Hand Held GPS - Combination Land and Marine

[onerabbit]

Hahahaha, we're all pist with the weather stonecold, but the jackets are nearly here, so its time to go cod fishing very soon. (I'd like to line you up for a run out)
After reading back on this thread a few times, I have to agree, SatNav is here for an arguement, plenty of claims, but little substance.
In answer to the original question, lots of people are happy with Garmin 72 as an affordable hand-held GPS.

Muzz

PS, This is a great place to learn heaps of stuff SatNav, settle down & become one of the regulars & people will take you quite seriously, p!ss people around and you will get the same back, c'mon bloke, I'm sure you have plenty of good stuff to share.
M

[SatNav]

1. The claim of yours onerabbit of GPS accuracy being down to a few feet is something that you will find absolutely impossible to substantiate and it is ridiculous comments like that from inexperienced people like you who I have no hesitation in standing on as comments like that serve other people absolutely no purpose what so ever, except to misguide others as you are.

2. If people are going to make comment then at least get it right as there is way too many misconceptions pushed by people like onerabbit that others do not need to inherit.

[onerabbit]

Hhhmmmmmmmmmmm

[onerabbit]

I really dont wish to enter into an arguement with you SatNav, but you claim that I make ridiculous comments, am inexperienced & as such misguide others.

I doubt that I will respond to any of your future posts in case I offend your sensitive nature any further.


Muzz

[SatNav]

1. Now ignoring your claims that my comments are of "little substance", which by the way we can continnue with any time you like, that is if you have anything specific to discuss apart from your unsubstantiated claims

2. What you have to do first is justify your ridiculous claims that GPS accuracy is "down to a few feet" as so far you have failed any request to do so and if this is based on only your opinion then your opinion is totally incorrect

3. I have no hesitation in implying somebody who makes such claims as being inexperienced with GPS accuracy as this is simply what it is, inexperience as I can absolutely asure you that you have no ability to justify such accuracy claims, this I can asure you.

[insideout]

1. NO GPS72 is accurate down to a few feet
2. Anybody who claims GPS accuracy down to a few feet knows little about GPS
3. There is approx 8 metres (25 feet plus) error based on the 3 most prominent sources of GPS error
4. Would defy anybody to justify a claim of a few feet


Blackened, If anybody including yourself would like to refute anything said then please feel free to discuss.

i work with a gps thats accurate down to 10mmx10mm......

[insideout]

actually i lie ,its 15mmx15mm

[Richo1]

Hi all,
It has been a great read and has certainly got the brain ticking. From my understanding no GPS unit is 100% accurate all of the time . Unless you have other systems like DPGS etc incorporated with your GPS unit. Don't know if you will find this of any use or not, but I copied this of the Australian Maritime Safety Authority Website (AMSA)

Status and Accuracy of GPS
When introduced in 1993 the GPS Standard Positioning System available to civilian users incorporated a deliberate degradation of the system's accuracy using a technique known as Selective Availability. Horizontal positional accuracies of 100 metres 95 per cent of the time were guaranteed. On 1 May 2000 the US Department of Defense discontinued the use of selective availability and a much higher degree of accuracy immediately became available. A new performance standard for GPS was published in October 2001.

The new horizontal accuracy standards are based on Signal in Space errors and state a global average error of <13 metres and worst site error of < 36 metres. The signal received by the user on the ground is subject to other variable influences not included in the standards and the actual accuracy achieved will vary with ionospheric conditions, geographic location, time of day,and sophistication of the receiver.

A world wide study over 24 hours at a period of high solar activity was conducted in June 2000 to determine the actual accuracy achieved by a representative single frequency receiver. The results were:-

95 per cent of the world-wide coverage had an accuracy better than 16.4 metres 95 per cent of the time, and
All of the world-wide coverage had an accuracy of better than 23 metres 95 per cent of the time.

Differential GPS
Differential GPS involves the use of reference stations ashore whose geographical position is very precisely known. By measuring the distance measurements to all satellites in view and using the surveyed position of the station's antenna DGPS is able to:-

Monitor the integrity of the GPS satellite transmissions and immediately notify users to disregard any satellite operating outside specification, and
Provide differential corrections in order to improve the accuracy of the navigation solution.
AMSA's DGPS network, when completed in 2002, will provide DGPS coverage to approximately 60 per cent of the Australian coast. Accuracy of the AMSA DGPS network is specified to be better than 10 metres 95 per cent of the time.

I believe that the accuracy of GPS has improved since this was written. Hope this has helped.

Regards Richo

PS Just bought a garmin GPS 72 and having lots of fun with it.

[SatNav]

1.GPS accuracy specifications are effectively the same today as those published in 2001, nothing has really changed.

