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SF1 vs. Waas
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RandyRo
Posted 11/29/2007 01:25 (#248490)
Subject: SF1 vs. Waas



North Central ND
Can anyone tell me what exactly the John Deere SF1 signal is? Is it there own satellite network or is it basically Waas? If it's not waas, is it as accurate as an Outback running on Waas?

Edited by RandyRo 11/29/2007 01:43
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peth
Posted 11/29/2007 08:03 (#248543 - in reply to #248490)
Subject: RE: SF1 vs. Waas


Guelph Ontario Canada
SF1 is Deere's own correction signal which is available without a subscription.  The receiver uses WAAS plus the SF1 correction signal for position.  SF1 / SF2 is similar to Omnistar XP / HP. 
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Jacob Bolson
Posted 11/29/2007 09:23 (#248593 - in reply to #248543)
Subject: RE: SF1 vs. Waas


Iowa
peth - 11/29/2007 08:03

SF1 / SF2 is similar to Omnistar XP / HP.

Can you provide a reference for that comparison? Everything I have seen links SF2 to OmniSTAR XP and places OmniSTAR HP above SF2.
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CSIJF
Posted 11/29/2007 11:07 (#248686 - in reply to #248490)
Subject: Re: SF1 vs. Waas


SF1 is a John Deere Signal. Waas has about +/- 3ft accuracy, SF1 has +/- 13" accuracy SF2 has a +/- 4" accuracy and RTk ofcourse has a +/- 1" accuracy.
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Farmpond
Posted 11/29/2007 12:56 (#248770 - in reply to #248686)
Subject: Re: SF1 vs. Waas


SF1 is a signal that they purchase from a third party (NASA I beleive). My two cents it to stay away from all DEERE electronics unless you want to start getting stuck with only DEERE electronics in the future. They don't like to play with other companies products, so you have to buy more overpriced stuff from mother deere.
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precisionagsouth
Posted 11/29/2007 13:44 (#248814 - in reply to #248770)
Subject: Re: SF1 vs. Waas


I'll add an "AMEN!" to the "overpriced" statement....$700 for a HarvestDoc keycard is straight ridiculous
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peth
Posted 11/29/2007 16:06 (#248901 - in reply to #248593)
Subject: RE: SF1 vs. Waas


Guelph Ontario Canada

Jacob Bolson - 11/29/2007 09:23
peth - 11/29/2007 08:03 SF1 / SF2 is similar to Omnistar XP / HP.
Can you provide a reference for that comparison? Everything I have seen links SF2 to OmniSTAR XP and places OmniSTAR HP above SF2.

Note my use of the term "similar" and not "exactly".  I was referencing correction signals, not accuracy claims.  What you stated could be right but I have not seen any impartial data that wasn't produced by a manufacturer that objectively evaluates GPS performance. I have seen some older studies but nothing current. Please post some links if you have them I would be interested in reading them. I would imagine there is a university study out there somewhere.



Edited by peth 11/29/2007 21:27
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peth
Posted 11/29/2007 16:08 (#248903 - in reply to #248770)
Subject: Re: SF1 vs. Waas


Guelph Ontario Canada

That third party company is not NASA, it is a wholly owned John Deere company called NavCom. http://www.navcomtech.com/StarFire/

Your comment about JD not playing nice is valid. After all JD is a iron company first - makes sense that they want you to use their equipment. Bottom line is that there are plenty of products on the market ... buy what works for you, your equipment, and the degree of proprietary components that you and your pocket book are comfortable with.

Proprietary components isn't a new concept for Deere - hydraulic couplers is one good example from the past. 


 



Edited by peth 11/29/2007 17:03
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dvswia
Posted 11/29/2007 16:30 (#248913 - in reply to #248770)
Subject: Ditto on Deere not playing nice


sw corner ia.
Been that way for as long as I can remember, too.
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tuck
Posted 11/29/2007 17:48 (#248942 - in reply to #248490)
Subject: Re: SF1 vs. Waas


MN
I cannot tell you exactly what it is but the accuracy is +or- 13 inches for sf1 +or- 4 on sf2. What I do know from pricing both Outback and Deere is the Deere system is twice the cost. The S2 outback will give you better than 13 inch accuracy I would say it is closer to 5-6 inches and half the cost plus greater mobility between vehicles. No brainer.
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Paul VDB
Posted 11/29/2007 17:57 (#248950 - in reply to #248942)
Subject: Re: SF1 vs. Waas



Burgessville, Ontario
Most of you know I am a John Deere dealer - so take my comments with a grain of salt.

Nine times out of ten I get beat by price on entry level (inexpensive) guidence systems. However, if you are looking for guidence and documentation - and a comparible level of accuracy and support - most systems start to level out. Make sure you compare apples to apples. Every product has its place and need in the market. It just would be boring if there was no choice in the market.

