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Accuracy of maps from GPS - has it always been like this?

Can someone clear something up for me please? I use a Forerunner 405 to record my runs and then upload to Garmin Connect - has the route that shows on the maps always been so inaccurate, or is this since it switched to Bing?

For example, look at the picture below, the route is off to the side of the road when I clearly was running on the pavement.

This sounds mad, but I honestly can't remember whether it was like this when we were on Google Maps or not, but I can't remember it being this bad.

Is it the maps fault, or the general inaccuracy of the GPS in my forerunner?

0 GAZHOWELL over 15 years ago

Hmm, I've just downloaded that extension for Google Chrome that switches the maps back to Google Maps from Bing and I get this:

So it looks like it may not be Bing maps' fault.... unless it is Bing and then the conversion back to GMaps keeps Bing's inaccuracy?!?

Confusing.

0 Former Member over 15 years ago

Well, I've seen my Oregon 400i act somewhat like that when walking the streets of NY City, in the urban canyon that caused the signal to bounce off the buildings, thus becoming degraded

I've also seen my Nuvi 765T and 1490T show me driving about 100 feet or so off the side of the road when I was right in my lane... No explanation for that other than perhaps really lousy GPS satellites geometry. It lasted only a few minutes though.

Why do I remember these two incidents? Because they are so rare. Generally, I can not only see my track on the road, but on the correct side of a relatively narrow road.

Does it happen often with your 405 or is it a single occurrence? If it is a single occurrence, just ignore it.Try looking at your track on Google Earth. Use Google to find how to convert your gpx file to kml, then you'll be able to see it on Google's aerials.

0 Former Member over 15 years ago

Looks to me like you've got a constant offset there rather than an inaccuracy. Have you got the wrong datum set anywhere ?

0 GAZHOWELL over 15 years ago

Well, I've seen my Oregon 400i act somewhat like that when walking the streets of NY City, in the urban canyon that caused the signal to bounce off the buildings, thus becoming degraded

I've also seen my Nuvi 765T and 1490T show me driving about 100 feet or so off the side of the road when I was right in my lane... No explanation for that other than perhaps really lousy GPS satellites geometry. It lasted only a few minutes though.

Why do I remember these two incidents? Because they are so rare. Generally, I can not only see my track on the road, but on the correct side of a relatively narrow road.

Does it happen often with your 405 or is it a single occurrence? If it is a single occurrence, just ignore it.Try looking at your track on Google Earth. Use Google to find how to convert your gpx file to kml, then you'll be able to see it on Google's aerials.

Looking back at old runs and zooming in, it seems to be like this for every run. I think I've never noticed before as I don't really zoom in I just look at the overview map where you see your whole route. It seems to be the same on Google Earth as well (I don't need to convert the gpx as Garmin Connect has got a Google Earth button on the activities page that does it all for you)

Looks to me like you've got a constant offset there rather than an inaccuracy. Have you got the wrong datum set anywhere ?

Excuse my ignorance but what does that mean?

0 Dr Phil over 15 years ago

I've seen this happen if I have not got a good lock before setting out. The tracks merge after a short while generally.

It may not be the device but the map. I know over here they changed the maps to take into account the proliferation of GPS devices. NZ Map Overhail
I know this was a while ago, but the possibility is there.

0 Former Member over 15 years ago

Keep in mind that even the best GPS units can give you errors of 10 meters or so. Since this error appeared at the start of your workout, I'm guessing the sattelites didn't lock on yet.

0 Former Member over 14 years ago

I have noticed a marked deterioration in accuracy since Bing was introduced. Before, I found the tracking was extremely accurate, reliably picking my start point. Now it seems to place me randomly around my start point but sufficiently far away to mess up my first mile times. It does seem to get better as distance increases but it is just not accurate enough at the outset. A definite step backwards.

0 DW152 over 14 years ago

I have noticed a marked deterioration in accuracy since Bing was introduced. Before, I found the tracking was extremely accurate, reliably picking my start point. Now it seems to place me randomly around my start point but sufficiently far away to mess up my first mile times. It does seem to get better as distance increases but it is just not accurate enough at the outset. A definite step backwards.

The choice of maps on Garmin Connect will not affect your "first mile times." That is calculated on the Garmin device from the GPS trackpoints and has nothing to do with any map -- it's just trigonometry.