My Garmin has a sense of humour

dag_on_a_bike

Today my Garmin Edge 705 displayed a sense of humour.

I was told that the grade was -7% when I know the gradient was actually 12%.

Later on it merrily told me it was 45%. Nearer 5% in reality.

Anyone else had such odd readings?

neilo23

At first I thought you'd written "My GERMAN has a sense of humour". That would be strange ;-)
(I live there so I'm allowed to say that).

pdstsp

Loaded bike route toaster route onto mine earlier this year from Birkenhead to Shrewsbury. Got off mersey ferry, pressed "do route" and no little pink line. Rode for 5 minutes and had another go - still no red line. Finally zoomed right out on the map and found the route was actually in Egypt, running towards Syria. No real problem and found my own way there (Shrewsbury not Syria), but when I got back and looked on bikeroute toaster the route was fine - weird.

Also on lejog earlier this year it has me reaching 112 mph.

bobtbuilder

DAG on a bike wrote:

Today my Garmin Edge 705 displayed a sense of humour.

I was told that the grade was -7% when I know the gradient was actually 12%.

Later on it merrily told me it was 45%. Nearer 5% in reality.

Anyone else had such odd readings?

I had EXACTLY this problem on my last ride. It was the first time it had happened. I'm waiting to see if it was a one-off or whether it happens again before calling Garmin support.

In addition, it was showing my speed as 13-14mph when I was tanking along in the biggest gear and should have been nearer 28-30mph

Chrissz

According to my 500, our Sunday run across the marshes, with a wonderful view of the sea to our immediate right, took place at 500ft above sea level!! Despite the fact that in places we were actually below sea level!!

chiark

It's the altimeter, I guess... It seems to be quite badly affected by temperature, hence the daft grade readings?

Chrissz

I think that as it works off barometric pressure it may get thrown out as the weather changes???

Dave Cornwall

This could be the reason why it isn't reading very accurately?

A GPS, as we all know, gets it position from the Satelites, giving a bearing from them to the GPS unit. Where the bearing lines cross will be where the GPS thinks it is, both horizontally and vertically. Normally it requires 3 to get a fix in the horizontal plane and 4 or more to give an altitude.

The accuracy depends upon the satelite position relative to the receiver. If the GPS is only fixed onto those that are relatively low on the horizon, the accuracy of the position fix will be degraded. The most accurate fixes are achieved when the bearings from the satelites to the GPS unit cross at right angles, and the more signals it receives, the more accurate the position given will be.

MaxwellBygraves

My 800 seems to work fine except for the gradient field.

Regularly just gives random gradients, uphills on downhills, etc

Haven't had any other niggles though so can't be bothered to cause a faff.

Bit annoying though that for a top end product for which you pay a premium and it still has pretty basic errors...

JamesB

Answer from my enquiry to Garmin re altimetyer is yes it works off barometric pressure therefore weather changes affect stable altitude readings;

However it also can cross reference to map altitudes ; so their advice was save a waypoint of known altitude, adjust in `save ` field altitude to what actual map reading is, and then when Garmin is started it looks at waypoint height and automatically adjusts to it.

However yesterday for first few minutes on a walk Garmin 705 read - 695% grade going uphill, which did not appera to be correct

Water around sensor hole will affect readings too, as it delays / affects sensor reacting to pressure changes. Just shake Garmin dry to remove water droplets

Nuggs

bobtbuilder wrote:

In addition, it was showing my speed as 13-14mph when I was tanking along in the biggest gear and should have been nearer 28-30mph

Oh yeah, blame the Garmin...

(Hello mate, LTNS)

freehub

Going through Manchester I regularly see gradients of 400% and upwards. I've being known to ride my bike at over 50,000ft as well.

nevman

not me of course, but a mates Garmin went into autopause on Alpe d`Huez as he was going so slow.Embarrasing.