Guangdong along China，s southwestern coastline via theIndo-China peninsula. The routes extended westward tothe Indian Ocean through the Malacca Strait and furtherto the Arabian Sea and Arabian Peninsula via the IndianPeninsula， and finally ended in the 10-plus routes alongthe coast of East Africa. Geographically speaking， the mapcovered a total area that spans from 44 to 122 degrees eastlongitude and from 32 degrees north latitude to 8 degreessouth latitude. The water area included the West PacificOcean and the North Indian Ocean. And the land areaspread from Southeast Asia to East Africa and includesthe names of 540 places. The painting of the map wasthe result of the application of a combination of multiple
风帆航行技术，能“船行八面风”。正是由于对风帆的使用已驾轻就熟，船队才能随心所欲地纵横驰骋在浩瀚的汪洋大海上。
绘制和应用《郑和航海图》。航海图是航海活动特别是远洋航海活动最基本的也是必不可少的工具之一。《郑和航海图》是中国历史上流传至今的一部最早的远洋航海用图。它涵盖的地域广阔，航线漫长，记录的地名众多。该图运用中国传统绘画手法，写实与写意相结合，以长卷画轴的形式自右向左，形象化地展现以南京宝船厂为起点，出长江口，沿着中国东
nautical techniques like compass navigation， celestialnavigation， object navigation， terrestrial navigation andstandard navigation speed.
Celestial navigation. Zheng，s fleet ingeniously shapeda full set of celestial navigation techniques by combiningthe traditional Chinese astronomical observation and the“Stellar Technique for Ocean Navigation.” When sailingin the ocean， the fleet could be guided by observingcoastal objects， the heavenly bodies and the compass.If no objects on land were visible， observation of thesun， the stars and the compass was the basic means fornavigation. The “Stellar Technique for Ocean Navigation”served as a method to locate where the ship was inlatitude by studying the elevation of the stars in the sky.When using this technique， Zheng，s fleet observed morestars that usually involved in both south-north and east-west direction for verification. Those Chinese navigationtechniques were far more advanced than those adoptedby other countries in the world.
Terrestrial navigation. In this technique， fixed objectson land were used for reference to determine the directionand distance of the trip. It was mainly adopted in offshorevoyages. Based on nautical experience， the navigatorsreminded by surrounding objects， could have a clearpicture of the location of potential obstacles， peaks，islands， shoals， reefs， narrow watercourses， as well as the
南海岸线直达福建广东，再沿印度支那半岛向西南行，过马六甲海峡向西进入印度洋，再经印度半岛到阿拉伯海和阿拉伯半岛，直到东非沿岸的数十条航路。用今天的地理概念来说，《郑和航海图》的跨度为东经44度至东经122度，北纬32度至南纬8度。就水域来说，包括太平洋西部和印度洋北部；就陆地来说，包括亚洲东南部到非洲东部的广大地区，记录地名多达540多个。它的绘制，是罗盘导航、天文导航、物标导航、地文导航、标准航速（更数）等多种航海技术的综合运用。
天文航海术。郑和船队创造性地继承了古代中国航海观察天象的传统，配合运用“过洋牵星术”，形成了一整套天文航海术。船队在海上航行，一靠对沿岸地形地物的观察，二靠日月星辰的指引，三靠罗盘的导向。在波光接天的海洋中，周围无地物可寻时，“昼则观日，夜则观星，阴晦观指南针”就是船队导
depth of water， the symbols ofports and the correct direction.Zheng，s fleet also employedother techniques in actualvoyages like measuring thedepth of water through plumbbobs.
The nautical techniques used by Zheng，s fleet werefirst-class. They helped create the brilliance of theexpedition. Regretfully， Zheng，s voyages to the WesternOcean haven，t been appropriately studied by historians.Most works on world history don，t mention Zheng He，sseven expeditions or their geographical discoveries. Thatis quite unfair. Despite the bigger influence of the greatgeographical discoveries on world history， the nauticaltechniques Zheng，s fleet employed went far beyond thoseadopted by European navigators， so did the nauticalaccomplishments it achieved.
航的三种基本方法。郑和船队使用牵星术时，使用的星辰较多，并且常常是南北或东西两星同时并用，互相核正。这些导航技术超过了当时世界其他国家的天文导航水平。
地文航海术。地文航海术主要以陆地上固定的目标作为参照物或陆标，来确定航行的方向和距离。它属于近海航行时所使用的方法。由于航海经验的积累，船队实际航行时，对航行途中的碍航物、山峰、岛屿、浅滩、礁石、险狭水道、水深、底质、港口标志以及正确的定位与航向，均有明确的提示。郑和船队在实际航行中，还运用了其他技术，如用铅锤测量水深等。
郑和下西洋所应用的航海技术，在当时是世界一流的。它成就了世界航海探险的辉煌。然而令人遗憾的是，多少年来，在世界历史的研究中，郑和下西洋并没有得到应有的评价，许多世界通史着作的地理大发现部分没有提到中国郑和的七下西洋。这是不公正的。地理大发现虽然在世界历史上的客观影响大于郑和下西洋，然而郑和下西洋的航海水平及航海成就却远远超过了欧洲航海家。