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45 lines
1.7 KiB
Plaintext
45 lines
1.7 KiB
Plaintext
title: $:/plugins/tiddlywiki/geospatial/docs/geodifference
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caption: geodifference operator
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tags: $:/tags/GeospatialDocs
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!! `geodifference` operator
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The `geodifference` operator calculates the difference between two or more [[GeoJSON Polygon Features|GeoJSON Polygon Feature]].
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Each input list item is interpreted as a [[GeoJSON Polygon Feature Collection]] containing polygons.
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```
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[geodifference[]]
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```
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!! `geolookup` operator
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The `geolookup` operator identifies the polygon(s) within a [[GeoJSON Polygon Feature]] that correspond to a particular point, and returns the JSON properties of that polygon.
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Each input list item is interpreted as a [[GeoJSON Point Feature]] and the operand is interpreted as a [[GeoJSON Polygon Feature Collection]].
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For example, here we lookup the point 100.5,0.5 in the [[GeoJSON Polygon Feature Collection]] stored in the tiddler `TestData` and then extracts the indexes `0` and `animal` from the resulting JSON:
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```
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<$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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