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. When transforming the values of the elevation data it is recommended to keep the no data value unchanged.

const ExaggeratedElevationLayer = BaseElevationLayer.createSubclass({
  load: function() {
    // add loadable dependencies here and include
    // their returned promises in the
    // addResolvingPromise() method
    this._elevation = new ElevationLayer({
      url: "//elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"
    });
    this.addResolvingPromise(this._elevation.load());
  },

  fetchTile: function(level, row, col, options) {
    // must resolve to an object with the following properties:
    // 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
    return this._elevation.fetchTile(level, row, col, options).then(function(data) {
      let exaggeration = this.exaggeration;
      // `data` is an object that contains the width of the tile in pixels,
      // the height of the tile in pixels, and the values of each pixel
      for (let i = 0; i < data.values.length; i++) {
         // each value represents an elevation sample for the
         // given pixel position in the tile
         // check if the value is a no data value
         if (data.values[i] !== data.noDataValue) {
           // multiply the elevation value by the exaggeration value
           data.values[i] *= exaggeration;
         }
      }
      return data;
    }.bind(this))
  }
});

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.

let 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.
Show inherited properties Hide inherited properties
Name Type Summary Class
Stringmore details

The name of the class.

more detailsAccessor
Extentmore details

The full extent of the layer.

more detailsLayer
Stringmore details

The unique ID assigned to the layer.

more detailsLayer
Stringmore details

Indicates how the layer should display in the LayerList widget.

more detailsLayer
Booleanmore details

Indicates whether the layer's resources have loaded.

more detailsLayer
Errormore details

The Error object returned if an error occurred while loading.

more detailsLayer
Stringmore details

Represents the status of a load operation.

more detailsLayer
Object[]more details

A list of warnings which occurred while loading.

more detailsLayer
Numbermore details

The opacity of the layer.

more detailsLayer
SpatialReferencemore details

The spatial reference of the layer.

more detailsBaseElevationLayer
TileInfomore details

The tiling scheme information for the layer.

more detailsBaseElevationLayer
Stringmore details

The title of the layer used to identify it in places such as the LayerList widget.

more detailsLayer
Stringmore details For BaseElevationLayer the type is always "base-elevation". more detailsBaseElevationLayer
Booleanmore details

Indicates if the layer is visible in the View.

more detailsLayer

Property Details

declaredClass Stringreadonly inherited
Since: ArcGIS API for JavaScript 4.7

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.when(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.

listMode String inherited

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

Value Description
show The layer is visible in the table of contents.
hide The layer is hidden in the table of contents.
hide-children If the layer is a GroupLayer, BuildingSceneLayer, KMLLayer, MapImageLayer, TileLayer or WMSLayer, hide the children layers from the table of contents.

Possible Values:"show"|"hide"|"hide-children"

Default Value:show
loaded Booleanreadonly inherited

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

Default Value:false
loadError Errorreadonly inherited

The Error object returned if an error occurred while loading.

Default Value:null
loadStatus Stringreadonly inherited

Represents the status of a load operation.

Value Description
not-loaded The object's resources have not loaded.
loading The object's resources are currently loading.
loaded The object's resources have loaded without errors.
failed The object's resources failed to load. See loadError for more details.

Possible Values:"not-loaded"|"loading"|"failed"|"loaded"

Default Value:not-loaded
loadWarnings Object[]readonly inherited

A list of warnings which occurred while loading.

opacity Number inherited

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;
spatialReference SpatialReferenceautocast

The spatial reference of the layer.

Default Value:class="hljs-built_in">module:esri/geometry/SpatialReference#WebMercator SpatialReference.WebMercator
tileInfo TileInfoautocast

The tiling scheme information for the layer.

The title of the layer used to identify it in places such as the LayerList widget.

If the layer is loaded from a portal item, the title of the portal item will be used. If a layer is loaded as part of a webmap or a webscene, then the title of the layer as stored in the webmap/webscene will be used.

