Garmin v phone app

wobbem

Tried using my smart phone app in Epping forest yesterday but couldn't get a signal from a sat, would I get the same problem using a Garmin, are they worth it, do they lose their signal?

Bar Shaker

Very likely would be the same.

biff55

no it wouldn't be the same.
phones use land based telecoms transmitters to locate position whereas proper gps units
lock onto satelites in orbit , thus making tracking more possible in remote locations.
which garmin ? most will be better than maps on a phone.

chedabob

Depends what you mean by couldn't get a signal. Did the phone locate you and the map didn't show? If you've got good GPS signal, then the Garmin should work better because the maps are stored on the device (some apps for phones can predownload the maps though).

biff55
They do, but it's only until the true GPS kicks in, which can take up to 60 seconds, or if the GPS isn't working at all.

wobbem

chedabob wrote:

Depends what you mean by couldn't get a signal. Did the phone locate you and the map didn't show? If you've got good GPS signal, then the Garmin should work better because the maps are stored on the device (some apps for phones can predownload the maps though).

The phone took ages trying to locate me , I gave up.
Been checking out bluetooth gps reciever moduals - for £20 -30 sounds like they can get more fixes and quicker which might be an option.

http://www.mobilefun.co.uk/bluetooth-gp ... 2Bproducts

Granted Garmin has Ordanance survey installed which is a great feature, I can buy maps for my phone ( Augmentra ) but £150 for GB! :shock:

What predownload maps apps are you talking about?

Bar Shaker

Phones with true GPS (iPhone and some Nokias, amongst others) work in the same way as a Garmin but they can also triangulate from the mobile phone masts. The phone knows where the masts are and looks at the signal strength from all the masts it can 'see'. This second mode has varying accuracy but can be useful and can be accurate, depending on the number of masts seen.

Phones download maps to suit where the user is and these maps are far more detailed than most GPS maps. You can switch between aerial view, satellite/road map and terrain maps. The catch is you need a 3G signal to download the maps. GPS units have their maps built in, or on a memory card and are only reliant on a GPS signal. 4 satellites is the minimum for a fix. Most have screen that shows the strength of those satellites that are available to the user.

Garmins suffer under heavy tree cover, just as phones do, but phones can get a phone signal in these conditions, making them sometimes the better choice.

Heavy tree cover, with thick cloud cover/rain, will degrade the very weak signals from satellites quite badly.

Anonymous

A proper garmin or similar GPS receiver will be able to lock on much more accurately to GPS under heavier tree cover, or in deep gullies, where the phone may struggle.
They also tend to have much higher levels of error-correction in their design and will give more accurate results.

At the end of the day, a GPS receiver in a phone is just a gimmicky add-on.

Bar Shaker

Yeehaa, that's not how GPS works.

The error correction is only from the number of satellites the unit can read. The signals are a time stamp and are compared to the strongest of the signals, giving a delay between the when the signals were sent and when they were received. Divide the difference by the speed of light and you have your distance from the satellites. Triangulate this and it gives you your position in 3 dimensions.

The radio signal speeds are affected by areas of high gravity so those directly above give more accurate results than those near the horizon, which has travelled close to the earth's surface before being read. The unit, phone or PND, either does GPS or it doesn't. As the info is all digital, its received or it isn't. A £120 TomTom will be as accurate as a £600 iPhone, if both receive the same signal information. I use Golfshot on my iPhone and this can be compared with known golf course data for positioning. The Dilution of Precision is very good and accuracy of location is normally less than 3m.

The Galileo satellite system will offer better signal strength and better accuracy, by using more decimal places for the time stamp, but is likely to be charged for by licensing receivers.

The US Global Positioning System is more than accurate enough for blokes on push bikes.

wobbem

I just found out that I'd have to buy topo maps for a garmin as well.......

Herbie The Dog

wobbem wrote:

I just found out that I'd have to buy topo maps for a garmin as well.......

You can...but they are crap.

Try openstreetmap.com for better topo maps...and free.

Anonymous

Bar Shaker wrote:

Yeehaa, that's not how GPS works.

It really is. GPS has an inherent inaccuracy. Garmin quotes this as around 10m for their devices. This is due to all sorts of environmental conditions, reflected signals, intermittent signals and so on.
Now, on a very basic level, what you can do to reduce the inaccuracy, is take many samples, then average out the location. That's basically the underpinnings of error correction.
The better devices will have better algorithms for detecting and dealing with offset inaccuracies, and also far more sensitive antennae.

