eTrex reception in moderate tree coverage

[nemethmik]

I used an eTrex Legend for 3 weeks and now a Vista. I was quite happy with the Legend until I had a trip in Cuyamaca (San Diago County, CA USA) tree covered area and found the reception of the eTrex very disappointing. In the valley of the Sweetwater River, which is moderately covered by trees, approximately 30% of the route was traced by the eTrex.

What do you, old geocachers, think; shall I keep the eTrex GPSrs or can I expect significantly better reception from a Magellan Meridian?

I've learned from the reports in this forum that the Garmin GPS V has very good reception but I regard the $370 - $500 price too high for me.

[+DD214]

I've had a Meridian Gold for the past month, and I've been very impressed. I've been in some really sketchy environments (thick trees, canyons, etc.), and I have yet to lose reception. Since I knew that I was going to be in thick forests and canyons, reception was the primary factor when I purchased my GPSr, and I have not been let down yet; In fact it is more capable that I ever expected. 2 thumbs up for the Meridians.

[jfitzpat]

FWIW, you might get better tracks from your eTrex if you carry it face up (top of daypack, etc.) Dangling at the end of the lanyard does not put the unit in its best attitude for tree cover reception.

 

That said, many users report better reception with QH ant. setups. Personally, I just don't see it. Usually, if my Vista is having trouble, a GPS 320 or a Meridian Green is having trouble as well (canyon with poor view of the sky, hills, etc.)

 

I know of spots all over SoCal where one brand or another can get a lock, but the others are lost, but 'trouble' seems to be pretty evenly split. But, that is just my experience (which is mostly not the typical follow-the-arrow geocaching usage). Others feel pretty strongly that reception in their area is dramatically bettern with particular receivers. Ideally, you should rent or borrow before you buy - then try several units and find the one best suited to your usage.

 

-jjf

[+Gimpy]

Up here in Western NY, we've got some pretty heavy tree cover in the summer & fall.There are a number of us in the area that have purchased the eTrex line of gpsr. Mostly the Vista, the top of the line eTrex.Most all of us have sold them, mainly because of the failure to hold satellite lock under a canopy of tree cover.Don't have any experience with maggies, but the Garmin line of units with the quad helix antenna design has worked really well. I have the MAP76, III Plus & the V. I rarely lose lock in any conditions.Just the experiences of myself & other cachers in upstate NY. Folks in other areas of the country have reported that they have no problems with the Vista. I really liked the units size & features, but for caching in the woods,the frustration with not holding a fix was too much.

 

"Gimpy"

[+RAD Dad]

Like jfitzpat said, orientation of the GPS makes a big difference, your body blocks sat reception worse than the trees. If I let my Legend dangle from my neck via the lanyard, I can lose reception in even light tree cover, but if I keep it up on my shoulder (I stick it between my pack strap and shoulder) it keeps reception very well, even in heavier tree cover. I've heard that the meridian line gets better reception due to the quad helix antenna, but those things are huge. I like small gadgets, so the trade off is worth it.

 

ummmm....not sure what to say here....so ummm, well errrr, uhhhh, well I guess that's it.

[+Navdog]

I have both a Vista and a GPSV. I use the GPSV 90% of the time because it is easy to carry it in a custom case with the swivel antenna sticking out of the case on the shoulder strap of my pack. This keeps my hands free and allows the unit to keep a constant sat lock and record an unbroken track log. The Vista is a wonderful little unit but is much more fussy about its orientation to keep a constant sat lock. Your experience with the Etrex track logs may be because you were not holding the unit out in front of you and in a horizontal position. Carrying the unit in your hand at your side while walking or in a shirt pocket just doesn't work with this type of patch antenna. You may try experimenting with a case that you can attach to the shoulder strap that is as close to a horizontal position and still allow you to reach it.

 

The adventures of Navdog, Justdog, and Otterpup

[Bagbug]

http://www.gpsinformation.net/mgoldreview/sportrak-pro-rev.html

 

Amazing reception under tree cover !

 

Bag

[Night Tracker]

I have learned to hold my Mag.315 antena up at eye level to get the best out of it under the trees. My brother has a Venture he holds it flat in his hand out away from his body for best results in heavy cover, Mine gets more sats. then his when we're together. He has installed velcro on the back of his Venture and sticks it high on his pack The neck strap keeps it from getting lost, works well for him.

[+AngryElf]

Badbug,

 

Thanks for the link to the review. Just what I was looking for. I have a Sportrak Pro on order. Can't play with it yet so I guess I will just read about it for now.

[jfitzpat]

quote:

---

Originally posted by Bagbug:

http://www.gpsinformation.net/mgoldreview/sportrak-pro-rev.html

 

Amazing reception under tree cover !

 

Bag

---

 

I think you might reading too much into the review. The reviewer noted that sensitivity was primarily subjective observation. The review also notes that the lack of scatter on the plots is principally due to "auto averaging", which cannot be disabled. As Kerry has pointed out, with some good data, in the past, averaging can actually decrease accuracy in many circumstances.

