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<section id="known-differences-between-versions">
<span id="differences"></span><h1>Known differences between versions<a class="headerlink" href="#known-differences-between-versions" title="Permalink to this headline">¶</a></h1>
<p>Once in a while, a new version of PROJ causes changes in the existing behavior.
In this section we track deliberate changes to PROJ that break from previous
behavior. Most times that will be caused by a bug fix. Unfortunately, some bugs
have existed for so long that their faulty behavior is relied upon by software
that uses PROJ.</p>
<p>Behavioural changes caused by new bugs are not tracked here, as they should be
fixed in later versions of PROJ.</p>
<section id="version-4-6-0">
<h2>Version 4.6.0<a class="headerlink" href="#version-4-6-0" title="Permalink to this headline">¶</a></h2>
<p>The default datum application behavior changed with the 4.6.0 release. PROJ
will now only apply a datum shift if both the source and destination coordinate
system have valid datum shift information.</p>
<p>The PROJ 4.6.0 Release Notes states</p>
<blockquote>
<div><p>MAJOR: Rework <code class="xref c c-func docutils literal notranslate"><span class="pre">pj_transform()</span></code> to avoid applying ellipsoid to ellipsoid
transformations as a datum shift when no datum info is available.</p>
</div></blockquote>
</section>
<section id="version-5-0-0">
<h2>Version 5.0.0<a class="headerlink" href="#version-5-0-0" title="Permalink to this headline">¶</a></h2>
<section id="longitude-wrapping-when-using-custom-central-meridian">
<h3>Longitude wrapping when using custom central meridian<a class="headerlink" href="#longitude-wrapping-when-using-custom-central-meridian" title="Permalink to this headline">¶</a></h3>
<p>By default PROJ wraps output longitudes in the range -180 to 180. Previous to
PROJ 5, this was handled incorrectly when a custom central meridian was set with
<a class="reference internal" href="../operations/projections/wintri.html#cmdoption-arg-lon_0"><code class="xref std std-option docutils literal notranslate"><span class="pre">+lon_0</span></code></a>. This caused a change in sign on the resulting easting as seen
below:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ proj +proj=merc +lon_0=110
-70 0
-20037508.34 0.00
290 0
20037508.34 0.00
</pre></div>
</div>
<p>From PROJ 5 on onwards, the same input now results in same coordinates, as seen
from the example below where PROJ 5 is used:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ proj +proj=merc +lon_0=110
-70 0
-20037508.34 0.00
290 0
-20037508.34 0.00
</pre></div>
</div>
<p>The change is made on the basis that <span class="math notranslate nohighlight">\(\lambda=290^{\circ}\)</span> is a full
rotation of the circle larger than <span class="math notranslate nohighlight">\(\lambda=-70^{\circ}\)</span> and hence
should return the same output for both.</p>
<p>Adding the <code class="docutils literal notranslate"><span class="pre">+over</span></code> flag to the projection definition provides
the old behavior.</p>
</section>
</section>
<section id="version-6-0-0">
<h2>Version 6.0.0<a class="headerlink" href="#version-6-0-0" title="Permalink to this headline">¶</a></h2>
<section id="removal-of-proj-def-dat">
<h3>Removal of <code class="file docutils literal notranslate"><span class="pre">proj_def.dat</span></code><a class="headerlink" href="#removal-of-proj-def-dat" title="Permalink to this headline">¶</a></h3>
<p>Before PROJ 6, the <code class="file docutils literal notranslate"><span class="pre">proj_def.dat</span></code> was used to provide general and per-projection
parameters, when <code class="docutils literal notranslate"><span class="pre">+no_defs</span></code> was not specified. It has now been removed. In case,
no ellipsoid or datum specification is provided in the PROJ string, the
default ellipsoid is GRS80 (was WGS84 in previous PROJ versions).</p>
</section>
<section id="changes-to-deformation">
<h3>Changes to <a class="reference internal" href="../operations/transformations/deformation.html#deformation"><span class="std std-ref">deformation</span></a><a class="headerlink" href="#changes-to-deformation" title="Permalink to this headline">¶</a></h3>
<section id="reversed-order-of-operation">
<span id="differences-deformation"></span><h4>Reversed order of operation<a class="headerlink" href="#reversed-order-of-operation" title="Permalink to this headline">¶</a></h4>
<p>In the initial version of the of <a class="reference internal" href="../operations/transformations/deformation.html#deformation"><span class="std std-ref">deformation</span></a> operation
the time span between <span class="math notranslate nohighlight">\(t_{obs}\)</span> and <span class="math notranslate nohighlight">\(t_c\)</span> was determined by the
expression</p>
<div class="math notranslate nohighlight">
