GPS test on Mansfield

[king tut]

I recently received the Garmin 76 CSX as a birthday present on my 31st birthday, and I have been trying to figure the darn thing out for the last few weeks. It took many attempts, a few computer upgrades, and many hours before I could upload the Mapsource software on my computer. I downloaded some free maps off of a few websites and am finally enjoying the GPS features, as the GPS comes without any real maps, rendering it virtually useless when you first receive it. I tested it out on Camels Hump a few weeks ago, and then played around a little more with it before heading out yesterday to do an impromptu hike up Mansfield. This was a dual mission hike, with the purpose of figuring out my GPS and also conditioning my legs for hiking season. The prior hike two weeks ago up Camel's Hump from the Winooski River had left my legs partially paralyzed and full of seizures for about 4 days as the 4,000 foot plus elevation gain had been too much for my first hike of the season.

I watched the U.S. VS Australia World Cup tune up match and then headed out to the Stevensville RD trailhead on Mansfield, getting there just before 11:30 AM. I took the trail up to Butler Lodge, then up to the Forehead, over the ridge, to the top of Mansfield, then down the Laura Cowles trail, over the CCC trail, then back up and down the Maple Ridge trail to the parking lot. My legs felt great, as I made the approximately 10 mile trek in around 4 hours and never felt overly winded. I was walking in and out of clouds the entire day and walking down stream beds as the trail was no longer a trail, rather a small river bed.

I am still trying to fine tune the GPS unit, as it seems to have a few flaws. It recorded the elevation gain at around 4280 feet, where I would guess that it would be closer to 3600-3700 feet. It also recorded the distance at 8.3 miles, where the trial signs would indicate that the hike was around 10 miles. if anyone has any suggestions on what kind of fixes to make to the Garmin 76CSX, i am all ears.

I have been able to pull up a contour change/elevation change chart on the Mapsource software, but have not found a way to save or copy the image, so it seems a bit of a mystery how to post elevation charts on websites. Any suggestions out there?

The one thing I was able to do was transfer the gps coordinates into Google Earth. here is a map of the trek.

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It would be nice to post the Google Maps as an interactive map, but i am not sure how to do that either. I swear I used to be smart, tech savvy and young, but soon I will turn into one of those old people that can't program a VCR.

 

[Mohamed Ellozy]

It would be nice to post the Google Maps as an interactive map, but i am not sure how to do that either. I swear I used to be smart, tech savvy and young, but soon I will turn into one of those old people that can't program a VCR.

I can't program a VCR, but perhaps I can program a computer

I assume you would like to do something like what I have done on my blog: Mount Lafayette, June 4, 2010 (you will have to scroll down a bit to see the map). Here is how I did it:

1. Save my MapSource tracks plus waypoints a a GPX file
2. Open GPX file in Google Earth (I guess you did 1 and 2)
3. Save file as KMZ or KML
4. Fire up maps.google.com, click on My Maps
5. Import KML or KMZ file and edit it
6. Click on Link button, click "Customize and preview embedded map"
7. When happy with centering, size etc, copy HTML and enter in blog (need to do "Edit HTML, I think)

Sounds complex, but really is quite easy once you have gotten the hang of it.

 

[DougPaul]

I am still trying to fine tune the GPS unit, as it seems to have a few flaws. It recorded the elevation gain at around 4280 feet, where I would guess that it would be closer to 3600-3700 feet. It also recorded the distance at 8.3 miles, where the trial signs would indicate that the hike was around 10 miles. if anyone has any suggestions on what kind of fixes to make to the Garmin 76CSX, i am all ears.

* Set auto-calibration for the altimeter and turn the GPS on an hour or so before the hike to let the calibration do its bit. (I let the unit autocalibrate on the 1-3hr drive to the trailhead.)

* Make sure you clear the trip computer and accumulated altitude at the start of the hike and read it out at the end. (ie don't include the last hike or drive in the numbers...)

* Carry the GPS where it has a good skyview. At the very top of a pack with the antenna pointed up is generally pretty good. (Carrying the GPS on top of your head is even better... )

* Different methods of measuring the distance and elevation gain give different numbers. Get used to it.

Doug

 

[MichaelJ]

The biggest reason for a different measure of distance within the GPS itself is that to try to cut out randomness and variation, it doesn't count minor distances if it thinks you've stopped moving. This is entirely in the "flat" 2-D plane. So if you're doing a steep ascent at about 1mph, in x-y you're doing less (think sines and cosines), and the GPS may just stop accumulating distance because it thinks you're not moving and it's just seeing a weaker signal. Generally the track file will reflect the distance correctly because it's taking points no matter what.

My recommendation is to turn on constant GPX logging to the SD card (does this model have one? or have sufficient internal memory?) This option is, on the 60CSx, found in Setup->Data Card Setup on the Tracks page. Now, no matter what you do with your tracks in the unit (save/delete/etc.), there is a completely separate track log, with timestamps (which are deleted when you "save" a track) and waypoints. If you turn off the GPS or reset the trip computer, the separate log continues just marked as a new track in the file. Then, after you've done any transfers to/from your computer, while the GPS is still connected, go to Setup->Interface->USB Storage. Now your GPS will change modes and on your computer you will see your GPS as an external hard drive and you can just copy the .GPX file off of it. Make sure to "eject" the GPS from the computer. When you do so, the GPS will restart, then you can disconnect it. Also keep an eye on available space, or delete the files off the GPS as you copy them (delete, not trash or recycle). Then, you can load that .GPX file into anything you want - Mapsource, topo software, GPX tools on the web, Google Earth, Google Maps, etc. It also means that you can fully separate your real-time use of the GPS for navigation, from its use as a tracker.

