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103 lines
3.3 KiB
Plaintext
103 lines
3.3 KiB
Plaintext
title: $:/plugins/tiddlywiki/geospatial/docs
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! Filter Operators
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!! `geopoint` operator
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The `geopoint` operator converts separate latitude, longitude and (optionally) altitude numbers into a [[GeoJSON Point Feature]] that can be used with other geospatial primitives.
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The coordinates are specified as two or three operands:
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```
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[geopoint<latitude>,<longitude>,<attitude>]
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```
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Any operands that cannot be interpreted as a valid number will be interpreted as the value zero.
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For example:
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```
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<$text text={{{ [geopoint[51.751944],[-1.257778]] }}}/>
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```
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Returns:
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```
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{"type":"Feature","properties":{},"geometry":{"type":"Point","coordinates":[51.751944,-1.257778,0]}}
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```
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!! `geodistance` operator
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The `geodistance` operator calculates the distance between two points in [[GeoJSON Point Feature]] format. The points are specified as two operands. An optional third operand specifies the units as `miles`, `kilometers`, `degrees` or `radians` (defaults to `miles`).
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```
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<$let
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oxford={{{ [geopoint[51.751944],[-1.257778]] }}}
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new-york={{{ [geopoint[40.730610],[-73.935242]] }}}
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>
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<$text text={{{ [geodistance<oxford>,<new-york>] }}}/>,
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<$text text={{{ [geodistance<oxford>,<new-york>,[miles]] }}}/>,
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</$let>
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```
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!! `geounion` operator
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The `geounion` operator calculates the union between two or more [[GeoJSON Polygon Features|GeoJSON Polygon Feature]].
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Each input list item is interpreted as a [[GeoJSON Polygon Feature Collection]] containing polygons.
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```
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[geounion[]]
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```
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!! `geointersect` operator
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The `geointersect` operator calculates the intersection between two or more [[GeoJSON Polygon Features|GeoJSON Polygon Feature]].
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Each input list item is interpreted as a [[GeoJSON Polygon Feature Collection]] containing polygons.
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```
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[geointersect[]]
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```
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!! `geodifference` operator
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The `geodifference` operator calculates the difference between two or more [[GeoJSON Polygon Features|GeoJSON Polygon Feature]].
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Each input list item is interpreted as a [[GeoJSON Polygon Feature Collection]] containing polygons.
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```
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[geodifference[]]
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```
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!! `geolookup` operator
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The `geolookup` operator identifies the polygon(s) within a [[GeoJSON Polygon Feature]] that correspond to a particular point, and returns the JSON properties of that polygon.
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Each input list item is interpreted as a [[GeoJSON Point Feature]] and the operand is interpreted as a [[GeoJSON Polygon Feature Collection]].
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For example, here we lookup the point 100.5,0.5 in the [[GeoJSON Polygon Feature Collection]] stored in the tiddler `TestData` and then extracts the indexes `0` and `animal` from the resulting JSON:
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```
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<$text text={{{ [geopoint[100.5],[0.5]geolookup{TestData}jsonget[0],[animal]] }}}/>
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```
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!! `olc-decode` operator
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The `olc-decode` operator converts an [[OpenLocationCode|https://github.com/google/open-location-code]] shortcut into the [[GeoJSON Point Feature]] at its centre or the [[GeoJSON Polygon Feature]] representing the bounds of the area identified by the input code.
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```
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[olc-decode:bounds[9C3WQP2R+QV]]
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[olc-decode:point[9C3WQP2R+QVH]]
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```
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!! `olc-encode` operator
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The `old-encode` operator converts separate latitude and longitude numbers into an [[OpenLocationCode|https://github.com/google/open-location-code]] shortcut code with a specified length (defaults to 11 characters).
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```
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[olc-encode[51.751944],[-1.257778]]
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[olc-encode[51.751944],[-1.257778],[11]]
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```
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