Garmin v phone app

Anonymous

Oh, I get it, HUGE apple fanboi.

Bar Shaker

yeehaamcgee wrote:

A-GPS isn't a GPS lock though. It will start off by guessing position based on cell location, which is takes as a rough lock This can have a rather massive error margin. Then, once it's locked on to sattelites, it narrows it down further.

That's not what A-GPS is, it is what non GPS phones use. A-GPS is:

http://en.wikipedia.org/wiki/Assisted_GPS

monkeylizard

Bar Shaker wrote:

monkeylizard wrote:

From the Garmin website:

"Sources of GPS signal errors


I think some of the difference between units has to be down to receiver design. From the list above the receiver can affect the multipath, the clock errors and the number of visible satellites. I would expect (or at the very least hope) that more attention was paid to receiver design in a purpose-built GPS unit than one in a phone.

Multipath is solely down to the structures around the user. Any unit can and will be affected by this. Clock errors do occur but modern clock speeds are now so fast that these are negligible. Modern Smartphones will have better chip speeds than £200 GPS units. Older GPS units suffered from this quite badly.

The number of visible satellites has nothing to do with the receiver and is solely down to the terrain around the users. Being in a valley or being surrounded by tall buildings will cut down the number of visible satellites.

The chip in iPhones is a Broadcom 4750. Its a dedicated GPS chip with impressive signal reception abilities. http://www.gpsworld.com/gps/ion-broadcom-unveils-single-chip-gps-receiver-1158. This is no mickey mouse solution.

I'm not slagging off the iPhone or any particular GPS unit - I was just making generic points.

I'm not sure how whether a satellite is visible to the GPS can have nothing to do with the receiver. If the receiver is badly designed it will be a contributing factor in whether or not it sees the signal from a satellite. And multipath is caused solely by conditions between transmitter and receiver, but different receivers can cope with multipath fading in different ways.

Bar Shaker

monkeylizard wrote:

I'm not sure how whether a satellite is visible to the GPS can have nothing to do with the receiver. If the receiver is badly designed it will be a contributing factor in whether or not it sees the signal from a satellite. And multipath is caused solely by conditions between transmitter and receiver, but different receivers can cope with multipath fading in different ways.

I understand what you meant now. Yes, putting the GPS chip at the bottom of a handset or of a PND would greatly reduce the visibility of satellites.

Kiblams

I have always used phone apps (never an iPhone, but Android and WM6), and test them by using them for my commute through the city, and I have found that they are very accurate and I can confidently say this as when overlayed on a may the path is very close if not exact to my position on the road.

Anonymous

yeehaamcgee wrote:

A-GPS isn't a GPS lock though. It will start off by guessing position based on cell location, which is takes as a rough lock This can have a rather massive error margin. Then, once it's locked on to sattelites, it narrows it down further.

Suggest you do some research on A-GPS.

It doesn't guess anything. A-GPS does a lot more than just get the position of the cell tower whilst trying to get the real GPS. The cell has a GPS receiver in it and is constantly acquiring the data from all the satellites, providing the phone with information that it would have to download initially from one satellite to find out where the rest of the constellation is, quicker than it can do alone via GPS. Additionally with the cell location from multiple towers and the cell's knowledge of where the phone is, it can provide the GPS location of the tower and a calculation of the true location of the phone based on it's offset from the tower, and then the phone can on top do extra calculations by only having acquired one or two satellites.

The lock is pretty accurate at that point. Once it has enough satellites, it drops the A-GPS connection and continues with the satellite stream instead.

Anonymous

You're right abotu the A-GPS.
Most odd. In the manual for my phone, it explicitly details how it first uses cell data to triangulate a position, then locks on using GPS to hone it further, when set to A-GPS mode.
Curiout, but yes, I was incorrect.

Bar Shaker

I didn't know the masts collected that much data.

Each mast is operating like a WAAS cell and as the phone's GPS gets the DoP offset data from the mast, it may well be more accurate than a standard Garmin style unit.

Yeehaa, that system was the norm 2-3 years ago and still provides location services for non GPS phones. Does your phone definitely have A-GPS?

Kiblams

My latest phone has A-GPS, but I have never turned it on :shock:

Anonymous

[b]Bar Shaker[/b] wrote:

Yeehaa, that system was the norm 2-3 years ago and still provides location services for non GPS phones. Does your phone definitely have A-GPS?

It's a pretty old phone, so that may be it.
I can choose GPS positioning methods from the following, and can chose to have more than one active at any time, presumably as a fallback...

