# GPS placement and reception.



## kapusta (Jan 17, 2004)

How much a a difference does it make in terms of reception and location accuracy where you carry the gps on a ride?

I've got an Oregon 450. I have been wearing it in a camera pouch against my chest, but does that meaningfully interfere with reception? I am sort of hunched over it, but not much.

Other options include wearing it on my hip (attach it to the waist strap). Or just stick it in the top of may pack (just a layer of nylon covering it). Would either of these option make a meaningful difference in reception? 

I plan to mount it on the bars when I road ride, but I'm not too comfortable with that on the mtb. It just seems like it will get jarred and shaken more than I would like.

Thanks


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## Metamorphic (Apr 29, 2011)

I usually run my iphone in the top of my camel pack and it works fine. One time I took it out to take a picture, then, since I was almost back to the car, just stuffed it in the front of my bib. It got noticeably worse reception with my body over it blocking the satellites; lots of long straight line segments where it was not receiving. So I'd say yes it can matter, and that higher up on your body is probably better because its less likely to get its signal blocked by your body.


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## ghettocruiser (Jun 21, 2008)

I seemed to get best results putting my handheld in the top of my pack in a level orientation.

I cannot substantiate this claim with anything objective.


As I've mentioned before, I think the sharp little pothole impacts that my hand-held stuff gets on the road bike bar are harsher than the tire-volume-and-suspension-damped bumps it gets on my XC and DH bikes.


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## kapusta (Jan 17, 2004)

ghettocruiser said:


> As I've mentioned before, I think the sharp little pothole impacts that my hand-held stuff gets on the road bike bar are harsher than the tire-volume-and-suspension-damped bumps it gets on my XC and DH bikes.


Hmmm, good point.

I do run 33s on my road bike, with around 55 psi front, so it's not like a rock hard front end, but perhaps I'll try to figure out a way to dampen the vibration further.


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## Harold (Dec 23, 2003)

I put my Oregon 450 on my stem on the mtb, and on the bars on my commuter occasionally (I ride on 35's at about 50psi). No problems, but it has been ejected in crashed on the mtb before.

Either way, the Oregon 350 has a patch antenna, which works best with the antenna facing the sky. That means the screen needs to face upwards. However you accomplish that is fine. Your body can interfere with the reception a little, so on the bars with my body leaning over it probably reduces reception for me, but I put it on the bars so I can use it to navigate when I need to. On top of the camelbak would work well, assuming you could strap it down to keep the screen pointed up.


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## ghettocruiser (Jun 21, 2008)

kapusta said:


> I do run 33s on my road bike, with around 55 psi front, so it's not like a rock hard front end, but perhaps I'll try to figure out a way to dampen the vibration further.


That's pretty soft for a road-going bike, so it's probably fine.

But for a skinny deep-section carbon tubular at 115 PSI... every rough section of pavement is probably sharper accelerations than a rock garden on a DH rig.

The Garmin Edge series is obviously fine with both, but the jarring my old etrex used to take on the road stem was often enough to turn it off from battery shake.


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## Dino Sore (May 20, 2006)

I have an Oregon 450 and I either put it in my jersey pocket or, if I'm using my Camelbak, clip it to my shoulder strap. Reception has been fine either way.


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## johnnyspoke (Sep 15, 2005)

I have a Vista HCx, and for a year or two I mounted it on my camelback strap, so it was in a similar position to your Oregon. Generally it worked well, but in tough conditions (heavy trees, north facing steep canyons) accuracy was so-so. I could tell from the tracks afterward it struggled a bit at times. For the last couple of years I thrown it in the top pocket of a camelback and in the same tough conditions it tracks much better. However, I didn't notice a change in more average conditions.


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## kapusta (Jan 17, 2004)

*Some very interesting results*

So, I tried wearing it on my right hip today, again in the camera pouch. Part of the ride with the screen facing in, part of the ride facing out.

I got some really interesting results. It seems like it would often put my location (track) 50-100' (sometimes more) to the right of the direction I was facing/traveling  Did not matter which way the screen was facing (in or out).

I could tell on several section where I backtracked, and my tracks were a similar shape, but 200' apart, and they always off in the same direction (to the right or the direction of travel).

This also showed itself on switchbacks. On right handed switchbacks, the track looks like a twisted loop (like I was turning left for 190 deg rather then right for 80 deg), and on left hand ones it always looks like a wide, gradual curve. Both of these would be consistent with the GPS thinking I was a ways off the the right of wherever I was.

I wondering if it is the placement on my hip, or the nylon camera case.

I also notice in a number of spots where I stopped to mark a way-point, the track takes a sharp jog over to the left to where the way-point is, and then goes back to the right as I get moving again. This would be consistent with the issue being the hip placement pushing my track to the right, and when I pull the unit out to mark the way-point, it places me correctly. I went back and looked at another track I did on my hip, and noticed the same thing.

Also, the auto calibartion for the altimeter did not seem to work well. I calibrated the altimeter at the beginning of the ride at the parking lot elevation (this is the elevation from google earth, and also the elevation this unit recorded there previously) At the end of the ride when I got back, it was reading a ~100' higher. As I hung around the parking lot after the ride (15-20 minutes) with the unit out and laying flat, the elevation dropped about 40'. .

I am wondering if it had been getting bad elevation data from the gps. and had been using that bad data to auto-calibrate (incorrectly) the barro elevation data.


