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diff --git a/www/faq.html b/www/faq.html index 0c53a5af..b3a7defd 100644 --- a/www/faq.html +++ b/www/faq.html @@ -311,6 +311,26 @@ product=0×7523</code>. Do not copy those hex numbers slavishly, they are examples. To get the right numbers, you will need to dig up the vendor and product ID of your USB-serial converter device.</p> +<h1 id="startup">Why does getting a fix take so long after powerup?</h1> + +<p>The GPSD daemon takes between 0.1 and 0.6 seconds to handshake with +your hardware. After that, if the GPS is reporting fixes, you will +get them instantly.</p> + +<p>If you are starting a GPS for the first time, or after it has been +powered off for more than two weeks, this is a 'cold start'; it needs +to get a new satellite ephemeris to do its job. The satellites +broadcast this information very slowly (at 50bps) on a fixed schedule, +and it can take up to 20 minutes.</p> + +<p>Warm start on a modern GPS with a good skyview (4 or more sats +visible) normally takes about 30 seconds. (Vendor spec sheets fib by +quoting this time only, leaving out the cold-start lag to fetch +ephemeris.) If it's taking longer, the first thing to suspect is that +your skyview is poor. Especially if you're indoors.</p> + +<p>The best advice is: go outside and be patient for a few minutes.</p> + <h1 id="timelag">Why does GPS time lag wall time by 11-15 seconds?</h1> <p>Your GPS may have dropped its leap-second offset. You can tell you |