[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[gpsd-dev] [PATCH 6/9] Correct definitions of cold start, warm start, et
From: |
Sanjeev Gupta |
Subject: |
[gpsd-dev] [PATCH 6/9] Correct definitions of cold start, warm start, etc |
Date: |
Fri, 17 Apr 2015 22:54:54 +0800 |
---
www/gps-hacking.html | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
diff --git a/www/gps-hacking.html b/www/gps-hacking.html
index bee0274..bba9b1f 100644
--- a/www/gps-hacking.html
+++ b/www/gps-hacking.html
@@ -394,7 +394,7 @@ Of course the quality of signal at your location matters as
well.</p>
<p>If a GPS has not been on for several months, then it has no current
almanac available. It was to wait to download one before it can
generate a fix. This can take just under 15 mins. This is sometimes
-called an <dfn>autonomous start</dfn>, notably in Garmin's documentation.</p>
+called an <dfn>cold start</dfn>.</p>
<p>While the almanac download takes 15 minutes, you have to be there for the
start of it, otherwise you have to wait for the next cycle. So if you are
@@ -402,12 +402,11 @@ unlucky and just miss the start of one, it could take
just under 29 minutes
to obtain, and on average closer to 22 min.</p>
<p>If a GPS has not been on for a day (four to six hours) then it has
-an almanac but no valid satellite ephemerides, and must download at
-least three before it can generate an accurate fix. This is sometimes
-called a <dfn>cold start</dfn>. Each satellite has its own ephemeris that must
-be downloaded if a current copy is not fresh. It takes about a minute
-per sat to get the ephemeris, or a minute total if your GPS has
-multiple receivers as most do now.</p>
+a valid almanac but no valid satellite ephemerides, and must download at
+least four before it can generate an accurate fix. This is sometimes
+called a <dfn>warm start</dfn>. Each satellite has its own ephemeris
+that must be downloaded if a current copy is not fresh.
+</p>
<p>GPSes store ephemerides is non-volatile memory, either internal
flash storage or battery-backed SRAM. Thus, a GPS does not need to
@@ -416,14 +415,14 @@ consider old data to be invalid after a while. In normal
operation
the GPS occasionally gets refreshes of ephemeris and almanac data
from the satellites it's listening to.</p>
-<p>For both an autonomous start and a cold start if the sat signal is
-momentarily lost, the process will have to restart and you'll get
+<p>For both an cold start and a warm start, if the sat signal is
+momentarily lost, the process may have to restart and you'll get
more delay.</p>
<p>If a GPS has been on recently, in the current location, then this
-is sometimes called <dfn>warm start</dfn> or <dfn>hot start</dfn> and
+is sometimes called <dfn>hot start</dfn> and
an accurate fix can be generated quite quickly. This will usually be
-under a minute for a modern GPS, perhaps as low as 15 seconds.</p>
+a few seconds for a modern GPS.</p>
<p>Here's <a href="http://gpsinformation.net/main/warmcold.htm">more
on this issue</a>. Details about the satellite signals and there
--
2.1.4
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, (continued)
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Gary E. Miller, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Sanjeev Gupta, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Gerry Creager - NOAA Affiliate, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Sanjeev Gupta, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Gerry Creager - NOAA Affiliate, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Sanjeev Gupta, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Gary E. Miller, 2015/04/17
- Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Eric S. Raymond, 2015/04/18
Re: [gpsd-dev] [PATCH 5/9] Define TTFF, Frank Nicholas, 2015/04/17
[gpsd-dev] [PATCH 6/9] Correct definitions of cold start, warm start, etc,
Sanjeev Gupta <=
[gpsd-dev] [PATCH 7/9] Correctly define autonomous and A-GPS mode, Sanjeev Gupta, 2015/04/17