If the layer is loaded from a portal item, the title of the portal item will be used. If a layer is loaded as part of a webmap or a webscene, then the title of the layer as stored in the webmap/webscene will be used.

type Stringreadonly

For BaseElevationLayer the type is always "base-elevation".

visible Boolean inherited

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

Show inherited methods Hide inherited methods
Name Return Type Summary Class
Promisemore details

Adds a promise to the layer's loadable chain.

more detailsBaseElevationLayer
more details

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

more detailsLayer
Promise<ElevationSampler>more details

Creates an elevation sampler for the given Extent by querying the service layer for elevation data and caching it so values may be sampled quickly afterwards.

more detailsBaseElevationLayer
Promise<LayerView>more details

Called by the views, such as MapView and SceneView, when the layer is added to the Map.layers collection and a layer view must be created for it.

more detailsLayer
more details

Destroys the layer and any associated resources (including its portalItem, if it is a property on the layer).

more detailsLayer
Booleanmore details

Emits an event on the instance.

more detailsLayer
Promise<Object>more details

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

more detailsLayer
Promise<ElevationTileData>more details

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

more detailsBaseElevationLayer
Number[]more details

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

more detailsBaseElevationLayer
Booleanmore details

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

more detailsLayer
Booleanmore details

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).

more detailsLayer
Booleanmore details

isRejected() may be used to verify if creating an instance of the class is rejected.

more detailsLayer
Booleanmore details

isResolved() may be used to verify if creating an instance of the class is resolved.

more detailsLayer
Promisemore details

Loads the resources referenced by this class.

more detailsLayer
Objectmore details

Registers an event handler on the instance.

more detailsLayer
Promise<ElevationQueryResult>more details

Queries the service layer for elevation values for the given geometry.

more detailsBaseElevationLayer
Promisemore details

when() may be leveraged once an instance of the class is created.

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

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

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

createElevationSampler(extent, options){Promise<ElevationSampler>}
Since: ArcGIS API for JavaScript 4.12

Creates an elevation sampler for the given Extent by querying the service layer for elevation data and caching it so values may be sampled quickly afterwards. The resolution of the cached data can be set using the demResolution option. In many cases, auto demResolution can be used to get high quality elevation samples without the need to know exactly where the data in the service is located. This is particularly useful for services which combine elevation data from many sources (such as the world elevation service). If more control, or higher quality samples are required, use either finest-contiguous or a fixed {number} resolution.

Parameters:
Specification:
extent Extent

The extent for which to create the sampler.

options Object
optional

Additional query options. See the table below.

Specification:
demResolution Number|String
optional
Default Value: auto

Controls the horizontal resolution (cell size) in meters from which elevation data is sampled (defaults to auto). See ElevationLayer for more details.

noDataValue Number
optional
Default Value: 0

The value to use when there is no data available.

Returns:
Type Description
Promise<ElevationSampler> An elevation sampler.
createLayerView(view, options){Promise<LayerView>}inherited

Called by the views, such as MapView and SceneView, when the layer is added to the Map.layers collection and a layer view must be created for it. This method is used internally and there is no use case for invoking it directly.

Parameters:
view *

The parent view.

options Object
optional

An object specifying additional options. See the object specification table below for the required properties of this object.

Specification:
signal AbortSignal
optional

A signal to abort the creation of the layerview.

Returns:
Type Description
Promise<LayerView> Resolves with a LayerView instance.
See also:
destroy()inherited
Since: ArcGIS API for JavaScript 4.17

Destroys the layer and any associated resources (including its portalItem, if it is a property on the layer). The layer can no longer be used once it has been destroyed.

The destroyed layer will be removed from its parent object like Map, WebMap, WebScene, Basemap, Ground, or GroupLayer.

See also:
emit(type, event){Boolean}inherited
Since: ArcGIS API for JavaScript 4.5

Emits an event on the instance. This method should only be used when creating subclasses of this class.

Parameters:
type String

The name of the event.

event Object
optional

The event payload.

