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diff --git a/faq.html b/faq.html new file mode 100644 index 00000000..18107520 --- /dev/null +++ b/faq.html @@ -0,0 +1,325 @@ +<!DOCTYPE html> +<html class="writer-html5" lang="en" > +<head> + <meta charset="utf-8" /><meta name="generator" content="Docutils 0.17.1: http://docutils.sourceforge.net/" /> + + <meta name="viewport" content="width=device-width, initial-scale=1.0" /> + <title>FAQ — PROJ 9.0.0 documentation</title> + <link rel="stylesheet" href="_static/pygments.css" type="text/css" /> + <link rel="stylesheet" href="_static/css/theme.css" type="text/css" /> + <link rel="shortcut icon" href="_static/favicon.png"/> + <link rel="canonical" href="https://proj.orgfaq.html"/> + <!--[if lt IE 9]> + <script src="_static/js/html5shiv.min.js"></script> + <![endif]--> + + <script data-url_root="./" id="documentation_options" src="_static/documentation_options.js"></script> + <script src="_static/jquery.js"></script> + <script src="_static/underscore.js"></script> + <script 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the EPSG registry, what do I do?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#i-found-a-bug-in-proj-how-do-i-get-it-fixed">I found a bug in PROJ, how do I get it fixed?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#how-do-i-contribute-to-proj">How do I contribute to PROJ?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#how-do-i-calculate-distances-directions-on-the-surface-of-the-earth">How do I calculate distances/directions on the surface of the earth?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#what-is-the-best-format-for-describing-coordinate-reference-systems">What is the best format for describing coordinate reference systems?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#why-is-the-axis-ordering-in-proj-not-consistent">Why is the axis ordering in PROJ not consistent?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#why-am-i-getting-the-error-cannot-find-proj-db">Why am I getting the error “Cannot find proj.db”?</a></li> +<li class="toctree-l2"><a class="reference internal" href="#what-happened-to-proj-4">What happened to PROJ.4?</a></li> +</ul> +</li> +<li class="toctree-l1"><a class="reference internal" href="glossary.html">Glossary</a></li> +<li class="toctree-l1"><a class="reference internal" href="zreferences.html">References</a></li> +</ul> + + </div> + </div> + </nav> + + <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap"><nav class="wy-nav-top" aria-label="Mobile navigation menu" style="background: #353130" > + <i data-toggle="wy-nav-top" class="fa fa-bars"></i> + <a href="index.html">PROJ</a> + </nav> + + <div class="wy-nav-content"> + <div class="rst-content"> + <div role="navigation" aria-label="Page navigation"> + <ul class="wy-breadcrumbs"> + <li><a href="index.html" class="icon icon-home"></a> »</li> + <li>FAQ</li> + <li class="wy-breadcrumbs-aside"> + <a href="https://github.com/OSGeo/PROJ/edit/8.2/docs/source/faq.rst" class="fa fa-github"> Edit on GitHub</a> + </li> + </ul><div class="rst-breadcrumbs-buttons" role="navigation" aria-label="Sequential page navigation"> + <a href="community/rfc/rfc-7.html" class="btn btn-neutral float-left" title="PROJ RFC 7: Drop Autotools, maintain CMake" accesskey="p"><span class="fa fa-arrow-circle-left" aria-hidden="true"></span> Previous</a> + <a href="glossary.html" class="btn btn-neutral float-right" title="Glossary" accesskey="n">Next <span class="fa fa-arrow-circle-right" aria-hidden="true"></span></a> + </div> + <hr/> +</div> + <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article"> + <div itemprop="articleBody"> + + <section id="faq"> +<span id="id1"></span><h1>FAQ<a class="headerlink" href="#faq" title="Permalink to this headline">¶</a></h1> +<div class="contents topic" id="contents"> +<p class="topic-title">Contents</p> +<ul class="simple"> +<li><p><a class="reference internal" href="#faq" id="id3">FAQ</a></p> +<ul> +<li><p><a class="reference internal" href="#which-file-formats-does-proj-support" id="id4">Which file formats does PROJ support?</a></p></li> +<li><p><a class="reference internal" href="#can-i-transform-from-abc-to-xyz" id="id5">Can I transform from <em>abc</em> to <em>xyz</em>?</a></p></li> +<li><p><a class="reference internal" href="#coordinate-reference-system-xyz-is-not-in-the-epsg-registry-what-do-i-do" id="id6">Coordinate reference system <em>xyz</em> is not in the EPSG registry, what do I do?</a></p></li> +<li><p><a class="reference internal" href="#i-found-a-bug-in-proj-how-do-i-get-it-fixed" id="id7">I found a bug in PROJ, how do I get it fixed?</a></p></li> +<li><p><a class="reference internal" href="#how-do-i-contribute-to-proj" id="id8">How do I contribute to PROJ?</a></p></li> +<li><p><a class="reference internal" href="#how-do-i-calculate-distances-directions-on-the-surface-of-the-earth" id="id9">How do I calculate distances/directions on the surface of the earth?