WMS:Images

Images are one of the four basic object types that is supported in the Map module. An image is typically a scanned map or aerial photo in TIFF or JPEG format. Images can be imported to WMS and displayed in the background to aid in the placement of objects as they are being constructed or simply to enhance a plot. Images can also be draped or "texture mapped" onto a TIN or 2D grid.

WMS supports the following image types:

• TIFF

• JPEG

• MrSID

• ECW

Importing an Image

The first step in using a new digital image for either background display or for texture mapping is to import the image. This can be done by either selecting the Import command in the Images menu or using the Open command in the File menu with the correct extension and opening an image file (TIFF, JPEG, or MRSID). Image files will be either georeferenced (contain coordinate information embedded) or not.

Multiple Images

WMS now allows more than one image at a time, however most will want to insure that each image is in the same coordinate system and that they are adjacent or it will do little good to have more than one image.

Geo-Referenced TIFF Files

Without embedded coordinate information about the image, it must be registered to real world coordinates when first imported. Some image files have the coordinate information embedded as part of the image and are referred to as georeferenced images. When a georeferenced image is imported to WMS, the image is automatically registered.

Additionally, some images contain companion world files (separate text files with the coordinate information) that can be used to georeference the image. WMS automatically recognizes some world files and when they are the images are automatically georeferenced using the included information. If the world file is not recognized automatically it can still be imported from the registration dialog.

Image Display Options

Once an image is imported, the Display Options command in the Display menu can be used to control how the image is displayed. The Image Display Options button of the Map tab brings up the Image Display Options dialog. The following display options are available:

Draw on XY plane behind all objects

If this option is selected, the image is drawn in the background prior to drawing any other objects. This mode is used to aid in the creation of new objects or to simply enhance a plot. The image is only displayed in plan view.

Texture map to surface when shaded

If this option is selected, the image is "draped" or texture mapped over the designated surface (TIN or 2D Grid). The image must be registered such that the surface lies within the domain of the image. The surface is texture mapped when the image is shaded using the Shade command.

Screen Capture

Displays created by WMS can be captured to a TIFF image file using the Screen Capture command. These images can then be used in WMS as backgrounds, or can be used as images in other applications or report documents.

When the Screen Capture command is issued the image currently in the Graphics window is converted internally to a TIFF image. Since the real coordinates of the screen corners are already known the image is automatically registered as it is captured. These images and registration points can be exported and read back into WMS at a later time.

Image Crop Collar

Many of the images available for use in WMS are the standard USGS map series. These maps have been scanned as is and contain the information on the collar (border) of the maps. This information is okay and in fact some may want to see it, but often it is convenient to remove the collar (especially when tiling multiple images together).

The Crop Collar command, available by right-clicking on an image in the Project Explorer, can be used to automatically remove the collar from the image for display.

Exporting Images

The Export command, available when right-clicking on the image in the Project Explorer is used to save a registered image. This command is most useful after screen capturing or cropping an image, or multiple images so that you can save the new area as an image file.

Related Topics

• Map Module
• Registering an Image