Polygon Layer documentation - coordinate specification

Background

Polygon layer coordinate specification

The documentation for polygon layer specifies the following data format

/**
   * Data format:
   * [
   *   {
   *     // Simple polygon (array of coords)
   *     contour: [[-122.4, 37.7], [-122.4, 37.8], [-122.5, 37.8], [-122.5, 37.7], [-122.4, 37.7]],
   *     zipcode: 94107,
   *     population: 26599,
   *     area: 6.11
   *   },
   *   {
   *     // Complex polygon with holes (array of coords)
   *     contour: [
   *       [[-122.4, 37.7], [-122.4, 37.8], [-122.5, 37.8], [-122.5, 37.7], [-122.4, 37.7]],
   *       [[-122.45, 37.73], [-122.47, 37.76], [-122.47, 37.71], [-122.45, 37.73]]
   *     ],
   *     zipcode: 94107,
   *     population: 26599,
   *     area: 6.11
   *   },
   *   ...
   * ]
   */

I’ve just generated an example which has coordinates in the form of

{
  "geometry":{
    "type":"Polygon",
    "coordinates":[
      [
        [-162.96333331843185, 23.963333318432139,-94860.0,1.0],
        [-162.89693422519478, 23.963333318432139,-95135.0,1.0]
        ... etc
     ]
   ]
}
}

Where the elevation is specified as the 3rd value in each coordinate array (as per GeoJSON).

Which gives

Should the documentation reflect that you can specify the elevation in the coordinate array, as well as in the getElevation prop?

And is this a valid way to supply the elevation?

---

Related issue from my mapdeck library

Update

The same works for pathLayer too, where you can specify the elevation in the coordinates [ ] array

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To Do List

• Add label and assign to milestone
• Coding
• Doc update
• Whats new update
• Test

[mdsumner]

No problem!

[SymbolixAU]

@mdsumner I had the same question - hopefully this helps

Setting up some data (in R)

poly1<- matrix(c(0,0,0,0,1,1000,1,1,50000,1,0,25000,0,0,0), ncol = 3, byrow = T)
poly2<- matrix(c(0,0,0,0,-1,1000,-1,-1,50000,-1,0,25000,0,0,0), ncol = 3, byrow = T)

poly1 <- sf::st_sfc( sf::st_polygon( x = list( poly1 ) ) )
poly2 <- sf::st_sfc( sf::st_polygon( x = list( poly2 ) ) )

poly1 <- sf::st_sf( geometry = poly1 )
poly2 <- sf::st_sf( geometry = poly2 )

sf <- rbind( poly1, poly2 )
sf$id <- 1:2

The polygons have a Z attribute. I’m making two plots, one using the extrusion, and one without

Non-extruded

Just using the Z attribute on the data

mapdeck() %>%
	add_polygon(
		data = sf
		, fill_colour = "id"
	)

Extruded

uses getElevation to extrude the polygon from the map

mapdeck() %>%
	add_polygon(
		data = sf
		, elevation = 100000
		, fill_colour = "id"
	)

So the Z is applied for each vertex. The extrusion is applied to the whole polygon, while respecting the initial Z elevation (as both the base and top surfaces are tilted)