9.2 Web Layers and Services (Web Feature Layers, Vector Tile Layers, Map Image Layers)

Web Layers and Services

Quick Answer: Web Layers are the individual services that make up Web Maps and Web Scenes. ArcGIS Pro allows you to publish several types of web layers, including Web Feature Layers for vector querying and editing, Vector Tile Layers for fast rendering, Map Image Layers for dynamic or cached enterprise mapping, Tile Layers for rasters, and Scene Layers for 3D data.

When you publish a map to a portal, you are essentially publishing its constituent layers as web services. Understanding the different types of web layers and their appropriate use cases is critical for optimizing performance, enabling the right capabilities, and ensuring data integrity on the web.

Web Feature Layers (Feature Services)

Web Feature Layers (WFLs), traditionally known as Feature Services, expose vector geometry and attributes over the web. They are the most versatile type of web layer because they provide access to the actual raw data rather than just a picture of the data.

Characteristics & Use Cases

• Client-Side Rendering: The client (e.g., a web browser or ArcGIS Pro) downloads the vector features and renders them locally. This allows for dynamic styling and high-quality display at any scale.
• Querying: Users can perform complex spatial and attribute queries against the data.
• Editing: WFLs are the primary service type used when you need to enable web-based editing. Field workers using mobile apps like ArcGIS Field Maps rely on feature layers.
• Performance: Because features are downloaded to the client, performance can degrade if the layer contains hundreds of thousands of complex polygons.

Map Image Layers (Map Services)

Map Image Layers, traditionally known as Map Services, are exclusively available when publishing to an ArcGIS Enterprise portal (federated server). They cannot be hosted directly on ArcGIS Online in the same way.

Characteristics & Use Cases

• Server-Side Rendering: The server draws the map based on the client's extent and sends back an image (e.g., PNG or JPEG).
• Dynamic or Cached: They can be drawn dynamically upon request, or pre-rendered into a cache of tiles.
• Complex Symbology: Because the heavy lifting is done by the robust Enterprise server, Map Image Layers are ideal for data with extremely complex, advanced cartography that web browsers might struggle to render.
• Large Datasets: They are highly efficient for displaying massive vector datasets where downloading the raw features to the client would be too slow.

Vector Tile Layers

Vector Tile Layers deliver vector data (points, lines, polygons) as pre-generated, generalized "tiles" containing geometry and attribute data, which are then rendered by the client using a separate style file.

Characteristics & Use Cases

• Speed and Scalability: Vector tiles are incredibly fast. They offer the speed of cached raster tiles but with much smaller file sizes.
• Dynamic Styling: Because the geometry is sent to the client, you can change the style (colors, symbols) of a vector tile layer without having to rebuild the tiles. You can serve one set of tiles with multiple distinct styles (e.g., a day map and a night map).
• High DPI Displays: Vector tiles render crisply on high-resolution screens because they are drawn natively by the client device.
• Basemaps: They are the modern standard for operational basemaps.

Tile Layers (Raster Tiles)

Tile Layers (or Raster Tile Layers) consist of pre-rendered image tiles (e.g., JPEG or PNG) generated at specific scale levels.

Characteristics & Use Cases

• Rasters and Imagery: This is the standard method for serving aerial photography, satellite imagery, and complex raster surfaces (like DEMs or heat maps).
• Static Content: Once generated, the tiles are static. If the underlying data changes, the cache must be updated or rebuilt.
• Performance: Highly performant for complex backgrounds because the client is just requesting simple images.

Scene Layers

Scene Layers are specialized web services designed for streaming large volumes of 3D data.

Characteristics & Use Cases

• 3D Optimization: Scene layers cache data into scalable nodes, allowing the client to quickly load only the features visible in the current 3D view.
• Types of Scene Layers: There are several subtypes, including 3D Object scene layers (for buildings), Point Cloud scene layers (for LiDAR data), Integrated Mesh scene layers (for photogrammetry), and Point scene layers (for large volumes of 3D points).
• Web Scenes: These layers are the building blocks of Web Scenes, consumed in the Scene Viewer or ArcGIS Earth.

Selecting Service Capabilities

When publishing a Web Feature Layer, you must configure its capabilities in the Sharing pane. These settings dictate what end-users can do with the service:

Carefully configuring these capabilities is vital for data security. If a layer is intended only for public viewing, you must ensure that Create, Update, and Delete capabilities are unchecked.