Q9h GPS not "true" GPS !!!!

Discussion in 'Moto Q 9h' started by mexiken, Jan 19, 2008.

  1. newtq

    newtq New Member

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    Doofer, how did you get the phone paired with the gps unit. Where in the 'Bluetooth Manager' screen do you add a gps receiver???

    Newtq
  2. zenkinz

    zenkinz New Member

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    there's no GPS receiver service in the bluetooth manager. All you need to do is to first pair the receiver with your Q9h, and then in your GPS software, use com port 1 to connect to your receiver.
  3. zenkinz

    zenkinz New Member

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    did you have your Q9h USB connection set as Activesync Serial or Mass storage? If you have it as former, it'll use com 1, which means the bluetooth com port will be invalid.
  4. zenkinz

    zenkinz New Member

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    The recent introduction of assisted GPS (or AGPS) technology a few years back, has indeed confused alot of people, thinking that it's the LBS (location-based service) . The fact is AGPS is essentially still a GPS solution, with added technology to speed up the location acquisition fix process (commonly known as Time to First Fix, or TTFF), which has always been the most time consuming process of GPS.

    Despite the recent introduction of sensitive GPS chipset such as SIRFIII, it doesn't improve the inherent TTFF challenge if you know how a fix acquisition happens. In order for a GPS receiver to triangulate one's position, it first must obtain a couple of data/information from the satellites, which broadcast this information for the receiver to download them. The first is almanac, which essentially documents all the available satellites and their basic information. Almanac usually are valid for a few months, so once you have your GPS receiver has received it, you will be spared from the time consuming process (of downloading the almanac), which can be more than 10 mins. The other data the receiver needs to download, is the ephemeris data, which is a more precise orbital path of the satellite, and the data usually last no more than 4 hours. Ephemeris data are broadcasted by the Satellite every 30 sec, over the duration of 30 sec. Not only the receiver needs a minimal signal strength to receive the data, the download process also must not be interrupted, otherwise the whole download must be repeated again. That's why it is always recommended that you should stay stationary (obviously only if the receiver is facing the open sky) during the TTFF process. When you have not used your receiver for more than 4 hours, this whole ephemeris data download process needs to happen, and that explains why the TTFF for cold start vs hot start is so different.

    The assisted GPS technology, attempts to improve TTFF. It attempts to address two weak points. Firstly, the ephemeris data that's received from the satellite is only valid for 4 hours. The technology involves in projecting the orbital path of the satellite that could be valid for a few days, up to a maximum of 10 days. While the length of the validity usually implies a lesser accurate path, the technology is actually maturing and a 5-7 days of projected path is actually quite accurate. The time consuming part of the problem, is addressed by making the data available through internet. That's why some people confuse the download of such data as data from cell station.

    This technology is available mostly in mobile devices, mainly because of the lack of GPS antenna, plus download of the ephemeris data is convenient in a mobile device. It was meant as a supplement, rather than a substitute, to the GPS chipset. A GPS chipset is still required, as long as you need a constant (every millisecond) tracking of one's precise (in terms of metres) position. There's no way you can achieve this just by cell station.

    I hope this clears up the misconception of AGPS, and dismiss the myth that a AGPS is not a real GPS.
  5. PacoJr67

    PacoJr67 Active Member

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    Thank you for this accurate description of GPS vs. aGPS.

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