GPSrChive Discussion Forum

On a short hike yesterday, the precision is sometimes excellent and other times a difference of 3 to 4m, this distance seems normal, but why the differences on a circuit yet without trees or houses, completely clear and beautiful sky.

mimichris wrote: ↑Wed Apr 05, 2023 9:28 am On a short hike yesterday, the precision is sometimes excellent and other times a difference of 3 to 4m, this distance seems normal, but why the differences on a circuit yet without trees or houses, completely clear and beautiful sky.

I also notice that the deviation is considerable, but the line is straight and the distance is even. The track does not move like a snake. Unless that's how I move.

I notice this inaccuracy by staying in the middle of the road or the path, sometimes an offset of 3 to 4m measured on the Google Earth map which I think is precise, likewise on the IGN satellite map of France.
But the precision tolerance for a good GPS is around 3m in the case of the 66sr in multi-band.
On the other hand, if I ride a bike, with any GPS like my old Edge 705, the track is perfect, is it due to the speed, certainly.

mimichris wrote: ↑Wed Apr 05, 2023 12:59 pm ... on the Google Earth map which I think is precise ...

Do not be fooled, it is not precise nor is it accurate!

GPSrChive wrote: ↑Wed Apr 05, 2023 3:22 pm
Do not be fooled, it is not precise nor is it accurate!

I think so too.
You should not compare yourself to the map, but to previous hikes.

Spoiler

67vs66sr10.jpg

All these lines are my 66sr tracks. The dark line is multiple overlapping tracks, I adjusted the map to it.
I also showed the distance most deviating from the "norm".

The IGN France maps are very precise, they are used to create IGN maps at 1/25,000, this is the reference and I have exactly the same offset as on Google Earth.
There is a geodesic system in France precise to the cm, we can access the terminals and markers, their positions and their precision.

mimichris wrote: ↑Thu Apr 06, 2023 9:09 am The IGN France maps are very precise, they are used to create IGN maps at 1/25,000, this is the reference and I have exactly the same offset as on Google Earth.
There is a geodesic system in France precise to the cm, we can access the terminals and markers, their positions and their precision.

I have been creating my own maps for more than a decade, frequently comparing my data to Google Earth satellite imagery, and have found their satellite imagery to shift inconsistently in random directions by several meters from one release to the next.

Any map that is aligned precisely with Google Earth satellite imagery today will not be aligned precisely when compared to future or past Google Earth satellite imagery releases.

IGN satellite :

*** Hotlinked image removed ***

Google Earth :

*** Hotlinked image removed ***

I did not understand how to load images, although I make you delete them, how to do please!

mimichris wrote: ↑Fri Apr 07, 2023 1:57 pm I did not understand how to load images, although I make you delete them, how to do please!

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Thank you!