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authorSanjeev Gupta <ghane0@gmail.com>2013-11-25 16:20:42 +0800
committerEric S. Raymond <esr@thyrsus.com>2013-11-25 04:22:17 -0500
commitcb2fd70d2e0c14d53d0585e3145ee08be8aa6322 (patch)
tree5da70d30236d042b540613f9a0ba73b24639b4ef /www
parent2c9477d6677f5a4840c6d9a6f9fc2685921544db (diff)
downloadgpsd-cb2fd70d2e0c14d53d0585e3145ee08be8aa6322.tar.gz
Correct Almanac / Ephermis confusion
Signed-off-by: Eric S. Raymond <esr@thyrsus.com>
Diffstat (limited to 'www')
-rw-r--r--www/faq.html.in10
1 files changed, 5 insertions, 5 deletions
diff --git a/www/faq.html.in b/www/faq.html.in
index 215ce1ca..89f6a62b 100644
--- a/www/faq.html.in
+++ b/www/faq.html.in
@@ -531,14 +531,14 @@ second.</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
+to get a new satellite <i>almanac</i> 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
+almanac.) 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>
@@ -547,14 +547,14 @@ your skyview is poor. Especially if you're indoors.</p>
<p>Your GPS may have dropped its leap-second offset. You can tell you
have this problem if your sentence timestamps look wrong at startup.
-Wait 20 minutes or so; the lag should go away.</p>
+Wait 20 minutes or so; the lag should go away, as the almanac is updated.</p>
<p>GPS satellites broadcast time using a clock without a leap-second
correction. They broadcast a leap-second correction once each complete
-reporting cycle along with the satellite ephemerides; it's up to the
+reporting cycle along with the satellite almanac; it's up to the
GPS firmware to add that correction to the time it puts in reports.
If your GPS has forgotten the current correction, you'll have to wait
-until the next ephemerides message for it.</p>
+until the next almanac message for it.</p>
<p>GPSes are supposed to retain the leap-second correction along with
the last fix in NVRAM when they power down, but we've observed that