 

[DougPaul]

The biggest reason for a different measure of distance within the GPS itself is that to try to cut out randomness and variation, it doesn't count minor distances if it thinks you've stopped moving.

IIRC, the speed threshold to distinguish moving from stationary is settable. (This decision is easy for driving, but it can be hard to distinguish between a slow walk and random variation in the computed position.)

If you use the tracklog (or set the threshold to 0) the estimated travel distance will be biased toward long because random drift while stationary will be included. The trip computer can also show the stationary time (as well as the moving time), so one can get an idea of the effect of the threshold.

The tracklog is usually a coarser sampling than the trip computer which will tend to bias the tracklog distance toward short. (The trip computer is based upon a 1/sec sampling.)

In other words, none of the methods for determining the distance is perfect.

This is entirely in the "flat" 2-D plane. So if you're doing a steep ascent at about 1mph, in x-y you're doing less (think sines and cosines), and the GPS may just stop accumulating distance because it thinks you're not moving and it's just seeing a weaker signal. Generally the track file will reflect the distance correctly because it's taking points no matter what.

The track file can also contain errors. The difference between 2-D and 3-D is pretty small except for rather steep sections of trail.

My recommendation is to turn on constant GPX logging to the SD card (does this model have one? or have sufficient internal memory?) This option is, on the 60CSx, found in Setup->Data Card Setup on the Tracks page. Now, no matter what you do with your tracks in the unit (save/delete/etc.), there is a completely separate track log, with timestamps (which are deleted when you "save" a track) and waypoints. If you turn off the GPS or reset the trip computer, the separate log continues just marked as a new track in the file. Then, after you've done any transfers to/from your computer, while the GPS is still connected, go to Setup->Interface->USB Storage. Now your GPS will change modes and on your computer you will see your GPS as an external hard drive and you can just copy the .GPX file off of it. Make sure to "eject" the GPS from the computer. When you do so, the GPS will restart, then you can disconnect it. Also keep an eye on available space, or delete the files off the GPS as you copy them (delete, not trash or recycle). Then, you can load that .GPX file into anything you want - Mapsource, topo software, GPX tools on the web, Google Earth, Google Maps, etc. It also means that you can fully separate your real-time use of the GPS for navigation, from its use as a tracker.

One can also accomplish the same thing with the normal track log. Set it to "wrap when full" mode and as long as you download it before it wraps, you will be fine. (The track log will contain the latest 10K points. This should cover at least several days of hiking if the recording rate is set to "auto" "norm" (the defaults). Normal tracklogs can be saved in .gpx format.

Doug

 

[king tut]

Lots of tech talk! I love it. Once i have a few minutes I am going to try out all these suggestions. This is so much better than dialing an 800 help number and waiting on hold to talk to someone named Samir. Thanks!

 

[MichaelJ]

Note for any readers - I played with a Colorado 450 today, and its methods of track storage are completely different. According to the owner, all the normally recorded tracks are available as GPX files at any time, because the unit presents itself as two disks (internal memory and SD card) at the same time as a GPS (for data transfers) when connected via USB. Also, apparently saving a track no longer strips the timestamp information out of it.

He didn't buy any maps with 3-D perspectives, but the topo did contain perspective shading, and the touch-screen was a heck of lot easier to use than the 60/76 buttons.

So ... big changes in the newer models.

 

[DougPaul]

Note for any readers - I played with a Colorado 450 today, and its methods of track storage are completely different. According to the owner, all the normally recorded tracks are available as GPX files at any time, because the unit presents itself as two disks (internal memory and SD card) at the same time as a GPS (for data transfers) when connected via USB. Also, apparently saving a track no longer strips the timestamp information out of it.

Some models probably removed the timestamps when saving tracks to save memory. Flash memory has gotten cheaper...

In the past, timestamps were deleted from tracks loaded into the GPS from a computer. This is to prevent anyone from forging a track to cheat in a race. (GPS tracks are used to score some kinds of races.) I rather suspect that this is still true.

He didn't buy any maps with 3-D perspectives, but the topo did contain perspective shading, and the touch-screen was a heck of lot easier to use than the 60/76 buttons.

How easy is it to use the touch-screen with gloves or mittens? Can you operate it by feel? Can you still see the screen with finger dirt and grease on it? Does it get scratched? Does DEET from your fingers harm it?

Doug

 

[Kevin Rooney]

So ... big changes in the newer models.

But does it do a better job as a navigational instrument? Or do they just lots of whistles, like a camera, phone, sweet potato masher, web brower, and coffee grinder?

 

[DougPaul]

But does it do a better job as a navigational instrument? Or do they just lots of whistles, like a camera, phone, sweet potato masher, web brower, and coffee grinder?

The signal reception and location computations are done by the GPS chipset. The rest is just display and presentation (which, of course, are a significant factor in the usability of the unit).

For instance, the SiRFStarIII chipset in the 60CSx is well known to perform pretty well. (It is responsible for the quantum leap in performance over the 60CS.) The newer SiRFStarIV (rumored to be in the new 62s) has a few db more sensitivity and has features for interference rejection according the spec sheets (http://www.sirf.com). Hopefully it will perform even better than the StarIII in the field.

The RF circuitry and antenna can also be factors. (Consumer GPS antennas are all pretty similar--professional units often use a choke-ring antenna which is significantly better than the consumer antennas.)

Doug

 

[MichaelJ]

But does it do a better job as a navigational instrument? Or do they just lots of whistles, like a camera, phone, sweet potato masher, web brower, and coffee grinder?

My coworker got it for a weeklong backpacking trip in the southwest. When he comes back I'll pass along what he thought of it.