# GLONASS - it makes a difference

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GPSTrackLog mentioned an online GPS prediction, planning tool at CalSky.

I'm delighted about this, not ony because I've been looking for a GPS planner but also because this one also lets you include GLONASS in it's calculations. If you want to see what a difference that makes, run the numbers with and without.

Edited by user13371

If I run the numbers, what will I see?

Not wanting to rain on anybody's parade, but do note that the OP links to data obtained at coordinates on a not too grassy knoll with surrounding higher peaks not too far from a consistently foggy river bottom.

On the other hand, those coordinates may provide a decent view of the source of the OP's bicycle.

Edited by 39_Steps

.

Edited by mineral2
... the OP links to data obtained at coordinates ... may provide a decent view of the source of the OP's bicycle.

Not quite, but thanks for pointing out the goof. You can enter your own location on that page, but I meant to post the more generic link:

http://www.calsky.com/?GPS=

ANYHOW... Put in your own coordinates, leave the GLONASS box unchecked, and see how many sats you have in view and what the PDOP number is. Then repeat with the GLONASS box checked. More satellites, lower PDOP numbers. It ain't rocket science.

Oh wait, yes it is!

Edited by user13371

I've used "Trimble Planning" for years, but had to download the program and then be sure to keep the latest almanac, etc. Now there's an online version that eliminates all that hassle.

Look for "Trimble planning Online".

Yup, it should - in theory, give a more truthful position most of the time if properly implemented and a simple centered average of the position from both systems is what's being done. About 30% less error actually.

The reality is indeed more complex. Not sure how well the GPS manufacturers have investigated ways of combining data from the two parallel systems. Kalman-filter like combining, or just, for the moment, using data from the system that has the lowest calculated EPE could be two possible methods of optimizing it

Certainly confirms my experience with my Etrex 20, with GLONASS on it is more accurate (at least within the UK and France where I use it).

Same here, It really does make a difference!

Here at N45 W075 it does make a difference, especially in the woods.

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