Image service properties in Image Server Viewer

Some of the properties of the image service are controlled by the image service administrator. This information includes the name of the image service, the processes applied, and metadata. There are also many properties you can alter to suit your requirements using the client application. These properties include the spatial reference system, default sampling method, mosaic method, compression method, and background color. The image service administrator can also control what properties the client can choose to alter. For example, a client might not always get to choose the Viewpoint mosaic method, because there are limited data sources this method can be used with. Therefore, the administrator can choose to remove it from the choices given to the client.

The image service properties

Field	Description
Spatial Reference System	Defines the spatial reference system based on which imagery should be displayed. Each request to the server is for an image based on a rectangular window in the specified spatial reference. Some client applications can define or redefine the required spatial reference.
Sampling Method	Defines the method by which raster pixels are sampled by the server to match the resolution of the client request. Depending on the application, the sampling method can be changed. More accurate radiometry values are obtained using the nearest neighbor sampling but can result in jagged edges of features. Bilinear interpolation provides smoother edges and lines but can result in some smoothing of the image.
Mosaic Method	An image returned to the client can be created from a number of input rasters. The mosaic method defines how the mosaic is created from different rasters. Closest to Center—Enables rasters to be sorted based on a default order where rasters that have their centers closest to the view center are placed on top. Closest to Nadir—Enables rasters to be sorted by the distance between the nadir position and view center. This is similar to the Closest to Center method but uses the nadir point to a raster, which may be different than the center, especially for oblique imagery. Closest to Viewpoint—Orders rasters based on a user-defined location and nadir location for the rasters using the Viewpoint tool. By Attribute—Enables raster ordering based on a defined metadata attribute and its difference from a base value. Most Northwest—Enables raster ordering in a view-independent way, where rasters with their centers most northwest are displayed on top. Seamline—Cuts the raster using the predefined seamline shape for each raster using optional feathering along the seams. Lock Raster—Enables a user to lock the display of a single or multiple rasters based on an ID or name.
Lock Raster ID	The image is locked to a specified raster ID if the mosaic method is defined as Lock Image. This can be used to display by default only one raster in a service. The raster ID is specified in the service table. If you know the ID of the raster you want to lock, you can enter it here. Refer to step 8 in Viewing image service metadata to learn about locking rasters.
Compression Method	Defines the method of compression in which to transmit the mosaicked raster data from the server to the client. If accessing the image services over a LAN, large data volumes do not cause a problem. However, when working over slower connections on the Internet, it is better to apply a compression to the imagery before transmission. This compression reduces the size of transmitted imagery but puts an additional load on the service provider to compress the data first. A setting of Uncompressed results in no compression being applied to the imagery, providing the highest quality but resulting in the maximum data transfer across the network. JPEG compression is an efficient compression method that can often compress imagery by about three to eight times with little degradation in the image quality. JPEG 2000 is wavelet based, which provides high compression ratios (8–15) with little degradation in the image quality but only when the size of the image transmitted is large. For small screen-sized requests, JPEG is generally better. JPEG 2000 also puts a heavier load on the service provider. LZ77 is an efficient lossless compression method that is primarily for imagery with similar pixels, such as scanned maps or results of classifications.
Compression Quality	Defines the quality of compression. A compression quality of 100 percent is the best. Values closer to 0 have very high compression ratios with little regard for quality. Values closer to 100 maintain visual quality while attempting to compress the image. A value of 100 may also indicate no loss in quality if using a lossless compression.
Background Color	Defines the default background color of the image service. Where there is no imagery, the specified color value is displayed.

Image service properties