Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-06-2014, 07:30   #1
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Inmarsat At High Latitudes?

I have a friend who worked in the media business as a producer for war-correspondents, and later a bureau chief for a major network.

In his opinion Iridium if fine if you want to chit-chat with grandma and grandpa but in his professional experience, if the call you are making is a call that counts, the last thing you want is to drop it, and because of this he is very firm in his endorsement of Inmarsat.

He is a very savvy guy and I tend to place a lot of stock in his opinion on something I have no experience with. However, I know that most of his experience tended to be in what you might call "hotter" climates than where we are going, fifty north or higher.

From my reading of an Inmarsat see-me map I found somewhere it looks like the altitude of the geostationary satellite where we are headed is <20 degrees, which seems pretty low to me. Any thoughts?

Second question, is there a basic way to work out the declination of the azimuth of the satellite? Or is it far enough away that if you aim in a southerly direction and more importantly have the right altitude, you can get a link?
__________________

__________________
Delancey is offline   Reply With Quote
Old 12-06-2014, 07:56   #2
Registered User

Join Date: May 2006
Posts: 463
Re: Inmarsat At High Latitudes?

Quote:
Originally Posted by Delancey View Post
I have a friend who worked in the media business as a producer for war-correspondents, and later a bureau chief for a major network.

In his opinion Iridium if fine if you want to chit-chat with grandma and grandpa but in his professional experience, if the call you are making is a call that counts, the last thing you want is to drop it, and because of this he is very firm in his endorsement of Inmarsat.

He is a very savvy guy and I tend to place a lot of stock in his opinion on something I have no experience with. However, I know that most of his experience tended to be in what you might call "hotter" climates than where we are going, fifty north or higher.

From my reading of an Inmarsat see-me map I found somewhere it looks like the altitude of the geostationary satellite where we are headed is <20 degrees, which seems pretty low to me. Any thoughts?

Second question, is there a basic way to work out the declination of the azimuth of the satellite? Or is it far enough away that if you aim in a southerly direction and more importantly have the right altitude, you can get a link?
Did he have experience pulling grib files in the High Latitudes?
Does Inmarsat have coverage where you are going?
Does Iridium have coverage where you are going?

I have no experience of Inmarsat and how much better it is than Iridium.

Iridium works fine and as long as its not one of the early phones, has the data option so you can download gribs (Don't choose too big an area)
__________________

__________________
Fuss is offline   Reply With Quote
Old 12-06-2014, 08:25   #3
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Re: Inmarsat At High Latitudes?

Inmarsat uses a few geostationary satellites at a very high altitude fixed at the equator. Iridium uses a larger constellation of pole-orbiting satellites at a lower altitude. Both systems rely on line of sight but use different approaches to get it. Inmarsat supposedly provides coverage up to seventy degrees.

Our intention is not to chit chat nor to download data, but to only make calls that count. The intent with weather is to receive pertinent info via text from shore support and depend on old-school observation for the rest. My understanding is that data on Inmarsat is very slow.
__________________
Delancey is offline   Reply With Quote
Old 12-06-2014, 08:31   #4
Registered User

Join Date: May 2006
Posts: 463
Re: Inmarsat At High Latitudes?

Quote:
Originally Posted by Delancey View Post
Inmarsat uses a few geostationary satellites at a very high altitude fixed at the equator. Iridium uses a larger constellation of pole-orbiting satellites at a lower altitude. My understanding is that data on Inmarsat is very slow.

Our intention is not to chit chat nor to download data. The intent with weather is to receive pertinent info via text from shore support and depend on old-school observation for the rest.
I think you mean't Iridium data downloads are slow.

Yes, true however data (grib) and other compressed weather data downloads are an important feature of Iridium and should be taken advantage of.

You need to do more homework as this feature should be used in the high latitudes where other forms of communication are not available.

Please talk to some sailors with experience.
__________________
Fuss is offline   Reply With Quote
Old 12-06-2014, 08:39   #5
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Re: Inmarsat At High Latitudes?

What no sailors here with experience? I've been fooling myself this whole time?
__________________
Delancey is offline   Reply With Quote
Old 12-06-2014, 08:51   #6
Registered User

Join Date: May 2006
Posts: 463
Re: Inmarsat At High Latitudes?

Quote:
Originally Posted by Delancey View Post
What no sailors here with experience? I've been fooling myself this whole time?
I just want to make the point, Having Iridium and not using the data function makes no sense.

It has large coverage and the data function for weather is more than adequate.

