How Google maps are located

Google mobile map is currently testing this new technology service-mylocation, which will allow mobile phone users without GPS receivers to still use its mobile phone map service to find their location, and navigate. So how is the positioning function of Google Maps implemented? How does it determine the user's location?

The mylocation service of Goole maps determines the relative location of the mobile phone based on the base station of the mobile communication network. This technology is called the CPS Technology in the industry. CPS is a fixed-Position System Technology complementary to GPs. It features a global mobile network communication system (GSM network) that uses the 10-point differential positioning technology, the mobile phone base station's multi-point reception is used for line locating and point calibration. It is not affected by any obstruction. As long as it can be accurately located within the range of mobile coverage, global positioning can be achieved without increasing the user's fees.

The wireless positioning technology is used to measure the parameters of the received radio waves and determine the location of the objects to be tested based on specific algorithms, the measurement parameters include transmission time, amplitude, phase, and angle of arrival. The positioning accuracy depends on the measurement method. The Positioning Technology in cellular mobile communication systems mainly includes the network-based and terminal-based positioning technologies. Among them, terminal-based positioning technology includes GPS, secondary GPS and enhanced observation time difference E-OTD (enhanced observed time difference) and other methods.

The method of mylocation should belong to the E-OTD Positioning Method theoretically -- the time difference between the Mobile Phone Based on the measurement data of the base station and several base stations around the service area, the time difference is used to calculate the location of the user relative to the base station. Google maps also uses a hybrid positioning technology that integrates two or more methods of the aforementioned positioning technology.

Game of speed and accuracy

Can I use a base station to determine the location, which is more accurate than GPS? This is the first question raised by many users. The answer to this question is hidden in the use of software. Users download the latest 2.0 beta version of Google Maps mobile from the Google map website to their mobile phones, you can use the mylocation service by sending the SMS "bluedot" to 33669. During use, you only need to press the "0" key on your mobile phone, and your location will be displayed as a blue point icon or a light blue area icon on Google's mobile map. If the mobile phone has a GPS Positioning System, the mylocation will automatically be consistent with the GPS Positioning System, and the location of the user's location will be exactly indicated by the blue dot icon. Without GPS,
My locaiton will display an approximate area range with the light blue area icon.

The light blue area and Blue Point show the difference in the precision between mylocation and GPS. Although the precision of mylocation is not as good as that of GPS, according to Google's analysis, the distance between my location and the range is within 1 km. This precision is more than enough for vehicle anti-theft positioning. In addition, my location was originally designed to make up for some deficiencies in GPS positioning. For example, if the GPS precision is high and the processing capability of mobile phones is poor, the Data Reading speed may be slow. Many car owners have encountered that when the GPS navigation system provides the correct guidance route, the car has already passed the correct intersection. The new positioning and tracking function brings many improvements to the user's speed and reduces the computing speed and consumes energy.
Lower. Steve, product manager of the Google mobile map service department, said the new tracking system would not collect users' mobile phone numbers and other information that could leak users' personal identities. You can click a link in the Help menu to disable this function. In addition, even if there is shelter in the room, mylocation is still valid.

The mylocation database is still under construction, so it takes some time to complete this service. Its database covers more than 20 countries, including the United States and most countries in Europe, Australia, New Zealand and Russia. China and Japan are the targets of its next plan.

Familiar Google Earth

Google mobile map's product manager Steve Lee said that Google's system would not collect users' phone numbers or other personal information, so users do not have to worry about infringement of their privacy. You can also disable this function.

Industry insiders who have used the software said they believe that ordinary users will welcome this feature. It is very useful, although it is only an improvement compared with the past positioning.

According to reports, unlike global satellite positioning, Google can only be used at home. In addition, the consumption of mobile phone battery by software is much smaller than that of GPS receiving chip. No, Google's software also has a defect, that is, the positioning is not very accurate. Google said that in many cases, the software positioning accuracy is within 400 to 1200, basically reaching the "Residential" level.

According to Steve Lee, the database of a certain Google system is under construction, and mobile phone users may not be able to locate it in some locations. Google's database covers more than 20 countries, including the United States, most European countries, Australia, New Zealand, and Russia. There is no data in China and Japan.

Although GPS chips are becoming increasingly popular on mobile phones, Google estimates that 85% of mobile phones around the world do not have GPS chips, making it impossible to use this satellite-based positioning service.

Google's software supports most smartphones, including Blackberry phones and the latest Nokia phones. However, the software cannot be used on Apple's iPhone, Motorola Q, Samsung Black Jack, and other mobile phones.

Google Stephen Lee said that after knowing the specific location of a user, Google will be able to display more targeted ads to help nearby sellers attract more customers. However, he said that Google will not immediately display ads on the map of its mobile phone and will do so in the future.

How does Google achieve this step? It may be like this: In versions 3.0 and earlier, some users' mobile phones are built in GPS. After positioning, while downloading Google map data through wireless networks, it also reports the CGI (globally unique) of the current mobile phone service zone ). After obtaining a large amount of such data, Google uses a certain algorithm (for example, drawing a circle on the map based on the data to calculate the center) to determine the approximate service area of each CGI. Therefore, when GPS is not used, Google software on the mobile phone can be positioned based on CGI.
After a period of use in this city, the previous judgment can be roughly verified.
1. the positioning accuracy of urban areas is high, which is about 300 meters. The accuracy of suburban areas ranges from 1 to 3 kilometers. It is basically equivalent to the base station (launch station) density of the local carrier.
2. The current location displayed on the map is basically near the base station (launch station.
Powerful Google!
Previously, various operators have done similar crude positioning applications. None of them can achieve Google's accuracy and be accepted by users. However, Google's algorithm does not require operators to provide GPS data for base stations (transmitting stations) so precisely.
It is said that Google is terrible because if the judgment basis is true, Google collects data on its own without the user's permission. There is a "Favorite Place" in the Google map layer, which shows the places people often go to. God knows how Google collects these things! Who knows, when we query the map data, do we also report our call records and text messages to Google?