隨著GPS定位精度越來高以及價格越來越低，因此GPS已經在民間被廣泛應用。汽車在行駛的過程會因為受到阻力而減速，因此可以透過GPS求得汽車的位置以及速度變化，之後再跟進一步求得汽車阻力參數，同時也是本研究的最主要目的。
GPS的輸出資料有虛擬距離、載波相位以及都卜勒觀測量三種。本研究對於汽車位置定位是以虛擬距離經過最小平方法(LS)處理後再透過差分法(DGPS)以及平滑化(Smoothing)來提高定位精度；都卜勒觀測量則用來測量汽車的速度，經過LS處理後便可求得汽車的速度。
經過LS處理後的GPS資料再經由座標轉換分別代入加權最小二次平方法(WLS)以及擴展式卡爾曼濾波器(EKF；Extended Kalman Filter)以估算汽車阻力參數。
本研究所採用的接收器接受頻率分別為1HZ以及10HZ，因此試驗分為1HZ試驗以及10HZ試驗。試驗進行過程中，汽車高速在筆直的道路行駛，之後再放掉油門並且排擋至空擋；汽車將會受到滾動摩擦力以及空氣阻力而減速。
從研究結果看出估算的值很接近參考值，1HZ實驗經過EKF位移與速度修正法估算的FR為0.1301，誤差為2%；CD為0.000299，誤差為0.17%，10HZ實驗經過EKF位移與速度修正法的FR為0.1238，誤差為9%；CD為0.000299，誤差為2%(將會在第4章節詳述)。結論是利用GPS估測汽車阻力參數是可行的，而且成本也比較低。

The accuracy and precision of GPS is getting higher and the prices are getting lower so GPS is being widely used in civil. Speed of vehicle will be decreased due to the resistance effect. Position and speed change of vehicle can be detected by GPS receiver in order to obtain resistance parameters of vehicle. This is the main purpose of this study.
There are three kinds of output data from GPS: Pseudo range, Carrier phase and Doppler. In this study, Pseudo range is a measurement to be used to estimate vehicle position. After processing of Least Square method to estimate vehicle position, Smoothing method and Differential GPS (DGPS) are for increasing accuracy. Doppler is a measurement for estimation speed of vehicle, after data processing of Least Square method to have speed of vehicle.
After GPS data processing of Least Square method and coordinate transformation, substituting speed and position of vehicle to Weight Least Square and Extended Kalman Filter to estimate vehicle resistance parameter.
Low frequency (1HZ) receiver and high frequency (10HZ) receiver have been used in this study. Therefore experiment is divided into 2 parts: low frequency experiment and high frequency experiment. While experiment processing, vehicle has been driven on a straight and flat road with high speed. Then accelerator is released and transmission gear is turned to neutral gear. Vehicle is deceleration due to aerodynamic drag and rolling resistance.
Comparing result of estimation with reference value, results of estimation are quite close with reference value. For 1HZ experiment, drag coefficient FR and CD after estimated by EKF are 0.1301 and 0.000299, error are 2% and 0.17%. For 10HZ experiment, drag coefficient FR and CD after estimated by EKF are 0.1238 and 0.000299, error are 9% and 2% Conclusion is estimation resistance of vehicle through GPS is feasible and low cost.
estimate vehicle resistance parameter.

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