56 lines
2.6 KiB
Markdown
56 lines
2.6 KiB
Markdown
Metatags
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--------
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Metatags are extra tags available, in order to display more data or to give better questions.The are calculated automatically on every feature when the data arrives in the webbrowser. This document gives an overview of the available metatags
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### \_lat, \_lon
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The latitude and longitude of the point (or centerpoint in the case of a way/area)
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### \_surface, \_surface:ha
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The surface area of the feature, in square meters and in hectare. Not set on points and ways
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### \_country
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The country code of the property (with latlon2country)
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### \_isOpen, \_isOpen:description
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If 'opening\_hours' is present, it will add the current state of the feature (being 'yes' or 'no')
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### \_width:needed, \_width:needed:no\_pedestrians, \_width:difference
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Legacy for a specific project calculating the needed width for safe traffic on a road. Only activated if 'width:carriageway' is present
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### \_direction:simplified, \_direction:leftright
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\_direction:simplified turns 'camera:direction' and 'direction' into either 0, 45, 90, 135, 180, 225, 270 or 315, whichever is closest. \_direction:leftright is either 'left' or 'right', which is left-looking on the map or 'right-looking' on the map
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### \_now:date, \_now:datetime, \_loaded:date, \_loaded:\_datetime
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Adds the time that the data got loaded - pretty much the time of downloading from overpass. The format is YYYY-MM-DD hh:mm, aka 'sortable' aka ISO-8601-but-not-entirely
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Calculating tags with Javascript
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In some cases, it is useful to have some tags calculated based on other properties. Some useful tags are available by default (e.g. **\_lat**, **lon**, **\_country**), as detailed above.
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It is also possible to calculate your own tags - but this requires some javascript knowledge.
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Before proceeding, some warnings:
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* DO NOT DO THIS AS BEGINNER
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* **Only do this if all other techniques fail**. This should _not_ be done to create a rendering effect, only to calculate a specific value
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* **THIS MIGHT BE DISABLED WITHOUT ANY NOTICE ON UNOFFICIAL THEMES**. As unofficial themes might be loaded from the internet, this is the equivalent of injecting arbitrary code into the client. It'll be disabled if abuse occurs.
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In the layer object, add a field **calculatedTags**, e.g.:
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"calculatedTags": { "\_someKey": "javascript-expression", "name": "feat.properties.name ?? feat.properties.ref ?? feat.properties.operator", "\_distanceCloserThen3Km": "feat.distanceTo( some\_lon, some\_lat) < 3 ? 'yes' : 'no'" }
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### distanceTo
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Calculates the distance between the feature and a specified point
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* longitude
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* latitude |