Vector Tile Service

Overview

Kinetica provides a Vector Tile Service (VTS) to generate Vector Tiles and support client-side visualization of the geospatial data contained within the tiles. The Vector Tile format generated follows the open standard Mapbox Vector Tile specification. The Kinetica VTS feeds a client-side Vector Tile renderer, such as Mapbox GL, by adding the VTS URL to the renderer's style configuration as a map layer source. Any Kinetica table or view that is defined with at least one WKT-type (geometry) column can be used as the data source for the layer parameter. The data source, geographical position, and zoom level of each Vector Tile are specified in a VTS request. The requested Vector Tile is then returned in the response.

The VTS offers a couple advantages over server-side WMS calls:

VTS supports client-side control of styling like image fill
When using vector tiles, the browser only requests new information as needed and caches data along the way; WMS output must be re-rendered on every pan/zoom

Configuration

VTS is configured via the gpudb.conf configuration file.

Settings:

Name	Default	Description	Allowable Values
`vts.max_vertices_per_chunk`	`20000000`	The maximum number of vertices within a chunk when rendering VTS tiles. If a chunk has more vertices than this limit, the VTS request will return an error.	Minimum is `0`
`vts.max_features_per_tile`	`200000`	The maximum number of features that will be returned in a VTS tile. This limit is applied at the chunk level, so the actual returned tile may have more features. If there are more features within the given tile within a chunk, the additional features will not be returned within the tile.	Minimum is `0`

Usage

Base VTS URI:

http://<db.host>:<db.port>/vts/<layer>/<z>/<x>/<y>?attributes=<columns>

Important

The VTS URL needs to be specified in the client-side visualizer's configuration.

URI parameters:

Name	Description	Allowable Values
`layer`	Name of data source table or view.	A valid table name, in `[schema_name.]table_name` format, using standard name resolution rules
`attributes`	List of column names.	A comma separated list of column names from the `layer` source table / view. Must include a single geometry column and may include additional non-geometry columns.
`z`	Zoom level of the requested tile.	Non-negative integer. The maximum value is 30. Provide the parameter as `{z}` to have the client-side renderer dynamically set the value.
`x`	Horizontal index of the requested tile.	Non-negative integer. Provide the parameter as `{x}` to have the client-side renderer dynamically set the value.
`y`	Vertical index of the requested tile.	Non-negative integer. Provide the parameter as `{y}` to have the client-side renderer dynamically set the value.

Example

Below is a snippet of a Javascript Mapbox style specification using Kinetica's VTS URL as a source:

// Config
var tableName = "nyc_neighborhood";
var wktColumn = "geom";
var kineticaUrl = "http://localhost:9191/vts/";

// Mapbox GL
map.on('load', function () {
  map.addLayer({
    "id": tableName + "_layer",
    "version": 8,
    "type" : "fill",
    "source": {
      "type": "vector",
      "tiles": [kineticaUrl + tableName + "/{z}/{x}/{y}?attributes=" + wktColumn], // Note Mapbox uses the params in curly braces as dynamic values. Don't change those.
      "maxzoom": 20
    },
    "source-layer": tableName,
    "paint": {
      "fill-color": "#EDF00F",
      "fill-outline-color": "#000000"
    }
  });
});

Limitations and Cautions

Since VTS sends feature information for each table row to the browser, the client can get overwhelmed with data; performance is dependent upon client hardware