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1 <html><head><title>pgLatLon v0.1 documentation</title></head><body>
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2 <h1>pgLatLon v0.1 documentation</h1>
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3
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4 <p>pgLatLon is a spatial database extension for the PostgreSQL object-relational
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5 database management system providing geographic data types and spatial indexing
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6 for the WGS-84 spheroid.</p>
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7
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8 <p>While many other spatial databases still use imprecise bounding boxes for many
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9 operations, pgLatLon supports more precise geometric calculations for all
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10 implemented operators. Efficient indexing of geometric objects is provided
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11 using fractal indices. Optimizations on bit level (including logarithmic
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12 compression) allow for a highly memory-efficient non-overlapping index suitable
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13 for huge datasets.</p>
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14
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15 <p>Unlike competing spatial extensions for PostgreSQL, pgLatLon is available under
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16 the permissive MIT/X11 license to avoid problems with viral licenses like the
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17 GPLv2/v3.</p>
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18
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19 <h2>Installation</h2>
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20
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21 <h3>Automatic installation</h3>
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22
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23 <p>Prerequisites:</p>
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24
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25 <ul>
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26 <li>Ensure that the <code>pg_config</code> binary is in your path (shipped with PostgreSQL).</li>
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27 <li>Ensure that GNU Make is available (either as <code>make</code> or <code>gmake</code>).</li>
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28 </ul>
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29
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30 <p>Then simply type:</p>
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31
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32 <pre><code>make install
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33 </code></pre>
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34
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35 <h3>Manual installation</h3>
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36
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37 <p>It is also possible to compile and install the extension without GNU Make as
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38 follows:</p>
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39
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40 <pre><code>cc -Wall -O2 -fPIC -shared -I `pg_config --includedir-server` -o latlon-v0001.so latlon-v0001.c
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41 cp latlon-v0001.so `pg_config --pkglibdir`
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42 cp latlon.control `pg_config --sharedir`/extension/
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43 cp latlon--0.1.sql `pg_config --sharedir`/extension/
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44 </code></pre>
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45
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46 <h3>Loading the extension</h3>
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47
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48 <p>After installation, you can create a database and load the extension as
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49 follows:</p>
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50
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51 <pre><code>% createdb test_database
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52 % psql test_database
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53 psql (9.5.4)
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54 Type "help" for help.
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55
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56 test_database=# CREATE EXTENSION latlon;
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57 </code></pre>
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58
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59 <h2>Reference</h2>
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60
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61 <h3>1. Types</h3>
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62
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63 <p>pgLatLon provides four geographic types: <code>epoint</code>, <code>ebox</code>, <code>ecircle</code>, and
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64 <code>ecluster</code>.</p>
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65
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66 <h4><code>epoint</code></h4>
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67
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68 <p>A point on the earth spheroid (WGS-84).</p>
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69
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70 <p>The text input format is <code>'[N|S]<float> [E|W]<float>'</code>, where each float is in
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71 degrees. Note the required white space between the latitude and longitude
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72 components. Each floating point number may have a sign, in which case <code>N</code>/<code>S</code>
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73 or <code>E</code>/<code>W</code> are switched respectively (e.g. <code>E-5</code> is the same as <code>W5</code>).</p>
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74
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75 <p>An <code>epoint</code> may also be created from two floating point numbers by calling
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76 <code>epoint(latitude, longitude)</code>, where positive latitudes are used for the
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77 northern hemisphere, negative latitudes are used for the southern hemisphere,
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78 positive longitudes indicate positions east of the prime meridian, and negative
