intended? Maybe I misunderstood the meaning of
the confidence percentage.<br>
</div>
</div>
</blockquote>
Overall yes what you observe is intended. It is really difficult to
document every aspect of what some functions does, as there are a
lot of heuristics added to make things work smoothly and describing
everything can be confusing (and here there are considerations
related to import/export of ESRI WKT in additions of purely
identification issues). But documentation contributions that could
makes things clearer are welcome. Perhaps the doc could be modified
to indicate that 100% also takes into account registered alias
names.<br>
<blockquote type="cite"
cite="mid:CADRrdKuQF9500z84NJ2uGnveGjBG+czgr5G4vYY8Oc6yzP+pwQ@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>Thanks.<br>
</div>
.___ ._ ..._ .. . ._. .___ .. __ . _. . __.. ... .... ._ .__<br>
<div>
<div>
<div dir="ltr" data-smartmail="gmail_signature">Entre dos
pensamientos racionales <br>
hay infinitos pensamientos irracionales.<br>
<br>
</div>
</div>
</div>
</div>
<br>
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</blockquote>
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