電話記錄 GPS 距離是否一定準過 GPS 手錶呢?

wai896

電話有AGPS幫助下是否一定會準確點呢?

因已試多次電話同好多隻手錶比較,電話距離都會比手錶多.....

bunbun

參考一下, 呢d數據:
https://www.longrun.hk/thread-21947-1-2.html

大文DaiMan

我發覺手錶也不準，我隻係Polar，個人經驗它約略比大會少250m左右，最諷刺就用它去度Polar20K萬宜跑居然最唔準，衝線果陣係20.4km. 自己度自己都唔準

awolswat

其實真的不要太在意GPS準確度,
港大廈太密集, 什麼靈敏度最高的GPS Device 都有誤差!
我個人覺得只作參考之用.

keithchan

經常有跑友討論及比較不同GPS錶的準確性，但都忽略最重的一點，就是GPS是如何度出距離，明白這一點，相信亦會明白點解就算相同手錶，會度出不同距離。

”現時一般GPS跑步手錶（即一般休閒用途），都是建基於WAAS (Wide Area Augmentation System) 標準，即在95%使用時間有3米誤差，一般為3至5米。在其餘5%時間，誤差可能在10米以上。要決定位置，GPS系統需要從最少3個人造衛星（4個更佳）取得訊號，再計算位置，通常每5秒取點一次。當我們跑步時，要計算的點並不是成一直線，而是在95%時間在我們3至5米內（在另外5%時間，該點可能在10米以外）， 再連接在一起計算。除此之外， GPS手錶的準確性亦會受天氣、是否有障礙物及是否有干擾等因素影響。”　取自：http://www.facebook.com/soleusrunninghk/posts/194066310803097

又有關比賽賽道量度方法及與GPS量度之分別, 可參考以下文章 (英文):
http://www.riverregionrunners.org/html/gps_accuracy_article.html

wai896

bunbun 發表於 2014-2-11 10:02
參考一下, 呢d數據:
https://www.longrun.hk/thread-21947-1-2.html

我有入去睇架...............

wai896

keithchan 發表於 2014-2-11 12:32
經常有跑友討論及比較不同GPS錶的準確性，但都忽略最重的一點，就是GPS是如何度出距離，明白這一點，相信亦 ...

依個網都知都有睇,只係奇怪無論用乜錶乜手機同一段路試幾多次都好難每次一樣,咁即係真係得個睇字

water

自己跑同一段路都會因為內外線每次都唔同啦。另AGPS只會加速fix時間，對準確度冇幫助的。

keithchan

我意思喺其實唔駛太在意絕對距離，GPS錶只喺一種輔助工具．就算喺經專業量度嘅比賽路線，你比賽時都唔會跑倒實際量度嘅距離，況且按國際標準，每公里都要比實際長度多出１米．

divejy

同一隻表或同一部電話，同一段距離，我相信每次的數據都有機會唔同！

~Ben.W~

我試過用電話同garmin f220跑， 總距離都有出入。

wai896

唔該各位師兄,我只係想知點解今時今日既科技都攪唔掂個距離問題.............

keithchan

唔喺冇方法，但要應用到消費電子產品就冇乜可能．

Tiny discrepancies between the GPS receiver's onboard clock and GPS time, which synchronizes the whole global positioning system, mean distances calculated can drift. There are two solutions to this problem. The first would be to use an atomic clock in each receiver costing $100,000. The second is to use some clever mathematical trickery to account for the time-keeping error based on how the signals from three or more satellite signals are detected by the receiver, which essentially allows the receiver to reset its clock.

There is also an intrinsic error source in GPS associated with the way the system works. GPS receivers analyze three signals from satellites in the system and work out how long it has taken each signal to reach them. This allows them to carry out a trilateration calculation to pinpoint the exact location of the receiver. The signals are transmitted by the satellites at a specific rate.　Unfortunately, the electronic detector in standard GPS devices is accurate to just 1 percent of a bit time. This is approximately 10 billionths of a second (10 nanoseconds). Given that the GPS microwave signals travel at the speed of light, this equates to an error of about 3 meters. So standard GPS cannot determine position to greater than 3-metre accuracy. More sophisticated GPS receivers used by the military are ten times more accurate to 300 millimeters.

來自：
http://www.mio.com/technology-gps-accuracy.htm

monkey_lulu

民用嘅衛星定位係咁上下㗎喇。