GPS冷启动、暖启动和热启动.doc

.关于GPS冷启动、暖启动和热启动的一种解释GPS*器的启动时间是一个目前比较混乱，同时如果不具备一定的GPS知识比较难以理解的一个概念。本文借助于外文的一些解释，希望能够用比较简单的语言让GPS爱好者们加深认识。关于几个启动时间的解释也只是一家之言，大家还可以进一步探讨。GPS的启动是一个比较有趣的话题，因为通过这个话题，可以作为深入了解GPS专业知识的一个门径。Hot Start - The GPS receiver remembers its last calculated position and which satellites were in view, the almanac used, and the UTC Time. It then performs a reset and attempts to acquire satellites and calculate a new position based upon the previous information. This is the quickest re-acquisition of a GPS lock.热启动-GPS*器保存有其最后计算的可视卫星的位置、almanac(历书)和UTC时间，在重启以后，GPS*器以保存的上述内容为基础获取和计算当前卫星的最新位置。Warm Start - The GPS receiver remembers its last calculated position, almanac used, and knows the UTC Time, but not which satellites were in view. It then performs a reset and attempts to obtain the satellite signals and calculate a new position. The receiver has a general idea of which satellites to look for because it knows its last position and the almanac helps identify which satellites are visible in the sky. This takes longer than a Hot Start but not as long as a Cold Start.暖启动-GPS*器保存有最后计算的卫星的位置、历书和UTC时间，但保存的内容不是当前可视卫星的数据。GPS*器重启以后尝试去获得当前卫星和信号并计算其新位置。*器基于其最后的位置和历书得以大概知道当前天空中的可视卫星。Cold Start - The GPS receiver dumps all information and resets. It then attempts to locate satellites and then calculate a GPS lock. This takes the longest because there is no known information. The GPS receiver has to attempt to lock a satellite signal from all of the satellites, basically like polling, which takes a lot longer than knowing which satellites to look for. This re-acquisition of a GPS lock takes the longest.冷启动：GPS*器清空了所有历史信息并重启，然后它尝试定位并锁定卫星，由于没有先前信息，这将花去很长的时间。GPS*器采用类似于轮询的方法，从所有的卫星中锁定信号，这将比事前知道该搜索哪些卫星要慢不少。这一类重新获取锁定要花最长的时间。比较和小结热启动就是启动时可视的卫星信息和之前保存的信息是基本一致的。暖启动和热启动的区别在于经管也保存了之前的卫星信息，可视搜星的时候可视卫星（当前卫星）并不是以前记忆的信息的卫星，但是保存的历史信息仍然有利于快速定位当前卫星。冷启动，最好理解，就是在没有历史信息的情况下一个一个轮询的方式搜星定位，所需时间最长。关键名词解释：Almanac 和 EphemerisThe satellites broadcast two types of data, Almanac and Ephemeris. Almanac data is course orbital parameters for all SVs. Each SV broadcasts Almanac data for ALL SVs. This Almanac data is not very precise and is considered valid for up to several months. Almanac 数据是反映所有卫星状况的比较粗略的轨道参数，每一个卫星都会广播所有卫星的Almanac 数据，这类数据不是十分精确，有效期长达几个月。Ephemeris data by comparison is very precise orbital and clock correction for each SV and is necessary for precise positioning. EACH SV broadcasts ONLY its own Ephemeris data. This data is valid for a period of time (maybe several hours) as determined by information contained in the broadcast. The Ephemeris data is broadcast by each SV every 30 seconds. Ephemeris 数据相比之下是十分精确的轨道和时钟纠正信息，每一颗卫星只会广播自己的Ephemeris 数据，这类数据的有效期或许有几个小时（取决于广播信息的包含的内容）。Ephemeris 数据每隔30秒广播一次。GPS开机定位分为冷启动、温启动和热启动三种： 冷启动：以下