GPS for Dummies.pdf - Engineering Surveyor

310Part IV: Using Web-hosted Mapping ServicesTo display a map, you tell GPS Visualizer what GPS data you plan on using:1. Click the Browse button next to the File #1 text box and choose thelocation of the sample_calif.gpx file.See preceding step list.2. From the Background map drop-down list box, choose US: USGS TopoMap, Single Image.While you’re there, check out the other background map options.3. Select the Open in New Window check box (lower left of the screen).4. Click the Draw the Map button (lower left of the screen).A new window shows a map with the GPS data overlaid on it (as shownin Figure 19-5). Some of the features displayed on the map include• Waypoints: Any GPS waypoints that were included with the uploadeddata are plotted on the map, identified by a circle and the waypointname. When you move the cursor over a waypoint label, the waypointname changes color so it’s easier to see. You can also click anddrag a waypoint label to move it. When you do, a line is drawn fromthe waypoint label to actual waypoint location. This is useful if thewaypoint label obscures something you want to see on the map.• Tracks: The GPS track data showing the travel route is drawn on themap. By default, GPS Visualizer shows the elevation for differentsegments of the track path in different colors; note the legend at thebottom of the map with what the different colors mean. When youcreate a map, you can have other data (such as speed, heading, orslope) displayed in color on the track path.• Background opacity: At the bottom of the map is a series of smallrectangles that let you fade the background map image. Click oneof the rectangles to set how faded you want the background mapto appear. The rectangle on the far right displays the map in fullcolor. The rectangle on the far left fades the map completely towhite (so it isn’t visible). Fade the background map to better seethe colors of your track log and waypoints.GPS Visualizer can show an elevation profile based on track data. Click theDraw a profile link at the top of the Web page to use this feature.TerraSever-USATerraServer-USA is a popular Web site that provides free USGS topographicmaps and aerial photos of the United States. (Chapter 20 contains an extensivedescription of the site and detailed instructions to display aerial photos.)Nearly all the commands used for viewing aerial photos also apply to displayingtopographic maps. Visit the Web site www.terraserver-usa.com.