“精确”is always used to describe a measure instrument to express the measurement of the instrument is very accurate, like 精确的测量，精确（精密is better here）的仪器。 So it means very “准确”: ). It can be used the places where things should be very accurate. Like 精确的射击,精确地瞄准，精确的数据，and so on. "准确”alway means correct but more than correct("正确”). It may mean very correct.:) We can both say 准确的数据 and 正确的数据，but they may be used in defferent places. (正确的数据 emphasizes the data not wrong but correct; 准确的数据 emphasizes the data is accurate; 精确的数据emphasizes the data extremely accurate.) All in all, I think the defference among them is how accurate it means. It looks like 精确>准确>正确。 Hope this helps.:)

精确-accurate 准确-correct

精确的：means "precise" "rigorous" 准确的：means "just right" or "correct" Resembling a photograph, especially representing or simulating something with great accuracy and fidelity of detail. 像照片的和照片相像的，尤指细节准确、高度精确的与某物相似 A point on a map marking a precise location or target. 精确位置地图上的点，作为精确位置或定点目标 He warned us against pressuring upon the accuracy of all the definitions in dictionaries. 他警告我们不要认为词典里的一切释义都是准确可靠的。

same meaning, "correct"... but "精确" is much more heavily than "准确" for example, when someone ask you how to go somewhere, you just need to give him a "correct direction" "正确方向" when you doing a experimentin in a lab, you should write down the "correct data" "精确数据"

这两者在程度上有区别，精确在准确的基础上更上一个层次，强调很高的正确率