VIEWER INSTRUCTIONS

3. Accessing the Map Layers

The Table of Contents (TOC) on the right side of the Viewer lists all the data layers available in the Map. These layers are grouped by common themes. When the Viewer is first accessed, most items showing in the Layers list are groups of themes.

"StreetMap USA" is a group of base data, which provides administrative boundaries, roads, railroads, airports, and local landmarks. The "Hydrography" group provides the base stream and waterbody layers. The "SPARROW Model Results" group provides access to the SPARROW nitrogen- and phosphorus-model results. The "Imagery" group provides access to USGS topographic maps and digital aerial orthophotos served from the Microsoft TerraServer. "Background" is an individual map layer showing the States in the Northeastern USA and surrounding Canadian Provinces.

Within a group, there can be multiple subgroupings of thematic information. For instance, "SPARROW Model Results" is a primary group in the TOC Layers list. By clicking on the plus box () for "SPARROW Model Results", the Viewer TOC will refresh to show two new subgroups, "Nitrogen" and "Phosphorus".

Notice that there are boxes next to the group names Nitrogen and Phosphorus. In this case, the indicates that there are multiple layers listed under each group. In the following example, we want to view some of the nitrogen results data. To do so, click on the button next to the "Nitrogen" group heading, the results of which should resemble the following in the TOC:

As shown above, there are several layers available showing various nitrogen results from the SPARROW Model.

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