Thanks

Paul
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il weedman
Posted 11/29/2007 20:16 (#249062 - in reply to #248770)
Subject: Re: SF1 vs. Waas


St. Charles, MO & Piper City, IL
I will agree with you about Deere system being a proprietary product. With that being said and my past selling and using Trimble steering systems I will have to say I sure am impressed with the G* systems that we own now and use on the farm. It is a very easy system to teach and to use. And about the $700 keycards, I guess you havn't had to pay Ag Leader for $750 unlock codes to use different features on the Insight.
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CB In The Cab
Posted 11/29/2007 23:54 (#249307 - in reply to #248490)
Subject: Re: SF1 vs. Waas


Central To Everything and Close to Nothing
Talk about apples and oranges, and maybe bananas too....... Before anyone makes any wild claims about accuracy, you had better make sure you know what you are talking about and read the fine print in the advertising. In the guidance market, most rated accuracies are quoted on a pass to pass in a certain time period a certain percentage of the time. In the case of Deere and Trimble, their rated accuracy is based on a 15 minute interval 95% of the time. Are they more accurate than the rated accuracy? Most of the time, yes, but they can drift within their rated accuracy. Is a Trimble running WAAS more accurate than a JD StarFire iTC running SF1, proably not, I think Trimble is making a stronger statement with their rated accuracy. In theory, someone selling a WAAS like product could claim a +/-1" accuracy only to have the fine print say based on a 5 minute interval, 10% of the time!!

Unfortunately, like Peth's comments, there is no standardized body out there to rate the accuracies of these products and until then the buyer will have to decide on their own which company claim to believe. If you aren't sure, contact a local dealer who will give you a demo and find out for yourself. Any precision ag dealer worth their salt will be out there in a heartbeat to show off their wares.

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precisionagsouth
Posted 11/30/2007 09:03 (#249479 - in reply to #249062)
Subject: Re: SF1 vs. Waas


The Insight at least comes unlocked for harvest out of the box though. Can you do ANYTHING with a mobile processor if you have a 60 series combine and need HarvestDoc?
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peth
Posted 11/30/2007 09:31 (#249498 - in reply to #249479)
Subject: Re: SF1 vs. Waas


Guelph Ontario Canada

You cant compare a mobile processor / original greenstar screen to an Insight - not even close to being the same level of product.  See the apples vs oranges vs bananas comment in this thread.  A GS2 screen vs the Insight is a more realistic comparison, and yes the GS2 is ready for harvest right out of the box.  You cant do anything with your computer without an operating system or programs on it ... its the same with a mobile processor in a 60 series combine.

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Jacob Bolson
Posted 11/30/2007 10:45 (#249549 - in reply to #249307)
Subject: Re: SF1 vs. Waas


Iowa
CB In The Cab - 11/29/2007 23:54

Unfortunately, like Peth's comments, there is no standardized body out there to rate the accuracies of these products and until then the buyer will have to decide on their own which company claim to believe.

That is why two standards projects currently underway by ASABE are absolutely critical:
X587: Assessment and Reporting of GPS Receiver Dynamic Accuracy
X605: GPS Based Auto-Guidance Systems Testing
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Farmpond
Posted 12/1/2007 06:41 (#250132 - in reply to #248903)
Subject: Re: SF1 vs. Waas


We all know that Deere GPS comes from NavCom. But if you look at where the signal is actually generated from NavCom has purchased it from NASA through a parntership to get access to unused signals on some of NASA's satelittes.
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peth
Posted 12/1/2007 07:57 (#250153 - in reply to #250132)
Subject: Re: SF1 vs. Waas


Guelph Ontario Canada

 

Farmpond, 

I am splitting hairs here I realize - I stand corrected on my "not NASA" comment. 

In 2001 NavCom partnered with NASA's Real Time GISPSY network of reference stations, to add to the list of reference stations they had started in 1999.  So yes, NavCom uses correction signals from the GISPSY network, puts them through processing hubs (which may be part of GISPSY as I couldn't find a reference that explained who ran them) and then broadcasts the signals to Inmarsat's satellites, and back to earth.

 

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precision_shop
Posted 12/1/2007 08:04 (#250156 - in reply to #250132)
Subject: Re: SF1 vs. Waas


NASA??

Navcom use Inmarsat to deliver its corrections..

SF1 = Omnistar VBS/WAAS +/- 1 m
SF2 = Omnistar XP +/- 0.5 m

John Deere have no competitor for HP +/- 10cm

JD RTK = Other RTK (some debate this) +/- 2.5 cm

* over 24 Hours 2 Sigma
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alange
Posted 12/9/2007 14:55 (#256043 - in reply to #249307)
Subject: DGPS Accuracy and sunspots


Sunnyvale, CA
The biggest source of error in the GPS is the variability of the ionosphere. We are currently near the minimum of the 11.1 year solar sunspot cycle, with the new cycle to start sometime in the next 12 months. see www.spaceweather.com for more information on sunspots. the extra UV radiation that occurs from sunspots and solar flares causes the ionosphere to expand, which in turn changes the delay of a received GPS signal. DGPS corrections are designed to correct these ionosphere delays however, the corrections are not "perfect" and small errors will remain. So if you are looking at accuracy in December 2007, you will not have a full understanding of the DGPS errors in May of 2010 or 2011 or whenever the sunspot numbers are at the maximum. Since the current sunspot numbers are near zero, this is the best that GPS will behave until the end of the next cycle, in approximately 11 years, SF1 and WAAS have different networks of reference stations for creating the DGPS messages, and extrapolation of future accuracy includes a git of "guesswork." If you were to ask a GPS vendor what will happen to the accuracy of their DGPS receivers when the sunspots reach their maximum, you should expect an answer something like "we know DGPS will be less accurate than what it is now, and DGPS accuracy at the peak will depend upon the sunspot numbers at that time."
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