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79 longitudes indicate positions west of the prime meridian.</p>
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80
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81 <p>Latitudes exceeding -90 or +90 degrees are truncated to -90 or +90
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82 respectively, in which case a warning will be issued. Longitudes exceeding -180
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83 or +180 degrees will be converted to values between -180 and +180 (both
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84 inclusive) by adding or substracting a multiple of 360 degrees, in which case a
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85 notice will be issued.</p>
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86
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87 <p>If the latitude is -90 or +90 (south pole or north pole), a longitude value is
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88 still stored in the datum, and if a point is on the prime meridian or the
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89 180th meridian, the east/west bit is also stored in the datum. In case of the
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90 prime meridian, this is done by storing a floating point value of -0 for
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91 0 degrees west and a value of +0 for 0 degrees east. In case of the
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92 180th meridian, this is done by storing -180 or +180 respectively. The equality
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93 operator, however, returns true when the same points on earth are described,
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94 i.e. the longitude is ignored for the poles, and 180 degrees west is considered
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95 to be equal to 180 degrees east.</p>
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96
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97 <h4><code>ebox</code></h4>
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98
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99 <p>An area on earth demarcated by a southern and northern latitude, and a western
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100 and eastern longitude (all given in WGS-84).</p>
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101
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102 <p>The text input format is
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103 <code>'{N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float>'</code>, where each float is in
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104 degrees. The ordering of the four white-space separated blocks is not
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105 significant. To include the 180th meridian, one longitude boundary must be
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106 equal to or exceed <code>W180</code> or <code>E180</code>, e.g. <code>'N10 N20 E170 E190'</code>.</p>
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107
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108 <p>A special value is the empty area, denoted by the text represenation <code>'empty'</code>.
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109 Such an <code>ebox</code> does not contain any point.</p>
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110
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111 <p>An <code>ebox</code> may also be created from four floating point numbers by calling
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112 <code>ebox(min_latitude, max_latitude, min_longitude, max_longitude)</code>, where
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113 positive values are used for north and east, and negative values are used for
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114 south and west. If <code>min_latitude</code> is strictly greater than <code>max_latitude</code>, an
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115 empty <code>ebox</code> is created. If <code>min_longitude</code> is greater than <code>max_longitude</code> and
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116 if both longitudes are between -180 and +180 degrees, then the area oriented in
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117 such way that the 180th meridian is included.</p>
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118
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119 <p>If the longitude span is less than 120 degrees, an <code>ebox</code> may be alternatively
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120 created from two <code>epoints</code> in the following way: <code>ebox(epoint(lat1, lon1),
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121 epoint(lat2, lon2))</code>. In this case <code>lat1</code> and <code>lat2</code> as well as <code>lon1</code> and
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122 <code>lon2</code> can be swapped without any impact.</p>
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123
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124 <h4><code>ecircle</code></h4>
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125
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126 <p>An area containing all points not farther away from a given center point
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127 (WGS-84) than a given radius.</p>
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128
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129 <p>The text input format is <code>'{N|S}<float> {E|W}<float> <float>'</code>, where the first
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130 two floats denote the center point in degrees and the third float denotes the
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131 radius in meters. A radius equal to minus infinity denotes an empty circle
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132 which contains no point at all (despite having a center), while a radius equal
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133 to zero denotes a circle that includes a single point.</p>
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134
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135 <p>An <code>ecircle</code> may also be created by calling <code>ecircle(epoint(...), radius)</code> or
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136 from three floating point numbers by calling <code>ecircle(latitude, longitude,
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137 radius)</code>.</p>
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138
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139 <h4><code>ecluster</code></h4>
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140
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141 <p>A collection of points, paths, polygons, and outlines on the WGS-84 spheroid.
