Use background layers to display pictures behind your network. For example, you might want to display a picture of a neighborhood behind your network, so you can relate elements in your network to structures and roads depicted in the picture. You can add, delete, edit and rename background layers in the Background Layers Manager.

You can add multiple pictures to your hydraulic model for use as background layers, and turn off the ones you don't want to show and turn on those you do. Additionally, you can create groups of pictures in folders, so you can hide or show an entire folder or group of pictures at once.

To add or delete background layers, open the Background Layers manager: click View > Background Layers (Ctrl+2).

You can use shapefiles, Microstation dgn files, Bentley DgnDb files, AutoCAD DXF files, and raster (also called bitmap) pictures as background images for your model. These raster image formats are supported: bmp, jpg, jpeg, jpe, jfif, gif, tif, tiff, png, and sid.

World Files

Some image formats support associated world files that contain information so that images can be placed spatially. The following file formats support an associated world file:

• bmp
• jpg
• jpeg
• jpe
• jfif
• tif
• tiff
• png
• gif

The associated world file can have two different extensions. You can use the extension of the image file plus "w". For example, a file named example.jpeg would have a world file named example.jpegw. Or you can use a shorter extension which uses the first letter of the original extension, the last letter of the original extension plus "w". For example, example.jpeg could have a world file named example.jgw.

World files do not specify a coordinate system; this information is generally stored somewhere else in the raster file itself or in another companion file.

The generic meanings of world file parameters are:

1. Line 1: A: x component of the pixel width (x-scale)
2. Line 2: D: y component of the pixel width (y-skew)
3. Line 3: B: x component of the pixel height (x-skew)
4. Line 4: E: y component of the pixel height (y-scale), almost always negative
5. Line 5: C: x-coordinate of the center of the upper left pixel
6. Line 6: F: y-coordinate of the center of the upper left pixel

Click one of the following links to learn more about using background layers: