pgLatLon

annotate README.html @ 13:4489b4d7d9c8

Updated manual installation instructions in README files to match version 0.3
author jbe
date Fri Sep 02 14:31:58 2016 +0200 (2016-09-02)
parents 7c1c76e7d341
children e319679cefbd
rev   line source
jbe@11 1 <html><head><title>pgLatLon v0.3 documentation</title></head><body>
jbe@11 2 <h1>pgLatLon v0.3 documentation</h1>
jbe@0 3
jbe@0 4 <p>pgLatLon is a spatial database extension for the PostgreSQL object-relational
jbe@0 5 database management system providing geographic data types and spatial indexing
jbe@0 6 for the WGS-84 spheroid.</p>
jbe@0 7
jbe@0 8 <p>While many other spatial databases still use imprecise bounding boxes for many
jbe@11 9 operations, pgLatLon aims to support more precise geometric calculations for
jbe@11 10 all implemented operators. Efficient indexing of geometric objects is provided
jbe@2 11 using space-filling fractal curves. Optimizations on bit level (including
jbe@2 12 logarithmic compression) allow for a highly memory-efficient non-overlapping
jbe@2 13 index suitable for huge datasets.</p>
jbe@0 14
jbe@11 15 <p>pgLatLon is a lightweight solution as it only depends on PostgreSQL itself (and
jbe@11 16 a C compiler for building).</p>
jbe@11 17
jbe@0 18 <p>Unlike competing spatial extensions for PostgreSQL, pgLatLon is available under
jbe@0 19 the permissive MIT/X11 license to avoid problems with viral licenses like the
jbe@0 20 GPLv2/v3.</p>
jbe@0 21
jbe@0 22 <h2>Installation</h2>
jbe@0 23
jbe@0 24 <h3>Automatic installation</h3>
jbe@0 25
jbe@0 26 <p>Prerequisites:</p>
jbe@0 27
jbe@0 28 <ul>
jbe@0 29 <li>Ensure that the <code>pg_config</code> binary is in your path (shipped with PostgreSQL).</li>
jbe@0 30 <li>Ensure that GNU Make is available (either as <code>make</code> or <code>gmake</code>).</li>
jbe@0 31 </ul>
jbe@0 32
jbe@0 33 <p>Then simply type:</p>
jbe@0 34
jbe@0 35 <pre><code>make install
jbe@0 36 </code></pre>
jbe@0 37
jbe@0 38 <h3>Manual installation</h3>
jbe@0 39
jbe@0 40 <p>It is also possible to compile and install the extension without GNU Make as
jbe@0 41 follows:</p>
jbe@0 42
jbe@13 43 <pre><code>cc -Wall -O2 -fPIC -shared -I `pg_config --includedir-server` -o latlon-v0003.so latlon-v0003.c
jbe@13 44 cp latlon-v0003.so `pg_config --pkglibdir`
jbe@0 45 cp latlon.control `pg_config --sharedir`/extension/
jbe@13 46 cp latlon--*.sql `pg_config --sharedir`/extension/
jbe@0 47 </code></pre>
jbe@0 48
jbe@0 49 <h3>Loading the extension</h3>
jbe@0 50
jbe@0 51 <p>After installation, you can create a database and load the extension as
jbe@0 52 follows:</p>
jbe@0 53
jbe@0 54 <pre><code>% createdb test_database
jbe@0 55 % psql test_database
jbe@0 56 psql (9.5.4)
jbe@0 57 Type "help" for help.
