BaseElevationLayer

Class: esri/layers/BaseElevationLayer
Inheritance: BaseElevationLayer Layer Accessor
Since: ArcGIS API for JavaScript 4.4

BaseElevationLayer is intended to be extended for creating custom elevation layers. You create a custom ElevationLayer by calling createSubclass() on the BaseElevationLayer.

If the new layer needs to fetch and prepare resources, you can initialize properties asynchronously prior to loading the layer. This is handled in the load() method. This method is called once, either by you or by the view, when the layer is about to be displayed. In the body of the method you can call addResolvingPromise() to add a promise that has to be resolved before the layer is considered loaded.

You must overwrite the logic in the fetchTile() method to return the values of the custom elevation data. This can be done to exaggerate actual elevation values or for mapping thematic data as an elevation layer.

var ExaggeratedElevationLayer = BaseElevationLayer.createSubclass({
  load: function() {
    // add loadable dependencies here and include
    // their returned promises in the
    // addResolvingPromise() method
    this.addResolvingPromise(promiseReturnedFromLoadableResource);
  }

  fetchTile: function(level, row, col) {

    // Must resolve to an object with the following properties:
    return {
      // values <number[]>: an array of elevation values for each pixel
      // width <number>: the width of the tile in pixels
      // height <number>: the height of the tile in pixels
      // noDataValue <number>: value of pixels where no elevation data is present
    };
  }
});

Once the layer is created, you must add it to the layers of the Map.ground property and add the map to a SceneView instance.

var map = new Map({
  basemap: "satellite",
  ground: {
    layers: [ new ExaggeratedElevationLayer() ]
  }
});
sceneView.map = map;
See also:

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.
NameTypeSummaryClass
String

The name of the class.

more details
more detailsAccessor
Extent

The full extent of the layer.

more details
more detailsLayer
String

The unique ID assigned to the layer.

more details
more detailsLayer
String

Indicates how the layer should display in the LayerList widget.

more details
more detailsLayer
Boolean

Indicates whether the layer's resources have loaded.

more details
more detailsLayer
Error

The Error object returned if an error occurred while loading.

more details
more detailsLayer
String

Represents the status of a load operation.

more details
more detailsLayer
Object[]

A list of warnings which occurred while loading.

more details
more detailsLayer
Number

The opacity of the layer.

more details
more detailsLayer
SpatialReference

The spatial reference of the layer.

more details
more detailsBaseElevationLayer
TileInfo

The tiling scheme information for the layer.

more details
more detailsBaseElevationLayer
String

The title of the layer used to identify it in places such as the Legend and LayerList widgets.

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more detailsLayer
String

The layer type.

more details
more detailsBaseElevationLayer
Boolean

Indicates if the layer is visible in the View.

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more detailsLayer

Property Details

declaredClassStringreadonly inherited

The name of the class. The declared class name is formatted as esri.folder.className.

The full extent of the layer. By default, this is worldwide. This property may be used to set the extent of the view to match a layer's extent so that its features appear to fill the view. See the sample snippet below.

Example:
// Once the layer loads, set the view's extent to the layer's fullextent
layer.then(function(){
  view.extent = layer.fullExtent;
});

The unique ID assigned to the layer. If not set by the developer, it is automatically generated when the layer is loaded.

Indicates how the layer should display in the LayerList widget. The known values are listed below.

ValueDescription
showThe layer is visible in the table of contents.
hideThe layer is hidden in the table of contents.
hide-childrenIf the layer is a GroupLayer, hide the children layers from the table of contents.
Default Value: show

loadedBooleanreadonly inherited

Indicates whether the layer's resources have loaded. When true, all the properties of the object can be accessed.

Default Value: false

loadErrorErrorreadonly inherited

The Error object returned if an error occurred while loading.

Default Value: null

loadStatusStringreadonly inherited

Represents the status of a load operation.

ValueDescription
not-loadedThe object's resources have not loaded.
loadingThe object's resources are currently loading.
loadedThe object's resources have loaded without errors.
failedThe object's resources failed to load. See loadError for more details.
Default Value: not-loaded

loadWarningsObject[]readonly inherited

A list of warnings which occurred while loading.

The opacity of the layer. This value can range between 1 and 0, where 0 is 100 percent transparent and 1 is completely opaque.

Default Value: 1
Example:
// Makes the layer 50% transparent
layer.opacity = 0.5;

spatialReferenceSpatialReference autocast

The spatial reference of the layer.

The tiling scheme information for the layer.