 

The data does seem to show that the unit tested has a much improved WAAS implementation. (Pros and cons of WAAS have been covered in other threads). Certainly it is a nice ergonomic improvement over the Map330. But, if I am reading the review correctly, some users may still be better off with either the Meridian or an eTrex model.

 

-jjf

[Bagbug]

Here is what Joe (from gpsinformation.com) has to say about the same review.

 

"

I want to "second" Jack's comments on the Sportrak Pro.

 

I could hardly believe the accuracy demonstrated by the multiple plots

Jack made. But they repeated over and over and day after day. The

Sportrak Pro is the most stable and accurate consumer model GPS we have

tested. When using WAAS, the scatter plots are extremely compact and do

not show the usual (for other models) dispersion of points EVEN WHEN the

GPS is placed under moderate tree cover.

 

I think Magellan has demonstrated a "breakthrough" in GPS accuracy in a

consumer model GPSR.

"

 

You have a map76 or a 76s ? hehehe

 

Bag

[Kerry.]

quote:

---

Originally posted by jfitzpat:

quote:

---

Originally posted by Bagbug:

http://www.gpsinformation.net/mgoldreview/sportrak-pro-rev.html

 

Amazing reception under tree cover !

 

Bag

---

 

I think you might reading too much into the review.

 

-jjf

---

 

Me thinks so too once one sees comments like detecting differences of 0.8m between datum's with a single freq unit with auto-averaging it sort of makes one a little cautious.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by jfitzpat:

quote:

---

Originally posted by Bagbug:

http://www.gpsinformation.net/mgoldreview/sportrak-pro-rev.html

 

Amazing reception under tree cover !

 

Bag

---

 

I think you might reading too much into the review.

 

-jjf

---

 

Me thinks so too once one sees comments like detecting differences of 0.8m between datum's with a single freq unit with auto-averaging it sort of makes one a little cautious.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[jfitzpat]

quote:

---

Originally posted by Bagbug:

 

You have a map76 or a 76s ? hehehe

 

Bag

---

 

Actually, my daughters and I primarily geocache with a map and compass. I have taken to carrying a Vista with me to the mountains. Optimum reception isn't the primary issue for me.

 

Size and weight are a big issue when a rope and rack puts your pack at 30 pounds to start. Frankly, if the Vista did not include a barometric altimeter, which I carried anyway and almost weighed as much, I probably would leave the Vista behind.

 

A backup compass and 1:100000 map is nice, but aside from size and replacing an altimeter, the only reason I carry the Vista is reliability and durability. The eTrex line still has the widest operating temperature range that I can find. I have also yet to find another handheld commercial line as physically durable. I'm not just talking specs, I'm talking dropping units off cliffs and expecting them to work when it is so cold and wet that taking off a glove is a real physical hardship.

 

Now, I have stated many times that there are many nice units out there with strengths and weaknesses that should be considered when someone is selecting a unit (see the archives if you are interested).

 

I'm sure that the new Magellan unit is a fine receiver. The reason that I cautioned you is that, from a scientific or technical viewpoint, amazing reception isn't really established. The original reviewer clearly understood this, which is why the comments were qualified as "subjective", and why charts were followed with some points on why certain data might be misleading. Distinguishing general impressions from quantitive measurements reflects well on the reviewer(s).

 

As Kerry pointed out, some of the measurements exceed the statistical variation in the overall system (ex. some measurements seem to exceed the threshold of the low-pass filter style signal processing built into the unit). Why this matters, or how it impacts the credibility of certain other measurements is not always immediately obvious to people who do not work or study in technical fields.

 

(I was going to make a crack about guessing that your own career leaned towards food services, then follow it with a "hehehe", but I did not think you would see the humor. For some reason, I don't picture your ability to 'take' and 'dish' as being in balance. )

 

-jjf

[jfitzpat]

quote:

---

Originally posted by Bagbug:

 

You have a map76 or a 76s ? hehehe

 

Bag

---

 

Actually, my daughters and I primarily geocache with a map and compass. I have taken to carrying a Vista with me to the mountains. Optimum reception isn't the primary issue for me.

 

Size and weight are a big issue when a rope and rack puts your pack at 30 pounds to start. Frankly, if the Vista did not include a barometric altimeter, which I carried anyway and almost weighed as much, I probably would leave the Vista behind.

 

A backup compass and 1:100000 map is nice, but aside from size and replacing an altimeter, the only reason I carry the Vista is reliability and durability. The eTrex line still has the widest operating temperature range that I can find. I have also yet to find another handheld commercial line as physically durable. I'm not just talking specs, I'm talking dropping units off cliffs and expecting them to work when it is so cold and wet that taking off a glove is a real physical hardship.

 

Now, I have stated many times that there are many nice units out there with strengths and weaknesses that should be considered when someone is selecting a unit (see the archives if you are interested).