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142 Each path, polygon, or outline must cover a longitude range of less than
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143 180 degrees to avoid ambiguities.</p>
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144
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145 <p>The text input format is a white-space separated list of the following items:</p>
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146
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147 <ul>
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148 <li><code>point ({N|S}<float> {E|W}<float>)</code></li>
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149 <li><code>path ({N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float> ...)</code></li>
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150 <li><code>outline ({N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float> ...)</code></li>
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151 <li><code>polygon ({N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float> ...)</code></li>
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152 </ul>
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153
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154 <p>Paths are open by default (i.e. there is no connection from the last point in
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155 the list to the first point in the list). Outlines and polygons, in contrast,
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156 are automatically closed (i.e. there is a line segment from the last point in
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157 the list to the first point in the list) which means the first point should not
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158 be repeated as last point in the list. Polygons are filled, outlines are not.</p>
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159
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160 <h3>2. Indices</h3>
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161
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162 <p>Two kinds of indices are supported: B-tree and GiST indices.</p>
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163
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164 <h4>B-tree indices</h4>
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165
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166 <p>A B-tree index can be used for simple equality searches and is supported by the
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167 <code>epoint</code>, <code>ebox</code>, and <code>ecircle</code> data types. B-tree indices can not be used for
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168 geographic searches.</p>
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169
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170 <h4>GiST indices</h4>
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171
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172 <p>For geographic searches, GiST indices must be used. The <code>epoint</code>, <code>ecircle</code>,
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173 and <code>ecluster</code> data types support GiST indexing. A GiST index for geographic
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174 searches can be created as follows:</p>
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175
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176 <pre><code>CREATE TABLE tbl (
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177 id serial4 PRIMARY KEY,
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178 loc epoint NOT NULL );
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179
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180 CREATE INDEX name_of_index ON tbl USING gist (loc);
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181 </code></pre>
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182
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183 <p>GiST indices also support nearest neighbor searches when using the distance
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184 operator (<code><-></code>) in the ORDER BY clause.</p>
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185
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186 <h4>Indices on other data types (e.g. GeoJSON)</h4>
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187
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188 <p>Note that further types can be indexed by using an index on an expression with
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189 a conversion function. One conversion function provided by pgLatLon is the
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190 <code>GeoJSON_to_ecluster(float8, float8, text)</code> function:</p>
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191
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192 <pre><code>CREATE TABLE tbl (
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193 id serial4 PRIMARY KEY,
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194 loc jsonb NOT NULL );
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195
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196 CREATE INDEX name_of_index ON tbl USING gist((GeoJSON_to_ecluster("loc")));
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197 </code></pre>
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198
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199 <p>When using the conversion function in an expression, the index will be used
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200 automatically:</p>
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201
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202 <pre><code>SELECT * FROM tbl WHERE GeoJSON_to_ecluster("loc") && 'N50 E10 10000'::ecircle;
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203 </code></pre>
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204
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205 <h3>3. Operators</h3>
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206
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207 <h4>Equality operator <code>=</code></h4>
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208
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209 <p>Tests if two geographic objects are equal.</p>
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210
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211 <p>The longitude is ignored for the poles, and 180 degrees west is considered to
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212 be equal to 180 degrees east.</p>
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213
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214 <p>For boxes and circles, two empty objects are considered equal. (Note that a
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215 circle is not empty if the radius is zero but only if it is negative infinity,
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216 i.e. smaller than zero.) Two circles with a positive infinite radius are also
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217 considered equal.</p>
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218
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219 <p>Implemented for:</p>
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220
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221 <ul>
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222 <li><code>epoint = epoint</code></li>
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223 <li><code>ebox = ebox</code></li>
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224 <li><code>ecircle = ecircle</code></li>
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225 </ul>
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226
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227 <p>The negation is the inequality operator (<code><></code> or <code>!=</code>).</p>
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228
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229 <h4>Linear ordering operators <code><<<</code>, <code><<<=</code>, <code>>>>=</code>, <code>>>></code></h4>
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230
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231 <p>These operators create an arbitrary (but well-defined) linear ordering of
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232 geographic objects, which is used internally for B-tree indexing and merge
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233 joins. These operators will usually not be used by an application programmer.</p>
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234
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235 <h4>Overlap operator <code>&&</code></h4>
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236
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237 <p>Tests if two geographic objects have at least one point in common. Currently
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238 implemented for:</p>
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239
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240 <ul>
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241 <li><code>epoint && ebox</code></li>
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242 <li><code>epoint && ecircle</code></li>
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243 <li><code>epoint && ecluster</code></li>
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244 <li><code>ebox && ebox</code></li>
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245 <li><code>ecircle && ecircle</code></li>
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246 <li><code>ecircle && ecluster</code></li>
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247 </ul>
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248
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249 <p>The <code>&&</code> operator is commutative, i.e. <code>a && b</code> is the same as <code>b && a</code>. Each
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250 commutation is supported as well.</p>
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251
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252 <h4>Distance operator <code><-></code></h4>
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253
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254 <p>Calculates the shortest distance between two geographic objects in meters (zero
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255 if the objects are overlapping). Currently implemented for:</p>
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256
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257 <ul>
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258 <li><code>epoint <-> epoint</code></li>
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259 <li><code>epoint <-> ecircle</code></li>
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260 <li><code>epoint <-> ecluster</code></li>
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261 <li><code>ecircle <-> ecircle</code></li>
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262 <li><code>ecircle <-> ecluster</code></li>
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263 </ul>
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264
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265 <p>The <code><-></code> operator is commutative, i.e. <code>a <-> b</code> is the same as <code>b <-> a</code>.
