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57guy 19-04-2012 14:01

IPad GPS is off 100 ft
 
I have been using iNav X on my iPad for about a year and it has been right on. Today I was leaving the marina which has a narrow entrance and the tracking crumbs showed I was going over the ground about 100 feet from the channel. I came into the marina about a week ago and still have last weeks track on the map. It was right down the center of the channel.
I have iNav x on my wife's iPad and when I turned it on, it was perfect and showed me the slip I was in.

So I know it's not iNav X and must be the Gps in my iPad . Is there a way to adj the gps or check out the accuracy
Thanks
P
Gee

jackdale 19-04-2012 14:27

Re: IPad GPS is off 100 ft
 
Check that the GPS is set for a horizontal datum of WGS84.

Jetexas 19-04-2012 14:29

Re: IPad GPS is off 100 ft
 
Probably not the GPS on your iPad -- probably the atmospheric conditions and sat signals.

I believe the iPad and iPhones have a 6-channel GPS. It sets your location using up to six sattelite signals. Most dedicated GPS units have 15+ channels.

The more sattelites it can connect to at once, the more precise your location.

You can get an add-on GPS dongle to make your iPad more precise. The Bad Elf gets good reviews. It's 66-channel.

s/v Jedi 19-04-2012 14:56

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by Jetexas (Post 934996)
Probably not the GPS on your iPad -- probably the atmospheric conditions and sat signals.

I believe the iPad and iPhones have a 6-channel GPS. It sets your location using up to six sattelite signals. Most dedicated GPS units have 15+ channels.

The more sattelites it can connect to at once, the more precise your location.

You can get an add-on GPS dongle to make your iPad more precise. The Bad Elf gets good reviews. It's 66-channel.

The Apple devices have 12-channel receivers. You only need 5-6 satellite locks for optimum accuracy. 66 channels is nice with a 32 satellite GPS constellation of which any receiver can only see half. :D

ciao!
Nick.

barnakiel 19-04-2012 15:07

Re: IPad GPS is off 100 ft
 
Sometimes just after the unit hooks up the accuracy is less than perfect (my guess from 'normal' gps, I do not have iThings yet). I would let it sit for like ten minutes and try again.

b.

nitpik 19-04-2012 15:21

Re: IPad GPS is off 100 ft
 
I do not believe it is specifically an iPad problem, but rather, it has something to do with the gps accuracy the military "allows" us to have. I have used several laptops with various chart software, several different USB pucks, and now the iPad. In all cases, there are situations where positional accuracy is not as close as we would like ...... sometimes within 10', and sometimes 30'+ . It varies from chart to chart, and from day to day.
It is still much better than my old RDF radio device (remember those?!) and my King Loran.
We all use discretion with gps and electronic charts anyway, no? Just don't rely on your gps to allow you to pass two feet on the safe side of that shoal in fog or at night. (or anytime, for that matter!)
So, a positional accuracy of +/- 50' is something I can live with ....... it does not make the iPad any less useful to me. (best piece of technology I have had in my hands since the earth started to cool!):popcorn:
There, my bias is showing.

s/v Jedi 19-04-2012 15:57

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by barnakiel (Post 935011)
(...I do not have iThings yet).

http://www-personal.umd.umich.edu/~c...20No%20Cat.jpg

:thumb:
Nick.

Sailmonkey 19-04-2012 16:00

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by barnakiel (Post 935011)
Sometimes just after the unit hooks up the accuracy is less than perfect (my guess from 'normal' gps, I do not have iThings yet). I would let it sit for like ten minutes and try again.

b.


I have one I thing that will not become many.......I already feel like the borg are watching me

s/v Jedi 19-04-2012 16:18

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by Sailmonkey (Post 935048)
I have one I thing that will not become many.......I already feel like the borg are watching me

Yes, scary :D

http://4.bp.blogspot.com/-pHtvyO1yOb...n-7of9_005.jpg

:thumb:
Nick.

Ex-Calif 19-04-2012 16:24

Quote:

Originally Posted by 57guy
I have been using iNav X on my iPad for about a year and it has been right on. Today I was leaving the marina which has a narrow entrance and the tracking crumbs showed I was going over the ground about 100 feet from the channel. I came into the marina about a week ago and still have last weeks track on the map. It was right down the center of the channel.
I have iNav x on my wife's iPad and when I turned it on, it was perfect and showed me the slip I was in.

So I know it's not iNav X and must be the Gps in my iPad . Is there a way to adj the gps or check out the accuracy
Thanks
P
Gee

I use an external gps. The xgps150 has a nice sattelite strength app that show which sattelites are seen and what the signal strengths are. Maybe there is a stand alone app on the store for 3g/4g ipads.