</a></p></li> +<li><p><a class="reference internal" href="#what-is-the-best-format-for-describing-coordinate-reference-systems" id="id10">What is the best format for describing coordinate reference systems?</a></p></li> +<li><p><a class="reference internal" href="#why-is-the-axis-ordering-in-proj-not-consistent" id="id11">Why is the axis ordering in PROJ not consistent?</a></p></li> +<li><p><a class="reference internal" href="#why-am-i-getting-the-error-cannot-find-proj-db" id="id12">Why am I getting the error “Cannot find proj.db”?</a></p></li> +<li><p><a class="reference internal" href="#what-happened-to-proj-4" id="id13">What happened to PROJ.4?</a></p></li> +</ul> +</li> +</ul> +</div> +<section id="which-file-formats-does-proj-support"> +<h2>Which file formats does PROJ support?<a class="headerlink" href="#which-file-formats-does-proj-support" title="Permalink to this headline">¶</a></h2> +<p>The <a class="reference internal" href="apps/index.html#apps"><span class="std std-ref">command line applications</span></a> that come with PROJ only support text +input and output (apart from <strong class="program">proj</strong> which accepts a simple binary data +stream as well). <strong class="program">proj</strong>, <strong class="program">cs2cs</strong> and <strong class="program">cct</strong> expects +text files with one coordinate per line with each coordinate dimension in a +separate column.</p> +<div class="admonition note"> +<p class="admonition-title">Note</p> +<p>If your data is stored in a common geodata file format chances are that +you can use <a class="reference external" href="https://gdal.org/">GDAL</a> as a frontend to PROJ and transform your data with the +<strong class="program">ogr2ogr</strong> application.</p> +</div> +</section> +<section id="can-i-transform-from-abc-to-xyz"> +<h2>Can I transform from <em>abc</em> to <em>xyz</em>?<a class="headerlink" href="#can-i-transform-from-abc-to-xyz" title="Permalink to this headline">¶</a></h2> +<p>Probably. PROJ supports transformations between most coordinate reference systems +registered in the EPSG registry, as well as a number of other coordinate reference +systems. The best way to find out is to test it with the <strong class="program">projinfo</strong> +application. Here’s an example checking if there’s a transformation between +ETRS89/UTM32N (EPSG:25832) and ETRS89/DKTM1 (EPSG:4093):</p> +<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>./projinfo -s EPSG:25832 -t EPSG:4093 -o PROJ +<span class="go">Candidate operations found: 1</span> +<span class="go">-------------------------------------</span> +<span class="go">Operation No. 1:</span> + +<span class="go">unknown id, Inverse of UTM zone 32N + DKTM1, 0 m, World</span> + +<span class="go">PROJ string:</span> +<span class="go">+proj=pipeline</span> +<span class="go"> +step +inv +proj=utm +zone=32 +ellps=GRS80</span> +<span class="go"> +step +proj=tmerc +lat_0=0 +lon_0=9 +k=0.99998 +x_0=200000 +y_0=-5000000</span> +<span class="go"> +ellps=GRS80</span> +</pre></div> +</div> +<p>See the <strong class="program">projinfo</strong> <a class="reference internal" href="apps/projinfo.html#projinfo"><span class="std std-ref">documentation</span></a> for more info on +how to use it.</p> +</section> +<section id="coordinate-reference-system-xyz-is-not-in-the-epsg-registry-what-do-i-do"> +<h2>Coordinate reference system <em>xyz</em> is not in the EPSG registry, what do I do?<a class="headerlink" href="#coordinate-reference-system-xyz-is-not-in-the-epsg-registry-what-do-i-do" title="Permalink to this headline">¶</a></h2> +<p>Generally PROJ will accept coordinate reference system descriptions in the form +of WKT, WKT2 and PROJ strings. If you are able to describe your desired CRS +in either of those formats there’s a good chance that PROJ will be able to make +sense of it.</p> +<p>If it is important to you that a given CRS is added to the EPSG registry, you +should contact your local geodetic authority and ask them to submit the CRS for +inclusion in the registry.</p> +</section> +<section id="i-found-a-bug-in-proj-how-do-i-get-it-fixed"> +<h2>I found a bug in PROJ, how do I get it fixed?<a class="headerlink" href="#i-found-a-bug-in-proj-how-do-i-get-it-fixed" title="Permalink to this headline">¶</a></h2> +<p>Please report bugs that you find to the issue tracker on GitHub. <a class="reference internal" href="community/contributing.html#add-bug-report"><span class="std std-ref">Here’s how</span></a>.</p> +<p>If you know how to program you can also try to fix it yourself. You are welcome +to ask for guidance on one of the <a class="reference internal" href="community/channels.html#channels"><span class="std std-ref">communication channels</span></a> used +by the project.</p> +</section> +<section id="how-do-i-contribute-to-proj"> +<h2>How do I contribute to PROJ?