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1 <html><head><title>pgLatLon v0.3 documentation</title></head><body>
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2 <h1>pgLatLon v0.3 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 aims to support more precise geometric calculations for
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10 all implemented operators. Efficient indexing of geometric objects is provided
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11 using space-filling fractal curves. Optimizations on bit level (including
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12 logarithmic compression) allow for a highly memory-efficient non-overlapping
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13 index suitable for huge datasets.</p>
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14
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15 <p>pgLatLon is a lightweight solution as it only depends on PostgreSQL itself (and
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16 a C compiler for building).</p>
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17
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18 <p>Unlike competing spatial extensions for PostgreSQL, pgLatLon is available under
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19 the permissive MIT/X11 license to avoid problems with viral licenses like the
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20 GPLv2/v3.</p>
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21
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22 <h2>Installation</h2>
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23
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24 <h3>Automatic installation</h3>
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25
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26 <p>Prerequisites:</p>
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27
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28 <ul>
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29 <li>Ensure that the <code>pg_config</code> binary is in your path (shipped with PostgreSQL).</li>
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30 <li>Ensure that GNU Make is available (either as <code>make</code> or <code>gmake</code>).</li>
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31 </ul>
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32
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33 <p>Then simply type:</p>
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34
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35 <pre><code>make install
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36 </code></pre>
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37
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38 <h3>Manual installation</h3>
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39
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40 <p>It is also possible to compile and install the extension without GNU Make as
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41 follows:</p>
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42
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43 <pre><code>cc -Wall -O2 -fPIC -shared -I `pg_config --includedir-server` -o latlon-v0002.so latlon-v0002.c
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44 cp latlon-v0002.so `pg_config --pkglibdir`
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45 cp latlon.control `pg_config --sharedir`/extension/
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46 cp latlon--0.1--0.2.sql latlon--0.2.sql `pg_config --sharedir`/extension/
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47 </code></pre>
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48
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49 <h3>Loading the extension</h3>
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50
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51 <p>After installation, you can create a database and load the extension as
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52 follows:</p>
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53
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54 <pre><code>% createdb test_database
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55 % psql test_database
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56 psql (9.5.4)
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57 Type "help" for help.
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58
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59 test_database=# CREATE EXTENSION latlon;
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60 </code></pre>
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61
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62 <h2>Reference</h2>
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63
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64 <h3>1. Types</h3>
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65
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66 <p>pgLatLon provides four geographic types: <code>epoint</code>, <code>ebox</code>, <code>ecircle</code>, and
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67 <code>ecluster</code>.</p>
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68
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69 <h4><code>epoint</code></h4>
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70
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71 <p>A point on the earth spheroid (WGS-84).</p>
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72
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73 <p>The text input format is <code>'[N|S]<float> [E|W]<float>'</code>, where each float is in
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74 degrees. Note the required white space between the latitude and longitude
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75 components. Each floating point number may have a sign, in which case <code>N</code>/<code>S</code>
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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>
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77
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78 <p>An <code>epoint</code> may also be created from two floating point numbers by calling
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79 <code>epoint(latitude, longitude)</code>, where positive latitudes are used for the
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80 northern hemisphere, negative latitudes are used for the southern hemisphere,
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81 positive longitudes indicate positions east of the prime meridian, and negative
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82 longitudes indicate positions west of the prime meridian.</p>
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83
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84 <p>Latitudes exceeding -90 or +90 degrees are truncated to -90 or +90
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85 respectively, in which case a warning will be issued. Longitudes exceeding -180
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86 or +180 degrees will be converted to values between -180 and +180 (both
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87 inclusive) by adding or substracting a multiple of 360 degrees, in which case a
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88 notice will be issued.</p>
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89
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90 <p>If the latitude is -90 or +90 (south pole or north pole), a longitude value is
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91 still stored in the datum, and if a point is on the prime meridian or the
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92 180th meridian, the east/west bit is also stored in the datum. In case of the
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93 prime meridian, this is done by storing a floating point value of -0 for
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94 0 degrees west and a value of +0 for 0 degrees east. In case of the
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95 180th meridian, this is done by storing -180 or +180 respectively. The equality
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96 operator, however, returns true when the same points on earth are described,
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97 i.e. the longitude is ignored for the poles, and 180 degrees west is considered
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98 to be equal to 180 degrees east.</p>
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99
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100 <h4><code>ebox</code></h4>
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101
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102 <p>An area on earth demarcated by a southern and northern latitude, and a western
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103 and eastern longitude (all given in WGS-84).</p>
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104
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105 <p>The text input format is
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106 <code>'{N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float>'</code>, where each float is in
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107 degrees. The ordering of the four white-space separated blocks is not
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108 significant. To include the 180th meridian, one longitude boundary must be
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109 equal to or exceed <code>W180</code> or <code>E180</code>, e.g. <code>'N10 N20 E170 E190'</code>.</p>
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110
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111 <p>A special value is the empty area, denoted by the text represenation <code>'empty'</code>.