jbe@0 58
jbe@0 59 test_database=# CREATE EXTENSION latlon;
jbe@0 60 </code></pre>
jbe@0 61
jbe@0 62 <h2>Reference</h2>
jbe@0 63
jbe@0 64 <h3>1. Types</h3>
jbe@0 65
jbe@0 66 <p>pgLatLon provides four geographic types: <code>epoint</code>, <code>ebox</code>, <code>ecircle</code>, and
jbe@0 67 <code>ecluster</code>.</p>
jbe@0 68
jbe@0 69 <h4><code>epoint</code></h4>
jbe@0 70
jbe@0 71 <p>A point on the earth spheroid (WGS-84).</p>
jbe@0 72
jbe@0 73 <p>The text input format is <code>'[N|S]&lt;float&gt; [E|W]&lt;float&gt;'</code>, where each float is in
jbe@0 74 degrees. Note the required white space between the latitude and longitude
jbe@0 75 components. Each floating point number may have a sign, in which case <code>N</code>/<code>S</code>
jbe@0 76 or <code>E</code>/<code>W</code> are switched respectively (e.g. <code>E-5</code> is the same as <code>W5</code>).</p>
jbe@0 77
jbe@0 78 <p>An <code>epoint</code> may also be created from two floating point numbers by calling
jbe@0 79 <code>epoint(latitude, longitude)</code>, where positive latitudes are used for the
jbe@0 80 northern hemisphere, negative latitudes are used for the southern hemisphere,
jbe@0 81 positive longitudes indicate positions east of the prime meridian, and negative
jbe@0 82 longitudes indicate positions west of the prime meridian.</p>
jbe@0 83
jbe@0 84 <p>Latitudes exceeding -90 or +90 degrees are truncated to -90 or +90
jbe@0 85 respectively, in which case a warning will be issued. Longitudes exceeding -180
jbe@0 86 or +180 degrees will be converted to values between -180 and +180 (both
jbe@0 87 inclusive) by adding or substracting a multiple of 360 degrees, in which case a
jbe@0 88 notice will be issued.</p>
jbe@0 89
jbe@0 90 <p>If the latitude is -90 or +90 (south pole or north pole), a longitude value is
jbe@0 91 still stored in the datum, and if a point is on the prime meridian or the
jbe@0 92 180th meridian, the east/west bit is also stored in the datum. In case of the
jbe@0 93 prime meridian, this is done by storing a floating point value of -0 for
jbe@0 94 0 degrees west and a value of +0 for 0 degrees east. In case of the
jbe@0 95 180th meridian, this is done by storing -180 or +180 respectively. The equality
jbe@0 96 operator, however, returns true when the same points on earth are described,
jbe@0 97 i.e. the longitude is ignored for the poles, and 180 degrees west is considered
jbe@0 98 to be equal to 180 degrees east.</p>
jbe@0 99
jbe@0 100 <h4><code>ebox</code></h4>
jbe@0 101
jbe@0 102 <p>An area on earth demarcated by a southern and northern latitude, and a western
jbe@0 103 and eastern longitude (all given in WGS-84).</p>
jbe@0 104
jbe@0 105 <p>The text input format is
jbe@0 106 <code>'{N|S}&lt;float&gt; {E|W}&lt;float&gt; {N|S}&lt;float&gt; {E|W}&lt;float&gt;'</code>, where each float is in
jbe@0 107 degrees. The ordering of the four white-space separated blocks is not
jbe@0 108 significant. To include the 180th meridian, one longitude boundary must be
jbe@0 109 equal to or exceed <code>W180</code> or <code>E180</code>, e.g. <code>'N10 N20 E170 E190'</code>.</p>
jbe@0 110
jbe@0 111 <p>A special value is the empty area, denoted by the text represenation <code>'empty'</code>.
