Aerial Maps

The U. S. Department of Defense devised the idea of GPS in the 1970s to accurately establish the location of ballistic missile submarines before launching missiles. All the older techniques were flawed and affected by limits in range, atmospheric conditions, subject to adversary jamming, and greatly degraded by interference.

The Global Positioning System (GPS) is a remote sensor navigation system based on a network of 24 to 32 satellites above the earth and five ground stations which are responsible for the precise orbit of all of the satellites. The satellites continuously transmit signal information to earth from their orbit at an altitude of 10,900 miles, which circles the entire world, 24 hours a day, 7 days a week. Each satellite orbits the earth in slightly less than 12 hours. There are no setup charges or subscription fees to use GPS. Each of the GPS satellites transmits a unique signal. GPS receivers acquire the streamed data from the closest satellites and then match the signals to each satellite and its orbital position. The distance from the unit is then calculated from each satellite and from this the GPS device can accurately determine its geographic location.

A GPS receiver needs to be able to lock on to the signal of at least three satellites to work out latitude and longitude and track movement. With four or more satellites the receiver can establish the device's latitude, longitude and altitude. Once this has been determined, the GPS receiver can calculate speed, trip distance, bearing, and other such information. Most handheld GPS units contain base GPS maps but the units can be hooked up to a computer to download more specific outdoor GPS maps. In order to be able to lock onto four signals, a GPS device must have at least four channels, although most modern units have 12 channels. There are always at least 5 satellites "visible" at any one position of the earth at a time. GPS is not weather dependant; it can be used in any type of weather. It can also be used on land, in the air and for nautical applications. Some conditions can slightly limit its use, such as heavy foliage, steep mountains or tall buildings.

GPS can be used for military and surveying use, as well as air, land and sea navigation, but also pet and vehicle tracking.

GPS maps provide map images, route data, point-of-interest coordinates, and track data for GPS devices. GPS map software is generally written for computers, PDAs, and specific brands of GPS units such as Bushnell and Magellan. Many GPS maps are able to upload tracks, waypoints, and routes to GPS units.

Magellan GPS handheld units utilize detailed topographic maps, marine cartography and street maps. Some Magellan GPS units can utilize National Geographic software as well. Bushnell GPS units also use topographic maps, marine maps and street maps.  This is a great way to enjoy the world's best-kept secrets while you safely explore back-roads and scenic routes. Both companies have teams of cartographers who develop digital geographic data for use with their products to supplement their GPS units mapping detail to improve navigation.

You can view and manage all your Magellan GPS and Bushnell GPS maps directly on your computer. You can then plan trips, build routes, create custom directions, mark waypoints and find geo-caches. You can also add pictures and journal notes or import geo-caches from your bookmarked or favorite web sites complete with images, hints and logs. You can transfer seamless GPS data from the software on your computer to your compatible Magellan GPS or Bushnell GPS unit.  Accuterra provides GPS maps that cover metro areas, roads, city streets and recreational points of interest, as well as lakes, fishing spots, and topographic maps. 

Aerial photography involves taking photographs of the land from an elevated location. Platforms for aerial photography consist of helicopters, balloons, blimps, fixed-wing aircraft, kites, and parachutes. Aerial photography is used in cartography in order to create aerial maps, land-use planning, movie production, surveillance, environmental studies, artistic projects and even for property analysis. Aerial photography is often incorporated into GIS systems.

Aerial photography presents issues not involved in non-aerial photography such as the need to correct perspective. Aerial photographs are generally taken at an angle which means the perspective of the photograph will be inaccurate. Most GIS's can correct this distortion and thus aerial photographs are an excellent data source for aerial photo maps.

Maps created from Aerial photographs are either photographic-image orthophoto base maps or line-drawn cartographic base maps. Orthophoto base maps are created from corrected aerial photographs and scaled. The advantage of using aerial view maps is that they illustrate actual ground features, such as natural features in addition to other mapped features. Cartographic base maps are line-drawn and show political boundaries, rivers, streams, railroads and other features. The advantage of these types of aerial view map is that they offer a simplified format to clearly show items of interest. Topographic maps are either Orthophoto or Cartographic maps created from Aerial photography which also contain contour lines to show changes in elevation of the ground surface.  Accuterra specializes in providing state-of-the-art aerial maps for your portable Magellan and Bushnell GPS Devices.