Collate

"Collator" or "Schema" functions which form VectorTiles from collections of GeoTrellis Features. Any function can be considered a valid "collator" if it satisfies the type:

collate: (Extent, Iterable[Feature[G,D]]) => VectorTile

Usage

Create a VectorTile from some collection of GeoTrellis Geometries:

val tileExtent: Extent = ... // Extent of _this_ Tile
val geoms: Iterable[Feature[Geometry, Map[String, String]]] = ...  // Some collection of Geometries

val tile: VectorTile = Collate.withStringMetadata(tileExtent, geoms)

Create a VectorTile via some custom collation scheme:

def partition(f: Feature[G,D]): String = ...
def metadata(d: D): Map[String, Value] = ...

val tileExtent: Extent = ... // Extent of _this_ Tile
val geoms: Iterable[Feature[G, D]] = ...  // Some collection of Geometries

val tile: VectorTile = Collate.generically(tileExtent, geoms, partition, metadata)

Writing your own Collator Function

We provide a few defaults here, but any collation scheme is possible. Collation just refers to the process of organizing some Iterable collection of Geometries into various VectorTile Layers. Creating your own collator is done easiest with generically. It expects a partition function to guide Geometries into separate Layers, and a metadata transformation function.

Partition Functions

A valid partition function must be of the type:

partition: Feature[G,D] => String

The output String is the name of the Layer you'd like a given Feature to be relegated to. Notice that the entire Feature is available (i.e. both its Geometry and metadata), so that your partitioner can make fine-grained choices.

Metadata Transformation Functions

One of these takes your D type and transforms it into what VectorTiles expect:

metadata: D => Map[String, Value]

You're encouraged to review the Value sum-type in geotrellis.vectortile

On Winding Order

VectorTiles require that Polygon exteriors have clockwise winding order, and that interior holes have counter-clockwise winding order. These assume that the origin (0,0) is in the top-left corner.

Any custom collator which does not call generically must correct for Polygon winding order manually. This can be done via the vectorpipe.winding function.

But why correct for winding order at all? Well, OSM data makes no guarantee about what winding order its derived Polygons will have. We could correct winding order when our first RDD[OSMFeature] is created, except that its unlikely that the clipping process afterward would maintain our winding for all Polygons.

Linear Supertypes

AnyRef, Any

Value Members

final def !=(arg0: Any): Boolean

Definition Classes
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final def ##(): Int

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final def ==(arg0: Any): Boolean

Definition Classes
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final def asInstanceOf[T0]: T0

Definition Classes
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def byGeomType[G <: Geometry, D](f: Feature[G, D]): String

Can be used as the partition argument to generically.
Can be used as the partition argument to generically. Splits Geometries by their subtype, naming three Layers: points, lines and polygons.
def byOSM(tileExtent: Extent, geoms: Iterable[OSMFeature]): VectorTile

Give each Geometry type its own VectorTile layer, and store the ElementData as-is.
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
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Annotations
@throws( ... )
final def eq(arg0: AnyRef): Boolean

Definition Classes
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def equals(arg0: Any): Boolean

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def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
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@throws( classOf[java.lang.Throwable] )
def generically[G <: Geometry, D](tileExtent: Extent, geoms: Iterable[Feature[G, D]], partition: (Feature[G, D]) ⇒ String, metadata: (D) ⇒ Map[String, Value]): VectorTile

Given some Feature and a way to determine which Layer it should belong to (by layer name), collate each Feature into the appropriate Layer and form a VectorTile.
Given some Feature and a way to determine which Layer it should belong to (by layer name), collate each Feature into the appropriate Layer and form a VectorTile. Polygon winding order is corrected.
tileExtent
The Extent of this Tile.
geoms
The Features to collate into various Layers.
partition
The means by which to place a certain Feature into a certain Layer. The String is returns is the name of the Layer the collate the Feature into.
metadata
The means by which to transform some Feature's metadata into the type that VectorTiles expect.
final def getClass(): Class[_]

Definition Classes
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def hashCode(): Int

Definition Classes
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def intoOneLayer[G <: Geometry, D](f: Feature[G, D]): String

Partition all Features into a single Layer.
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
final def ne(arg0: AnyRef): Boolean

Definition Classes
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final def notify(): Unit

Definition Classes
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final def notifyAll(): Unit

Definition Classes
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final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
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def toString(): String

Definition Classes
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final def wait(): Unit

Definition Classes
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Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
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Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
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@throws( ... )
def withStringMetadata[G <: Geometry](tileExtent: Extent, geoms: Iterable[Feature[G, Map[String, String]]]): VectorTile
def withoutMetadata[G <: Geometry, D](tileExtent: Extent, geoms: Iterable[Feature[G, D]]): VectorTile

Collate some collection of Features into a VectorTile while dropping any metadata they might have had.
Collate some collection of Features into a VectorTile while dropping any metadata they might have had. The resulting Tile has three Layers, labelled points, lines, and polygons.
tileExtent
The CRS Extent of the Tile to be created.

Related Doc: package vectorpipe

object Collate

Usage

Writing your own Collator Function

Partition Functions

Metadata Transformation Functions

On Winding Order

Value Members

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: Any): Boolean

final def asInstanceOf[T0]: T0

def byGeomType[G <: Geometry, D](f: Feature[G, D]): String

def byOSM(tileExtent: Extent, geoms: Iterable[OSMFeature]): VectorTile

def clone(): AnyRef

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def finalize(): Unit

def generically[G <: Geometry, D](tileExtent: Extent, geoms: Iterable[Feature[G, D]], partition: (Feature[G, D]) ⇒ String, metadata: (D) ⇒ Map[String, Value]): VectorTile

final def getClass(): Class[_]

def hashCode(): Int

def intoOneLayer[G <: Geometry, D](f: Feature[G, D]): String

final def isInstanceOf[T0]: Boolean

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

def withStringMetadata[G <: Geometry](tileExtent: Extent, geoms: Iterable[Feature[G, Map[String, String]]]): VectorTile

def withoutMetadata[G <: Geometry, D](tileExtent: Extent, geoms: Iterable[Feature[G, D]]): VectorTile

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