Bluetooth GPS
Assisted GPS
Integrated GPS
Wifi/Network
Network based

Anonymous

Looks like the list from a Nokia to me, and with fairly up to date software (maybe from a Maps update).

Note there's a known issue with Nokia when WiFi/Network is enabled that can screw up positioning. That option should allow it to get a location based on a nearby WiFi hotspot (this is the kind of data that Google are getting grief about having acquired positions of WiFi access points when they drove around with their camera cars!). Handy for positioning when you're in a building though, but the reported bugs can screw up GPS positioning outdoors so best turned off. Though maybe they've fixed it now.

Bluetooth GPS is only needed if you have an external Bluetooth GPS. Network based is the fall back if you have no GPS reception at all and it just reports your location to the nearest cell.

For tracking I just have Integrated GPS and Assisted GPS turned on, and the rest off to ensure I'm getting only satellite positioning.

Kiblams wrote:

My latest phone has A-GPS, but I have never turned it on :shock:

Some turn it off because it does use data. That's the downside but it should only be a small amount of data when acquiring or re-acquiring the lock.

Mine is set to not use A-GPS when roaming abroad because of the extortionate roaming data charges, especially in the US (£8 per MB Orange... no thanks!!).

Bar Shaker

It sounds like you don't have a dedicated GPS chip but have pseudo GPS from mast/wifi locations etc. It's good enough for what phones are normally used for but couldn't run the golf app I listed.

The tech in the latest phones has moved on a lot.

wobbem

Kiblams wrote:

My latest phone has A-GPS, but I have never turned it on :shock:

Just ordered one of these, will report back if it makes any difference.
http://www.mobilefun.co.uk/bluetooth-gp ... 2Bproducts

Laurence25

I use a map.

Anonymous

Paper maps. Pah! :P

Actually, if I want an OS map, I do the same. I have the maps at home then photocopy the parts I want and stick them in a clear plastic pocket sleeve. Much cheaper than the very expensive OS tiles for mapping apps like View Ranger!

Anonymous

Bar Shaker wrote:

It sounds like you don't have a dedicated GPS chip but have pseudo GPS from mast/wifi locations etc. It's good enough for what phones are normally used for but couldn't run the golf app I listed.

The tech in the latest phones has moved on a lot.

It sounds like you're not reading that list. Integrated GPS and apparently A-GPS are two of the options.

Bar Shaker

I can't see why a phone with a Dedicated GPS chip would include a menu link to a Bluetooth GPS. What phone is it?

Anonymous

Bar Shaker wrote:

I can't see why a phone with a Dedicated GPS chip would include a menu link to a Bluetooth GPS. What phone is it?

All modern Symbian based Nokias with Integrated GPS also include the Bluetooth GPS option (where Bluetooth is available). It's just standard in the software and provides an extra option if you want it. The options are just based on the hardware that it detects as being present. If a BT chip is in there then it will offer that option.

The advantage of a Bluetooth GPS over the internal is the antenna is bigger, better and not obstructed by the components of a compact phone, and isn't having to deal with other transmitters and receivers in close proximity. The downside is it doesn't have A-GPS, though I'm not sure if the phone can still use A-GPS combined with the BT GPS data to better achieve a lock, or if the lock is entirely down to the BT GPS.

Note that by default the Bluetooth option is normally disabled, with Internal and Assisted GPS enabled.

Kiblams

I have used both external bluetooth GPS (with 52 channels I think) and the internal GPS in my a few phones, and the accuracy seemed to be the same when overlayed on a map. :? Though it was a little quicker at finding satelites with the external GPS.

shoddy

Ohh dear this has all got very technical.
For what its worth, i always take an OS map/compass when im out and about (incase batteries run out!).
If im on by bike, i use my old Garmin etrex which i find is excellent if a little limited with functionality.
If im walking i use a Garmin Oregon 450 which i think is awesome. i have OS maps (national parks) loaded onto it and its just like reading a paper map.

I have experience with military GPS systems and these handheld units are very good when compaired to them.
Units like these are expensive and i can see why some would prefer to use a phone that they already own.
The great thing about all GPS devices like these is that they offer 'trackback' functions so if you get lost and you lose your map/compass they can get you off a mountain safely.

With all things like this, it is important to understand how to navigate properly in the first instance and then just use the gadgets to make life easier. I would never rely solely on a phone or GPSr.

GiantMike

I rode Epping Forest on Sunday and Monday, both days my Garmin Edge 605 had a great signal even though it was in my back pocket for most of the ride.