You didn't answer the question on wether Inmarsat has coverage where you will be going.

The answer to this question will make it clear to you which service is most suitable.
__________________
Fuss is offline   Reply With Quote
Old 12-06-2014, 08:57   #7
Registered User
 
ksanders's Avatar

Join Date: Sep 2012
Location: ALASKA
Boat: BAYLINER 4788
Posts: 130
Re: Inmarsat At High Latitudes?

I use satellite at high latitudes all the time because that is the area that I am home ported out of.

We are right now at 60 degrees north and get 2 mbps download speeds.

We use a KVH minivsat service, which is not tied to any one satellite constellation. KVH rents transponder space from a variety of companies to provide global coverage.
__________________
Kevin Sanders
Bayliner 4788
Seward, Alaska
ksanders is offline   Reply With Quote
Old 12-06-2014, 09:03   #8
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Re: Inmarsat At High Latitudes?

Quote:
Originally Posted by Delancey View Post
Inmarsat supposedly provides coverage up to seventy degrees.
For the reasons stated I have an inclination towards Inmarsat. The problem with the geosationary equatorial-orbiting satellites is that the higher you go in latitude the lower the relative altitude of the satellite, hence Inmarsat no talkie above seventy degrees.

Most of my friends experiences were dealing with people typically working a lot closer to the equator.

Iridium pole orbits and so provides truly global coverage, but I am not going above seventy and would rather not drop a call that counts, which is the purpose of the phone to begin with.
Attached Thumbnails
Click image for larger version

Name:	inmarsat-isatphone-pro-satellite-angle-map.png
Views:	234
Size:	273.4 KB
ID:	82917  
__________________
Delancey is offline   Reply With Quote
Old 12-06-2014, 09:17   #9
Registered User

Join Date: Feb 2012
Posts: 270
Re: Inmarsat At High Latitudes?

About 15 years ago I used Inmarsat on an icebreaker in Antarctica (66 south ?)and Iridium hand-held phones from continental Antarctica (80 South ?), for both calls, and internet. For Inmarsat we needed to point the dish close to the horizon, and for Iridium signal strength varied with the orbits. I believe Iridium works all the way to the pole.
__________________
homeless is offline   Reply With Quote
Old 12-06-2014, 10:14   #10
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Inmarsat At High Latitudes?

Delancey,
You ask some good questions....
(and yes INMARSAT does have some EXCELLENT services/system....but you must compare apples to apples and oranges to oranges...)
In order to give accurate answers we need to know WHAT type of INMARSAT system and WHAT type of Iridium system you are trying to compare??
And, of course WHERE you will be sailing/cruising...

1) I'm going to make an assumption here that you are talking about handheld satphones???
(understand that if you're comparing the typical INMARSAT terminals used by war-correspondents, to a handheld sat phone, then yes they are superior....but, if you actually compare an Iridium handheld satphone against an INMARSAT handheld satphone, the Iridium wins easily....ESPECIALLY at higher latitudes!!)


2) A good rule of thumb for geostationary satellite comms (of any type) is "70 degrees"....meaning if you're more than 70 degrees away from the satellite, your signals will be extremely marginal or non-existent....
This means if you're above 70* latitude and/or more than 70* away in longitude from the satellite, you're not likely to have success...
And, for manual operation (not 3-axis-stabliized terminals), I'd use 60 degrees as my max....with anything above 55 degrees considered marginal / unreliable, for handheld / manual INMARSAT satphones...
{now "technically" the line-of-sight from the Clarke Belt down to the earth is about 80* max....and back in the early 1980's, I was part of the home/support team that installed the first geostationary satellite terminals (mostly for TV) in the Resolute Bay area, at 75*N, where we had "look angles" of only about 4* degrees, from, our 6m dish.....and it worked....but NOT recommended|}



3) Before even considering "look angles" to the satellites, understand that in order for an INMARSAT handheld phone (isatPhonePro) to access their satellites (geostationary) you must point the antenna towards the satellite....
The pointing of this small antenna does NOT have to be precise, as an example you can say "Southeast, about 30 degrees above the horizon". and if you're within 20 - 30 degrees you're good-to-go...

There is NO pointing required for using an Iridium handheld phone, nor any Iridium device....as their satellites orbit at only 485 miles altitude, vs. 22,300 miles....





4) Your readings of INMRSAT's coverage is correct...if you are venturing to high latitudes, the look angles are LOW (and the slant distance is great...and the path loss is a bit higher), so "handheld sat phone" connections using INMARSAT is problematic...

