In about three years the sat nav technology has gone through a drastic advancement so as the survey team, currently using the latest techno survey cars. Initially they used only a laptop computer and a small display screen as the main equipment for survey but now the whole setup has changed, the entire car is packed with technology with hardly enough room to get in.
The Survey Car
The exterior appearance of the car look quiet regular to other cars, holding a luggage box on the top. However once the lid of the car is removed, you can see an industrial GPS antenna and a perspex dome hiding in which when driving around the town, gains attention of the people. The dome contains an array of about 6 cameras that are video cameras which constantly capture images while the car is in motion. Out of 6 cameras, three are placed to the front, one on each side and one covering the right shoulder view. Altogether as the car is traveling, the video camera’s are positioned to cover all road, side roads and footpath.
The data put down from the camera is then integrated with the GPS signal while each frame of the video is Geo referenced. In case there is a mismatch among map data, the image is reference in order to obtain precise information. GPS is the main instrument for the survey which need to have great industrial strength since it is a crucial system. The antenna works fine for ground but in case of tunnel mapping, Gyros and motion sensors are used as back up by the GPS.
Moving inside the survey car, you can find a single laptop replaced by latest technological equipments with amazing storage capabilities. To run the equipment stable, the car equips its own battery and power inverter. Placed on the shelf is the disk array that holds about four 750GB hard drives. The surveying data for each may may not exceed 700Gb hence without downloading to the office, the car will be able to survey for about the whole week with the 750GB drive in PC.
The car has got all necessary equipments, a network and docking station for a laptop, a wireless connection between keyboard and mouse and a microphone which is suspended from the roof to allow the surveying person to report what he is seeing. A simple keyboard, touch screen display and trackball controls all these equipments.
The Survey Car On The Road
As the car moves around the road, the video cameras starts capturing the features of the route while the analyst starts dropping icon, describing the POIs for GPS track is recording all these information. At office, the datas are downloaded and processed.
Processing Data In The Office
The video image and voice file is reference geographically with the GPS position. These info when loaded into the system provides number of POI on the map which could be later used to determine the current database. A database is determined as the end result of the information which helps to generate maps that are been currently used in daily life in sat nav device.
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One Response to “How sat nav maps are made?”[...] GPS satellites revolve around earth in a very accurate orbit two times a day, transmitting information via signals to the earth. The GPS receivers on the earth fetches the signals to triangulate user’s exact position. Basically, the GPS receiver analysis the time a signal was sent to the satellite with the time it received the signal. The difference in time indicate the distance of the satellite. Along with the distance measurement from other satellites, the receiver exactly determines the user’s location and displays it on the electronic map of the unit. [...]