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266 Each commutation is supported as well.</p>
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267
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268 <p>For short distances, the result is very accurate (i.e. respects the dimensions
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269 of the WGS-84 spheroid). For longer distances in the order of magnitude of
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270 earth's radius or greater, the value is only approximate (but the error is
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271 still less than 0.2% as long as no polygons with very long edges are involved).</p>
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272
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273 <p>The functions <code>distance(epoint, epoint)</code> and <code>distance(ecluster, epoint)</code> can
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274 be used as an alias for this operator.</p>
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275
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276 <p>Note: In case of radial searches with a fixed radius, this operator should
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277 not be used. Instead, an <code>ecircle</code> should be created and used in combination
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278 with the overlap operator (<code>&&</code>). Alternatively, the functions
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279 <code>distance_within(epoint, epoint, float8)</code> or <code>distance_within(ecluster, epoint,
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280 float8)</code> can be used for fixed-radius searches.</p>
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281
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282 <h3>4. Functions</h3>
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283
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284 <h4><code>center(circle)</code></h4>
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285
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286 <p>Returns the center of an <code>ecircle</code> as an <code>epoint</code>.</p>
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287
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288 <h4><code>distance(epoint, epoint)</code></h4>
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289
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290 <p>Calculates the distance between two <code>epoint</code> datums in meters. This function is
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291 an alias for the distance operator <code><-></code>.</p>
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292
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293 <p>Note: In case of radial searches with a fixed radius, this function should not be
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294 used. Use <code>distance_within(epoint, epoint, float8)</code> instead.</p>
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295
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296 <h4><code>distance(ecluster, epoint)</code></h4>
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297
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298 <p>Calculates the distance from an <code>ecluster</code> to an <code>epoint</code> in meters. This
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299 function is an alias for the distance operator <code><-></code>.</p>
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300
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301 <p>Note: In case of radial searches with a fixed radius, this function should not be
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302 used. Use <code>distance_within(epoint, epoint, float8)</code> instead.</p>
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303
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304 <h4><code>distance_within(</code>variable <code>epoint,</code> fixed <code>epoint,</code> radius <code>float8)</code></h4>
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305
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306 <p>Checks if the distance between two <code>epoint</code> datums is not greater than a given
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307 value (search radius).</p>
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308
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309 <p>Note: In case of radial searches with a fixed radius, the first argument must
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310 be used for the table column, while the second argument must be used for the
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311 search center. Otherwise an existing index cannot be used.</p>
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312
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313 <h4><code>distance_within(</code>variable <code>ecluster,</code> fixed <code>epoint,</code> radius <code>float8)</code></h4>
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314
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315 <p>Checks if the distance from an <code>ecluster</code> to an <code>epoint</code> is not greater than a
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316 given value (search radius).</p>
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317
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318 <h4><code>ebox(</code>latmin <code>float8,</code> latmax <code>float8,</code> lonmin <code>float8,</code> lonmax <code>float8)</code></h4>
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319
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320 <p>Creates a new <code>ebox</code> with the given boundaries.