I also have the bad elf gps and it is also good.

In regards to errors on one ipad and not the other this is really strange and the first I have heard of this. To be honest I back up my ipad navionics with the iphone so I am always reading from 2 sources.

Unfortunately I would not use the ipad or iphone for close quarters primary nav - i.e. in foggy conditions.

Maybe I am old school but when conditions are visual and landmarks are available I navigate with coastal charts, eyeballs and bearing compass and use gps as a reference/backup.

s/v Jedi 19-04-2012 16:31

Re: IPad GPS is off 100 ft
 
The best thing to see in foggy or otherwise dark and evil conditions is the radar overlay matching the chart precisely.

iPads with the right software rule.
http://sv-jedi.smugmug.com/photos/i-...SHFRHmR-XL.jpg

ciao!
Nick.

David M 19-04-2012 18:09

Re: IPad GPS is off 100 ft
 
I'm wondering if the iPad does not do WAAS? Does anyone know?

I know it does triangulation with cell towers to help its accuracy. Perhaps with no cell towers within range and no WAAS, it has no sort of differential and therefore a less than decent position? Opinions?

Ex-Calif 19-04-2012 18:20

OK just went on an app diversion and found MotionX programs. Quite nice with a rudimentary gos accuracy report and signal strength.

Not as good as the xgps150 app which shows the satellite array and each satellites strength but still useful.

s/v Jedi 19-04-2012 18:33

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by David M (Post 935135)
I'm wondering if the iPad does not do WAAS? Does anyone know?

I know it does triangulation with cell towers to help its accuracy. Perhaps with no cell towers within range and no WAAS, it has no sort of differential and therefore a less than decent position? Opinions?

I think it uses cell towers for approximate position when there is no GPS lock, plus that position to get a quicker GPS lock. I don't think cell towers can improve the accuracy from GPS which is a couple of meters.

EDIT: note that on the picture I posted above the GPS lock is not from the internal GPS but from a Maretron N2K sensor.

ciao!
Nick.

David M 19-04-2012 18:34

Re: IPad GPS is off 100 ft
 
I was wondering that as well...thanks Nick.

GPSNavX 19-04-2012 18:36

Re: IPad GPS is off 100 ft
 
iNavX reports the accuracy of the GPS in the "HPE:" field in the Instruments banner and view. Typically the amount of Horizontal Position Error will be under 20'. So I would check that first. iNavX, Navionics, MotionX, etc. all use "Location Services" to plot their position. So if one app has any plotting error, the others most likely will.

Ex-Calif 19-04-2012 18:52

Quote:

Originally Posted by GPSNavX
iNavX reports the accuracy of the GPS in the "HPE:" field in the Instruments banner and view. Typically the amount of Horizontal Position Error will be under 20'. So I would check that first. iNavX, Navionics, MotionX, etc. all use "Location Services" to plot their position. So if one app has any plotting error, the others most likely will also.

The motionx app also reports that position will be accurate from 30-300 feet.

I rarely see an error greater than 20 but it could be worse at times.

I wonder if different ipad covers affect reception? Shouldn't but could, I am guessing...

s/v Jedi 19-04-2012 18:54

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by David M (Post 935154)
I was wondering that as well...thanks Nick.

I just took my iPad 2 outside and got an accuracy of 16 feet. This is OUTSIDE WAAS area, so just plain old GPS accuracy. Better than can be expected because I always learned that was 15 meters, i.e. 50 feet.

ciao!
Nick.

Ex-Calif 19-04-2012 19:02

Quote:

Originally Posted by David M
I'm wondering if the iPad does not do WAAS? Does anyone know?

I know it does triangulation with cell towers to help its accuracy. Perhaps with no cell towers within range and no WAAS, it has no sort of differential and therefore a less than decent position? Opinions?

I believe it does not as the aviation sites all talk about using an external aviation grade gps for position accuracy.

http://www.foreflight.com/support/gps

This one is interesting - scroll down to FlyWi article. It is a waas gps that can provide services for up to 4 iOS devices at once - that's cool... (but pricey)

http://www.flightguide.com/flight_guide_iefb.html#flywi

57guy 19-04-2012 19:04

One point to make, I have two iPads. One the GPS is off on it and the other, GPS is accurate. So it's not a government problem or software problem.

Ozbullwinkle 19-04-2012 19:07

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by s/v Jedi (Post 935060)


Hey Nick, Can you tell me where I can get one of these - looks like a perfect iCrew to me....:thumb::thumb::thumb:

Steve

s/v Jedi 19-04-2012 19:21

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by Ozbullwinkle (Post 935187)
Hey Nick, Can you tell me where I can get one of these - looks like a perfect iCrew to me....:thumb::thumb::thumb:

Steve

Be warned that they don't come like that initially...

http://fwnet.ipower.com/images/2009/...ne-300x381.jpg

cheers,
Nick.

