GPSrChive Discussion Forum

This doesn't seem to fit any of the existing topics. I've used a 66i for several years and wanted to compare it with the 66sr and 67i on actual hikes in narrow canyons and other steep terrain. Therefore I headed to the Columbia River Gorge.

Hike 1 (May 6, 66i, 66sr & 67i): Larch Mountain Trail from Multnomah Falls parking to Multnomah Basin Road.

Hike 2 (May 6, 66i, 66sr & 67i): Eagle Creek Trail from Big John parking to Skoonichuk Falls.

Hike 3 (May 20, 66sr & 67i): Same as Hike 2.

Please feel free to turn tracks on and off with the controls on the left. You can download them using the Export button.

Technical stuff: The 67i and 66sr were mounted upright on opposite shoulder straps of my backpack, with the top of each unit slightly below the shoulder. The 66i was mounted upright (most of the time) on the center rear of the backpack lid, with the top of the unit a couple of inches below the top of the backpack. Firmware: 67i 4.80; 66sr 5.70; 66i 9.50. CPE or EPO files were current. Tracks from this May are unedited. Tracks from earlier hikes with the 66i had been cleaned up somewhat.

I repeated Hike 3 because I was guiding a youth group and wanted to see how a different day, with probably very different satellite constellations, would affect the results. I had read several of the discussions about the relative accuracy of the 66sr and the 67 series, and noticed that some of those tests were made only once, over a small distance. My results suggest that it would be better to repeat such tests over a significant distance on multiple days. (I know that others have mentioned this, but there still seems to be confusion on this point.)

My impressions: All three units work very well; certainly much better than my old 62s did. Portions of each hike are very difficult for even the most recent units, with narrow canyons, heavy timber, and cliffs overhanging the trail in places. However, the 66sr and 67i tend to have much less error in the most difficult locations. See the Lower Punchbowl Trail at Eagle Creek on May 6, or various locations along the Larch Mountain Trail.

At any given time, any one of the units might be the most consistent or accurate, but the 66sr and 67i are more consistent and accurate than the 66i, on average. By "consistent" I mean that they show a similar location in each direction on the hike. I'm really not certain whether the 66sr or 67i is more accurate overall. There are long stretches where one or the other is more consistent. On average, they appear nearly the same to me.

However, the 67i wanders much less than the others when standing still (others have mentioned this). Also, when I went into the Multnomah Falls Visitor Center, the 66sr produced the worst errors and actually gave a "lost satellite reception" message. Later, in my dining room, the 66sr gradually lost all of its Galileo satellites, while the 67i continued to show several of them the entire time (they were standing upright, side-by-side on the table). Strangely, the 66sr and 67i frequently show different Galileo satellites, and the 66sr seems to show more of them, at a higher signal strength, when out in the open.

*** CalTopo GPX Exports Added Below ***

Thank you for sharing these great hikes!

I know many readers have been wanting to see direct comparisons between the new GPSMAP 67 and previous models, and I suspect they will be very happy to see the testing you have shared.

I noticed that during Hike 2, the GPSMAP 66i recorded one substantial deviation compared to the others.


Any thoughts on what may have happened here?

I'm familiar with this area having windsurfed in the Gorge for 30 years. Looks like a good test with high ridges on each side and dense forest. It looks (to me) like 66sr and 67i performed similarly. It appears you had the recording set to "auto". The 67 laid a few more points than the 66sr. Each device had a few spots where they lost the trail, but overall, most of the track looks fairly accurate 99+% of the time. Both performed better than the 66i, but it's not going to get you lost. It's nice to see improvements in reception in this generation of devices.

Thanks for the GPX data DL links

Yes, thanks to GPSrChive for adding the download links!

Track recording was indeed set to Auto on both. I forgot to mention that. All units had all multi-GNSS and multi-band options turned on, where possible.