Not sure how high of latitudes you're looking at cruising, but your instincts here are good....
Iridium is going to best for you!!
Quote:
Originally Posted by Delancey View Post
From my reading of an Inmarsat see-me map I found somewhere it looks like the altitude of the geostationary satellite where we are headed is <20 degrees, which seems pretty low to me. Any thoughts?




5) Regarding "pointing"....as I wrote above, Iridium requires NO pointing at all...
INMARSAT systems DO require pointing....but, the pointing of the handheld sat phone's small antennas does not need to be too precise...
Quote:
Originally Posted by Delancey View Post
Second question, is there a basic way to work out the declination of the azimuth of the satellite? Or is it far enough away that if you aim in a southerly direction and more importantly have the right altitude, you can get a link?
Please tell me WHERE you are planning on cruising, and I can be more precise/detailed in my answers...
But, in general, getting your INMARSAT handheld IsatPhonePro's antenna pointed within 20 - 30 degrees of the satellite usually works....(but as you venture to higher latitudes, it gets a bit more critical..)
All other INMARSAT terminals require fairly precise pointing....

Iridium systems, do not require pointing...



6) If all you want is to make / receive phone calls from remote locales, high latitudes, etc...(which appears to be the case)
Quote:
Originally Posted by Delancey View Post
Iridium pole orbits and so provides truly global coverage, but I am not going above seventy and would rather not drop a call that counts, which is the purpose of the phone to begin with.
Then, Iridium is the best choice, hands-down, no question at all...


BUT...
But, understand this about ALL handheld sat phones...
You're NOT going to receive calls when it is below decks in a locker, or sitting on a shelf!!!
They are NOT designed for this...
So, if you need a "phone" that will ring when someone calls you, you are going to need to have at the least an external fixed-mount antenna, and probably a "docking station"...
If, all you need is to make a phone call, or receive them when the phone is out in the cockpit (such as sitting in a drink/cup-holder), then you are good-to-go...




7) Sorry, I don't sit behind my keyboard 24/7...
Quote:
Originally Posted by Delancey View Post
What no sailors here with experience? I've been fooling myself this whole time?
But, in addition to starting my sailing/cruising life as a kid in the mid-1960's....I've made my living in the commercial sat comm business for decades....
And, I've used both Iridium and INMARSAT....
So, hopefully all of this above will be helpful to you...




I hope this helps...
Please advise if you need further info...

Fair winds...

John
s/v Annie Laurie
__________________
ka4wja is offline   Reply With Quote
Old 12-06-2014, 10:48   #11
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Re: Inmarsat At High Latitudes?

Thanks for the feedback, much appreciated. Strictly talking hand held sat phones, for what it's worth my friend was talking the same, not a terminal. The trip is a New York to Falmouth passage leaving early in July and I doubt we will go much higher than 50.

I have to look a bit more at costs. One appeal for Iridium is that I can go to an actual brick and mortar establishment here in the the city to rent one as opposed to dealing with someone from the internet. I expect there is a learning curve involved and it's always nice to have a real person standing in front of you explaining things.

Like I said, I have a lot of faith in my friends opinion for dealing with places like Bosnia, or Africa, or the Middle East, and he is also a sailor, but Trans-Atlantic is not his area of specific expertise.

One quick thought, is Iridium coverage actually better at the poles than at the equator, for having the polar orbit? As in, because the pole-orbiting satellites cross the poles while the earth spins, do they actually end up spending more time at the poles than they do at any other point over the surface of the earth?
__________________
Delancey is offline   Reply With Quote
Old 12-06-2014, 11:30   #12
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Inmarsat At High Latitudes?

Delancey,
I usually charge clients a lot for these type of details...
So, you're getting a lot for free!


Seriously...
I understand having faith in your friend's opinion, and I don't wish to imply they don't know of what the speak (not at all)....
But, I think you may be misunderstanding a few things???

INMARSAT is a great company, and provides great services, and for those filling stories from the field (via IP terminals, or even digital video terminals) they are truly great....
But, for PORTABLE HANDHELD satellite phones, Iridium wins hands-down, NO competition at all...

(it is possible that he had a bad experience with an Iridium phone, etc... or maybe he's so used to INMARSAT and its fine services, etc. that he would never recommend Iridium, etc. I, of course, cannot actually know...just throwing out some possibilities....
But, regardless, it really matters not to this discussion...)