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112 Such an <code>ebox</code> does not contain any point.</p>
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113
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114 <p>An <code>ebox</code> may also be created from four floating point numbers by calling
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115 <code>ebox(min_latitude, max_latitude, min_longitude, max_longitude)</code>, where
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116 positive values are used for north and east, and negative values are used for
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117 south and west. If <code>min_latitude</code> is strictly greater than <code>max_latitude</code>, an
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118 empty <code>ebox</code> is created. If <code>min_longitude</code> is greater than <code>max_longitude</code> and
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119 if both longitudes are between -180 and +180 degrees, then the area oriented in
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120 such way that the 180th meridian is included.</p>
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121
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122 <p>If the longitude span is less than 120 degrees, an <code>ebox</code> may be alternatively
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123 created from two <code>epoints</code> in the following way: <code>ebox(epoint(lat1, lon1),
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124 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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125 <code>lon2</code> can be swapped without any impact.</p>
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126
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127 <h4><code>ecircle</code></h4>
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128
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129 <p>An area containing all points not farther away from a given center point
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130 (WGS-84) than a given radius.</p>
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131
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132 <p>The text input format is <code>'{N|S}<float> {E|W}<float> <float>'</code>, where the first
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133 two floats denote the center point in degrees and the third float denotes the
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134 radius in meters. A radius equal to minus infinity denotes an empty circle
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135 which contains no point at all (despite having a center), while a radius equal
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136 to zero denotes a circle that includes a single point.</p>
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137
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138 <p>An <code>ecircle</code> may also be created by calling <code>ecircle(epoint(...), radius)</code> or
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139 from three floating point numbers by calling <code>ecircle(latitude, longitude,
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140 radius)</code>.</p>
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141
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142 <h4><code>ecluster</code></h4>
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143
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144 <p>A collection of points, paths, polygons, and outlines on the WGS-84 spheroid.
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145 Each path, polygon, or outline must cover a longitude range of less than
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146 180 degrees to avoid ambiguities.</p>
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147
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148 <p>The text input format is a white-space separated list of the following items:</p>
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149
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150 <ul>
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151 <li><code>point ({N|S}<float> {E|W}<float>)</code></li>
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152 <li><code>path ({N|S}<float> {E|W}<float> {N|S}<float> {E|W}<float> ...)</code></li>
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153 <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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154 <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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155 </ul>
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156
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157 <p>Paths are open by default (i.e. there is no connection from the last point in
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158 the list to the first point in the list). Outlines and polygons, in contrast,
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159 are automatically closed (i.e. there is a line segment from the last point in
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160 the list to the first point in the list) which means the first point should not
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161 be repeated as last point in the list. Polygons are filled, outlines are not.</p>
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162
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163 <h3>2. Indices</h3>
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164
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165 <p>Two kinds of indices are supported: B-tree and GiST indices.</p>
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166
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167 <h4>B-tree indices</h4>
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168
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169 <p>A B-tree index can be used for simple equality searches and is supported by the
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170 <code>epoint</code>, <code>ebox</code>, and <code>ecircle</code> data types. B-tree indices can not be used for
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171 geographic searches.</p>
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172
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173 <h4>GiST indices</h4>
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174
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175 <p>For geographic searches, GiST indices must be used. The <code>epoint</code>, <code>ecircle</code>,
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176 and <code>ecluster</code> data types support GiST indexing. A GiST index for geographic
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177 searches can be created as follows:</p>
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178
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179 <pre><code>CREATE TABLE tbl (
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180 id serial4 PRIMARY KEY,
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181 loc epoint NOT NULL );
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182
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183 CREATE INDEX name_of_index ON tbl USING gist (loc);
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184 </code></pre>
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185
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186 <p>GiST indices also support nearest neighbor searches when using the distance
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187 operator (<code><-></code>) in the ORDER BY clause.</p>
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188
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189 <h4>Indices on other data types (e.g. GeoJSON)</h4>
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190
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191 <p>Note that further types can be indexed by using an index on an expression with
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192 a conversion function. One conversion function provided by pgLatLon is the
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193 <code>GeoJSON_to_ecluster(float8, float8, text)</code> function:</p>
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194
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195 <pre><code>CREATE TABLE tbl (
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196 id serial4 PRIMARY KEY,
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197 loc jsonb NOT NULL );
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198
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199 CREATE INDEX name_of_index ON tbl USING gist((GeoJSON_to_ecluster("loc")));
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200 </code></pre>
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201
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202 <p>When using the conversion function in an expression, the index will be used
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203 automatically:</p>
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204
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205 <pre><code>SELECT * FROM tbl WHERE GeoJSON_to_ecluster("loc") && 'N50 E10 10000'::ecircle;
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206 </code></pre>
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207
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208 <h3>3. Operators</h3>