About the 66i's deviation on Hike 2: If you zoom in, you'll see that all of the units (especially the 66sr) were struggling quite a bit in the section immediately northwest of there. There are tall cliffs immediately uphill, visible in Google Earth. I believe that the trail is farther uphill than Google Earth shows it, and might be directly against the cliff at that point. The pin is in the middle of the deviation:

Google Earth

Screen Shot 2023-05-29 at 8.15.20 PM.jpg

Both the 66sr and the 66i had some fairly large, but short, glitches in the east end of Hike 1. The 66i was also bad coming out of the tunnel under I-84 and in the Visitor's Center. Then there's this area:

Dutchman's Tunnel

Screen Shot 2023-05-29 at 8.39.24 PM.jpg

From north to south here, the trail goes through Dutchman's Tunnel, a major overhang in the cliff, and then traverses some steep switchbacks just before Wiesendanger Falls. All of the units were pretty far off in this section.

To be more accurate, you should not record by car but put in time and 1 second, it sticks better to the terrain.

Thanks for sharing Matt16598! This gives some great insights for people who want to compare the results of the different devices.

mimichris wrote: Tue May 30, 2023 6:31 am To be more accurate, you should not record by car but put in time and 1 second, it sticks better to the terrain.

You mean "Auto" as in automatic instead of "car"? Just to prevent any confusion.

JungleJim wrote: Tue May 30, 2023 7:50 am Thanks for sharing Matt16598! This gives some great insights for people who want to compare the results of the different devices.

mimichris wrote: Tue May 30, 2023 6:31 am To be more accurate, you should not record by car but put in time and 1 second, it sticks better to the terrain.

You mean "Auto" as in automatic instead of "car"? Just to prevent any confusion.

You're right, I haven't read it, It is Google that mistranslated because I don't know English, having not been to school for long, I am 82 years old. Of course it should read AUTOMATIC, not car.

For my backcountry navigation purposes on foot or horseback, the comparison showed no advantage to the multi-band feature.

Two hikes shown there are both excellent comparisons of multi-band vs. no-multi-band. I stepped through the tracks on Basecamp. The 66i (without multi-band) recorded only three track points that were outliers. Those are the ones noted in the original post, I think. All three were in sequence from 6 May 2023, 19:23Z to 19:24Z. The worst of the three was about 115m off. They added 0.1 mile to the recorded length of the hike. I did not see any comparable outliers from the tracks recoded by the 67i or the 66sr, both of which have multi-band. For record keeping purposes, you could easily delete those three outliers in Basecamp. They show up immediately in track properties since the hiker's steady 3 mph pace jumps to 64 mph. Even in the field, those track points would have been obvious outliers on the 66i display.

A couple of things to note in the comparison:

Looking at the images posted at the web site, consider that the test was done with all devices set to their default "auto" tracking resolution according to the description. From the .gpx files, you see that the default resolution on the 66i is about one-third the resolution of the 67i and the 66sr. But that has nothing to do with accuracy. It's just a difference in the default setting, which a user can change.

All devices did amazingly well at recording elevation. It was almost suspiciously accurate. They were typically within 50 feet elevation of one another and within 80 feet of what the Garmin Topo NA US 2022.20 map showed.

If knowing your current or average speed in real time is important, then the occasional outlier recorded by the 66i without multi-band would be a problem for that since one or two extreme outliers can have a big effect on cumulative distance and speed. As I said above, that's only an issue in real time. Afterwards, it's easy to delete outliers in Basecamp to get fairly accurate distance and speed calculations.

The tests were not done in expedition mode. I would like to know if the 67i can use multi-band in expedition mode. Expedition mode on the 66i overrides certain user option settings. I would also like to see a similar comparison between the 67i and 66i where both are in expedition mode. At least once a year, I go on a hike where I need to use expedition mode. I've had two 66i devices. Both recorded absurd elevations in expedition mode. I don't mean occasionally absurd. I mean consistently absurd. That has led me to believe that this is either a firmware bug or a documentation failure. By that, I mean that if the 66i is not designed to record elevation in expedition mode, that limitation should be documented and it should not record ridiculous numbers in place of the elevation. I've reported it multiple times to Garmin through several past firmware revisions.

You remind me, I also find the incredibly consistent elevation values to be very unlikely, and I suspect they were edited after the fact.

Perhaps the OP can share the original GPX files taken directly from each device without any editing?

The .gpx files are labled "original." I routinely go through my tracks and delete outliers, but even if the OP did that, it wouldn't change the impressive accuracy of elevations on all the rest of the track points.