Overlay Overview

You can use the IRIS Overlay utility to draw overlays or maps for display on top of other IRIS/Open products. Overlays are used for product output and the real-time display.

An overlay can consist of the following:

• Geographical and political boundaries displayed with or without latitude and longitude lines or range rings.
• Text strings to label areas of interest, such as cities.
• Bitmap Icons that can be constructed by the user and applied to the overlay. Icons can represent any feature, for example, airports, train stations, and similar.
• The lines, text and icons mentioned above can be separated into different layers within the overlay file. Then at display time, either all or only a subset of these layers may be displayed giving yielding overlays that appear different based on which layers are active. Layers can be drawn in different colors.
• Underlays are filled regions of color displayed under the radar images where there is no weather data. Underlays are typically used to indicate areas of water.

Each overlay is defined in an ASCII file using a connect-the-dots approach (sometimes called a vector approach). This allows overlays to be drawn to any scale factor.

You use the Overlay utility to create and modify your own overlays in a window on your workstation.

Typically, you get the basic map (coastlines, borders, rivers) from Vaisala and then customize it to meet your needs. It is often convenient to make separate layers for different interests (river catchments, airports). IRIS supports up to 20 overlay files.

IRIS overlays are ASCII files so you can edit them with any text editor (vi, or emacs which is distributed with IRIS).