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209
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210 <h4>Equality operator <code>=</code></h4>
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211
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212 <p>Tests if two geographic objects are equal.</p>
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213
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214 <p>The longitude is ignored for the poles, and 180 degrees west is considered to
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215 be equal to 180 degrees east.</p>
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216
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217 <p>For boxes and circles, two empty objects are considered equal. (Note that a
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218 circle is not empty if the radius is zero but only if it is negative infinity,
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219 i.e. smaller than zero.) Two circles with a positive infinite radius are also
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220 considered equal.</p>
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221
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222 <p>Implemented for:</p>
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223
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224 <ul>
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225 <li><code>epoint = epoint</code></li>
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226 <li><code>ebox = ebox</code></li>
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227 <li><code>ecircle = ecircle</code></li>
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228 </ul>
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229
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230 <p>The negation is the inequality operator (<code><></code> or <code>!=</code>).</p>
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231
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232 <h4>Linear ordering operators <code><<<</code>, <code><<<=</code>, <code>>>>=</code>, <code>>>></code></h4>
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233
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234 <p>These operators create an arbitrary (but well-defined) linear ordering of
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235 geographic objects, which is used internally for B-tree indexing and merge
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236 joins. These operators will usually not be used by an application programmer.</p>
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237
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238 <h4>Overlap operator <code>&&</code></h4>
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239
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240 <p>Tests if two geographic objects have at least one point in common. Currently
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241 implemented for:</p>
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242
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243 <ul>
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244 <li><code>epoint && ebox</code></li>
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245 <li><code>epoint && ecircle</code></li>
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246 <li><code>epoint && ecluster</code></li>
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247 <li><code>ebox && ebox</code></li>
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248 <li><code>ecircle && ecircle</code></li>
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249 <li><code>ecircle && ecluster</code></li>
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250 </ul>
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251
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252 <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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253 commutation is supported as well.</p>
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254
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255 <h4>Lossy overlap operator <code>&&+</code></h4>
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256
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257 <p>Tests if two geographic objects may have at least one point in common. Opposed
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258 to the <code>&&</code> operator, the <code>&&+</code> operator may return false positives and is
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259 currently implemented for:</p>
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260
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261 <ul>
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262 <li><code>epoint &&+ ecluster</code></li>
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263 <li><code>ebox &&+ ecircle</code></li>
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264 <li><code>ebox &&+ ecluster</code></li>
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265 <li><code>ecircle &&+ ecluster</code></li>
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266 <li><code>ecluster &&+ ecluster</code></li>
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267 </ul>
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268
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269 <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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270 commutation is supported as well.</p>
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271
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272 <p>Where two data types support both the <code>&&</code> and the <code>&&+</code> operator, the <code>&&+</code>
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273 operator computes faster.</p>
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274
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275 <h4>Distance operator <code><-></code></h4>
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276
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277 <p>Calculates the shortest distance between two geographic objects in meters (zero
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278 if the objects are overlapping). Currently implemented for:</p>
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279
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280 <ul>
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281 <li><code>epoint <-> epoint</code></li>
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282 <li><code>epoint <-> ecircle</code></li>
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283 <li><code>epoint <-> ecluster</code></li>
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284 <li><code>ecircle <-> ecircle</code></li>
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285 <li><code>ecircle <-> ecluster</code></li>
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286 </ul>
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287
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288 <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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289 Each commutation is supported as well.</p>
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290
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291 <p>For short distances, the result is very accurate (i.e. respects the dimensions
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292 of the WGS-84 spheroid). For longer distances in the order of magnitude of
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293 earth's radius or greater, the value is only approximate (but the error is
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294 still less than 0.2% as long as no polygons with very long edges are involved).</p>
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295
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296 <p>The functions <code>distance(epoint, epoint)</code> and <code>distance(ecluster, epoint)</code> can
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297 be used as an alias for this operator.</p>
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298
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299 <p>Note: In case of radial searches with a fixed radius, this operator should
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300 not be used. Instead, an <code>ecircle</code> should be created and used in combination
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301 with the overlap operator (<code>&&</code>). Alternatively, the functions
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302 <code>distance_within(epoint, epoint, float8)</code> or <code>distance_within(ecluster, epoint,
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303 float8)</code> can be used for fixed-radius searches.</p>
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304
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305 <h3>4. Functions</h3>
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306
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307 <h4><code>center(circle)</code></h4>
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308
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309 <p>Returns the center of an <code>ecircle</code> as an <code>epoint</code>.</p>
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310
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311 <h4><code>distance(epoint, epoint)</code></h4>
