garmin 500 GPS

chatlow

I have just got a garmin 500 premium and I am finding that the GPS accuracy will be around 60ft.

Is this the norm? I have got software v3.30 and GPS: 2.60

adr82

Where are you getting the 60ft measurement from? Anyway, GPS accuracy will change from moment to moment depending on how many of the satellites are currently visible in the sky from the position of the receiver. It can also be significantly affected by environmental obstructions (trees, hills, buildings, etc) blocking line of sight to the satellites. Don't expect it to work like in the movies where you can instantly and reliably pinpoint your location to the nearest metre.

chatlow

Getting the accuracy in the GPS settings and also had it as a data field when I tested it. I don't expect it to be bang on but read online that 20-40ft is the norm. To be honest, I am new to this and I just want to make sure the unit is working correctly as bought it on ebay and it will be going away for Christmas after I test it.

junglist_matty

Did you let it lock onto satellites after you turned it on? If not, it takes a short while (couple of mins) after turning on to get a good lock on current satellite positions, if you don't wait and set off, it still works, but will be off accuracy by a country mile.

chatlow

yup - I retract my first comment - let it load for a minute and it went down to 19ft.

How accurate is the gradient measurement in %?

Also - if I attach the speed/cadence sensor, then will the Garmin use this as it's primary source for speed and distance or will it still use GPS?

Thanks

ManOfKent

chatlow wrote:

yup - I retract my first comment - let it load for a minute and it went down to 19ft.

How accurate is the gradient measurement in %?

Also - if I attach the speed/cadence sensor, then will the Garmin use this as it's primary source for speed and distance or will it still use GPS?

Thanks

I find the trace often weaves away from the line of the road, particularly wooded hillsides and other places where the satellite contact may be patchy.

The gradient measurement seems generally fairly reasonable, although there's sometimes a lag in showing changes and I don't suppose any of us will get off the bike to perform a scientific assessment of whether the gradient is really 15% as per the Garmin, or only 13%.

You can set the Garmin to use the sensor or GPS for the speed/distance measurement. I can't remember what the default setting is but it was mentioned on another thread recently. Mine runs on GPS.

chris_bass

chatlow wrote:

yup - I retract my first comment - let it load for a minute and it went down to 19ft.

How accurate is the gradient measurement in %?

Also - if I attach the speed/cadence sensor, then will the Garmin use this as it's primary source for speed and distance or will it still use GPS?

Thanks

It will use the speed sensor over GPS, but it still logs location points so when you upload it you will see a map, if you set wheel size to auto then it will work out your wheel size for you so its pretty accurate.

i'm not sure i trust the % gradient, mine (god rest its sole!) used to change dramatically with the weather. if it was a clear day my total climb on my way to work was about 100 meters less than on a rainy day. so i'd guess the gradient is also affected, good as a rough estimate though.

rolf_f

The gradient measurement is meaningless - your instinct should be more accurate. Lets say that the horizontal measurement is accurate to about 20 feet as suggested above. So, if you travel 20 feet, the GPS could register anything between 0 and 60 feet travelled. Even if the vertical measurement was 100% accurate (which of course is far from the truth), then if you climbed one foot in that distance, the recorded gradient could be anything from 1 in 60 to vertical. Reality isn't that extreme but it is fairly clear that the combination of vertical and horizontal errors over a short distance renders the calculation very inaccurate.

GiantMike

The vertical accuracy of GPS is pants compared to the horizontal accuracy

kajjal

If you set it to update every second thats as accurate as it gets.

noodleman

I did a 16 mile run yesterday. I used strava and my edge 500 as back up. My edge kept losing signal along remote wooded canal paths but my phone didnt lose it at all. In total, my garmin only logged 12 miles of the sixteen. I would have thought the garmin would have been the better unit for gps but obviously not. :?

shmooster

noodleman wrote:

I did a 16 mile run yesterday. I used strava and my edge 500 as back up. My edge kept losing signal along remote wooded canal paths but my phone didnt lose it at all. In total, my garmin only logged 12 miles of the sixteen. I would have thought the garmin would have been the better unit for gps but obviously not. :?

Your phone has the advantage of aGPS, it can use wifi/phone signals for additional accuracy. If it's a newer phone it can also use the russian Glonass GPS system.

cougie

Thats interesting - I keep seeing people talking about how their bike GPS is more accurate than the iphone etc gps.

If i look at tracks of my rides recorded on my iphone - it looks spot on on the map.

noodleman

I agree. I was always led to believe a dedicated gps unit would be more accurate than a phone.

elderone

My 500 has been replaced under warrantee for elevation issues and it was month old.The replacement one has also gone back to garmin as faulty.Not very impressed at all as never had an issue with the 200.
I have been using my phone for strava and the accuracy has been much better than garmin.To be fair with a £10 cycle computer and phone for strava i,m getting the same info as my expensive 500 (hr and cadence excepted).

wongataa

noodleman wrote:

I agree. I was always led to believe a dedicated gps unit would be more accurate than a phone.

With the Garmin 500/510/800/810 you can tell it to log it's position every second. You can't do this on a phone so the resultant track log is more accurate from the Garmin as it more accurately follows you path.

kwi

Plus the phone probably defaults to 'Follow Road', haven't messed about with the Garmin enough yet to see if that is a switchable option. My old plotter some times had me in the sea for a good few miles.

smoggysteve

Change your Garmin to 1 second interval instead of smart accuracy. The 500 is quite glitchy in smart mode. I Have one and over the course of a year have noticed the differences and 1 second if so much better.

smoggysteve

cougie wrote:

Thats interesting - I keep seeing people talking about how their bike GPS is more accurate than the iphone etc gps.

If i look at tracks of my rides recorded on my iphone - it looks spot on on the map.

A garmin has elevation accuracy. A smartphone does not. The Garmin will record your elevation. The iphone has to get this from the 2D map you use. Depending on who owns the map the calculation form 2D to 3D will differ.

shmooster

It depends on the smartphone, some have barometers built in (Galaxy S4 does I think, though none of the apple ones). Whether an app uses it or not of course depends on its usefulness. Some of the apps also do elevation correction as a post step (NASA has a worldwide database of elevation for any point) , I believe Strava does this.