 

I'm sure that the new Magellan unit is a fine receiver. The reason that I cautioned you is that, from a scientific or technical viewpoint, amazing reception isn't really established. The original reviewer clearly understood this, which is why the comments were qualified as "subjective", and why charts were followed with some points on why certain data might be misleading. Distinguishing general impressions from quantitive measurements reflects well on the reviewer(s).

 

As Kerry pointed out, some of the measurements exceed the statistical variation in the overall system (ex. some measurements seem to exceed the threshold of the low-pass filter style signal processing built into the unit). Why this matters, or how it impacts the credibility of certain other measurements is not always immediately obvious to people who do not work or study in technical fields.

 

(I was going to make a crack about guessing that your own career leaned towards food services, then follow it with a "hehehe", but I did not think you would see the humor. For some reason, I don't picture your ability to 'take' and 'dish' as being in balance. )

 

-jjf

[+Gimpy]

quote:

---

Originally posted by Bagbug:

 

 

You have a map76 or a 76s ? hehehe

 

Bag

---

 

Yup. I've got a MAP76, among other units.And it's a fantastic unit. And that's from personal experience under all kinds of conditions. Not from reading it in a review.

 

"Gimpy"

[+Gimpy]

quote:

---

Originally posted by Bagbug:

 

 

You have a map76 or a 76s ? hehehe

 

Bag

---

 

Yup. I've got a MAP76, among other units.And it's a fantastic unit. And that's from personal experience under all kinds of conditions. Not from reading it in a review.

 

"Gimpy"

[SpongeBob SquarePants]

quote:

---

Originally posted by jfitzpat:

quote:

---

Originally posted by Bagbug:

http://www.gpsinformation.net/mgoldreview/sportrak-pro-rev.html

 

Amazing reception under tree cover !

 

Bag

---

 

I think you might reading too much into the review. The reviewer noted that sensitivity was primarily subjective observation. The review also notes that the lack of scatter on the plots is principally due to "auto averaging", which cannot be disabled. As Kerry has pointed out, with some good data, in the past, averaging can actually decrease accuracy in many circumstances.

 

The data does seem to show that the unit tested has a much improved WAAS implementation. (Pros and cons of WAAS have been covered in other threads). Certainly it is a nice ergonomic improvement over the Map330. But, if I am reading the review correctly, some users may still be better off with either the Meridian or an eTrex model.

 

-jjf

---

 

I performed many of the GPS surveys for the WAAS reference stations around the country. Using fancy dual-frequency surveying receivers, differential techniques, and post-processing software, we determined the antenna locations to within 1cm horizontal and 2cm vertical (95% probability). So that's the kind of accuracy I'm used to squeezing out of GPS. But I personally own a Garmin eTrex Vista, and I understand that until the government launches another "Geo" (WAAS communications satellite) or other ways to get the signal to those of us in urban or forested environments, we handheld users will have our gripes about the reception, apparently misleading "accuracy" values between GPS-only and WAAS-enabled modes, etc.

 

But be patient. The future is bright for WAAS. I tend to think that support for it will grow among aviation, marine, agricultural, and (yes) even recreational users to the point where the government will keep improving our ability to receive the signal using our handhelds. Gosh, not too long ago we were complaining about 100m accuracy from Selective Availability, remember?

 

Enjoy!

 

Randy Van Steen

[jfitzpat]

quote:

---

Originally posted by SpongeBob SquarePants:

 

But be patient. The future is bright for WAAS. I tend to think that support for it will grow among aviation, marine, agricultural, and (yes) even recreational users to the point where the government will keep improving our ability to receive the signal using our handhelds. Gosh, not too long ago we were complaining about 100m accuracy from Selective Availability, remember?

 

---

 

I wasn't trying to be critical of WAAS in my original post. I am a little skeptical if WAAS will ever meet the needs of IFR aviation, but, as you mentioned, a lot will depend upon the number of birds and the density of ground stations. Also, I can't argue with anyone who likes Spongebob. Squidward is my first animated role model since Bullwinkle retired...

 

-jjf

[Kerry.]

WAAS is really a system caught up in the before and after syndrome. The cost for many countries is really totally prohibitive when comparing the 12 odd billion $'s for the basic GPS system todate, which gives world coverage and the 5 billion and counting for WAAS which still isn't even fully implemented and only provides limited coverage anyway.

 

Will be interesting to see what happens in time.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

WAAS is really a system caught up in the before and after syndrome. The cost for many countries is really totally prohibitive when comparing the 12 odd billion $'s for the basic GPS system todate, which gives world coverage and the 5 billion and counting for WAAS which still isn't even fully implemented and only provides limited coverage anyway.

 

Will be interesting to see what happens in time.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Cache Canucks]

I've used my eTrex Vista in some moderately dense central Ontario bush (with an equally dense overhead tree canopy), and have had good results. 90%+ of the time, I was able to get position accuracy of 10 metres or less.

 

In fact, although the lack of accuracy makes the position plot unusable, my Vista will often track one or two '12 o'clock high' satellites even while indoors.