Kamis, 05 Juni 2008

Google Maps

Google Maps (for a time named Google Local) is a free web mapping service application and technology provided by Google that powers many map-based services including the Google Maps website, Google Ride Finder and embedded maps on third-party websites via the Google Maps API. It offers street maps, a route planner, and an urban business locator for numerous countries around the world.

A related product is Google Earth, a standalone program for Microsoft Windows, Mac OS X, and Linux which offers more globe-viewing features.

Google Maps features a map that users can pan (by dragging the mouse) and zoom (by using the mouse wheel). Users may enter an address, intersection or general area to quickly find it on the map.

Users can also search for businesses and attractions (for example, theatres, restaurants and hotels) in or near a given place. For example, a user can enter a query such as "Waffles in Ottawa" to find restaurants serving waffles in the city.
Like many other map services, Google Maps can generate driving directions between any pair of locations in the United States and Canada, as well as many other countries. It shows turn-by-turn instructions, an estimate of the trip time, and the distance between the two locations. Since July 2007, a user can drag any point on the route to another location to add a waypoint, and instantly see the revised route and length while dragging.

Starting November 21, 2007, users with a Google account can adjust the location of markers for businesses and other destinations. According to a video posted on "YouTube" "Sometimes a location can be a little off on a map and your friends can't find you. Now you can fix that." If a user moves the marker by more than 200 meters, the change must go through moderation before it appears online.

Google Maps offers five viewing modes by default: Map (topographic and street map), Satellite (satellite and high-resolution aerial photographs), "Terrain" (geographic features in high relief with street overlay), Street View (ground level 360 degree view of certain streets, introduced on May 30, 2007), and Traffic' (traffic congestion maps).

The "link to this page" link on each Google Maps map targets a URL which can be used to find the location on the map at a later time. The latitude and longitude can be used as input to NASA World Wind or TerraServer-USA, which in some cases have higher-resolution imagery.

Satellite view
Google Maps provides high-resolution satellite images for most urban areas in Canada and the United States (including Hawaii, Alaska, Puerto Rico, and the U.S. Virgin Islands) as well as parts of New Zealand, Australia, Egypt, France, Germany, Hong Kong, Hungary, Iran, Iceland, Italy, Ireland, Iraq, Japan, Taiwan, the Bahamas, Bermuda, Kuwait, Mexico, the Netherlands, the United Kingdom, and many other countries. Google Maps also covers many cities including Moscow, Istanbul, and most of India.

Various governments have complained about the potential for terrorists to use the satellite images in planning attacks[1]. Google has blurred some areas for security (mostly in the United States),[citation needed] including the U.S. Naval Observatory area (where the official residence of the Vice President is located), and until recently,[citation needed] the United States Capitol and the White House (which formerly featured erased housetop). Other well-known government installations are visible including Area 51 in the Nevada desert.

With the introduction of an easily pannable and searchable mapping and satellite imagery tool, Google's mapping engine prompted a surge of interest in satellite imagery. Sites were established which feature satellite images of interesting natural and man-made landmarks, including such novelties as "large type" writing visible in the imagery, as well as famous stadia and unique earth formations.

Although Google uses the word "satellite", some of the high-resolution imagery is aerial photography taken from airplanes rather than from satellites.

Like many other Google web applications, Google Maps uses JavaScript extensively. As the user drags the map, the grid squares are downloaded from the server and inserted into the page. When a user searches for a business, the results are downloaded in the background for insertion into the side panel and map - the page is not reloaded. Locations are drawn dynamically by positioning a red pin (composed of several partially-transparent PNGs) on top of the map images.

The technique of providing greater user-interactivity by performing asynchronous network requests with Javascript and XMLHttpRequest has recently become known as Ajax. Maps actually uses XmlHttpRequest sparingly, preferring a hidden IFrame with form submission because it preserves browser history. It also uses JSON for data transfer rather than XML, for performance reasons. These techniques both fall under the broad Ajax umbrella.

The GIS (Geographic Information System) data used in Google Maps are provided by Tele Atlas, NAVTEQ, and MAPIT MSC, Malaysia,[3] while the small patches of high-resolution satellite imagery are largely provided by DigitalGlobe and its QuickBird satellite, with some imagery also from government sources. The main global imagery base called NaturalVue was derived from Landsat 7 imagery by MDA Federal (formerly Earth Satellite Corporation). This global image base provides the essential foundation for the entire application.

Google Maps for Mobile
In late 2006, Google introduced a Java application called Google Maps for Mobile, which is intended to run on any Java based phone or mobile device. Most, if not all, web based features are available from within the application. On November 28th, 2007, Google Maps for Mobile 2.0 was released. It introduced a GPS-like location service that does not require a GPS receiver. As of April 20, 2008, this service is available for the following platforms:
• Windows Mobile
• Nokia/Symbian (S60 3rd edition only)
• Symbian OS (UIQ v3)
• BlackBerry
• Phones with Java-Platform (MIDP 2.0 and up), for example the Sony Ericsson K800i

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