jbe@0 112 Such an <code>ebox</code> does not contain any point.</p>
jbe@0 113
jbe@0 114 <p>An <code>ebox</code> may also be created from four floating point numbers by calling
jbe@0 115 <code>ebox(min_latitude, max_latitude, min_longitude, max_longitude)</code>, where
jbe@0 116 positive values are used for north and east, and negative values are used for
jbe@0 117 south and west. If <code>min_latitude</code> is strictly greater than <code>max_latitude</code>, an
jbe@0 118 empty <code>ebox</code> is created. If <code>min_longitude</code> is greater than <code>max_longitude</code> and
jbe@0 119 if both longitudes are between -180 and +180 degrees, then the area oriented in
jbe@0 120 such way that the 180th meridian is included.</p>
jbe@0 121
jbe@0 122 <p>If the longitude span is less than 120 degrees, an <code>ebox</code> may be alternatively
jbe@0 123 created from two <code>epoints</code> in the following way: <code>ebox(epoint(lat1, lon1),
jbe@0 124 epoint(lat2, lon2))</code>. In this case <code>lat1</code> and <code>lat2</code> as well as <code>lon1</code> and
jbe@0 125 <code>lon2</code> can be swapped without any impact.</p>
jbe@0 126
jbe@0 127 <h4><code>ecircle</code></h4>
jbe@0 128
jbe@0 129 <p>An area containing all points not farther away from a given center point
jbe@0 130 (WGS-84) than a given radius.</p>
jbe@0 131
jbe@0 132 <p>The text input format is <code>'{N|S}&lt;float&gt; {E|W}&lt;float&gt; &lt;float&gt;'</code>, where the first
jbe@0 133 two floats denote the center point in degrees and the third float denotes the
jbe@0 134 radius in meters. A radius equal to minus infinity denotes an empty circle
jbe@0 135 which contains no point at all (despite having a center), while a radius equal
jbe@0 136 to zero denotes a circle that includes a single point.</p>
jbe@0 137
jbe@0 138 <p>An <code>ecircle</code> may also be created by calling <code>ecircle(epoint(...), radius)</code> or
jbe@0 139 from three floating point numbers by calling <code>ecircle(latitude, longitude,
jbe@0 140 radius)</code>.</p>
jbe@0 141
jbe@0 142 <h4><code>ecluster</code></h4>
jbe@0 143
jbe@0 144 <p>A collection of points, paths, polygons, and outlines on the WGS-84 spheroid.
jbe@0 145 Each path, polygon, or outline must cover a longitude range of less than
jbe@0 146 180 degrees to avoid ambiguities.</p>
jbe@0 147
jbe@0 148 <p>The text input format is a white-space separated list of the following items:</p>
jbe@0 149
jbe@0 150 <ul>
jbe@0 151 <li><code>point ({N|S}&lt;float&gt; {E|W}&lt;float&gt;)</code></li>
jbe@0 152 <li><code>path ({N|S}&lt;float&gt; {E|W}&lt;float&gt; {N|S}&lt;float&gt; {E|W}&lt;float&gt; ...)</code></li>
jbe@0 153 <li><code>outline ({N|S}&lt;float&gt; {E|W}&lt;float&gt; {N|S}&lt;float&gt; {E|W}&lt;float&gt; {N|S}&lt;float&gt; {E|W}&lt;float&gt; ...)</code></li>
jbe@0 154 <li><code>polygon ({N|S}&lt;float&gt; {E|W}&lt;float&gt; {N|S}&lt;float&gt; {E|W}&lt;float&gt; {N|S}&lt;float&gt; {E|W}&lt;float&gt; ...)</code></li>
jbe@0 155 </ul>
jbe@0 156
jbe@0 157 <p>Paths are open by default (i.e. there is no connection from the last point in
jbe@0 158 the list to the first point in the list). Outlines and polygons, in contrast,
