The Selector Map Page

The main page of the GPS Tracker program is the selector map page. This page displays the map containing the network of trail segments that you can choose from to build a track for analysis. (The selector map should not be confused with the print map which is designed to display a selected track for printing. The selector map on the main map page would not normally be printed, although you could choose to print it using the browser's print command.)

This page also contains the buttons for backing segments off of a selected track and for displaying a selected track in another window. It also displays the statistics for the currently selected track.

The Selector Map

The selector map is shown on the main page of the GPS Tracker program. It displays the network of trail segments that you can choose from to build a track for analysis. The selector map is implemented using Google Maps and so the features of the map are fairly typical of the features found on Google Maps.

You can zoom in or zoom out on the map to show more or less detail, as needed. The drop down box in the top left corner of the map shows the current zoom level and you can change the zoom level by selecting a different value from the list.

You can move the map by holding down the left mouse button over the map and dragging it to a new position. To move the map a large distance it's sometimes useful to zoom out to a smaller scale before moving it and then zoom back in over the new postion.

The map also features four map types which are listed in the top right corner. These map types are the following:

The default map type used by GPS Tracker is Terrain but you can change that to one of the others by clicking on the name.
Areas

GPS Tracker contains trail segments from several different trail systems including Shenandoah National Park and Massanutten Mountain, however not all of the trail segments in the program are drawn on the map at the same time. Instead they're divided up into logical groupings called "Areas" and only the segments in the current area are drawn on the map at one time. This is done to reduce the amount of processing power that would be required to draw the entire trail network at once.

The list of Areas that may be choosen is given in a drop down list at the top of the Selector Map page. The default Area is "Shenadoah National Park - Northern Section". This means that when the page first comes up the map will be centered on the northern section of Shenadoah National Park and only the trail segments in that section will be drawn. You can select a different Area by choosing it from the dropdown box and hitting the "Go" button. That will redraw the map centered on the new section and only showing the segments in that section.

In the case where a segment in the current area connects to a segment in a different area, the adjoining segments will be drawn on the current area map also. If you click on one of them it will add the segment to the track it's building and then automatically switch the map to the new area, centering the map on the new area and drawing the segment network in that area.
The Zoom Level

The selector map on the main map page can be shown at a number of different zoom levels ranging from 4 (the widest view showing the least detail) to 17 (the closest view showing the most detail.) The current zoom level is displayed in the drop down box in the top left corner of the map.

Some features of the GPS Tracker map display are only available at certain zoom levels. The red selector dots that you click on to add a segment to the selected route are only available for zoom levels 13 through 17. The light blue dots which mark the ends of the segments are only available for zoom levels 10 through 17. At any zoom levels below these ranges the map doesn't have enough detail to make these features useful.
Trail Segments

Trail segments are shown on the selector map as a network of lines. The ends of each segment are marked by a light blue dot. It's these trail segments that can be added together to build a track that can be analyzed for distance and elevation data.

The definition of what makes a "trail segment" in GPS Tracker is rather arbitrary. All trail segment data is taken from actual GPS tracks that were collected in the field and then split up to make the segments. The point where the tracks are split will usually be a trail intersection or a trailhead. However, sections that are less than about a tenth of a mile will usually just be included in an adjacent segment. Track surfaces can include anything from single track trail to dirt roads to paved roads.

The color of the trail segment indicates whether it's been selected as part of the track or not. The following colors indicate the state of the segment:

Figure 1 shows examples of the three colors of segments.

Examples of trail segments
Figure 1  Examples of Trail Segments

Selector Dots

Each trail segment on the map is shown with a red dot approximately in the middle of the segment. This red dot it is the "selector dot". Figure 2 shows an example of a selector dot.

Example of a selector dot
Figure 2  Example of a selector dot

The selector dot is what you click on to add a segment to the selected track. When you hover over the selector dot it displays a tool tip with the name of the trail that the segment is a part of.

Selector dots are only shown on the map at zoom levels 13 and greater. At zoom levels less than this there is not enough detail in some areas of the map to make them useable.

Selector dots will either be enabled or disabled to indicate whether or not they are a valid choice for the current track. GPS Tracker will only let you choose segments that are contiguous with the current track. In other words it will not let you choose a track with "gaps" in it. When the map first comes up and no segments have been chosen, all the selector dots are enabled, indicating that all the segments are legal choices as the first segment. Once the first segment has been chosen, only those segments which are directly connected to the last selected segments are legal choices and the selector dots for all other segments are disabled.
The "You Are Here" Arrow

GPS Tracker will display a small arrow with the words "You Are Here" to indicate your current position on the map when you're building a track. The "You Are Here" arrow is shown in figure 1.

The "You Are Here" arrow is always shown at the end of the selected track in the direction of travel. It's not shown until you've selected at least two segments though. This is because you have to select at least two segments in order to establish a direction of travel. When you choose the first segment of a track, GPS Tracker cannot determine which direction you intend to travel on that segment. Therefore it makes all the segments that attach to either end of the segment legal choices. It's not until you choose a segment at one end or the other that the program can establish a direction of travel.
The Buttons

The buttons on the main page are used with the selected track. Note that the buttons are grayed out until you begin building a track, then they are all enabled. If you clear all the segments out of the selected track the buttons will be disabled again. The following buttons area available:
The Route Statistics

The distance and elevation statistics appear at the bottom of the main page. These are updated dynamically and always represent the state of the currently selected track. The following statistics are displayed:
The Predefined Track List

The drop down list at the bottom of the page contains a list of predefined tracks. These are tracks for which the segment list has been specified in advance. If you choose one of these tracks from the list and hit the "GO" button the page will reload and display the specifed track as if you had manually choosen the segemnts that make it up.