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312
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313 <p>Calculates the distance between two <code>epoint</code> datums in meters. This function is
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314 an alias for the distance operator <code><-></code>.</p>
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315
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316 <p>Note: In case of radial searches with a fixed radius, this function should not be
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317 used. Use <code>distance_within(epoint, epoint, float8)</code> instead.</p>
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318
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319 <h4><code>distance(ecluster, epoint)</code></h4>
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320
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321 <p>Calculates the distance from an <code>ecluster</code> to an <code>epoint</code> in meters. This
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322 function is an alias for the distance operator <code><-></code>.</p>
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323
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324 <p>Note: In case of radial searches with a fixed radius, this function should not be
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325 used. Use <code>distance_within(epoint, epoint, float8)</code> instead.</p>
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326
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327 <h4><code>distance_within(</code>variable <code>epoint,</code> fixed <code>epoint,</code> radius <code>float8)</code></h4>
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328
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329 <p>Checks if the distance between two <code>epoint</code> datums is not greater than a given
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330 value (search radius).</p>
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331
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332 <p>Note: In case of radial searches with a fixed radius, the first argument must
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333 be used for the table column, while the second argument must be used for the
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334 search center. Otherwise an existing index cannot be used.</p>
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335
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336 <h4><code>distance_within(</code>variable <code>ecluster,</code> fixed <code>epoint,</code> radius <code>float8)</code></h4>
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337
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338 <p>Checks if the distance from an <code>ecluster</code> to an <code>epoint</code> is not greater than a
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339 given value (search radius).</p>
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340
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341 <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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342
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343 <p>Creates a new <code>ebox</code> with the given boundaries.
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344 See "1. Types", subsection <code>ebox</code> for details.</p>
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345
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346 <h4><code>ebox(epoint, epoint)</code></h4>
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347
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348 <p>Creates a new <code>ebox</code>. This function may only be used if the longitude
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349 difference is less than or equal to 120 degrees.
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350 See "1. Types", subsection <code>ebox</code> for details.</p>
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351
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352 <h4><code>ecircle(epoint, float8)</code></h4>
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353
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354 <p>Creates an <code>ecircle</code> with the given center point and radius.</p>
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355
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356 <h4><code>ecircle(</code>latitude <code>float8,</code> longitude <code>float8,</code> radius <code>float8)</code></h4>
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357
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358 <p>Creates an <code>ecircle</code> with the given center point and radius.</p>
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359
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360 <h4><code>ecluster_concat(ecluster, ecluster)</code></h4>
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361
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362 <p>Combines two clusters to form a new <code>ecluster</code> by uniting all entries of both
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363 clusters. Note that two overlapping areas of polygons annihilate each other
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364 (which may be used to create polygons with holes).</p>
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365
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366 <h4><code>ecluster_concat(ecluster[])</code></h4>
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367
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368 <p>Creates a new <code>ecluster</code> that unites all entries of all clusters in the passed
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369 array. Note that two overlapping areas of polygons annihilate each other (which
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370 may be used to create polygons with holes).</p>
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371
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372 <h4><code>ecluster_create_multipoint(epoint[])</code></h4>
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373
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374 <p>Creates a new <code>ecluster</code> which contains multiple points.</p>
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375
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376 <h4><code>ecluster_create_outline(epoint[])</code></h4>
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377
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378 <p>Creates a new <code>ecluster</code> that is an outline given by the passed points.</p>
|
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379
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380 <h4><code>ecluster_create_path(epoint[])</code></h4>
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381
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382 <p>Creates a new <code>ecluster</code> that is a path given by the passed points.</p>
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383
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384 <h4><code>ecluster_create_polygon(epoint[])</code></h4>
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385
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386 <p>Creates a new <code>ecluster</code> that is a polygon given by the passed points.</p>
|
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387
|
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388 <h4><code>ecluster_extract_outlines(ecluster)</code></h4>
|
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389
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390 <p>Set-returning function that returns the outlines of an <code>ecluster</code> as <code>epoint[]</code>
|
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391 rows.</p>
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392
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393 <h4><code>ecluster_extract_paths(ecluster)</code></h4>
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394
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395 <p>Set-returning function that returns the paths of an <code>ecluster</code> as <code>epoint[]</code>
|
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396 rows.</p>
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397
|
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398 <h4><code>ecluster_extract_points(ecluster)</code></h4>
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399
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400 <p>Set-returning function that returns the points of an <code>ecluster</code> as <code>epoint</code>
|
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|
401 rows.</p>
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402
|
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403 <h4><code>ecluster_extract_polygons(ecluster)</code></h4>
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404
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405 <p>Set-returning function that returns the polygons of an <code>ecluster</code> as <code>epoint[]</code>
|
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|
406 rows.</p>
|
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407
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408 <h4><code>empty_ebox</code>()</h4>
|
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409
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410 <p>Returns the empty <code>ebox</code>.