\[dt = t_c - t_{obs}\]</div>
<p>With version 6.0.0 this has been reversed in order to behave similarly to
the <a class="reference internal" href="../operations/transformations/helmert.html#helmert"><span class="std std-ref">Helmert operation</span></a>, which determines time differences as</p>
<div class="math notranslate nohighlight">
\[dt = t_{obs} - t_c\]</div>
<p>Effectively this means that the direction of the operation has been reversed,
so that what in PROJ 5 was a forward operation is now an inverse operation and
vice versa.</p>
<p>Pipelines written for PROJ 5 can be migrated to PROJ 6 by adding <a class="reference internal" href="../operations/pipeline.html#cmdoption-arg-inv"><code class="xref std std-option docutils literal notranslate"><span class="pre">+inv</span></code></a>
to forward steps involving the deformation operation. Similarly
<a class="reference internal" href="../operations/pipeline.html#cmdoption-arg-inv"><code class="xref std std-option docutils literal notranslate"><span class="pre">+inv</span></code></a> should be removed from inverse steps to be compatible with
PROJ 6.</p>
</section>
<section id="removed-t-obs-parameter">
<h4>Removed <code class="docutils literal notranslate"><span class="pre">+t_obs</span></code> parameter<a class="headerlink" href="#removed-t-obs-parameter" title="Permalink to this headline">¶</a></h4>
<p>The <code class="docutils literal notranslate"><span class="pre">+t_obs</span></code> parameter was confusing for users since it effectively
overwrote the observation time in input coordinates. To make it more clear
what is the operation is doing, users are now required to directly specify
the time span for which they wish to apply a given deformation. The parameter
<a class="reference internal" href="../operations/transformations/deformation.html#cmdoption-arg-dt"><code class="xref std std-option docutils literal notranslate"><span class="pre">+dt</span></code></a> has been added for that purpose. The new parameter is mutually
exclusive with <a class="reference internal" href="../operations/transformations/vgridshift.html#cmdoption-arg-t_epoch"><code class="xref std std-option docutils literal notranslate"><span class="pre">+t_epoch</span></code></a>. <a class="reference internal" href="../operations/transformations/deformation.html#cmdoption-arg-dt"><code class="xref std std-option docutils literal notranslate"><span class="pre">+dt</span></code></a> is used when deformation
for a set amount of time is needed and <a class="reference internal" href="../operations/transformations/vgridshift.html#cmdoption-arg-t_epoch"><code class="xref std std-option docutils literal notranslate"><span class="pre">+t_epoch</span></code></a> is used (in
conjunction with the observation time of the input coordinate) when
deformation from a specific epoch to the observation time is needed.</p>
</section>
</section>
</section>
<section id="version-6-3-0">
<h2>Version 6.3.0<a class="headerlink" href="#version-6-3-0" title="Permalink to this headline">¶</a></h2>
<section id="projinfo">
<h3>projinfo<a class="headerlink" href="#projinfo" title="Permalink to this headline">¶</a></h3>
<p>Before PROJ 6.3.0, WKT1:GDAL was implicitly calling <code class="docutils literal notranslate"><span class="pre">--boundcrs-to-wgs84</span></code>, to
add a <code class="docutils literal notranslate"><span class="pre">TOWGS84[]</span></code> node in some cases. This is no longer the case.</p>
</section>
</section>
<section id="version-7-0-0">
<h2>Version 7.0.0<a class="headerlink" href="#version-7-0-0" title="Permalink to this headline">¶</a></h2>
<section id="proj">
<h3>proj<a class="headerlink" href="#proj" title="Permalink to this headline">¶</a></h3>
<p>Removed <code class="docutils literal notranslate"><span class="pre">-ld</span></code> option from application, since it promoted use of deprecated
parameters like <code class="docutils literal notranslate"><span class="pre">+towgs</span></code> and <code class="docutils literal notranslate"><span class="pre">+datum</span></code>.</p>
</section>
<section id="cs2cs">
<h3>cs2cs<a class="headerlink" href="#cs2cs" title="Permalink to this headline">¶</a></h3>
<p>Removed <code class="docutils literal notranslate"><span class="pre">-ld</span></code> option from application, since it promoted use of deprecated
parameters like <code class="docutils literal notranslate"><span class="pre">+towgs</span></code> and <code class="docutils literal notranslate"><span class="pre">+datum</span></code>.</p>
</section>
<section id="utf-8-adoption">
<h3>UTF-8 adoption<a class="headerlink" href="#utf-8-adoption" title="Permalink to this headline">¶</a></h3>
<p>The value of all path, filenames passed to PROJ through function calls, PROJ
strings or environment variables should be encoded in UTF-8.</p>
</section>
</section>
</section>
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