A GPS device is optimised for GPS reception. A phone probably isn't, so I would expect it to lose a GPS signal earlier, especially under trees etc.

rudedog

Some good info there DeadKenny - I'm glad someone knows what they are talking about in this thread!

Anonymous

GiantMike wrote:

A GPS device is optimised for GPS reception. A phone probably isn't, so I would expect it to lose a GPS signal earlier, especially under trees etc.

Indeed. It's mostly a physical issue in that a dedicated device has one receiver dedicated to it.

But then if you use a Bluetooth GPS connecting to the phone, you have the same dedicated GPS, just you are viewing the results on a phone instead.

The great thing about all GPS devices like these is that they offer 'trackback' functions so if you get lost and you lose your map/compass they can get you off a mountain safely.

That's what's missing in a lot of the phone apps. Though I haven't checked if View Ranger does this. If it's navigation I'm after I just use the GPS to work out where I am and use a physical map as it's bigger and clearer, plus I may have marked trails on it.

Generally the GPS I use for tracking, not navigation.

With all things like this, it is important to understand how to navigate properly in the first instance and then just use the gadgets to make life easier. I would never rely solely on a phone or GPSr.

Definitely!

MrChuck

It's not just the receiver chip and the software that makes one device better than another. I've got a Garmin eTrex Vista, and while it probably isn't any better (in any really meaningful way) than an iPhone* in terms of picking up the signals and dong the navigation stuff, it's waterproof, it has rubber buttons that will work with gloves and when everything's covered in crap, it takes AA batteries so it's good for multi day trips, and it will take a few knocks.

Of course if you already have an iPhone whether these advantages are worth getting another device for is up to you and what you'd actually use it for.

*or smartphone of your choice

Bar Shaker

Totally agree Mr Chuck.

Its also worth remembering that there are different levels of performance between different models too. Nokia N95 is dire at GPS. E71 is actually really good. My eTrex (pre Vista) was not good at getting and holding a lock to weak satellites in poor conditions, my 196 was faultless.

Provided you understand the limitations of any GPS device and treat them as a nav aid or route recorder, they are fine. Its when you treat them as your primnary source of navigation that its going to end in tears.

For those have iPhones, there is a nice app that was recommended to me buy a group of soldiers who are in a certain regiment based in Hereford. Its called Theodolite and they weren't keen to discuss what they used it for. Amongst other things, it gives Lat Long to 4 decimal places and carries out Re angle calcs for distance finding. I like it as its very handy for giving you an instant lat/long if you need to check that you are where you think you are. It may run on other platforms.

Anonymous

So is bar shaker actually agreeing now that differing GPS units have differing levels of accuracy?
Cause you know, that was pretty much the only point I was trying to raise in all this, before you jumped down my throat.

GiantMike

Bar Shaker wrote:

Amongst other things, it gives Lat Long to 4 decimal places and carries out Re angle calcs for distance finding. I like it as its very handy for giving you an instant lat/long if you need to check that you are where you think you are. It may run on other platforms.

4 decimal places, as in 0.2m accuracy??

How? Maybe with PY code but not with CA code surely? Do the Hereford boys really use a smartphone app for positioning rather than encrypted GPS signals in dedicated ruggedised devices? Blimey.

Anonymous

Of course it's to 0.2m accuracy. This isn't just any GPS device we're tlaking about here, this is an iPhone, remember.

biff55

yeehaamcgee wrote:

Of course it's to 0.2m accuracy. This isn't just any GPS device we're tlaking about here, this is an iPhone, remember.

Yeah ! not even the SAS can do special ops without an iphone.

Anonymous

It'll be some kind of correction system in use to get it more accurate than the consumer signal.

Like A-GPS on mobiles, there are correction systems for dedicated GPS units such as DGPS and WAAS. DGPS requires an extra receiver though, whereas WAAS does not.

Most Garmin support DGPS but need the extra receiver, but Garmin do WAAS enabled units also so if you've got one of these it should correct down to an accuracy of 3m apparently, assuming it can acquire the ground based signal for corrections.

These systems should be better than A-GPS as they are more oriented towards differential correction, and tailored for stuff like aviation.

But getting 0.2m accuracy outside of military encrypted GPS? Hmm.

http://www.gpsinformation.org/dale/dgps.htm
http://www.maps-gps-info.com/gps-accuracy.html
http://www8.garmin.com/aboutGPS/waas.html


But anyway. Frankly even 10m accuracy (as any GPS unit, mobile or not can achieve) is fine enough for most people out cycling. Unless you're planning on digging for treasure, I can't see why you'd need anything more