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411 See "1. Types", subsection <code>ebox</code> for details.</p>
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412
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413 <h4><code>epoint(</code>latitude <code>float8,</code> longitude <code>float8)</code></h4>
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414
|
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415 <p>Returns an <code>epoint</code> with the given latitude and longitude.</p>
|
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416
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417 <h4><code>epoint_latlon(</code>latitude <code>float8,</code> longitude <code>float8)</code></h4>
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418
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419 <p>Alias for <code>epoint(float8, float8)</code>.</p>
|
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420
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421 <h4><code>epoint_lonlat(</code>longitude <code>float8,</code> latitude <code>float8)</code></h4>
|
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422
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423 <p>Same as <code>epoint(float8, float8)</code> but with arguments reversed.</p>
|
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424
|
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425 <h4><code>GeoJSON_to_epoint(jsonb, text)</code></h4>
|
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426
|
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427 <p>Maps a GeoJSON object of type "Point" or "Feature" (which contains a
|
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428 "Point") to an <code>epoint</code> datum. For any other JSON objects, NULL is returned.</p>
|
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429
|
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430 <p>The second parameter (which defaults to <code>epoint_lonlat</code>) may be set to a name
|
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431 of a conversion function that transforms two coordinates (two <code>float8</code>
|
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432 parameters) to an <code>epoint</code>.</p>
|
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433
|
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|
434 <h4><code>GeoJSON_to_ecluster(jsonb, text)</code></h4>
|
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|
435
|
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436 <p>Maps a (valid) GeoJSON object to an <code>ecluster</code>. Note that this function
|
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437 does not check whether the JSONB object is a valid GeoJSON object.</p>
|
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|
438
|
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439 <p>The second parameter (which defaults to <code>epoint_lonlat</code>) may be set to a name
|
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440 of a conversion function that transforms two coordinates (two <code>float8</code>
|
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441 parameters) to an <code>epoint</code>.</p>
|
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442
|
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443 <h4><code>max_latitude(ebox)</code></h4>
|
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444
|
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445 <p>Returns the northern boundary of a given <code>ebox</code> in degrees between -90 and +90.</p>
|
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|
446
|
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447 <h4><code>max_longitude(ebox)</code></h4>
|
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|
448
|
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449 <p>Returns the eastern boundary of a given <code>ebox</code> in degrees between -180 and +180
|
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450 (both inclusive).</p>
|
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451
|
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452 <h4><code>min_latitude(ebox)</code></h4>
|
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453
|
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454 <p>Returns the southern boundary of a given <code>ebox</code> in degrees between -90 and +90.</p>
|
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|
455
|
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|
456 <h4><code>min_longitude(ebox)</code></h4>
|
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|
457
|
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|
458 <p>Returns the western boundary of a given <code>ebox</code> in degrees between -180 and +180
|
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|
459 (both inclusive).</p>
|
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|
460
|
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461 <h4><code>latitude(epoint)</code></h4>
|
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462
|
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463 <p>Returns the latitude value of an <code>epoint</code> in degrees between -90 and +90.</p>
|
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|
464
|
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|
465 <h4><code>longitude(epoint)</code></h4>
|
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|
466
|
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467 <p>Returns the longitude value of an <code>epoint</code> in degrees between -180 and +180
|
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|
468 (both inclusive).</p>
|
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|
469
|
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|
470 <h4><code>radius(ecircle)</code></h4>
|
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|
471
|
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|
472 <p>Returns the radius of an <code>ecircle</code> in meters.</p>
|
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473 </body></html>
|