我用的是dopodP100，内置GPS模块。在使用过程中，特别是手持徒步或geocaching中，发现GPS的刷新率很慢，通常软件中的光标并不随着我的走动而变化，很有可能我走了半天，它还是原来的位置，等1,2分钟可能跳动一格，在行动范围不大的时候特别严重，这对geocaching是很不方便的。

我之前用过一个garmin的手持机，并没有这个现象，用的都是sirf的芯片，差距咋就这么大呢？

后来看到有人说到5HZ的GPS，心想可能这就是差别吧。可后来一查garmin的刷新率，也只有1HZ。

最近偶然看到了对STATIC NAVIGATION的介绍，一下子都明白了。

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以下内容转自：http://www.doyouhike.net/forum/comm_nav/11/241862,0,0,0.html

While most settings are best left untouched unless you want to experiment (always risky !), "Static Navigation" is one that should be looked at closely especially with the arrival of the new SiRFstarIII based receivers, as these ultra-powerful receivers take GPS reception to a new level and can work with very weak signals but when that happens, accuracy can be impacted. Observations over a 24 hour period show that with good signals, 95% of the positions reported by the GPS will be within a 15 meter radius, while with weak signals, 95% of the positions will be within a radius of 50 meters.

Current road navigation software is designed for GPS receivers that only operate with good signals so accuracy will be in the 15 meter area. Such software will "snap" the position to the closest road so in a dense urban area, with degraded accuracy it's going to be easy to make the wrong decision and produce "uncosmetic" results and possibly force a trip recalculation.

Instead of redesigning navigation software to take this account (one could imagine some type of dynamic filtering based on DOP) and risk increasing the processing load on the PDA and hurt user experience, the easy fix is to implement this fix directly by having GPS manufacturers activate "Static Navigation" by default and therefore freeze the position using some complex algorithms mainly speed dependent. The problem with this is that this will considerably hurt low speed pedestrian use, with the speed staying on "0" and 50 meter jumps (update threshhold). If you want to use your GPS receiver outside your car, you'll need to disable SN,

就是说sn这个算法是适合汽车导航，如果是户外这类低速运动，是需要关闭这个功能的，不过一般的蓝牙gps没有相应的硬开关，可以使用SiRFdemo关闭，但重新开机后又会打开（据说holux的是默认关闭的，但我在厂商网站和说明书上都没看到说明），在ppc上有很多相应的软件可以关闭的，例如 MMSirfSetup。

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我用了MMSirfSetup，效果是相当的好，现在感觉GPS是跟着人走了，虽然有一点过分活跃，但总感觉比以前不动好，试着走了一个cache，觉得明显好于之前。

不过网上有很多人用了MMSirfSetup后，把机器弄坏了的，我也曾发现一次死机，所以请大家谨慎操作。