Returns:
Type Description
Boolean true if a listener was notified
fetchAttributionData(){Promise<Object>}inherited

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

Returns:
Type Description
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:
Specification:
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.

signal AbortSignal
optional

An AbortSignal to abort the request. When overriding fetchTile, signal should be handled, for example by passing it on to request or by aborting pending operations. An aborted call to fetchTile should reject its returned promise with an error named AbortError. See also AbortController.

Returns:
Type Description
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.

out Number[]
optional

Array for storing the tile bounds or extent.

Returns:
Type Description
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.
Index Value
0 Minimum x-value
1 Minimum y-value
2 Maximum x-value
3 Maximum 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:
Type Description
Boolean Returns true if the class supports the input event.
isFulfilled(){Boolean}inherited

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).
isRejected(){Boolean}inherited

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been rejected.
isResolved(){Boolean}inherited

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been resolved.
load(signal){Promise}inherited

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.

The load() method only triggers the loading of the resource the first time it is called. The subsequent calls return the same promise.

It's possible to provide a signal to stop being interested into a Loadable instance load status. When the signal is aborted, the instance does not stop its loading process, only cancelLoad can abort it.

Parameter:
signal AbortSignal
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
Type Description
Promise Resolves 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 supported events.

Parameters:

An event or an array of events to listen for.

listener Function

The function to call when the event fires.

Returns:
Type Description
Object Returns an event handler with a remove() method that should be called to stop listening for the event(s).
Property Type Description
remove Function When called, removes the listener from the event.
Example:
view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});
queryElevation(geometry, options){Promise<ElevationQueryResult>}
Since: ArcGIS API for JavaScript 4.12

Queries the service layer for elevation values for the given geometry. The returned result contains a copy of the geometry with z-values sampled from elevation data from the service. The resolution from which the elevation is queried can be set using the demResolution option. In many cases, auto demResolution can be used to get high quality elevation samples without the need to know exactly where the data in the service is located. This is particularly useful for services which combine elevation data from many sources (such as the world elevation service). If more control, or higher quality samples are required, use either finest-contiguous or a fixed {number} resolution.

Parameters:
Specification:

The geometry to use for sampling elevation data.

options Object
optional

Additional query options. See the table below.

Specification:
demResolution Number|String
optional
Default Value: auto

Controls the horizontal resolution (cell size) in meters from which elevation data is sampled (defaults to auto). See the table below for more details on the different settings.

demResolution Description
auto Automatically chooses an appropriate resolution for each coordinate of the input geometry. The current implementation will try to use the finest available resolution given that the total required number of tile requests does not exceed a certain maximum amount (currently 20). Note that this may result in values being sampled from different resolutions.
finest-contiguous Sample elevation from the finest available resolution (cell size) across the entire geometry.
{number} Sample elevation from the resolution closest to the specified resolution (in meters).
returnSampleInfo Boolean
optional
Default Value: false

Indicates whether to return additional sample information for each coordinate.

noDataValue Number
optional
Default Value: 0

The value to use when there is no data available.

Returns:
Type Description
Promise<ElevationQueryResult> Resolves to an object with the sampled geometry, resolution information, and no data value.
See also:
when(callback, errback){Promise}inherited
Since: ArcGIS API for JavaScript 4.6

when() 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 instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

Returns:
Type Description
Promise Returns 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 when() in the same way
let view = new MapView();
view.when(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

Show inherited events Hide inherited events
Name Type Summary Class
{view: View,layerView: LayerView}
more details

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

more details Layer
{view: View,error: Error}
more details

Fires when an error emits during the creation of a LayerView after a layer has been added to the map.

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

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

more details Layer

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-create-errorinherited

Fires when an error emits during the creation of a LayerView after a layer has been added to the map.

Properties:
view View

The view that failed to create a layerview for the layer emitting this event.

error Error

An error object describing why the layer view failed to create.

See also:
Example:
// This function fires when an error occurs during the creation of the layer's layerview
layer.on("layerview-create-error", function(event) {
  console.error("LayerView failed to create for layer with the id: ", layer.id, " in this view: ", event.view);
});
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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