GPSMAP 67 GPS accuracy

[RickN55]

What is the GPS accuracy on the GPS satellite page on the 67? My 65s goes down and stops at 6feet (1.8m) all the time once switched on. Does the 67 better this ? Is it worth me upgrading to the 67 from the 65?

[Nail]

What is the GPS accuracy on the GPS satellite page on the 67? My 65s goes down and stops at 6feet (1.8m) all the time once switched on. Does the 67 better this ? Is it worth me upgrading to the 67 from the 65?

If GNSS is going to be important when choosing a new GPS, I'd wait.

Read this topic.

[mimichris]

I ask myself the question, is this data on the GPS reliable, in fact it is only an appreciation of the precision: the PDOP and the DOP.

If I remember on the old Garmin GPS it called this data: PDOP.

Spoiler

https://www.agsgis.com/What-is-PDOP-And ... _b_43.html

Spoiler

[Spoiler/]

[mimichris]

To continue concerning this precision, I notice that on the 66sr as soon as a certain number of satellites are acquired, the DPOP precision immediately goes to 1.8 whatever the number of satellites, and after one hour of operation this figure does not change. should change depending on this number and the quality of the received signal since it is based on the number and their position in the sky. On my smartphone and the GPSTest app, the PDOP changes depending on the number and quality of the signal, it is not always fixed.
So I consider this data as random but not absolute precision. This is just my opinion, can someone confirm or deny?
It is necessary to do fixed tests on a point known as the link that I had given concerning the precision of the 66sr, in RINEX mode.

[JungleJim]

How do you view the PDOP on the 66sr?

[Nail]

So I consider this data as random but not absolute precision. This is just my opinion, can someone confirm or deny?
It is necessary to do fixed tests on a point known as the link that I had given concerning the precision of the 66sr, in RINEX mode.

The only reliable source will be as you say RINEX and your gpx track. The rest is marketing. As you can see after the last update 67, you can improve customer well-being by displaying them better GNSS values.

[mimichris]

How do you view the PDOP on the 66sr?

This is the accuracy figure on the satellite page, for example 1.8m on the 66sr, at least this is what Garmin indicated on my GPSII+ (EPE). In reality it is the HDOP which is the PDOP with the altitude :

Spoiler

https://interpine.nz/gps-accuracy-estim ... hat-is-it/

[mimichris]

I couldn't correct my message, it's going too fast, so the previous one is cancelled.


In fact it is rather the HDOP which is like an indication of the precision on the Garmin, I was wrong. But these data all come together to give the precision. This is the accuracy figure on the satellite page, for example 1.8m on the 66sr, at least this is what Garmin indicated on my GPSII+ (EPE). the PDOP: Position (3D) dilution of precision, HDOP — Dilution of Precision (DOP)

Spoiler

https://interpine.nz/gps-accuracy-estim ... hat-is-it/

[JungleJim]

It’s all very interesting info (learning a lot on GNSS and receivers), but my take away is that what the unit displays as “accuracy” cannot be taken as an absolute. It is just a measure of confidence. In other words there’s an x percent chance that the position measured is within the displayed accuracy, but it could also be outside.

And it is not possible to compare it between GPSMAP series because we do not know how it is calculated since it is proprietary and Garmin won’t tell. Various sources list 50% for older devices, GPSrChive lists 95%. It could be the same for the 67 but it could also be different…

So I agree with Nail on this, you need the recorded track and RINEX data (which is broken on the 67 with firmware 4.80) to compare how accurate different devices are. In my experience the recorded tracks on the 67 are quite ok for my needs.

If you’re happy with the 65s I would not upgrade for now. If you need the bigger screen or the better battery life, I would wait a couple of firmware updates until the bugs have been ironed out.

[mimichris]

As you say, what counts is to have a trace faithful to the terrain and the maps, after the rest.......