jbe@0 159 are automatically closed (i.e. there is a line segment from the last point in
jbe@0 160 the list to the first point in the list) which means the first point should not
jbe@0 161 be repeated as last point in the list. Polygons are filled, outlines are not.</p>
jbe@0 162
jbe@0 163 <h3>2. Indices</h3>
jbe@0 164
jbe@0 165 <p>Two kinds of indices are supported: B-tree and GiST indices.</p>
jbe@0 166
jbe@0 167 <h4>B-tree indices</h4>
jbe@0 168
jbe@0 169 <p>A B-tree index can be used for simple equality searches and is supported by the
jbe@0 170 <code>epoint</code>, <code>ebox</code>, and <code>ecircle</code> data types. B-tree indices can not be used for
jbe@0 171 geographic searches.</p>
jbe@0 172
jbe@0 173 <h4>GiST indices</h4>
jbe@0 174
jbe@0 175 <p>For geographic searches, GiST indices must be used. The <code>epoint</code>, <code>ecircle</code>,
jbe@0 176 and <code>ecluster</code> data types support GiST indexing. A GiST index for geographic
jbe@0 177 searches can be created as follows:</p>
jbe@0 178
jbe@0 179 <pre><code>CREATE TABLE tbl (
jbe@0 180 id serial4 PRIMARY KEY,
jbe@0 181 loc epoint NOT NULL );
jbe@0 182
jbe@0 183 CREATE INDEX name_of_index ON tbl USING gist (loc);
jbe@0 184 </code></pre>
jbe@0 185
jbe@0 186 <p>GiST indices also support nearest neighbor searches when using the distance
jbe@0 187 operator (<code>&lt;-&gt;</code>) in the ORDER BY clause.</p>
jbe@0 188
jbe@0 189 <h4>Indices on other data types (e.g. GeoJSON)</h4>
jbe@0 190
jbe@0 191 <p>Note that further types can be indexed by using an index on an expression with
jbe@0 192 a conversion function. One conversion function provided by pgLatLon is the
jbe@0 193 <code>GeoJSON_to_ecluster(float8, float8, text)</code> function:</p>
jbe@0 194
jbe@0 195 <pre><code>CREATE TABLE tbl (
jbe@0 196 id serial4 PRIMARY KEY,
jbe@0 197 loc jsonb NOT NULL );
jbe@0 198
jbe@0 199 CREATE INDEX name_of_index ON tbl USING gist((GeoJSON_to_ecluster("loc")));
jbe@0 200 </code></pre>
jbe@0 201
jbe@0 202 <p>When using the conversion function in an expression, the index will be used
jbe@0 203 automatically:</p>
jbe@0 204
jbe@0 205 <pre><code>SELECT * FROM tbl WHERE GeoJSON_to_ecluster("loc") &amp;&amp; 'N50 E10 10000'::ecircle;
jbe@0 206 </code></pre>
jbe@0 207
jbe@0 208 <h3>3. Operators</h3>
jbe@0 209
jbe@0 210 <h4>Equality operator <code>=</code></h4>
jbe@0 211
jbe@0 212 <p>Tests if two geographic objects are equal.</p>
jbe@0 213
jbe@0 214 <p>The longitude is ignored for the poles, and 180 degrees west is considered to
jbe@0 215 be equal to 180 degrees east.</p>
jbe@0 216
jbe@0 217 <p>For boxes and circles, two empty objects are considered equal. (Note that a
jbe@0 218 circle is not empty if the radius is zero but only if it is negative infinity,
jbe@0 219 i.e. smaller than zero.) Two circles with a positive infinite radius are also
jbe@0 220 considered equal.</p>
jbe@0 221
jbe@0 222 <p>Implemented for:</p>
jbe@0 223
jbe@0 224 <ul>
jbe@0 225 <li><code>epoint = epoint</code></li>
jbe@0 226 <li><code>ebox = ebox</code></li>
jbe@0 227 <li><code>ecircle = ecircle</code></li>
jbe@0 228 </ul>
jbe@0 229
