OnEarth and its associated tools are capable of handling and serving vector datasets in multiple forms.
OnEarth supports a few different ways of accessing vector data. They are as follows:
Rasters (JPEG and PNG) (via MapServer)
OnEarth currently uses MapServer to create raster images on-the-fly from vector datasets. The oe_configure_layer tool can be used to configure vector layers that will be served by MapServer, as well as the styles that determine how the vector data is rendered.
Currently, OnEarth uses ESRI Shapefiles as a source data format for vector layers to be served by MapServer. The oe_vectorgen tool can be used to convert GeoJSON to Shapefiles.
Mapbox Vector Tiles (MVT) (via mod_onearth)
MVT tiles are a vector tile format supported by mapping clients like OpenLayers. Because they are tiled and optimized while still retaining vector data, they allow for increased performance while still providing the flexibility of client-side styling and access to the underlying metadata for each vector feature.
The OnEarth oe_vectorgen utility can be used to create MRF-like files that contain an entire pyramid of MVT tiles, similar to raster MRFs. These can then be configured by oe_configure_layer and served by the mod_onearth Apache module in the same way as raster layers.
GeoJSON (via MapServer)
OnEarth can also serve vector data in GeoJSON format, using the Web Feature Service (WFS) protocol. Similar to WMS, WFS allows vector data to be filtered by bounding box, in addition to numerous other filtering features. OnEarth uses MapServer to provide access to vector data via WFS. The oe_configure_layer tool is able to build and modify MapServer configurations.
Currently, OnEarth uses ESRI Shapefiles as a source data format for vector layers to be served by MapServer. The oe_vectorgen tool can be used to convert GeoJSON to Shapefiles.
The OnEarth distribution includes the onearth-vectorgen RPM, which installs the oe_vectorgen script and its associated dependencies.
Make sure your data is in the ESRI Shapefile format. The oe_vectorgen utility can be used to convert GeoJSON to Shapefile and reproject if necessary.
Create a layer configuration XML and use oe_configure_layer to configure the new vector layer.
Note that there are two vector-specific tags you'll need to use in your layer config -- <VectorType> refers to the type of vector data in your source file, i,e, Polygon, Line, Point, etc. and <VectorStyleFile> refers to a file containing the MapServer style configuration(s) you want to use with this layer. Refer to the MapServer STYLE reference for more information.
Note that Points need to be represented by a global SYMBOL object within the MapServer config. You'll want to add this to the MapServer header files (refer to the oe_configure_layer docs. For more information refer to the MapServer SYMBOL reference.
Make sure your input data is in ESRI Shapefile or GeoJSON format.
Use the oe_vectorgen utility to create a MVT MRF You'll need to create a oe_vectorgen configuration file that specifies the desired projection, the desired TileMatrixSet, and desired feature decimation parameters (if any).
Configure the new layer using oe_configure_layer Just like with raster layers, create a layer configuration XML. Make sure to specify 'PBF' in the <Compression> tag.
Vector tiles may be requested from OnEarth via WMTS or Tiled WMS. The following MIME types are supported as format options: application/x-protobuf;type=mapbox-vector and application/vnd.mapbox-vector-tile
For WMTS REST requests, use either pbf or mvt as the file extension.
Vector tiles are returned compressed with gzip encoding.
Common geometry types such as points, lines, and polygons are supported.
MVT-MRF
GeoJSON input
- Point
- LineString
- Polygon
Shapefile input
- Point
- Polyline
- Polygon
Shapefile
GeoJSON input
- GeometryCollection is NOT supported.
Shapefile input
- All Shapefile geometries supported by MapServer.
Note: OnEarth does not serve from GeoJSON files; they must be converted to MVT-MRF or Shapefile.