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321 See "1. Types", subsection <code>ebox</code> for details.</p>
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322
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323 <h4><code>ebox(epoint, epoint)</code></h4>
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324
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325 <p>Creates a new <code>ebox</code>. This function may only be used if the longitude
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326 difference is less than or equal to 120 degrees.
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327 See "1. Types", subsection <code>ebox</code> for details.</p>
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328
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329 <h4><code>ecircle(epoint, float8)</code></h4>
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330
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331 <p>Creates an <code>ecircle</code> with the given center point and radius.</p>
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332
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333 <h4><code>ecircle(</code>latitude <code>float8,</code> longitude <code>float8,</code> radius <code>float8)</code></h4>
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334
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335 <p>Creates an <code>ecircle</code> with the given center point and radius.</p>
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336
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337 <h4><code>ecluster_concat(ecluster, ecluster)</code></h4>
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338
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339 <p>Combines two clusters to form a new <code>ecluster</code> by uniting all entries of both
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340 clusters. Note that two overlapping areas of polygons annihilate each other
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341 (which may be used to create polygons with holes).</p>
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342
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343 <h4><code>ecluster_concat(ecluster[])</code></h4>
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344
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345 <p>Creates a new <code>ecluster</code> that unites all entries of all clusters in the passed
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346 array. Note that two overlapping areas of polygons annihilate each other (which
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347 may be used to create polygons with holes).</p>
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348
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349 <h4><code>ecluster_create_multipoint(epoint[])</code></h4>
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350
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351 <p>Creates a new <code>ecluster</code> which contains multiple points.</p>
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352
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353 <h4><code>ecluster_create_outline(epoint[])</code></h4>
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354
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355 <p>Creates a new <code>ecluster</code> that is an outline given by the passed points.</p>
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356
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357 <h4><code>ecluster_create_path(epoint[])</code></h4>
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358
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359 <p>Creates a new <code>ecluster</code> that is a path given by the passed points.</p>
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360
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361 <h4><code>ecluster_create_polygon(epoint[])</code></h4>
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362
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jbe@529
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363 <p>Creates a new <code>ecluster</code> that is a polygon given by the passed points.</p>
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364
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365 <h4><code>ecluster_extract_outlines(ecluster)</code></h4>
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366
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367 <p>Set-returning function that returns the outlines of an <code>ecluster</code> as <code>epoint[]</code>
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368 rows.</p>
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369
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370 <h4><code>ecluster_extract_paths(ecluster)</code></h4>
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371
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372 <p>Set-returning function that returns the paths of an <code>ecluster</code> as <code>epoint[]</code>
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|
373 rows.</p>
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374
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375 <h4><code>ecluster_extract_points(ecluster)</code></h4>
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376
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jbe@529
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377 <p>Set-returning function that returns the points of an <code>ecluster</code> as <code>epoint</code>
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jbe@529
|
378 rows.</p>
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379
|
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380 <h4><code>ecluster_extract_polygons(ecluster)</code></h4>
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381
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jbe@529
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382 <p>Set-returning function that returns the polygons of an <code>ecluster</code> as <code>epoint[]</code>
|
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jbe@529
|
383 rows.</p>
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384
|
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jbe@529
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385 <h4><code>empty_ebox</code>()</h4>
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386
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jbe@529
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387 <p>Returns the empty <code>ebox</code>.