jbe@0 230 <p>The negation is the inequality operator (<code>&lt;&gt;</code> or <code>!=</code>).</p>
jbe@0 231
jbe@0 232 <h4>Linear ordering operators <code>&lt;&lt;&lt;</code>, <code>&lt;&lt;&lt;=</code>, <code>&gt;&gt;&gt;=</code>, <code>&gt;&gt;&gt;</code></h4>
jbe@0 233
jbe@0 234 <p>These operators create an arbitrary (but well-defined) linear ordering of
jbe@0 235 geographic objects, which is used internally for B-tree indexing and merge
jbe@0 236 joins. These operators will usually not be used by an application programmer.</p>
jbe@0 237
jbe@0 238 <h4>Overlap operator <code>&amp;&amp;</code></h4>
jbe@0 239
jbe@0 240 <p>Tests if two geographic objects have at least one point in common. Currently
jbe@0 241 implemented for:</p>
jbe@0 242
jbe@0 243 <ul>
jbe@0 244 <li><code>epoint &amp;&amp; ebox</code></li>
jbe@0 245 <li><code>epoint &amp;&amp; ecircle</code></li>
jbe@0 246 <li><code>epoint &amp;&amp; ecluster</code></li>
jbe@0 247 <li><code>ebox &amp;&amp; ebox</code></li>
jbe@0 248 <li><code>ecircle &amp;&amp; ecircle</code></li>
jbe@0 249 <li><code>ecircle &amp;&amp; ecluster</code></li>
jbe@0 250 </ul>
jbe@0 251
jbe@0 252 <p>The <code>&amp;&amp;</code> operator is commutative, i.e. <code>a &amp;&amp; b</code> is the same as <code>b &amp;&amp; a</code>. Each
jbe@0 253 commutation is supported as well.</p>
jbe@0 254
jbe@11 255 <h4>Lossy overlap operator <code>&amp;&amp;+</code></h4>
jbe@11 256
jbe@11 257 <p>Tests if two geographic objects may have at least one point in common. Opposed
jbe@11 258 to the <code>&amp;&amp;</code> operator, the <code>&amp;&amp;+</code> operator may return false positives and is
jbe@11 259 currently implemented for:</p>
jbe@11 260
jbe@11 261 <ul>
jbe@11 262 <li><code>epoint &amp;&amp;+ ecluster</code></li>
jbe@11 263 <li><code>ebox &amp;&amp;+ ecircle</code></li>
jbe@11 264 <li><code>ebox &amp;&amp;+ ecluster</code></li>
jbe@11 265 <li><code>ecircle &amp;&amp;+ ecluster</code></li>
jbe@11 266 <li><code>ecluster &amp;&amp;+ ecluster</code></li>
jbe@11 267 </ul>
jbe@11 268
jbe@11 269 <p>The <code>&amp;&amp;+</code> operator is commutative, i.e. <code>a &amp;&amp;+ b</code> is the same as <code>b &amp;&amp;+ a</code>. Each
jbe@11 270 commutation is supported as well.</p>
jbe@11 271
jbe@11 272 <p>Where two data types support both the <code>&amp;&amp;</code> and the <code>&amp;&amp;+</code> operator, the <code>&amp;&amp;+</code>
jbe@11 273 operator computes faster.</p>
jbe@11 274
jbe@0 275 <h4>Distance operator <code>&lt;-&gt;</code></h4>
jbe@0 276
jbe@0 277 <p>Calculates the shortest distance between two geographic objects in meters (zero
jbe@0 278 if the objects are overlapping). Currently implemented for:</p>
jbe@0 279
jbe@0 280 <ul>
jbe@0 281 <li><code>epoint &lt;-&gt; epoint</code></li>
jbe@0 282 <li><code>epoint &lt;-&gt; ecircle</code></li>
jbe@0 283 <li><code>epoint &lt;-&gt; ecluster</code></li>
jbe@0 284 <li><code>ecircle &lt;-&gt; ecircle</code></li>
jbe@0 285 <li><code>ecircle &lt;-&gt; ecluster</code></li>
jbe@0 286 </ul>
jbe@0 287
jbe@0 288 <p>The <code>&lt;-&gt;</code> operator is commutative, i.e. <code>a &lt;-&gt; b</code> is the same as <code>b &lt;-&gt; a</code>.