<a class="headerlink" href="#how-do-i-contribute-to-proj" title="Permalink to this headline">¶</a></h2> +<p>Any contributions from the PROJ community is welcome. See <a class="reference internal" href="community/contributing.html#contributing"><span class="std std-ref">Contributing</span></a> for +more details.</p> +</section> +<section id="how-do-i-calculate-distances-directions-on-the-surface-of-the-earth"> +<h2>How do I calculate distances/directions on the surface of the earth?<a class="headerlink" href="#how-do-i-calculate-distances-directions-on-the-surface-of-the-earth" title="Permalink to this headline">¶</a></h2> +<p>These are called geodesic calculations. There is a page about it here: +<a class="reference internal" href="geodesic.html#geodesic"><span class="std std-ref">Geodesic calculations</span></a>.</p> +</section> +<section id="what-is-the-best-format-for-describing-coordinate-reference-systems"> +<h2>What is the best format for describing coordinate reference systems?<a class="headerlink" href="#what-is-the-best-format-for-describing-coordinate-reference-systems" title="Permalink to this headline">¶</a></h2> +<p>A coordinate reference system (CRS) can in PROJ be described in several ways: +As PROJ strings, Well-Known Text (WKT) and as spatial reference ID’s (such as EPSG +codes). Generally, WKT or SRID’s are preferred over PROJ strings as they can +contain more information about a given CRS. Conversions between WKT and PROJ +strings will in most cases cause a loss of information, potentially leading to +erroneous transformations.</p> +<p>For compatibility reasons PROJ supports several WKT dialects +(see <a class="reference internal" href="apps/projinfo.html#cmdoption-projinfo-o"><code class="xref std std-option docutils literal notranslate"><span class="pre">projinfo</span> <span class="pre">-o</span></code></a>). If possible WKT2 should be used.</p> +</section> +<section id="why-is-the-axis-ordering-in-proj-not-consistent"> +<h2>Why is the axis ordering in PROJ not consistent?<a class="headerlink" href="#why-is-the-axis-ordering-in-proj-not-consistent" title="Permalink to this headline">¶</a></h2> +<p>PROJ respects the axis ordering as it was defined by the authority in charge of +a given coordinate reference system. This is in accordance to the ISO19111 standard +<span id="id2">[<a class="reference internal" href="zreferences.html#id18" title="ISO. Geographic information – Referencing by coordinates. Standard, International Organization for Standardization, Geneva, CH, January 2019. URL: http://docs.opengeospatial.org/as/18-005r4/18-005r4.html.">ISO19111</a>]</span>. Unfortunately most GIS software on the market doesn’t follow this +standard. Before version 6, PROJ did not respect the standard either. This causes +some problems while the rest of the industry conforms to the standard. PROJ intends +to spearhead this effort, hopefully setting a good example for the rest of the +geospatial industry.</p> +<p>Customarily in GIS the first component in a coordinate tuple has been aligned with +the east/west direction and the second component with the north/south direction. +For many coordinate reference systems this is also what is defined by the authority. +There are however exceptions, especially when dealing with coordinate systems that +don’t align with the cardinal directions of a compass. For example it is not +obvious which coordinate component aligns to which axis in a skewed coordinate +system with a 45 degrees angle against the north direction. Similarly, a geocentric +cartesian coordinate system usually has the z-component aligned with the rotational +axis of the earth and hence the axis points towards north. Both cases are +incompatible with the convention of always having the x-component be the east/west +axis, the y-component the north/south axis and the z-component the up/down axis.</p> +<p>In most cases coordinate reference systems with geodetic coordinates expect the +input ordered as latitude/longitude (typically with the EPSG dataset), however, +internally PROJ expects an longitude/latitude ordering for all projections. This +is generally hidden for users but in a few cases it is exposed at the surface +level of PROJ, most prominently in the <strong class="program">proj</strong> utility which expects +longitude/latitude ordering of input date (unless <a class="reference internal" href="apps/proj.html#cmdoption-proj-r"><code class="xref std std-option docutils literal notranslate"><span class="pre">proj</span> <span class="pre">-r</span></code></a> is used).