Map Help


Network Requirements

A high speed Internet connection is required. Dial up connections are not acceptable. Satellite dish speeds are usable, DSL speeds and above are preferable.

Browser Compatibility

(as of November, 2011)
This Map has been tested and found to work properly on the following platforms with the latest versions of these browsers:
Windows XP SP3                        MacIntosh OS X v10.6.8
Internet Explorer 8 v8.0.6001.18702
Firefox v7.0.1
Opera v11.52
Safari v5.1.1
Google Chrome v15.0.874.106 m
     Firefox v7.0.1
Opera v11.52
Safari v5.0.3
Google Chrome v15.0.874.106


These browsers are free and available for downloading via the Internet. No effort has been made to make the map compatible with older browsers.


Map Controls

The top of the map looks similar to the image below. The various controls are marked and explained below.

MapHelpTopGraphic

About the map

The map is a Google Map with additional functionality added via Google's Map API(Application Programming Interface). This allows display of Town GIS data as layers over a standard map.

The graphic above shows the controls used by the additional map functionality and are explained below.

Map Layer Controls

Initially, when the map page is loaded, only the Town Boundary layer is shown.
Click on the checkbox next to the layer name to toggle that layer on / off.

*** Important Note About Layers ***
Layers do not have a fixed order. When a layer is displayed it becomes the topmost layer. The last layer displayed is the top layer. Clickable features on a layer may not be accessible unless the layer is the top layer or unless the feature is not below another feature on a higher layer. To make a visible layer the top layer, toggle it off then back on.


Zoom Controls

MapZoomControls
Double clicking the left mouse button anywhere on the map will zoom in one level and make the map center the "left double click" location.


Marker Controls

MapMarkerControls


Path Length Control


MapPathLengthControl
The Path Length Control provides a means to display the length of the marker path and a means to clear the path, set the length to zero. If the path length is greater than 2000 feet the length is displayed in miles otherwise the length is displayed in feet.


MapZoneFinderControl

*** Important Note About Verifying Zones ***
When the marker is close to a zone boundary it's important to zoom in as far as possible to ascertain whether or not the marker is within the zone.


Notes on Accuracy

If the Earth were a perfect sphere with no surface variation the map data would be accurate but, the world would be far less interesting. The Earth is not a sphere and upon it's surface are mountains, valleys, and other irregularities that complicate distance and elevation computations. Geoscientists have developed means of minimizing these computational errors to such an extent that the map data is useful providing the user is aware of the limitations and is prudent with it's use. To these users, maps provide a helpful means of visualizing the world around us.

Users are invited to get a feel for map accuracy with simple experiments.
Distance Measurement Experiments
A feel for the accuracy of map distance measurements can be had by comparing known distances with those obtained using the map. The distance between a nearby house and barn is 60 feet, using the map distance measuring tool I get a reading of 61.4 feet, an accuracy of 2.3%. Clearly, the map should not be used for precise measurements. But suppose, for some reason, an insurance company wanted to verify that the barn was at least 55 feet from the house, in this case the map would be an acceptable measuring tool.
Accuracy of longer distances might be tested by measuring the length of a road segment using both the map and a car's trip odometer. When this is done on a nearby road segment the results are: map - 4.06 miles, trip odometer - 4.1 miles, an accuracy or inaccuracy of about 1%.
Elevation Measurement Experiment
Change the map view to "Terrain". Zoom in until the elevation contour lines are visible and magnified enough to place the crosshair of the map marker directly on one of the contour lines that has an elevation label. With the map marker so placed, the elevation shown should agree with the elevation labeled for the contour line. When the marker is placed directly on a contour line results of much less than 0.5% error are easily obtained. When the marker is placed between contour lines, as will almost always be the case, the software has to examine the map around the marker and interpolate the result. Better results will be obtained in areas where the contour lines are closer together (steep slopes) than where they are further apart (flat areas on the map).