Noticed a funny scenario today. All afternoon I had 7-8 satellites locked (On my GT31) then at 5.00pm DST (Sydney time) things started to go bad, by 5.15pm I was down to only 5 and it stayed that way for the next 30 minutes before improving again. It didn't bother me as 5 is still enough to produce doppler speeds. Unfortunately a friend was 50 minutes into an hour attempt when his GW60 dropped to 4 satellites, thus producing invalid doppler data.
I looked at a few other tracks from KA72 and saw a similar thing.
Did anybody else notice this?

Is there a way to look at how many satellites should have been in view at that time?

There's a locosys survey out looks like they are planning a new unit. if you get to fill it in, request multiple GNNS if the watch also used glonass you'd have had plenty sats.

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decrepit said..
There's a locosys survey out looks like they are planning a new unit. if you get to fill it in, request multiple GNNS if the watch also used glonass you'd have had plenty sats.

Anyone got a link to the survey

I am answering my own question:

This is the predicted satellite availability for 20-Nov-18 at Coal Point. It shows a poor area around 3-4pm. It doesn't exactly align with the issues that we had one hour later, but it is close.

You can find this data here satpredictor2.deere.com/homePost
It also does Glonass

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kato said..

decrepit said..
There's a locosys survey out looks like they are planning a new unit. if you get to fill it in, request multiple GNNS if the watch also used glonass you'd have had plenty sats.

Anyone got a link to the survey

www.facebook.com/LOCOSYS.Club/

survey done. My thoughts

Completely waterproof. Connects to multiple satellite systems. Long battery life when being used. Large memory. Floats. A basic model (ie. large screen, fixed at 5hz, waterproof, wireless charging BT/WiFi) & one that does it all (customizable to the need of the athlete). Wireless charging (like phones). Large screen to read details. Blue Tooth to connect with headphones for audible data updates while sailing.

See new thread regarding the survey

Thanks for prompting my interest in the issue of Satellite coverage Andrew.

I looked up the Sat coverage for Sandy Point on friday. Interesting,



That looks OK, at least after dawn.

But look how much better if we have a 'GPS' that can use Glonass as well!

This is the predicted satellite availability for 20-Nov-18 at Coal Point. It shows a poor area around 3-4pm. It doesn't exactly align with the issues that we had one hour later, but it is close.

Daylight saving????

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sailquik said..
Thanks for prompting my interest in the issue of Satellite coverage Andrew.

I looked up the Sat coverage for Sandy Point on friday. Interesting,



That looks OK, at least after dawn.

But look how much better if we have a 'GPS' that can use Glonass as well!

Daffy, the graphs seem to have GMT as the reference time zone, maybe 11 hrs addition may might a difference?

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yoyo said..

This is the predicted satellite availability for 20-Nov-18 at Coal Point. It shows a poor area around 3-4pm. It doesn't exactly align with the issues that we had one hour later, but it is close.

Daylight saving????

I specified Australian Eastern Daylight Saving Time which is GMT +11, looks like Daffy didn't. The trouble is each time you change your location the time resets back to GMT

opps!

But I guess my main point was how much better it is with Multi GNSS.

OK here is the corrected graph for AEDST:

Looks like we will have good coverage for the morning session. and in this case we are lucky because the lowere coverage count coincides with high tide and by the time we can sail again, coverage count should be higher again.




Of even more interest is that the coverage pattern almost repeats each day into the future. So when I looked at the next few days the yellow bars were almost in the same place. Then I skipped ahead by a week at a time and found that the lower count coverage patten is getting slightly earlier by around about 45 minutes each week, 3 hours per month.

here is 23 Dec 2018:






And January 23 2019:

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sailquik said..
opps!

But I guess my main point was how much better it is with Multi GNSS.

Daffy, run the GPS Logit bluetooth unit at 10hz and you'll get the multiple GPS system sats.

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Roo said..

sailquik said..
opps!

But I guess my main point was how much better it is with Multi GNSS.

Daffy, run the GPS Logit bluetooth unit at 10hz and you'll get the multiple GPS system sats.

Exactly my plan Roo!

Hello Andrew, GPS shows up 4 minutes earlier every day. :)

"The orbital period is one-half a sidereal day, i.e., 11 hours and 58 minutes so that the satellites pass over the same locations or almost the same locations every day. "
-- en.wikipedia.org/wiki/Global_Positioning_System