jbe@0 289 Each commutation is supported as well.</p>
jbe@0 290
jbe@0 291 <p>For short distances, the result is very accurate (i.e. respects the dimensions
jbe@0 292 of the WGS-84 spheroid). For longer distances in the order of magnitude of
jbe@0 293 earth's radius or greater, the value is only approximate (but the error is
jbe@0 294 still less than 0.2% as long as no polygons with very long edges are involved).</p>
jbe@0 295
jbe@0 296 <p>The functions <code>distance(epoint, epoint)</code> and <code>distance(ecluster, epoint)</code> can
jbe@0 297 be used as an alias for this operator.</p>
jbe@0 298
jbe@0 299 <p>Note: In case of radial searches with a fixed radius, this operator should
jbe@0 300 not be used. Instead, an <code>ecircle</code> should be created and used in combination
jbe@0 301 with the overlap operator (<code>&amp;&amp;</code>). Alternatively, the functions
jbe@0 302 <code>distance_within(epoint, epoint, float8)</code> or <code>distance_within(ecluster, epoint,
jbe@0 303 float8)</code> can be used for fixed-radius searches.</p>
jbe@0 304
jbe@0 305 <h3>4. Functions</h3>
jbe@0 306
jbe@0 307 <h4><code>center(circle)</code></h4>
jbe@0 308
jbe@0 309 <p>Returns the center of an <code>ecircle</code> as an <code>epoint</code>.</p>
jbe@0 310
jbe@0 311 <h4><code>distance(epoint, epoint)</code></h4>
jbe@0 312
jbe@0 313 <p>Calculates the distance between two <code>epoint</code> datums in meters. This function is
jbe@0 314 an alias for the distance operator <code>&lt;-&gt;</code>.</p>
jbe@0 315
jbe@0 316 <p>Note: In case of radial searches with a fixed radius, this function should not be
jbe@0 317 used. Use <code>distance_within(epoint, epoint, float8)</code> instead.</p>
jbe@0 318
jbe@0 319 <h4><code>distance(ecluster, epoint)</code></h4>
jbe@0 320
jbe@0 321 <p>Calculates the distance from an <code>ecluster</code> to an <code>epoint</code> in meters. This
jbe@0 322 function is an alias for the distance operator <code>&lt;-&gt;</code>.</p>
jbe@0 323
jbe@0 324 <p>Note: In case of radial searches with a fixed radius, this function should not be
jbe@0 325 used. Use <code>distance_within(epoint, epoint, float8)</code> instead.</p>
jbe@0 326
jbe@0 327 <h4><code>distance_within(</code>variable <code>epoint,</code> fixed <code>epoint,</code> radius <code>float8)</code></h4>
jbe@0 328
jbe@0 329 <p>Checks if the distance between two <code>epoint</code> datums is not greater than a given
jbe@0 330 value (search radius).</p>
jbe@0 331
jbe@0 332 <p>Note: In case of radial searches with a fixed radius, the first argument must
jbe@0 333 be used for the table column, while the second argument must be used for the
jbe@0 334 search center. Otherwise an existing index cannot be used.</p>
jbe@0 335
jbe@0 336 <h4><code>distance_within(</code>variable <code>ecluster,</code> fixed <code>epoint,</code> radius <code>float8)</code></h4>
jbe@0 337
jbe@0 338 <p>Checks if the distance from an <code>ecluster</code> to an <code>epoint</code> is not greater than a
jbe@0 339 given value (search radius).</p>
jbe@0 340
jbe@0 341 <h4><code>ebox(</code>latmin <code>float8,</code> latmax <code>float8,</code> lonmin <code>float8,</code> lonmax <code>float8)</code></h4>
jbe@0 342
jbe@0 343 <p>Creates a new <code>ebox</code> with the given boundaries.