The title of the layer used to identify it in places such as the Legend and LayerList widgets.

typeString autocastreadonly

The layer type. For BaseElevationLayer the type is always base-elevation.

Indicates if the layer is visible in the View. When false, the layer may still be added to a Map instance that is referenced in a view, but its features will not be visible in the view.

Default Value: true
Example:
// The layer is no longer visible in the view
layer.visible = false;

Method Overview

NameReturn TypeSummaryClass
Promise

Adds a promise to the layer's loadable chain.

more details
more detailsBaseElevationLayer
Promise

An instance of this class is a Promise.

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more detailsLayer

Cancels a load() operation if it is already in progress.

more details
more detailsLayer

Emits an event on the instance.

more details
more detailsLayer
Promise<Object>

Fetches custom attribution data for the layer when it becomes available.

more details
more detailsLayer
Promise<ElevationTileData>

Fetches a tile at the given level, row, and column present in the view.

more details
more detailsBaseElevationLayer
Number[]

Returns the bounds of the tile as an array of four numbers that can be readily converted to an Extent object.

more details
more detailsBaseElevationLayer
Boolean

Indicates whether there is an event listener on the instance that matches the provided event name.

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more detailsLayer
Boolean

An instance of this class is a Promise.

more details
more detailsLayer
Boolean

An instance of this class is a Promise.

more details
more detailsLayer
Boolean

An instance of this class is a Promise.

more details
more detailsLayer
Promise

Loads the resources referenced by this class.

more details
more detailsLayer
Object

Registers an event handler on the instance.

more details
more detailsLayer
Promise

An instance of this class is a Promise.

more details
more detailsLayer
Promise

An instance of this class is a Promise.

more details
more detailsLayer

Method Details

addResolvingPromise(promiseToLoad){Promise}

Adds a promise to the layer's loadable chain. This is typically used in the load() method to ensure that all loadable resources required for the layer to function are loaded prior to this layer resolving and becoming loaded.

Parameter:
promiseToLoad Promise

A promise that must resolve for the layer to resolve and move from the loading status to being loaded.

Returns:
TypeDescription
PromiseResolves when the given promise resolves.
Example:
// the _elevationLayer must load() prior to the ExaggeratedElevationLayer
// resolving and moving to the "loaded" status
var ExaggeratedElevationLayer = BaseElevationLayer.createSubclass({
  load: function() {
    this._elevationLayer = new ElevationLayer({
      url: "//elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"
    });

    this.addResolvingPromise(this._elevationLayer.load());
  }
});

always(callbackOrErrback){Promise}inherited

An instance of this class is a Promise. Therefore always() may be used to execute a function if the promise is rejected or resolved. The input function will always execute no matter the response. For more information about promises, see the Working with Promises guide page.

Parameter:
callbackOrErrback Function
optional

The function to execute when the promise is rejected or resolved.

Returns:
TypeDescription
PromiseReturns a new promise for the result of callbackOrErrback.
Example:
// Although this example uses MapView, any class instance that is a promise may use always() in the same way
var view = new MapView();
view.always(function(){
  // This function will always execute whether or not the promise is resolved or rejected
});

cancelLoad()inherited

Cancels a load() operation if it is already in progress.

emit(type, event)protectedinherited

Since: ArcGIS API for JavaScript 4.5

Emits an event on the instance. This method should only be used when creating subclasses that inherit from Evented.

Parameters:
type String

The name of the event.

event Object

The event payload.

fetchAttributionData(){Promise<Object>}inherited

Fetches custom attribution data for the layer when it becomes available.

Returns:
TypeDescription
Promise< Object>Resolves to an object containing custom attribution data for the layer.

fetchTile(level, row, column, options){Promise<ElevationTileData>}

Fetches a tile at the given level, row, and column present in the view. This method must be overwritten to display custom elevation values in the Map.ground. Note that this method must return a promise that resolves to an object with the properties defined in ElevationTileData.

See the following samples for examples of how to overwrite this method:

Parameters:
level Number

The level of detail of the tile to fetch.

row Number

The row (y) position of the tile to fetch.

column Number

The column (x) position of the tile to fetch.

options Object
optional

Optional settings for the tile request.

Specification:
noDataValue Number
optional

The value representing pixels in the tile that don't contain an elevation value.

Returns:
TypeDescription
Promise< ElevationTileData>Resolves to an instance of ElevationTileData.

getTileBounds(level, row, column, out){Number[]}

Returns the bounds of the tile as an array of four numbers that can be readily converted to an Extent object. See the table in the returns section below for more details about the values returned by this method.