</p> +<p>In case of doubt about the axis order of a specific CRS <strong class="program">projinfo</strong> is +able to provide an answer. Simply look up the CRS and examine the axis specification +of the Well-Known Text output:</p> +<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">projinfo EPSG:4326</span> +<span class="go">PROJ.4 string:</span> +<span class="go">+proj=longlat +datum=WGS84 +no_defs +type=crs</span> + +<span class="go">WKT2:2019 string:</span> +<span class="go">GEOGCRS["WGS 84",</span> +<span class="go"> DATUM["World Geodetic System 1984",</span> +<span class="go"> ELLIPSOID["WGS 84",6378137,298.257223563,</span> +<span class="go"> LENGTHUNIT["metre",1]]],</span> +<span class="go"> PRIMEM["Greenwich",0,</span> +<span class="go"> ANGLEUNIT["degree",0.0174532925199433]],</span> +<span class="go"> CS[ellipsoidal,2],</span> +<span class="go"> AXIS["geodetic latitude (Lat)",north,</span> +<span class="go"> ORDER[1],</span> +<span class="go"> ANGLEUNIT["degree",0.0174532925199433]],</span> +<span class="go"> AXIS["geodetic longitude (Lon)",east,</span> +<span class="go"> ORDER[2],</span> +<span class="go"> ANGLEUNIT["degree",0.0174532925199433]],</span> +<span class="go"> USAGE[</span> +<span class="go"> SCOPE["unknown"],</span> +<span class="go"> AREA["World"],</span> +<span class="go"> BBOX[-90,-180,90,180]],</span> +<span class="go"> ID["EPSG",4326]]</span> +</pre></div> +</div> +</section> +<section id="why-am-i-getting-the-error-cannot-find-proj-db"> +<h2>Why am I getting the error “Cannot find proj.db”?<a class="headerlink" href="#why-am-i-getting-the-error-cannot-find-proj-db" title="Permalink to this headline">¶</a></h2> +<p>The file <a class="reference internal" href="resource_files.html#proj-db"><span class="std std-ref">proj.db</span></a> must be readable for the library to properly +function. Like other <a class="reference internal" href="resource_files.html"><span class="doc">resource files</span></a>, +it is located using a set of search +paths. In most cases, the following paths are checked in order:</p> +<blockquote> +<div><ul class="simple"> +<li><p>A path provided by the environment variable <span class="target" id="index-0"></span><a class="reference internal" href="usage/environmentvars.html#envvar-PROJ_LIB"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PROJ_LIB</span></code></a>.</p></li> +<li><p>A path built into PROJ as its resource installation directory +(typically ../share/proj relative to the PROJ library).</p></li> +<li><p>The current directory.</p></li> +</ul> +</div></blockquote> +<p>Note that if you’re using conda, activating an environment sets +<span class="target" id="index-1"></span><a class="reference internal" href="usage/environmentvars.html#envvar-PROJ_LIB"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PROJ_LIB</span></code></a> to a resource directory located in that environment.</p> +</section> +<section id="what-happened-to-proj-4"> +<h2>What happened to PROJ.4?<a class="headerlink" href="#what-happened-to-proj-4" title="Permalink to this headline">¶</a></h2> +<p>The first incarnation of PROJ saw the light of day in 1983. Back then it +was simply known as PROJ. Eventually a new version was released, known +as PROJ.2 in order to distinguish between the two versions. Later on both +PROJ.3 and PROJ.4 was released. By the time PROJ.4 was released the +software had matured enough that a new major version release wasn’t an +immediate necessity. PROJ.4 was around for more than 25 years before it +again became time for an update. This left the project in a bit of a +conundrum regarding the name. For the majority of the life-time of the product it was known as PROJ.4, but with the release of version 5 the name +was no longer aligned with the version number. As a consequence, it was +decided to decouple the name from the version number and once again simply +call the software PROJ.</p> +<p>Use of name PROJ.4 is now strictly reserved for describing legacy behavior +of the software, e.g. “PROJ.4 strings” as seen in <strong class="program">projinfo</strong> +output.</p> +</section> +</section> + + + </div> + </div> + <footer><div class="rst-footer-buttons" role="navigation" aria-label="Footer"> + <a href="community/rfc/rfc-7.html" class="btn btn-neutral float-left" title="PROJ RFC 7: Drop Autotools, maintain CMake" accesskey="p" rel="prev"><span class="fa fa-arrow-circle-left" aria-hidden="true"></span> Previous</a> + <a href="glossary.html" class="btn btn-neutral float-right" title="Glossary" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right" aria-hidden="true"></span></a> + </div> + + <hr/> + + <div role="contentinfo"> + <p>© Copyright 1983-2022. + <span class="lastupdated">Last updated on 22 Mar 2022. + </span></p> + </div> + + Built with <a href="https://www.sphinx-doc.org/">Sphinx</a> using a + <a href="https://github.com/readthedocs/sphinx_rtd_theme">theme</a> + provided by <a href="https://readthedocs.org">Read the Docs</a>. + + +</footer> + </div> + </div> + </section> + </div> + <script> + jQuery(function () { + SphinxRtdTheme.Navigation.enable(true); + }); + </script> + +</body> +</html>
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