2. AMSA's differential system statement is not 100% correct as the accuracy of some of the AMSA reference stations are in fact NOT accurate relative to WGS84 (several metres plus) but the system still meets differential requirements of less than 10 metres at 95%. GPS differential accuracy on the user end can only ever be as accurate as the accuracy of the reference station.

3. Quite strange isn't it that AMSA specify their differential accuracy provided as less than 10 metres at 95% and yet rabbit here wants to claim "down to a few feet" with a standalone non augmented handheld GPS 72. Quite amazing that some people actually believe this few feet GPS accuracy rubbish.

3. Insideout, You really mean you work with GPS that has a "relative accuracy" down in the centimetre area and since you have not stated what "type" of GPS methods you are inferring 15*15mm I would assume RTK? Are you saying 15mm position and 15mm Height?

[insideout]

yes thats correct! trimble gps tech, for a surveying company

[insideout]

in my view, a gps does not need to be super acc and people do not need to spend mega $$$ on them , just get one that will do the job,and ,get you into the general area. But do spend allitle more on you fish finder , to sound around that area, and ,put you on the fish.

if you do need to get super accurate , trimble tech starts at about $80,000............

[stonecold]

Just to ad some information regarding the Garmin gps 72. If you read the thread you'll see I picked one up the other day for some field work site estimates. Just for fun I turned the unit on for the trip betwn Alstonville and Casino on my way home. The track was plotted and saved. On the way to work the next day I did the same.
I can tell you that on several occassions driving across the top of Wollongbar, which by the way is a relatively straight piece of road, the track plotted actually crossed path with the one I had plotted the night before. I wasnt overtaking any cars!!!

Regardless the unit did get me back to within 15mts of my marked waypoint (a marker peg firmly driven into the ground in thick scrub) ...I'm happy.

Muzz let me know when your ready.......although given the last month or so I guess the weathers going to dictate that >

[onerabbit]

SatNav,

you obviously need me to explain the circumstances behind my original statement. I had made a mark in my own driveway, walked around the block, & yes (shock , horror ) the machine bought me back to within 2 feet of my original position.
I have already conceded that there is a variation depending on satellite positioning at the time, you origionally offered 8mtrs or 25ft.
I also understand that any given mark may "move around a bit"over a period of time. Thats what sounders are for.

OK, so if I am out at sea & we find a patch of good pearlies, which we then drift past, we may only run back up the breadcrumb trail 30-40mtrs to get back on the fish. Under these conditions I expect to get quite close to my previous position.
What is your big problem with that? Do the satellites move that fast??? By your handle you ellude to some knowledge on the subject, how about you stop being a smart-@rse who offers nothing but an arguement.

If, in fact you have a higher knowledge on a given subject, the site is here, eager to listen to what you have to say, thats what we're all here for, to share/learn.

However, I dont think you'll last if you continue as you are.
Really not trying to goad you into a war of words, but come on bloke, share your knowledge with us, not your frustration at the world.

Muzz

[Blackened]

G'day
Looks like I created a monster!! hahah. Nice reply muzz, easy to read and simple to understand One pointer tho mate, maybe if you number your points throughout your reply some members may be abler to understand it even easier? . Apart from that mate, nice work
Dave

[SatNav]

Hi Dave, deegee is right on the money, as far as affordable is concerned, $300 buys a reliable, waterproof unit that is accurate down to a few feet.
I did have an older Garmin 12, which was great also, until it did a swan dive from its cradle during a dodgy bar crossing. ( the garmin 72s have a locking clip on the cradle now.)
My present unit must be 3yrs old without a problem, I even have a second unit stored away, already loaded with marks should it be needed.
The units that joey-1987 described sound like the bee's knees, but with appropriate price tag, Garmin 72s are not real good inside.
The 12v adapter cable & cradle will cost you about $130 extra but is way better than batteries.

Hope it helps,

Muzz

1. Now those are your words rabbit, do you see any mention about a sounder? No
2. What stands out in the ridiculous comments arena " that is accurate down to a few feet." Simply not possible and has nothing to do with your sounding around excuses.
3. What else stands out as ridiculous? "Garmin 72s are not real good inside." Well the bad news is that no GPS is any good inside.
4. Your original statement was completely flawed and when this is finished you will be the last person who ever makes such a stupid statement again that a GPS72 "is accurate down to a few feet"
5. Do the satellites move that fast? If 4000 metres per second is fast then yes they do move pretty dam fast, obviously faster than you would imagine
6. Sharing knowledge? Exactly and the first thing you need to do rabbit is listen, you will obviously learn something that you don't understand and have been completely misguided about. This being GPS accuracy.