This function can be used inside fetchTile() so you can get the bounds of the current tile, convert it to an extent object, and request the desired data for the given extent. See the Custom ElevationLayer: Thematic data as elevation sample for an example of how this method works.

Parameters:
level Number

The level of detail (LOD) of the tile.

row Number

The tile's row (y) position in the dataset.

column Number

The tiles column (x) position in the dataset.

optional

Array for storing the tile bounds or extent.

Returns:
TypeDescription
Number[]Returns an array representing the tile bounds or extent. The array has four items, each representing one bound of the extent. The values of each item are described in the table below.
IndexValue
0Minimum x-value
1Minimum y-value
2Maximum x-value
3Maximum y-value
See also:

hasEventListener(type){Boolean}inherited

Indicates whether there is an event listener on the instance that matches the provided event name.

Parameter:
type String

The name of the event.

Returns:
TypeDescription
BooleanReturns true if the class supports the input event.

isFulfilled(){Boolean}inherited

An instance of this class is a Promise. Therefore isFulfilled() may be used to verify if the promise is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been fulfilled (either resolved or rejected).

isRejected(){Boolean}inherited

An instance of this class is a Promise. Therefore isRejected() may be used to verify if the promise is rejected. If it is rejected, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been rejected.

isResolved(){Boolean}inherited

An instance of this class is a Promise. Therefore isResolved() may be used to verify if the promise is resolved. If it is resolved, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been resolved.

Loads the resources referenced by this class. This method automatically executes for a View and all of the resources it references in Map if the view is constructed with a map instance.

This method must be called by the developer when accessing a resource that will not be loaded in a View.

Returns:
TypeDescription
PromiseResolves when the resources have loaded.

on(type, listener){Object}inherited

Registers an event handler on the instance. Call this method to hook an event with a listener. See the Events summary table for a list of listened events.

Parameters:
type String

The name of event to listen for.

listener Function

The function to call when the event is fired.

Returns:
TypeDescription
ObjectReturns an event handler with a remove() method that can be called to stop listening for the event.
PropertyTypeDescription
removeFunctionWhen called, removes the listener from the event.
See also:
Example:
view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});

otherwise(errback){Promise}inherited

An instance of this class is a Promise. Use otherwise() to call a function once the promise is rejected.

Parameter:
errback Function
optional

The function to execute when the promise fails.

Returns:
TypeDescription
PromiseReturns a new promise for the result of errback.
Example:
// Although this example uses MapView, any class instance that is a promise may use otherwise() in the same way
var view = new MapView();
view.otherwise(function(error){
  // This function will execute if the promise is rejected due to an error
});

then(callback, errback, progback){Promise}inherited

An instance of this class is a Promise. Therefore then() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the promise resolves (when the instance of the class loads). The errback executes if the promise fails. See the Working with Promises guide page for additional details.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

progback Function
optional

The function to invoke when the promise emits a progress update.

Returns:
TypeDescription
PromiseReturns a new promise for the result of callback that may be used to chain additional functions.
Example:
// Although this example uses MapView, any class instance that is a promise may use then() in the same way
var view = new MapView();
view.then(function(){
  // This function will execute once the promise is resolved
}, function(error){
  // This function will execute if the promise is rejected due to an error
});

Type Definitions

ElevationTileData

Describes elevation contained in the pixels that comprise an elevation tile.

Properties:
values Number[]

The elevation values of each pixel in the tile.

width Number

The width of the tile in pixels.

height Number

The height of the tile in pixels.

maxZError Number

The maximum allowed error of the Z-value for each value in meters.

noDataValue Number

Indicating the pixel values where no elevation data is present.

Event Overview

NameTypeSummaryClass
{view: View,layerView: LayerView}

Fires after the layer's LayerView is created and rendered in a view.

more details
more detailsLayer
{view: View,layerView: LayerView}

Fires after the layer's LayerView is destroyed and no longer renders in a view.

more details
more detailsLayer

Event Details

layerview-createinherited

Fires after the layer's LayerView is created and rendered in a view.

Properties:
view View

The view in which the layerView was created.

layerView LayerView

The LayerView rendered in the view representing the layer in layer.

See also:
Example:
// This function will fire each time a layer view is created for this
// particular view.
layer.on("layerview-create", function(event){
  // The LayerView for the layer that emitted this event
  event.layerView;
});

layerview-destroyinherited

Fires after the layer's LayerView is destroyed and no longer renders in a view.

Properties:
view View

The view in which the layerView was destroyed.

layerView LayerView

The destroyed LayerView representing the layer.

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