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## Harold (Dec 23, 2003)

kapusta said:


> So, I tried wearing it on my right hip today, again in the camera pouch. Part of the ride with the screen facing in, part of the ride facing out.
> 
> I got some really interesting results. It seems like it would often put my location (track) 50-100' (sometimes more) to the right of the direction I was facing/traveling  Did not matter which way the screen was facing (in or out).
> 
> ...


not surprised. auto calibration uses GPS elevation, so with the antenna facing off-kilter and throwing positional accuracy off, it would likewise throw off your auto calibration.


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## Mtn-Rider (May 21, 2010)

When I used a Vista HCx, the place for best gps reception was on top of my shoulder. I had a small camera pouch attached to one of the Camelbak straps, as far up as it would go, with the gps receiver inside it.

This setup gave the best reception even though I still got lots of tracking errors on every mtb ride, just less than with the gps anywhere else.


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## kapusta (Jan 17, 2004)

Mtn-Rider said:


> When I used a Vista HCx, the place for best gps reception was on top of my shoulder. I had a small camera pouch attached to one of the Camelbak straps, as far up as it would go, with the gps receiver inside it.
> 
> This setup gave the best reception even though I still got lots of tracking errors on every mtb ride, just less than with the gps anywhere else.


Did you try it on your bars as well?


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## Mtn-Rider (May 21, 2010)

kapusta said:


> Did you try it on your bars as well?


I had it on the stem for a while where it's more accessble but still had reception problems. Even worse, the batteries would shake, cut power, and restart the unit which really sucked.

I'm a happy camper now with a smartphone and an external bluetooth receiver using a quad helix antenna.


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## kapusta (Jan 17, 2004)

Mtn-Rider said:


> When I used a Vista HCx, the place for best gps reception was on top of my shoulder. I had a small camera pouch attached to one of the Camelbak straps, as far up as it would go, with the gps receiver inside it.
> 
> This setup gave the best reception even though I still got lots of tracking errors on every mtb ride, just less than with the gps anywhere else.


I tried the the shoulder position like you suggested. It does seem to work better than my chest or hip. I did an out and back, and the tracks were pretty tight to eachother compared to the other methods. It is still easily accessible, too. It is still tilted a bit forward when I am out of the saddle or leaning forwards pedaling. Might try it up higher to level it out.

Thanks for the tips, y'all.

I would not be so anal about this if I were not planning on using this data for maps that I plan to spend a lot of time and energy on.


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## Harold (Dec 23, 2003)

kapusta said:


> I tried the the shoulder position like you suggested. It does seem to work better than my chest or hip. I did an out and back, and the tracks were pretty tight to eachother compared to the other methods. It is still easily accessible, too. It is still tilted a bit forward when I am out of the saddle or leaning forwards pedaling. Might try it up higher to level it out.
> 
> Thanks for the tips, y'all.
> 
> I would not be so anal about this if I were not planning on using this data for maps that I plan to spend a lot of time and energy on.


If I am mapping trails, I walk. the slower speed with 1sec recording results in pretty darn good tracks. with higher speed while riding, track accuracy drops some. especially in twisty stuff.


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## gps_dr (Feb 27, 2007)

For trail mapping I set my DeLorme to 10' intervals. Much closer on switchbacks than my Garmins. As always my slow uphill tracks are much more accurate representation than my downhills as they are limited to 1 spot per second.

Blocking signal with your body can cause reflected signals to be used instead, throwing off your position noticeably.


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## Gundam168 (Dec 19, 2012)

My GPS smartphone Huawei U8150 (as cheap as any smartphone can get) still tracked from inside my scooter's underseat compartment.


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## kapusta (Jan 17, 2004)

Gundam168 said:


> My GPS smartphone Huawei U8150 (as cheap as any smartphone can get) still tracked from inside my scooter's underseat compartment.


Yes, but how accurately? Have you checked it?


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## Gundam168 (Dec 19, 2012)

Yup. It's as accurate as if it was on my shirt pocket.


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## kapusta (Jan 17, 2004)

Gundam168 said:


> Yup. It's as accurate as if it was on my shirt pocket.


How did you check that?

FWIW, Mine is not terribly accurate in my pocket as opposed to on top of my shoulder.


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## Harold (Dec 23, 2003)

kapusta said:


> How did you check that?
> 
> FWIW, Mine is not terribly accurate in my pocket as opposed to on top of my shoulder.


Pretty sure that was an "at a glance" assessment.


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## Gundam168 (Dec 19, 2012)

kapusta said:


> How did you check that?
> 
> FWIW, Mine is not terribly accurate in my pocket as opposed to on top of my shoulder.


I went through the same route on two occassions. Once with the phone on my shirt pocket, and again with the phone in the underseat compartment. I can do it again if you want me to but then again you just have to take my word for it.

As a matter of fact, my cheap and cheerful 528MHz Huawei smartphone tracks better than my 1GHz Motorola Defy Plus.

Here are two tracks recorded at the same time by each device:










Both phones were strapped near the shoulder of my hydrator.


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## kapusta (Jan 17, 2004)

I'm not sure what those maps are supposed to be showing me


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## Harold (Dec 23, 2003)

kapusta said:


> I'm not sure what those maps are supposed to be showing me


they are showing you that both tracks are crap but that the second one is worse.


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## kapusta (Jan 17, 2004)

NateHawk said:


> If I am mapping trails, I walk. the slower speed with 1sec recording results in pretty darn good tracks. with higher speed while riding, track accuracy drops some. especially in twisty stuff.


I used the GPS on a hike recently and had the GSP on my shoulder the same as when I bike. It is more level, because I am not leaning forwards like when I am riding.

Anyway, it was more accurate and consistent (out and back) then when on the bike. Not sure how much had to do with my slower speed and how much had to do with the GPS position.

I don't think I have the patience to walk all the trails I want to map, so I'll just have to make the best of the data I get from riding.


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