jbe@0 344 See "1. Types", subsection <code>ebox</code> for details.</p>
jbe@0 345
jbe@0 346 <h4><code>ebox(epoint, epoint)</code></h4>
jbe@0 347
jbe@0 348 <p>Creates a new <code>ebox</code>. This function may only be used if the longitude
jbe@0 349 difference is less than or equal to 120 degrees.
jbe@0 350 See "1. Types", subsection <code>ebox</code> for details.</p>
jbe@0 351
jbe@0 352 <h4><code>ecircle(epoint, float8)</code></h4>
jbe@0 353
jbe@0 354 <p>Creates an <code>ecircle</code> with the given center point and radius.</p>
jbe@0 355
jbe@0 356 <h4><code>ecircle(</code>latitude <code>float8,</code> longitude <code>float8,</code> radius <code>float8)</code></h4>
jbe@0 357
jbe@0 358 <p>Creates an <code>ecircle</code> with the given center point and radius.</p>
jbe@0 359
jbe@0 360 <h4><code>ecluster_concat(ecluster, ecluster)</code></h4>
jbe@0 361
jbe@0 362 <p>Combines two clusters to form a new <code>ecluster</code> by uniting all entries of both
jbe@0 363 clusters. Note that two overlapping areas of polygons annihilate each other
jbe@0 364 (which may be used to create polygons with holes).</p>
jbe@0 365
jbe@0 366 <h4><code>ecluster_concat(ecluster[])</code></h4>
jbe@0 367
jbe@0 368 <p>Creates a new <code>ecluster</code> that unites all entries of all clusters in the passed
jbe@0 369 array. Note that two overlapping areas of polygons annihilate each other (which
jbe@0 370 may be used to create polygons with holes).</p>
jbe@0 371
jbe@0 372 <h4><code>ecluster_create_multipoint(epoint[])</code></h4>
jbe@0 373
jbe@0 374 <p>Creates a new <code>ecluster</code> which contains multiple points.</p>
jbe@0 375
jbe@0 376 <h4><code>ecluster_create_outline(epoint[])</code></h4>
jbe@0 377
jbe@0 378 <p>Creates a new <code>ecluster</code> that is an outline given by the passed points.</p>
jbe@0 379
jbe@0 380 <h4><code>ecluster_create_path(epoint[])</code></h4>
jbe@0 381
jbe@0 382 <p>Creates a new <code>ecluster</code> that is a path given by the passed points.</p>
jbe@0 383
jbe@0 384 <h4><code>ecluster_create_polygon(epoint[])</code></h4>
jbe@0 385
jbe@0 386 <p>Creates a new <code>ecluster</code> that is a polygon given by the passed points.</p>
jbe@0 387
jbe@0 388 <h4><code>ecluster_extract_outlines(ecluster)</code></h4>
jbe@0 389
jbe@0 390 <p>Set-returning function that returns the outlines of an <code>ecluster</code> as <code>epoint[]</code>
jbe@0 391 rows.</p>
jbe@0 392
jbe@0 393 <h4><code>ecluster_extract_paths(ecluster)</code></h4>
jbe@0 394
jbe@0 395 <p>Set-returning function that returns the paths of an <code>ecluster</code> as <code>epoint[]</code>
jbe@0 396 rows.</p>
jbe@0 397
jbe@0 398 <h4><code>ecluster_extract_points(ecluster)</code></h4>
jbe@0 399
jbe@0 400 <p>Set-returning function that returns the points of an <code>ecluster</code> as <code>epoint</code>
jbe@0 401 rows.</p>
jbe@0 402
jbe@0 403 <h4><code>ecluster_extract_polygons(ecluster)</code></h4>
jbe@0 404
jbe@0 405 <p>Set-returning function that returns the polygons of an <code>ecluster</code> as <code>epoint[]</code>
jbe@0 406 rows.</p>
jbe@0 407
jbe@0 408 <h4><code>empty_ebox</code>()</h4>
jbe@0 409
jbe@0 410 <p>Returns the empty <code>ebox</code>.