Your iPhone, despite marketing and a religious following bordering on a cult, is not the be-all and end all of all devices.
It is NOT the best phone, it is NOT the best camera, it is NOT the best gaming system, it is NOT the best GPS.
Seriously.

shoddy

The other advantage with GPSr's is that they are waterproof and rugged. There is no way that i would strap my phone to my rucksack whilst mountainbiking/running/walking in poor weather like i do with my oregon & etrex. It wouldnt last two minutes.

Herbie The Dog

shoddy wrote:

The other advantage with GPSr's is that they are waterproof and rugged. There is no way that i would strap my phone to my rucksack whilst mountainbiking/running/walking in poor weather like i do with my oregon & etrex. It wouldnt last two minutes.

I came across a MTBer on Dartmoor moaning that his beloved, can't live without iPhone was now ruined due to a unforecast downpour.

I had no sympathy as I pointed out to him that you can't forecast anything on Dartmoor. Apparantly he was waving it around in the cafe pre-ride like it was some sort of godlike device. iPhone 4 as well.

*snigger*

My Garmin Oregon does a lovely job thank you.

wobbem

Mines just a smart ph I picked up second hand on Ebay.
Being a cheap skate I keep mine in a plastic bag and use it just to (hopefully) check out where I am. Plus Ii use endomondo is great for recording your tracks.

Anonymous

Guy was picked up from the Glyders the other week, completely and utterly lost. He was trying to use his iPhone to navigate to the devil's appendix.
Mountain rescue teams saw him nearly walk off several cliff edges, blindly following his phone, ignoring what he saw with his eyes.
The most shameful thing is that as he was being led to safety by the search team, he refused to accept that what he was doing was in any way stupid or dangerous, apparently.

They should have left him there to die, as a warning to others :roll:

monkeylizard

I use Viewranger on a smartphone (with A-GPS switched off), wifey uses a Garmin. To be honest, when looking at the recorded traces of where we've taken the bikes there's not a huge amount of difference in accuracy. Both of them can throw a bit of a wobbly from time to time and get confused but then we're only looking at the traces to see how far, how fast, etc, it's not as though it's life and death. If you're out and about in the middle of nowhere and really need to know where you are, I wouldn't recommend relying on just a GPS of any sort.

Bar Shaker

Yeehaa, Until you know how GPS works and why Garmin don't use better algorithms (the algorithms are industry standard, you don't make your own up), or that they don't have some secret way of extracting more data from the digital time stamp, then there is no point discussing the merits of devices further. The accuracy is the signals, not the receivers. Try a GPS phone, especially one that also has a compass, you might be surprised. Especially if it has a terrain map.

A Garmin such as eTrek would not have helped the chap who was lost and nearly walking off cliffs. They only show lat/long and record track data. Not much good unless you also have, and can read, a good OS map.

Monkeylizard I agree with all of that. As a private pilot we are taught that GPS is useful only for confirming that you are where you already think you are. The last time these two information sources agreed is the only thing you can be certain of with regards to the GPS. If you don't know where you are, any GPS information could be right or could be wrong. For the times when your life may depend on it (such as flying from Beaconsfield into White Waltham), GPS is no substitute for proper map reading and navigation skills.

As a recorder of routes and route data, phones can be very useful.

Anonymous

Bar Shaker, give it a bloody rest. I've got and have had several phones with GPS, and several GPS devices, and a sat nav for the car. They all have wildly differing levels of accuracy.

monkeylizard

From the Garmin website:

"Sources of GPS signal errors

Factors that can degrade the GPS signal and thus affect accuracy include the following:

* Ionosphere and troposphere delays - The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error.
* Signal multipath - This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.
* Receiver clock errors - A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors.
* Orbital errors - Also known as ephemeris errors, these are inaccuracies of the satellite's reported location.
* Number of satellites visible - The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.
* Satellite geometry/shading - This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping."

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.

Anonymous

yeehaamcgee wrote:

It really is. GPS has an inherent inaccuracy.

It does in that the consumer GPS is deliberately less accurate than the military GPS signal. It's still fairly accurate though with the right equipment. Oh and the US DoD (who own the satellites) reserve the right to cripple or disable the signal if they see fit, but you'd probably only find that an issue if you were in a war zone

biff55 wrote:

no it wouldn't be the same.
phones use land based telecoms transmitters to locate position whereas proper gps units
lock onto satelites in orbit , thus making tracking more possible in remote locations.
which garmin ? most will be better than maps on a phone.

