Key concepts for image services
In this topic
- What data can be published as an image service?
- Image service parameters
- Image service capabilities
- Preparing image services
- Publishing image services
- Caching image data
- Using an image service
Raster and image data can be shared as an image service using ArcGIS Server. An image service provides access to raster data through a web service. You can also share the data as part of a document, such as a map or globe document, or as part of other services, such as a geodata service.
What data can be published as an image service?
The source for the image service can be a raster dataset (from a geodatabase or file on disk), a mosaic dataset, or a layer file referencing a raster dataset or mosaic dataset. Sharing raster datasets or raster layers that define on-the-fly processing, such as symbology or raster functions, is a core capability of image services and does not require an extension. The ArcGIS Image extension is required to share a mosaic dataset or a raster layer containing a mosaic function. This does not only affect the image service. For example, if you have a map document containing a mosaic dataset, you require the ArcGIS Image extension .
Lidar data can also be shared as an image service. You can add terrain datasets, LAS datasets, or LAS files to a mosaic dataset and share the mosaic dataset as an image service. This makes the lidar data available as a raster, not points, but the source files can be accessed if you enable the download capability on the image service. See Sharing lidar data.
Compiled image service definition files (.ISCDef), created using ArcGIS Image Server, are no longer published using ArcGIS for Server. You should convert the image service definition into a mosaic dataset. See Migrating ISDef to a mosaic dataset.
Location of data
When you publish an image service, the service definition and all the data will be moved onto the server. Rather than moving and duplicating your data on the server, you can do one of a few things:
- Ensure that the data is on a shared drive registered with the server. For example, if you will be publishing a mosaic dataset, create it in this shared location with data from the shared location.
- Ensure that the data is duplicated (replicated) on the server. For example, the data you use in the mosaic dataset exists in the same folder structure location in a registered location on the server, just as it does on your local machine.
Both of these options are set up by accessing the server properties when you make the connection to the server. They are not options set up when you publish the image service.
Image service parameters
The parameters of an image service control how the raster data is made available as an image service and either enable or limit how clients can interact with the image service. For example, there are default parameters that apply to all image services, regardless of the source, such as the default resampling method and allowed compression methods. Optional, on-the-fly processing can be configured for each image service by associating functions with the image service. There are also several parameters that only apply when the input for an image service is a mosaic dataset. These include controls to the catalog, such as determining the fields in the attribute table that will be visible to the client, and whether downloading or editing (such as adding) is allowed.
Image service capabilities
When you publish an image service, you should consider how clients will be connecting to the image service. An image service is always published with imaging capabilities, allowing clients to connect it using an ArcGIS for Server connection or via REST. However, you can also choose to publish an image service with the Open Geospatial Consortium, Inc. (OGC) Web Map Service (WMS) or Web Coverage Service (WCS) capabilities. By adding additional capabilities you allow clients to access your image service in an expanded variety of applications and devices.
Preparing image services
There are many things to consider when you are preparing to create an image service, because not all raster data is served in an equal manner; it depends on the capabilities and the operations you choose within them. There are several common questions to ask, such as:
- Is there one raster dataset or many raster datasets?
- Is the raster data for viewing as an image or as input for analysis?
- Does the data have multiple bands or need to be enhanced?
- Is any processing required?
To learn about each of these, see Preparing image services.
You also need to make sure the data is accessible to the server; otherwise, it will be moved to the server when the image service is published. It is recommended that you register your data locations with the server as mentioned above to avoid duplicating the data or making copies of large data collections. Additionally, if you will be making your image service editable by users, meaning allowing them to do things such as upload imagery, then the mosaic dataset needs to reside in an enterprise geodatabase that is registered with the server.
Publishing image services
Image services are published similarly to all other services using ArcGIS for Server. By default, the image services are always published with Image Service capabilities, and you can optionally choose the WMS and WCS capabilities. Users can then connect to these services as they would any other published ArcGIS for Server service.Learn about publishing image services
The ArcGIS Image extension
The ArcGIS Image extension is a license added to ArcGIS for Serverwhich extends the capability of serving raster data. Specifically, it allows you to serve a mosaic dataset or a raster layer containing a mosaic function. Therefore, if you are serving an image service, the following are true:
- Without the extension, you can serve a raster dataset or raster dataset layer.
- With the extension, you can serve a mosaic dataset or mosaic dataset layer.
It adds the ability to
- Put your valuable imagery into use quickly.
- Serve collections of imagery or lidar data as image services.
- Dynamically create and serve mosaics from the original imagery, without the need to precompute the mosaics.
- Serve multiple views using the original imagery.
- Access the catalogs of imagery that make up the mosaic dataset.
- Exploit overlapping imagery, perform on-the-fly image processing, and explore temporal changes using the advanced image serving capabilities of this extension.
Additionally, map and globe documents can contain raster data, but if you are serving one that contains a mosaic dataset, you will require the Image extension.
Creating, editing, or working with mosaic datasets in ArcGIS for Desktop is not affected by the ArcGIS Image extension (there is no extension for ArcGIS for Desktop).
Caching image data
Caching is only required when you must create the fastest possible service containing image data. Generally, the pyramids generated for raster datasets or the overviews generated for mosaic datasets result in image data being served at an acceptable rate. However, if you know that a particular image or area of interest will be repeatedly visited, you may want to generate a cache.
You can cache an image service or cache a map service or globe service containing raster data or an image service. Unless there is a need to cache all the contents of a map or globe service, it is generally recommended that you cache the vector data and not the image data, especially when they contain an image service.
Using an image service
You can access an image service the same way you would any other service—by first connecting to the GIS server, then choosing the image service that is available. As mentioned above, how you use the image service depends on the source data. Therefore, a published raster dataset can be used like a raster; however, a published mosaic dataset can be used like a single raster (image) or catalog.