Basecamp showing two different distances for same track?

Former Member over 11 years ago

Okay,

249 points in my track. For BASECAMP, the point-by-point view is showing a total distance of 14.7 miles. However, the elevation view is showing 12.2 miles.

Likewise, when I have one point selected in the point-by-point view, I noticed different elevation numbers between the two views. For example, point-by-point for point 100 showing 5024 ft whereas the point selected on the elevation view shows 5038.3 ft.

Comparing the two BASECAMP estimates of distance to what shows on my Oregon 600 - 14.72 mi. the point-by-point view matches. However, the 600 is showing me an elevation gain of 5411. This differs greatly from what is being show in the bottom summary window of the point-by-point view -- 4783 for ascent.

Summary:
MILEAGE
Basecamp point-by-point view (total shown at the bottom): 14.7 mi
Basecamp elevation view (total shown when all points in the point-by-point view are selected): 12.2 mi
Garmin 600: 14.72

ELEVATION GAIN
Basecamp point-by-point view (total shown at the bottom): 4783 ft (ascent); 4579 (descent)
Garmin 600: 5411 ascent / 5202 descent

Interestingly, the ascent/descent numbers show about the same difference between the two calculations (204 ft and 209 ft) - I assume that this could tell me something about the basic error in the GPS. However, I don't know what to make of the differences in the two totals in either the elevation or the miles.

I understand that there are sampling differences. However, it is not obvious to me what they should add up to such a great difference. As sampling inaccuracies should be equally likely to be overestimate for any given point or underestimates they should more, or less, balance out. Hence the differences in the ascent/descent numbers make sense to me.

But what about the large differences between total ascent and total miles?? How far did I walk yesterday??? And how many feet did I climb??

Thanks

0 Former Member over 11 years ago

Okay,

But what about the large differences between total ascent and total miles?? How far did I walk yesterday??? And how many feet did I climb??

Thanks

Attach a copy of your file and someone, maybe several, will give you some possible answers or reasons for the differences.

0 Former Member over 11 years ago

Track attached --

Thanks for the reply. I would have replied sooner but somehow I thought the thread would automatically notify me of the replies. I believe I now have that option set.

The .gpx file is attached. Any insights or explanations would be useful. I am sure this has something to do with differences in the algorithms Garmin is using to compute these figures. Having access to the algorithm (perhaps as an R file) would be very useful but I suspect not something that Garmin makes public.

0 Former Member over 11 years ago

This is a very interesting situation.
I loaded your GPX into MapSource and TopoFusion and they agree, the actual track is only 12.2 miles long just like the BaseCamp profile says.
The fact that the file has only 249 points and that each leg is very long indicates that you "saved" the original "tracklog" to the device. That step caused the device to "truncate" the log down to 249 points to conserve memory. That truncating also shortened the actual track to 12.2 miles but your device was kind enough to save the original distance (14.7mi) to the XML file in a way that BaseCamp could find it and display it in the Summary at the top of the Trackpoints window. The device also saved your ascent (5411ft) and descent (5144ft) in the XML file but BaseCamp did not use those in the Summary. For some reason it used the ascent/descent calc'd from the truncated 249 trackpoints.

There is nothing wrong with the device or BaseCamp.
To prevent this whole mess DO NOT save your tracklogs to the device. Just turn it off.
BaseCamp will upload the original tracklogs just fine.

I do not have a 600 but there might be a setting that will "save" your tracks without truncating them.
Or a setting to force recording the original track to a larger memory like the micro card instead of using the internal memory.

0 Former Member over 11 years ago

Many thanks. It appears that turning off a track in the 600 is the same as saving the track. Interesting.

0 atlas_cached over 11 years ago

First of all, No currently produced Garmin On The Trail GPSr truncates track data. Period. This practice stopped many years ago when Garmin first introduced 'mass storage mode' GPSr devices.

I just ran a quick and dirty experiment: I saved my current.gpx track log data on my Oregon 650t without deleting any data. I then copied my saved track log.gpx file and the current.gpx track log file to my computer, and imported them into BaeCamp.

And I do not like what I see.

The current.gpx from my Oregon 6xx contained four different 'legs' of data, so I used BaseCamp to combine them. The resulting GPX file contained exactly the same data as the current.gpx, with an identical number of track points.

Comparing the BaseCamp.gpx file with the OregonSaved.gpx file, I immediately saw my statistical data did not agree, and the OregonSaved.gpx file contained more track points than the current.gpx file.

What? How can this be?

Using a text editor, I was able to quickly identify the additional lines of data in the OregonSaved.gpx file.