That only applies to non GPS phones.

GPS phones have true GPS receivers in them. They also have a bonus over standalone GPS units in that they can use GSM to connect to a server to get the initial satellite data quicker than a standalone can, which aids getting a lock. This is known as Assisted GPS.

However phones have a disadvantage in that the receivers are often not as big as those in a standalone and they are crammed into a device that has many other transmitters and receivers, especially in smart phones that have GSM/3G/Bluetooth/WiFi. Plus metal casings on some phones can shield the signal.

Accuracy of GPS in a mobile can be affected by the software. The phone software or the application may include GPS filtering which copes with errors. A Garmin or similar may also be doing this.

A mobile phone with GPS can be as accurate as any stand alone device, but it depends a lot on the phone, how it's built, the software being used. Then of course for just plain maps you have an added advantage with a phone that if you can't get a GPS lock, you can get cell location and some will also locate based on known WiFi access points if you have WiFi in the phone (Google Maps and Nokia's Ovi Maps does this in more recent phones). Little use out in the country though and such positioning only tells you what you are near, not where you actually are, but it's handy for a rough location. Sports tracking software requires true GPS though.

As also mentioned, modern GPS phones have a compass too. Which is nice.

Sports tracking apps on phones are good in that they are cheap (sometimes free, like Sports Tracker for Nokia phones), and you can easily upload tracks even when you're out in the middle of nowhere, even live as you ride, and have photos taken along the way uploaded. Then share them on a tracker site, or Facebook or whatever, export to GPX files and so on.

Oh, and finally, if the phone's internal GPS isn't good enough or it doesn't have GPS at all, £50 or less can get you a standalone bluetooth GPS device that the phone can talk to, and you can then use any GPS app.


For an accuracy example in a phone (Nokia E72), here's a track from Monday doing the Whites descent at Afan:

http://bit.ly/9uSTX3

When moving it's fairly accurate. Note there are points when we had stopped and the position was drifting a bit so you can see the track wandering about. However there's a known issue with the software at the moment where it seems it's not filtering at all or properly (it was with the old Nokia ST beta). The tracks also tend to go in a straight line for short sections where the trail may have had little deviations in it. Alignment with the satellite view of Google Maps is not a judge of accuracy as Google's sat views don't match up perfectly with the real world.

In general for my purposes, which is tracking routes and knowing where I am, it's perfectly accurate enough for me.

biff55

very interesting points and info raised by all posters above.
however in reference to the original question , i'll bet £20 that my garmin dakota wipes the floor with any iphone app with regards to speed in signal lock and accuracy in tracking.
yeehaa's right , its just a gimick with phones rather than a serious satnav tool.
the fact that the dakota is waterproof , shockproof and half the weight and size of an iphone adds weight to its credentials as a usuable field device.

Bar Shaker

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.

biff55

^^ apple fanboi alert.
all well and good until the iphone packs in after a stray drip of sweat lands on it.

Anonymous

It's no gimmick.

Else these wouldn't exist:

http://www.viewranger.com/
http://www.sports-tracker.com/
http://www.endomondo.com/

The gimmickness of the phone is another matter, and I'd probably agree when it comes to an iPhone, but the above are not specific to Apple products and there are plenty of other (and better) GPS enabled smart phones. Apple aren't exactly experts in the field of signal technology whereas the likes of Nokia (rubbish though their software may be) have decades of experience and can get excellent reception for all kinds of signals, including GPS.

Yes, a GPS phone is not as accurate as a military grade GPS and nor is a Garmin. Neither phone or Garmin is recommended for piloting a plane either, but then GPS is not recommended for that anyway.

What do you expect to do with it ultimately? If you're looking at use for navigating outdoors when cycling the Garmin will not make a blind bit of difference. Both phone and Garmin will give you a 10 meter(ish) accuracy.

Oh and I disagree that the Garmin will be quicker at locking. At least for an accurate lock. A phone with A-GPS should be much quicker. To get an accurate lock a GPS device has to initially get the almanac of all available satellites which it gets by downloading it from one satellite. The rate of data from the satellite is slow compared to A-GPS getting it from the network. Also A-GPS can get an accurate ground level* time sync from atomic clocks. A-GPS also is an aid in built up areas where satellite signals are degraded. Try walking around the centre of London with a Garmin and then try it with a *decent* mobile with A-GPS and see how it works.

