BaseElevationLayer | API Reference | ArcGIS Maps SDK for JavaScript 4.31

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.

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Type	Summary	Class
String	The name of the class.	Accessor
Extent\|null\|undefined	The full extent of the layer.	Layer
String	The unique ID assigned to the layer.	Layer
String	Indicates how the layer should display in the LayerList widget.	Layer
Error	The Error object returned if an error occurred while loading.	Layer
String	Represents the status of a load operation.	Layer
Object []	A list of warnings which occurred while loading.	Layer
Boolean	Indicates whether the layer's resources have loaded.	Layer
Number	The opacity of the layer.	Layer
Map\|Basemap\|Ground\|GroupLayer\|CatalogDynamicGroupLayer\|CatalogLayer	The parent to which the layer belongs.	Layer
Boolean	When `true`, the layer can be persisted.	Layer
SpatialReference	The spatial reference of the layer.	BaseElevationLayer
TileInfo	The tiling scheme information for the layer.	BaseElevationLayer
String\|null\|undefined	The title of the layer used to identify it in places such as the LayerList widget.	Layer
String	For BaseElevationLayer the type is always "base-elevation".	BaseElevationLayer
TimeExtent\|null\|undefined	Specifies a fixed time extent during which a layer should be visible.	Layer
Boolean	Indicates if the layer is visible in the View.	Layer

Property Details

declaredClass Inherited Property declaredClass Stringreadonly Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.7 Accessor since 4.0, declaredClass added at 4.7.

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

fullExtent Inherited Property fullExtent Extent |null |undefinedautocast Inherited from Layer

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;
});

id Inherited Property id String Inherited from Layer

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

listMode Inherited Property listMode String Inherited from Layer

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"

loadError Inherited Property loadError Errorreadonly Inherited from Layer

The Error object returned if an error occurred while loading.

Default Value:null

loadStatus Inherited Property loadStatus Stringreadonly Inherited from Layer

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 Inherited Property loadWarnings Object[]readonly Inherited from Layer

A list of warnings which occurred while loading.

loaded Inherited Property loaded Booleanreadonly Inherited from Layer

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

Default Value:false

opacity Inherited Property opacity Number Inherited from Layer

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;

The parent to which the layer belongs.

persistenceEnabled Inherited Property persistenceEnabled Boolean Inherited from Layer Since: ArcGIS Maps SDK for JavaScript 4.28 Layer since 4.0, persistenceEnabled added at 4.28.

When true, the layer can be persisted. This property only has an effect for layers that are part of the WebMap or WebScene spec.

Default Value:false

spatialReference Property spatialReference SpatialReferenceautocast

The spatial reference of the layer.

Default Value:SpatialReference.WebMercator

tileInfo Property tileInfo TileInfoautocast

The tiling scheme information for the layer.

title Inherited Property title String |null |undefined Inherited from 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.

type Property type Stringreadonly

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

visibilityTimeExtent Inherited Property visibilityTimeExtent TimeExtent |null |undefinedautocast Inherited from Layer Since: ArcGIS Maps SDK for JavaScript 4.30 Layer since 4.0, visibilityTimeExtent added at 4.30.

Specifies a fixed time extent during which a layer should be visible. This property can be used to configure a layer that does not have time values stored in an attribute field to work with time. Once configured, the TimeSlider widget will display the layer within the set time extent. In the case that only one of the start or end date values are available, the layer remains visible indefinitely in the direction where there is no time value.

Aerial imagery can capture seasonal variations in vegetation, water bodies, and land use patterns. For example, in agricultural regions, aerial imageries taken during different growing seasons provide insights into crop health and productivity. Defining a fixed time extent on imageries from specific time periods provides temporal context and facilitates focused analysis based on specific time periods or events.

Default Value:null

See also

Sample - GraphicsLayer with visibilityTimeExtent

visible Inherited Property visible Boolean Inherited from Layer

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;

// Watch for changes in the layer's visibility
// and set the visibility of another layer when it changes
reactiveUtils.watch(
  () => layer.visible,
  (visible) => {
    if (visible) {
      anotherLayer.visible = true;
    } else {
      anotherLayer.visible = false;
    }
  }
);