jbe@0 411 See "1. Types", subsection <code>ebox</code> for details.</p>
jbe@0 412
jbe@0 413 <h4><code>epoint(</code>latitude <code>float8,</code> longitude <code>float8)</code></h4>
jbe@0 414
jbe@0 415 <p>Returns an <code>epoint</code> with the given latitude and longitude.</p>
jbe@0 416
jbe@0 417 <h4><code>epoint_latlon(</code>latitude <code>float8,</code> longitude <code>float8)</code></h4>
jbe@0 418
jbe@0 419 <p>Alias for <code>epoint(float8, float8)</code>.</p>
jbe@0 420
jbe@0 421 <h4><code>epoint_lonlat(</code>longitude <code>float8,</code> latitude <code>float8)</code></h4>
jbe@0 422
jbe@0 423 <p>Same as <code>epoint(float8, float8)</code> but with arguments reversed.</p>
jbe@0 424
jbe@0 425 <h4><code>GeoJSON_to_epoint(jsonb, text)</code></h4>
jbe@0 426
jbe@0 427 <p>Maps a GeoJSON object of type "Point" or "Feature" (which contains a
jbe@0 428 "Point") to an <code>epoint</code> datum. For any other JSON objects, NULL is returned.</p>
jbe@0 429
jbe@0 430 <p>The second parameter (which defaults to <code>epoint_lonlat</code>) may be set to a name
jbe@0 431 of a conversion function that transforms two coordinates (two <code>float8</code>
jbe@0 432 parameters) to an <code>epoint</code>.</p>
jbe@0 433
jbe@0 434 <h4><code>GeoJSON_to_ecluster(jsonb, text)</code></h4>
jbe@0 435
jbe@0 436 <p>Maps a (valid) GeoJSON object to an <code>ecluster</code>. Note that this function
jbe@0 437 does not check whether the JSONB object is a valid GeoJSON object.</p>
jbe@0 438
jbe@0 439 <p>The second parameter (which defaults to <code>epoint_lonlat</code>) may be set to a name
jbe@0 440 of a conversion function that transforms two coordinates (two <code>float8</code>
jbe@0 441 parameters) to an <code>epoint</code>.</p>
jbe@0 442
jbe@0 443 <h4><code>max_latitude(ebox)</code></h4>
jbe@0 444
jbe@0 445 <p>Returns the northern boundary of a given <code>ebox</code> in degrees between -90 and +90.</p>
jbe@0 446
jbe@0 447 <h4><code>max_longitude(ebox)</code></h4>
jbe@0 448
jbe@0 449 <p>Returns the eastern boundary of a given <code>ebox</code> in degrees between -180 and +180
jbe@0 450 (both inclusive).</p>
jbe@0 451
jbe@0 452 <h4><code>min_latitude(ebox)</code></h4>
jbe@0 453
jbe@0 454 <p>Returns the southern boundary of a given <code>ebox</code> in degrees between -90 and +90.</p>
jbe@0 455
jbe@0 456 <h4><code>min_longitude(ebox)</code></h4>
jbe@0 457
jbe@0 458 <p>Returns the western boundary of a given <code>ebox</code> in degrees between -180 and +180
jbe@0 459 (both inclusive).</p>
jbe@0 460
jbe@0 461 <h4><code>latitude(epoint)</code></h4>
jbe@0 462
jbe@0 463 <p>Returns the latitude value of an <code>epoint</code> in degrees between -90 and +90.</p>
jbe@0 464
jbe@0 465 <h4><code>longitude(epoint)</code></h4>
jbe@0 466
jbe@0 467 <p>Returns the longitude value of an <code>epoint</code> in degrees between -180 and +180
jbe@0 468 (both inclusive).</p>
jbe@0 469
jbe@0 470 <h4><code>radius(ecircle)</code></h4>
jbe@0 471
jbe@0 472 <p>Returns the radius of an <code>ecircle</code> in meters.</p>
jbe@0 473 </body></html>

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