What I do not understand is where the data originated? The additional track log entries do not exist anywhere in the current.gpx file taken from my Oregon 650t, the same gpx file used to create the saved track log on the device.

I have sent Garmin an email (with my GPX files and test results) requesting an explanation.

I will report here as soon as they respond.

0 Former Member over 10 years ago

same problem

I am having the same problems (2 files in Basecamp of the same track, but with different data).
Someone suggested to put off the tracklog, but how can that be done exactly (Oregon 600).
I know there is a current.gpx if you do not save the track on your device, but if turn off the
device and use my Oregon for a track the day after, would the current.gpx file not be overwritten?
Since I will go on vacation soon and do not have access to basecamp, how else can I see all these
trips in basecamp without saving each track. I hope someone can help me out.

BTW: I also found out that the correct file in basecamp is different from the saved tracklog in the
unit. How is this possible. I tested this 2 new Oregon 650T and my current Oregon 600.

Thanks in advance

0 Former Member over 10 years ago

Hello E-CAT,

I have an Oregon600. I have tested it several times against my Edge705 and GPSMAP76cSX and FR310XT. On a 5-6 mile hike all 3 got the same distance within 1% every time.

I recorded both GPX and FIT files on the Oregon600 and saved them to memory after each hike and found no truncating of the data. It was all there, every second of it.

I recommend you use just the GPX files because BaseCamp cannot use FIT.

I recommend you save each days track because the internal memory is huge at 1.7GB so you will have plenty of memory for saving your vacation hikes.

Where you carry the 600 makes a huge difference in the quality of the tracks you record.
The absolute worst place for satellite reception is hanging upsidedown from the bottom of a large pack.
On your belt is almost as bad. In a shirt pocket with the face against your body is a little better.
The antenna is at the top of the 600 on the backside.
The best place is face down at the top of your pack.
I use a camera case attached near the top of my CamelPak. It has a padded and very soft liner against the face of my 600.
A shovel handle or tent pole sticking up out of the pack makes a good place to attach a case that will hold the 600 vertically and away from things that will block reception.

Canyons and big trees and tall buildings will weaken reception and then if you place the gps in a place that further weakens reception you will most likely record a track of jagged lines that will not look at all like where you were walking and the distance will not be very good.

I found that carrying the 600 in my hand and looking at the damned thing all the time really distracted from enjoying the hike so I go a ways then stop for a snack or a drink and pull out the gps to see if I am where I should be.

I also print out some paper maps for backup and if I hike a State Park I will buy their trail map. Whatever you do have fun. :o

0 Bill_Roberts over 10 years ago

Same problem on Etrex 30

I hope this data gives you a clue to the problem.

The problem appears on my Etrex 30 device as well as in BaseCamp.

I drove 5 miles to the start of my walk. At that point I waited for a GPS fix then cleared the current track AND reset the trip data. During the walk the Trip Odometer jumped up by 5 miles (quite early on but not sure quite how early). The current track distance remained correct (go to Track Manager, select Current Track then View Map to see the distance readout at the top).

I walked 24.8 miles. At the end of the walk I saved the current track, then said "Yes" to clear the current track.

When I view the saved track it says "Distance: 29.9 mi" at the top. And yet the displayed track is definitely only 24.8 miles. I strongly suspect that the 29.9 miles includes the 5 mile driving leg. Occasionally, transiently, I have actually seen that driving leg on the track display. But I can't make it happen.

Loading into Basecamp, as described by others in this thread, the distance on the Graph tab is correct, but the distance readout at the top of the Properties tab is incorrect at 29.9 miles. Adding up the leg distances of the 1763 points (I wrote a program to do that) comes to 24.8 miles. Exporting the GPX file to Google Earth shows that the distance is 24.8 miles.

This has happened to me on my last two walks. On previous walks I have often forgotten to reset the current track and ended up including the driving leg but now I am very careful to reset it and therefore rather disappointed to see the driving leg included despite my best efforts. I thought that waiting for the GPS fix would have done the trick.

The Elevation Plot on the Etrex 30 also shows the correct distance.

As I said ... hope this helps! Track file attached.

0 Bill_Roberts over 10 years ago

I should have done Reply to Thread rather than Reply to post. Sorry :-)

0 Former Member over 10 years ago

Hello WJR,

I think the problem is you need to reset the Trip Data as well as clearing the current track log before you start.

Owners manual page 20.

The other solution is to use the File > Import function in BaseCamp and browse to your Etrex drive and Import just the track.

When you use the Device > Receive From Device function then BaseCamp brings in the Trip Data which can really screw things up if you did not clear it before starting.