Specifically....
Quote:
Originally Posted by Delancey View Post
The trip is a New York to Falmouth passage leaving early in July and I doubt we will go much higher than 50.
If you're looking for my overall recommendation for this passage...
I'd go with an Icom M-802 HF-DSC-SSB radiotelephone (sometimes referred to as "marine SSB"), where you can make/receive telephone calls thru Shipcom / WLO Radio....

But, if you're looking for just a recommendation for handheld sat phones. between Iridium and INMARSAT....
I'd go with Iridium....(mainly because it WORKS very well at sea and does NOT require any pointing....not because you're going from NY to Falmouth...



I have to look a bit more at costs. One appeal for Iridium is that I can go to an actual brick and mortar establishment here in the the city to rent one as opposed to dealing with someone from the internet. I expect there is a learning curve involved and it's always nice to have a real person standing in front of you explaining things.
Here again, I think you're on the right track...
And, here you'll also see that you're not going to be able to receive calls with the unit stowed below....test it at home, and you'll see....




Like I said, I have a lot of faith in my friends opinion for dealing with places like Bosnia, or Africa, or the Middle East, and he is also a sailor, but Trans-Atlantic is not his area of specific expertise.
There are more reasons than these to take some of this with a grain-of-salt...as I covered earlier..



One quick thought, is Iridium coverage actually better at the poles than at the equator, for having the polar orbit?
As odd as it may seem, the answer is actually No....
Iridium coverage is THE SAME everywhere on the surface of the Earth....(not accounting for obstructions, of course)
The system was designed to be this way, in both the orbital mechanics and in their satellite interconnects, etc. and continues to operate this way...
Despite what you may read on Wiki....you will get no more "connectivity" at the poles than you do elsewhere...

(oh, and they aren't actually "polar orbits"....they are 86* inclination, intersecting, and interconnecting..okay, no more rambling today...



BTW, If you wish to see how easy it is to make a phone call from your boat....have a look at this video...




I hope this helps...

Fair winds...

John
s/v Annie Laurie....
__________________
ka4wja is offline   Reply With Quote
Old 12-06-2014, 11:42   #13
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Re: Inmarsat At High Latitudes?

Quote:
Originally Posted by ka4wja View Post
Delancey,
I usually charge clients a lot for these type of details...
So, you're getting a lot for free!
Again, feedback much appreciated. Drinks are on me when we cross paths.

I've read all the threads and certainly appreciate the case to be made for HF/SSB and wouldn't for a moment dispute their utility, but in this case the trip is more of a delivery, so the intent with the sat phone is to provide a means of direct communication with a doctor as the primary goal. Any other uses are secondary.
__________________
Delancey is offline   Reply With Quote
Old 12-06-2014, 11:47   #14
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Inmarsat At High Latitudes?

delancey,
No worries....(I won't ramble on about other stuff...)
Quote:
Originally Posted by Delancey View Post
I've read all the threads and certainly appreciate the case to be made for HF/SSB and wouldn't for a moment dispute their utility, but in this case the trip is more of a delivery so the intent with the sat phone is to provide a means of direct communication with a doctor as the primary goal. Any other uses are secondary.
But, evidently you got a spare few minutes....so, maybe you could do me a favor???
Please take less than 5 minutes, and watch the video....and tell me what 'ya think, and you owe me nothing but an honest comment and a "thank you"...


Fair winds..

John
s/v Annie Laurie
__________________
ka4wja is offline   Reply With Quote
Old 12-06-2014, 12:03   #15
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,464
Re: Inmarsat At High Latitudes?

Preaching to the choir.

In this situation, the owner has neither the finances or the need for it once the boat gets to the other side, so for us it's a case of opting for lower cost and push-a-button functionality of a sat phone over the higher cost and learning curve of the radio.

I am at work (yuck) so will watch the vid later, but I will, and thanks again. Cheers!
__________________

__________________
Delancey is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Steel Tahitiana 32 Ready for High Latitudes Oceandrifter Classifieds Archive 1 14-08-2012 06:21
Solar Output in Higher Latitudes GeoPowers Electrical: Batteries, Generators & Solar 6 10-01-2010 21:42
Latitudes & Attitudes '09 Share the Sail and Cruisers Party Mustang Sally Cruising News & Events 0 05-07-2009 19:38
The Latitudes and Attitudes site is better irwinsailor The Library 3 09-02-2005 15:49
Hello from Latitudes and Attitudes Jack Tar Meets & Greets 2 28-02-2003 23:37



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 05:12.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.