Method Overview

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Return Type	Summary	Class
	Adds one or more handles which are to be tied to the lifecycle of the object.	Accessor
Promise	Adds a promise to the layer's loadable chain.	BaseElevationLayer
	Cancels a load() operation if it is already in progress.	Layer
Promise<ElevationSampler>	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.	BaseElevationLayer
Promise<LayerView>	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.	Layer
	Destroys the layer and any associated resources (including its portalItem, if it is a property on the layer).	Layer
Boolean	Emits an event on the instance.	Layer
Promise<Object>	Fetches custom attribution data for the layer when it becomes available.	Layer
Promise<ElevationTileData>	Fetches a tile at the given level, row, and column present in the view.	BaseElevationLayer
Number []	Returns the bounds of the tile as an array of four numbers that can be readily converted to an Extent object.	BaseElevationLayer
Boolean	Indicates whether there is an event listener on the instance that matches the provided event name.	Layer
Boolean	Returns true if a named group of handles exist.	Accessor
Boolean	`isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).	Layer
Boolean	`isRejected()` may be used to verify if creating an instance of the class is rejected.	Layer
Boolean	`isResolved()` may be used to verify if creating an instance of the class is resolved.	Layer
Promise	Loads the resources referenced by this class.	Layer
Object	Registers an event handler on the instance.	Layer
Promise<ElevationQueryResult>	Queries the service layer for elevation values for the given geometry.	BaseElevationLayer
	Removes a group of handles owned by the object.	Accessor
Promise	`when()` may be leveraged once an instance of the class is created.	Layer

Method Details

addHandles Inherited Method addHandles(handleOrHandles, groupKey) Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, addHandles added at 4.25.

Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.

// Manually manage handles
const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true }
);

this.addHandles(handle);

// Destroy the object
this.destroy();

Parameters

handleOrHandles WatchHandle|WatchHandle []

Handles marked for removal once the object is destroyed.

groupKey *

optional

Key identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.

addResolvingPromise Method 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 Method cancelLoad() Inherited from Layer

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

createElevationSampler Method createElevationSampler(extent, options){Promise<ElevationSampler>} Since: ArcGIS Maps SDK for JavaScript 4.12 BaseElevationLayer since 4.4, createElevationSampler added at 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 Inherited Method createLayerView(view, options){Promise<LayerView>} Inherited from Layer

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

Sample - Custom WebGL layer view

destroy Inherited Method destroy() Inherited from Layer Since: ArcGIS Maps SDK for JavaScript 4.17 Layer since 4.0, destroy added at 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 Inherited Method emit(type, event){Boolean} Inherited from Layer Since: ArcGIS Maps SDK for JavaScript 4.5 Layer since 4.0, emit added at 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 Inherited Method fetchAttributionData(){Promise<Object>} Inherited from Layer

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 Method 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 Method 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 Inherited Method hasEventListener(type){Boolean} Inherited from Layer

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.

hasHandles Inherited Method hasHandles(groupKey){Boolean} Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, hasHandles added at 4.25.

Returns true if a named group of handles exist.

Parameter

groupKey *

optional

A group key.

Returns

Type	Description
Boolean	Returns `true` if a named group of handles exist.

Example

// Remove a named group of handles if they exist.
if (obj.hasHandles("watch-view-updates")) {
  obj.removeHandles("watch-view-updates");
}

isFulfilled Inherited Method isFulfilled(){Boolean} Inherited from Layer

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 Inherited Method isRejected(){Boolean} Inherited from Layer

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 Inherited Method isResolved(){Boolean} Inherited from Layer

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 Inherited Method load(signal){Promise} Inherited from Layer

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 Inherited Method on(type, listener){Object} Inherited from Layer

Registers an event handler on the instance. Call this method to hook an event with a listener.

Parameters

type String|String []

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 Method queryElevation(geometry, options){Promise<ElevationQueryResult>} Since: ArcGIS Maps SDK for JavaScript 4.12 BaseElevationLayer since 4.4, queryElevation added at 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

geometry Point|Multipoint|Polyline

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

ElevationLayer.queryElevation

removeHandles Inherited Method removeHandles(groupKey) Inherited from Accessor Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, removeHandles added at 4.25.

Removes a group of handles owned by the object.

Parameter

groupKey *

optional

A group key or an array or collection of group keys to remove.

Example

obj.removeHandles(); // removes handles from default group

obj.removeHandles("handle-group");
obj.removeHandles("other-handle-group");

when Inherited Method when(callback, errback){Promise} Inherited from Layer Since: ArcGIS Maps SDK for JavaScript 4.6 Layer since 4.0, when added at 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 Type Definition 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

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Type	Summary	Class
{view: View,layerView: LayerView}	Fires after the layer's LayerView is created and rendered in a view.	Layer
{view: View,error: Error}	Fires when an error emits during the creation of a LayerView after a layer has been added to the map.	Layer
{view: View,layerView: LayerView}	Fires after the layer's LayerView is destroyed and no longer renders in a view.	Layer

Event Details

layerview-create Inherited Event layerview-create Inherited from Layer

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

View.whenLayerView()

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-error Inherited Event layerview-create-error Inherited from Layer

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

View.whenLayerView()

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-destroy Inherited Event layerview-destroy Inherited from Layer

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.