Ozbullwinkle 19-04-2012 20:15

Re: IPad GPS is off 100 ft
 
You are right & I take your warning - that is scary!

noelex 77 19-04-2012 21:05

Re: IPad GPS is off 100 ft
 
I think the iPad gps accuracy is not as good as the dedicated Gps units, particularly when the signal strength is low. If I watch the plot of position when a anchor a handheld Garman has a much tighter plot pattern.
The iPad is still great as a back up. The Navionics charts are a bargin.

jackdale 19-04-2012 21:29

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by Ex-Calif (Post 935068)

Maybe I am old school but when conditions are visual and landmarks are available I navigate with coastal charts, eyeballs and bearing compass and use gps as a reference/backup.

:thumb:

57guy 20-04-2012 05:54

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by GPSNavX (Post 935155)
iNavX reports the accuracy of the GPS in the "HPE:" field in the Instruments banner and view. Typically the amount of Horizontal Position Error will be under 20'. So I would check that first. iNavX, Navionics, MotionX, etc. all use "Location Services" to plot their position. So if one app has any plotting error, the others most likely will.

I checked the HPE field and it's bouncing from 98' to 164' which is about what the map is showing. Wonder what my solution is? My other iPad is showing 20' in the same spot.

I try to never cruise in bad weather, but an accurate GPS aids me in the Bahamas going thru narrow cuts. I'm allways on the flybridge watching for shallow water, but still keeping an eye on the chart plotter . Cannot do that any more with this iPad.

rtbates 20-04-2012 06:34

Re: IPad GPS is off 100 ft
 
Cause unknown, but the lesson sure should be clear!

jackdale 20-04-2012 06:55

Re: IPad GPS is off 100 ft
 
Quote:

Originally Posted by 57guy (Post 935375)
I checked the HPE field and it's bouncing from 98' to 164' which is about what the map is showing. Wonder what my solution is? My other iPad is showing 20' in the same spot.

I try to never cruise in bad weather, but an accurate GPS aids me in the Bahamas going thru narrow cuts. I'm allways on the flybridge watching for shallow water, but still keeping an eye on the chart plotter . Cannot do that any more with this iPad.

Use the Mark I eyeball. I never trust a chartplotter in a tight situation.

57guy 20-04-2012 14:02

I just got my GPS to show me setting at my dock.
I was talking to a friend who has an aircraft iPad business. He said when he has a problem with gps accuracy, he shuts the iPad off and reboots it.
I did this and sure enough my boat came off the land behind the marina and is setting at my dock.

He said h e uses the remote gps150 when he flys his plane. Sometimes the internal iPad gps does not pick up a good signal in his plane.
Gee

Ex-Calif 20-04-2012 22:18

Quote:

Originally Posted by 57guy
I just got my GPS to show me setting at my dock.
I was talking to a friend who has an aircraft iPad business. He said when he has a problem with gps accuracy, he shuts the iPad off and reboots it.
I did this and sure enough my boat came off the land behind the marina and is setting at my dock.

He said h e uses the remote gps150 when he flys his plane. Sometimes the internal iPad gps does not pick up a good signal in his plane.
Gee

That is how I am set up. I bought the original iPad with no 3g never consideing that gps didnt come with it. Doh!

I bought both the bad elf and the gpsx150. Both are good in ways. I like the gpsx150 bluetooth as I can set the puck outside.

I will still get the 3g next time but for those without either of these gos is a dream.

Gary russell 24-04-2012 17:55

Does an original I pad have gps

GPSNavX 24-04-2012 17:57

Re: IPad GPS is off 100 ft
 
Yes if it is the 3G model.

Gary russell 24-04-2012 18:01

How do I tell

GPSNavX 24-04-2012 18:58

Re: IPad GPS is off 100 ft
 
Run the "Settings" app, If "Cellular Data" lists as one of the settings, than it is a 3G model.

Gary russell 24-04-2012 19:06

Quote:

Originally Posted by GPSNavX
Run the "Settings" app, If "Cellular Data" lists as one of the settings, than it is a 3G model.

Thanks I must not have 3 g. So do I need to get one of the add on gps

GPSNavX 24-04-2012 19:08

Re: IPad GPS is off 100 ft
 
Yes you could use a Bad Elf GPS receiver. For those who have not already bought an iPad. Please buy the 3G or 4G model so you get a GPS receiver. Otherwise you end up spending just about the same in a kludgy GPS add on.


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