* - note that GPS is affected by the general theory of relativity and time on satellites appears to run faster than that on the ground, though the GPS system has inherent compensation for this, but it helps to have an accurate ground level time.

By the way, Sat navs in cars cheat. They have a map of all the roads and the lock will follow the road you are near. If the accuracy is not too great it can still work out from direction and speed that you are likely to be on the same road. That's why a decent car sat nav can even cope in a tunnel!

biff55 wrote:

all well and good until the iphone packs in after a stray drip of sweat lands on it.

You get a rugged outdoor waterproof case for it then :roll:

Anonymous

deadkenny wrote:

By the way, Sat navs in cars cheat. They have a map of all the roads and the lock will follow the road you are near.

But several car sat-navs, and GPS devices, including phones, will actually GIVE you real-time accuracey readings. That's not cheating, that's just giving you an exact feedback about it's current state.
My Navman, for example, will give you latitude and longitude figures. You can watch these, and see how they stray.

GPS manufacturers will also state at least minumum error margin, and at best, max, mean and minimum.

biff55

deadkenny wrote:

Oh and I disagree that the Garmin will be quicker at locking. At least for an accurate lock. A phone with A-GPS should be much quicker. To get an accurate lock a GPS device has to initially get the almanac of all available satellites which it gets by downloading it from one satellite. The rate of data from the satellite is slow compared to A-GPS getting it from the network. Also A-GPS can get an accurate time sync from atomic clocks. A-GPS also is an aid in built up areas where satellite signals are degraded. Try walking around the centre of London with a Garmin and then try it with a *decent* mobile with A-GPS and see how it works.

you are mistaken with this point.
my garmin will get a fix on upto 6 sattelites in under 10 seconds of stepping out of the front door.
yet to see any phone based gps match this , and i've seen a few in use while out riding with mates who have phone maps.

biff55

this is my outlook of the matter ,
you want to take pictures , buy camera
you want to make calls , buy phone
you want accurate mapping , buy gps.
thinking that an iphone will do all these things as well as dedicated devices is just marketing BS thats gone to your head.

Anonymous

biff55 wrote:

you are mistaken with this point.
my garmin will get a fix on upto 6 sattelites in under 10 seconds of stepping out of the front door.
yet to see any phone based gps match this , and i've seen a few in use while out riding with mates who have phone maps.

My Nokia can get a lock in 2 seconds with A-GPS. If you're ever up for a ride with me, I'm happy to illustrate . In fact it gets a lock that fast indoors if I'm near a window.

(with the exception of the current version of Sports Tracker which has a bug in it that prevents the lock sometimes, but that's nothing to do with the phone. Ovi Maps, Google Maps, the old Sports Tracker software, Endomondo, all within a few seconds).

biff55 wrote:

thinking that an iphone will do all these things as well as dedicated devices is just marketing BS thats gone to your head.

I'm not talking about iPhones.

Problem is a lot of people seem to think the only phones out there are iPhones. If your only experience is an iPhone then I'm not surprised you don't rate them as a professional device or of use outdoors. I don't either.

Bar Shaker

Biff you have identified the problem perfectly.

PNDs are rugged and generally are shower proof. A phone wrapped in cling film will be shower proof but its a lash up, as opposed to a purpose built solution.

The accuracy is there, the cost advantage is huge but the usability for some activities is not perfect.

By the way, if you want to see how the iPhone is driving what GPS will provide in the future, have a look at this... http://itunes.apple.com/us/app/golfscape-gps-rangefinder/id382051762?mt=8. Its an 'augmented reality' golf app. The software over lays distances to the pin, bunkers, ditches etc onto the image received from the phone's camera, based on GPS and compass info. You can pan around to see all the info and when the hole or bunkers are hidden, the screen will still over lay the info even though they may be over a crest of obscured by trees. It shows you the direction and distance to a hidden location.

Now imagine being able to pan around a valley and have the bridleways or paths over layed on what you see, together with distances to points like car parks, or river bridges etc. That might be very useful.

Anonymous

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.

biff55

sounds like its just one step away from taking the shot fot you.
maybe apple are saving that for the iphone 5.