Lesson 3b: The National Map Viewer Tool Functionality

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Lesson 3b: The National Map Viewer Tool Functionality: Legend, Measure, Elevation Profile, and Spot Elevations. In this lesson, we will provide the user with a demonstration of functionality and capabilities of tools in The National Map Viewer.

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Length: 00:06:42

Location Taken: US

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Lesson 3b:  The National Map Viewer Tool Functionality: Legend, Measure, Elevation Profile, and Spot Elevations. The National Map viewer is a primary access point for the ‘visualization’ of geospatial data that composes The National Map and functions as a tool to enable use of the data in a web environment. In this lesson, we will provide the user with a demonstration of functionality and capabilities of tools in The National Map Viewer.

By the end of this lesson, you will be able to use map tools to view the legend, measure a feature or find point coordinates, display an elevation profile, and retrieve a spot elevation.  A subsequent lesson will show how to utilize the viewer’s advanced tools to add data, draw, select and query.

The National Map viewer serves as a window into freely available base map data that is consistent on a national level, and provides resources to access the data through a variety of products and services.  To access the viewer click the link for ‘TNM Viewer’.

For help at any time, click the ‘Link to Help’ hyperlink.

First we’ll discuss the legend.   Click on the Legend Icon to open it.  The Legend displays labels and symbols for layers in the map. However, default settings dictate that base maps are not shown in the Legend, and when no operational layers are rendered in the map, the Legend tool is blank, as it now appears. For a layer to be shown in the Legend we first need to select a layer.  Let’s use the National Land Cover Database layer to demonstrate.

Notice that the NLCD layer is now visible.   Click on the Legend icon to display the labels and symbols for the NLCD layer. The legend supports dynamic, image, feature, KML layer types, and WMS layers with an associated legend URL. When no operational layers are rendered in the map, the Legend tool is blank.  The order in which layers appear in the Legend tool corresponds to the layer order in the map.

Next let’s discuss the Measurement tool. The measurement tool allows measuring the area of a polygon, length of a line, or finding the coordinates of a point.  

Click on the Location measurement icon and then click a point on the map.  The Measurement tool displays the coordinates for the point in decimal Degrees. Change the coordinate display format to degrees/minutes/seconds by altering the drop-down to DMS. 

To measure a distance click the Distance measurement icon and draw a polyline on the map by clicking two or more points, then double-click to finish drawing the polyline. The Measurement tool displays the total length of the polyline in miles.  To change the length unit, select the applicable unit of measure from the drop-down menu. Here we have changed the unit to Meters.

Click the Area measurement icon to measure the area of a polygon.  Draw a polygon on the map by clicking three or more points, and double-clicking to finish.  The Measurement tool displays the total area of the polygon in square miles. To change the area unit, select the applicable unit of measure from the drop-down menu.  Here we have changed the unit to acres.

The Elevation Profile widget displays the elevation profile for a measured line along with a web map.

Click on the Distance icon. Draw a polyline on the map by clicking two or more points, and double-click to finish drawing the polyline.

The Profile Result tab displays the Elevation Profile.  The elevation profile chart shows elevations from an initial starting point to an ending point including intermediate values along the profile showing locations and +/- elevation changes with respect to the starting point.

To view the elevation of a specific point, move the cursor over the Elevations Profile chart. The specific point elevation is displayed. As the mouse moves over the chart in the widget a red X is moved in the map corresponding with the location in the chart.

Click on the Measure tab. The Measurement tool displays the total length of the polyline, using the defined Default Length Unit. To change the length unit, select the applicable unit of measure from the drop-down menu.

Here we have changed the unit to Kilometers.

Lastly let’s view the Spot Elevation tool. The Spot Elevation tool returns the elevation of a given location.  You can click multiple locations to see the additional elevations in the list.

In this lesson, we discussed how to use map tools to view the legend, measure a feature or find point coordinates, display an elevation profile, and retrieve a spot elevation.  A subsequent lesson will show how to utilize the viewer’s advanced tools to add data, draw, select, and query.