最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
HTML5 Geolocation is used to locate the location of the user. HTML5 Geolocation API is used to obtain the user’s geographic location. In view of the fact that this feature may infringe upon the user’s privacy, the user location information is not available unless the user agrees. Internet Explorer 9, Firefox, Chrome, Safari and Opera support Geolocation . Note: Geolocation is more accurate for devices with GPS, such as iPhone. Please use the The following example is a simple geolocation example that returns the longitude and latitude of a user’s location: Instance resolution: Detect whether geolocation is supported If supported, run If The above example is a very basic geolocation script with no error handling. Error code: Permission denied-users do not allow geolocation Position unavailable-unable to get the current location Timeout-Operation timed out To display the results in a map, you need to access mapping services that use latitude and longitude, such as Google Maps or Baidu Maps: In the above example, we use the returned latitude and longitude data to display the location in Google Maps (using a still image). This page demonstrates how to display the location of a user on a map. However, geolocation is also useful for information about a given location. Can be used to: Update local information Show the points of interest around the user Interactive vehicle Navigation system (GPS) If T is successful, then Attribute Description coords.latitude Latitude of decimal number coords.longitude Longitude of decimal number coords.accuracy Position accuracy coords.altitude Above sea level in meters coords.altitudeAccuracy Altitude accuracy of position coords.heading Direction, measured in degrees from due north coords.speed Speed, in meters per second Timestamp Date / time of response The following example shows 11.37.1. Locate the location of the user ¶
11.37.2. Browser support ¶
11.37.3. HTML5-use geolocation ¶
getCurrentPosition() method to get the location of the user.Example ¶
varx=document.getElementById("demo");functiongetLocation() {if(navigator.geolocation){navigator.geolocation.getCurrentPosition (showPosition);}else{x.innerHTML="This browser does not support obtaining geographic locations.";}} functionshowPosition(position){x.innerHTML="latitude:"+position.coords. latitude+"
longitude:"+position.coords.longitude;} getCurrentPosition() method. If not, a message is displayed to the user. getCurrentPosition() if it runs successfully, it returns a coordinates object showPosition() function to obtain and display longitude and latitude 11.37.4. Handle errors and rejections ¶
getCurrentPosition() the second parameter of the method is used to handle errors. It specifies the function to run when it fails to get the user’s location:Example ¶
functionshowError(error){switch(error.code) {caseerror.PERMISSION_DENIED:x.innerHTML= "The user refused the request to obtain the geographic location."break;caseerror.POSITION_UNAVAILABLE: x.innerHTML="Location information is not available."break;caseerror.TIMEOUT:x.innerHTML=" Request for user geographic location timeout."break;caseerror.UNKNOWN_ERROR:x.innerHTML="Unknown error."break;}}
11.37.5. Display the results in the map ¶
Example ¶
functionshowPosition(position){varlatlon=position.coords.latitude+", "+position.coords.longitude;varimg_url="http://maps.googleapis.com/maps/api/staticmap?center="+latlon+"&zoom=14&size=400x300&sensor=false";document.getElementById("mapholder").innerHTML="";}
11.37.6. Information for a given location ¶
11.37.7.
getCurrentPosition() method-return data ¶ getCurrentPosition() method returns the object. Will always return latitude 、 longitude and accuracy Property. If available, other properties below are returned. 11.37.8. Geolocation object-other interesting methods ¶
watchPosition() -returns the user’s current location and continues to return to the updated location when the user moves (just like the GPS on the car). clearWatch() -stop watchPosition() method watchPosition() Method. You need a precise GPS device to test this example (such as iPhone):Example ¶
varx=document.getElementById("demo");functiongetLocation() {if(navigator.geolocation){navigator.geolocation.watchPosition (showPosition);}else{x.innerHTML="This browser does not support obtaining geographic locations.";}} functionshowPosition(position){x.innerHTML="latitude:"+position.coords.latitude+" <br>longitude:"+position.coords.longitude;}