|
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jbe@529
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388 See "1. Types", subsection <code>ebox</code> for details.</p>
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389
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390 <h4><code>epoint(</code>latitude <code>float8,</code> longitude <code>float8)</code></h4>
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jbe@529
|
391
|
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jbe@529
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392 <p>Returns an <code>epoint</code> with the given latitude and longitude.</p>
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393
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jbe@529
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394 <h4><code>epoint_latlon(</code>latitude <code>float8,</code> longitude <code>float8)</code></h4>
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395
|
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jbe@529
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396 <p>Alias for <code>epoint(float8, float8)</code>.</p>
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397
|
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jbe@529
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398 <h4><code>epoint_lonlat(</code>longitude <code>float8,</code> latitude <code>float8)</code></h4>
|
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jbe@529
|
399
|
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jbe@529
|
400 <p>Same as <code>epoint(float8, float8)</code> but with arguments reversed.</p>
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401
|
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jbe@529
|
402 <h4><code>GeoJSON_to_epoint(jsonb, text)</code></h4>
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403
|
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jbe@529
|
404 <p>Maps a GeoJSON object of type "Point" or "Feature" (which contains a
|
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|
405 "Point") to an <code>epoint</code> datum. For any other JSON objects, NULL is returned.</p>
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406
|
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jbe@529
|
407 <p>The second parameter (which defaults to <code>epoint_lonlat</code>) may be set to a name
|
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jbe@529
|
408 of a conversion function that transforms two coordinates (two <code>float8</code>
|
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jbe@529
|
409 parameters) to an <code>epoint</code>.</p>
|
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jbe@529
|
410
|
|
jbe@529
|
411 <h4><code>GeoJSON_to_ecluster(jsonb, text)</code></h4>
|
|
jbe@529
|
412
|
|
jbe@529
|
413 <p>Maps a (valid) GeoJSON object to an <code>ecluster</code>. Note that this function
|
|
jbe@529
|
414 does not check whether the JSONB object is a valid GeoJSON object.</p>
|
|
jbe@529
|
415
|
|
jbe@529
|
416 <p>The second parameter (which defaults to <code>epoint_lonlat</code>) may be set to a name
|
|
jbe@529
|
417 of a conversion function that transforms two coordinates (two <code>float8</code>
|
|
jbe@529
|
418 parameters) to an <code>epoint</code>.</p>
|
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jbe@529
|
419
|
|
jbe@529
|
420 <h4><code>max_latitude(ebox)</code></h4>
|
|
jbe@529
|
421
|
|
jbe@529
|
422 <p>Returns the northern boundary of a given <code>ebox</code> in degrees between -90 and +90.</p>
|
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jbe@529
|
423
|
|
jbe@529
|
424 <h4><code>max_longitude(ebox)</code></h4>
|
|
jbe@529
|
425
|
|
jbe@529
|
426 <p>Returns the eastern boundary of a given <code>ebox</code> in degrees between -180 and +180
|
|
jbe@529
|
427 (both inclusive).</p>
|
|
jbe@529
|
428
|
|
jbe@529
|
429 <h4><code>min_latitude(ebox)</code></h4>
|
|
jbe@529
|
430
|
|
jbe@529
|
431 <p>Returns the southern boundary of a given <code>ebox</code> in degrees between -90 and +90.</p>
|
|
jbe@529
|
432
|
|
jbe@529
|
433 <h4><code>min_longitude(ebox)</code></h4>
|
|
jbe@529
|
434
|
|
jbe@529
|
435 <p>Returns the western boundary of a given <code>ebox</code> in degrees between -180 and +180
|
|
jbe@529
|
436 (both inclusive).</p>
|
|
jbe@529
|
437
|
|
jbe@529
|
438 <h4><code>latitude(epoint)</code></h4>
|
|
jbe@529
|
439
|
|
jbe@529
|
440 <p>Returns the latitude value of an <code>epoint</code> in degrees between -90 and +90.</p>
|
|
jbe@529
|
441
|
|
jbe@529
|
442 <h4><code>longitude(epoint)</code></h4>
|
|
jbe@529
|
443
|
|
jbe@529
|
444 <p>Returns the longitude value of an <code>epoint</code> in degrees between -180 and +180
|
|
jbe@529
|
445 (both inclusive).</p>
|
|
jbe@529
|
446
|
|
jbe@529
|
447 <h4><code>radius(ecircle)</code></h4>
|
|
jbe@529
|
448
|
|
jbe@529
|
449 <p>Returns the radius of an <code>ecircle</code> in meters.</p>
|
|
jbe@529
|
450 </body></html>
|