http://www.gpsinformation.net/waas/vista-waas.html Observations:GPS accuracy is generally better at night when the ionospheric errors are less. WAAS ionospheric corrections are therefore less apparent at night. The reference-point accuracy is confirmed with the average night error of 0.8m. 剛好發現美國實驗夜間進行GPS定位精度實驗, 發現夜間Ionosphere誤差降到最低, 這也符合我對無線電研究的心得與理論, 不妨多利用精確基點核對看看是否符合這個觀察心得.