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GOJim

Oregon 700 GPS tracklog accuracy

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I have a new Oregon 700 but wondering about the accuracy of the tracks I record.  Recently went on a short hike with the gps tracking turned on.  I also used a phone app (A-GPS Tracker) to log my hike also, just out of curiosity.  Comparing them both 15" into the hike, I noticed the phone app was lagging behind the gps in distance covered.  After the hike, the gps had recorded 2.18 miles, while the phone app reported only 1.80 miles.  That's a rather large difference for a short hike, almost 0.4 mile.  When I uploaded the GPS file to mapping software Topofusion, for some reason the distance changed to 1.87 miles, but when that file is viewed on Garmin's Basecamp, its back to 2.18 miles.  The phone app mileage remained unchanged when opened in both programs.  So my questions are, why is there a difference between two gps units, which measurement is the correct, or most accurate one, and what's going on with the mapping program?  BTW, phone is an LG K8V running Android.  Any clarification I can get on this issue would be welcome.

 

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You need to look at the two tracks closely to see the reason for the variance.  It is usually down to the filtering that is going on.  The Oregon has a variety of filtering options, so a lot will also depend on what settings you are using.  I would suspect the Oregon recorded the random signal bounce when stopped as movement.  The phones usually have a lot of filtering applied and ignore this.  You can choose with the options on the Oregon to record or not record that sort of thing and filter after the fact.  It all depends on your use for the data.

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It will also depend on the frequency of track points created as well as the method. If you're recording time-based and very often (every 1 second), you're going to record a longer distance than if you're recording distance based and at a "normal" distance interval - say every 100 feet or so. I'm not sure which phone app you are using, but check to see if the tracking options can be modified so that your settings on the phone match settings on the GPS.

Finally, were you looking at the trip computer or the track log on the GPS? They are different, though there is a setting to sync the trip computer with the track log so that they are reading the same stats.

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The issue with TopoFusion is that it is probably filtering out some track points while basecamp is reading the entire file. You might notice that the track in TopoFusion is "smoothed", or rather contains longer straight segments between points while Basecamp shows more points and smaller segments between them. Again, the resolution at which data is recorded does make a difference. This idea has been a point of contention among cartographers and geographers regarding coastlines - the finer the scale at measuring, the longer the distance will be, despite there actually being a finite distance. It has to do with the nuances of every curve being measured.

My GPS always says I hiked farther than the mileage on maps, trail signs, and guidebooks. After correcting extra points, that distance will either fall in line or fall below the reference estimates.  Luckily, the Oregon 600 and 700 let you pause tracking when you're stopped so it doesn't keep collecting a birdsnest of points.

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Thanks to Red 90, Mineral2, and Atlas Cached for your valuable input on this topic.  I've got some work to do following everything up.

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On 11/19/2018 at 12:41 PM, Mineral2 said:

It will also depend on the frequency of track points created as well as the method. If you're recording time-based and very often (every 1 second), you're going to record a longer distance than if you're recording distance based and at a "normal" distance interval - say every 100 feet or so. I'm not sure which phone app you are using, but check to see if the tracking options can be modified so that your settings on the phone match settings on the GPS.
 

 

Which would you recommend to get the most accurate track for documenting hiking trails?

 

Also, my 60CSx greatly reduces the number of track points when a track is saved on the device.  Do you know if the new units also do this? Or can you hopefully save tracks with all their original data?  Thanks.

Edited by Cheminer Will

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The newer units, built in a time when flash memory is cheap, don't destroy your tracks as readily. Space on SD card is plentiful.

The 'auto' setting does a good job of recording switchbacks when needed and not dropping excess points when not. Barring that, Mineral2's advice of dropping by distance seems right to me.

If you need to reduce the number of points later, you can use GPSBabel's track simplifier. It can also "deblob" any tracks you have that recorded by time and have a clump of dropped points where you stopped for a water break, stop light, or whatever.

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Thanks Robert - I am hoping the new 66 series is able to somewhat reduce the mess of points caused by water breaks and such with its feature to stop recording points when you stop moving. So far I have fixed that issue only after the fact in Basecamp.  I have shied away from directly using tools like GPSBabel because I am not as technically proficient as many of you. But maybe it is not as hard to use as I think and I should be brave!  I hope the track simplifier can be used with the GUI version?

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11 hours ago, Cheminer Will said:

 

Which would you recommend to get the most accurate track for documenting hiking trails?

 

Also, my 60CSx greatly reduces the number of track points when a track is saved on the device.  Do you know if the new units also do this? Or can you hopefully save tracks with all their original data?  Thanks.

 

1. While the 'Automatic' settings for track log recordings work well for most situations, In all my hiking I have found that I still prefer recording by time at one second intervals. This works best for me when hiking twisty trails, as I find even the 'automatic' can skip or truncate the apexs of many switchbacks. I find it much easier to remove a few points in post processing for simplification rather than try to add information that has been omitted. I would rather 'dumb down' my tracks than try to determine where and when data is missing.

 

2. As Robertlipe pointed out, the 'newer' Garmin GPSr no longer do this. The Recorded GPX will be the same on the unit and anywhere you copy it to, with all track points intact.

 

 

7 hours ago, Cheminer Will said:

Thanks Robert - I am hoping the new 66 series is able to somewhat reduce the mess of points caused by water breaks and such with its feature to stop recording points when you stop moving. So far I have fixed that issue only after the fact in Basecamp.  I have shied away from directly using tools like GPSBabel because I am not as technically proficient as many of you. But maybe it is not as hard to use as I think and I should be brave!  I hope the track simplifier can be used with the GUI version?

 

The MAP 66 has the same 'Auto Pause' feature originally introduced with the Oregon 6x0. It does an excellent job of reducing all the spider-webs created when you stop for any period of time while recording a track log. For a visual example, see the Oregon 6x0 Review at GPSrChive.com.

 

There are a great many software options for cleaning up and editing tracks in post processing. Many of them are listed in the Software page at GPSrChive. I have spent much time using BaseCamp, and it is not the most friendly, but once you learn how it works, can be pretty efficient. I have Folders for each GPSr I use, so I can import raw tracks to one location then save edited tracks in another folder. Be careful with any of the 'Track Simplifier' options, as taking the easy way out is not always the easiest way out...

 

Always keep an archival copy of the original track log that is never touched with any editing software, so you can reverse any mistakes you may make in post processing. 

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Sometimes you get an answer to your questions that hits every point without wandering off track and really helps.  This was one of those.  Thanks Atlas!

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13 hours ago, Cheminer Will said:

Which would you recommend to get the most accurate track for documenting hiking trails?

 

<aside>

Documenting trails, you say?  I'm not sure how you plan to do this, but I'd like to put in a plug for OpenStreetMap, in case you're not already familiar.

 

OSM gratefully accepts GPS tracks, trails especially.  In their lingo, tracks are called "traces", and there's an upload a trace option.  This doesn't put them on the map directly, but makes them available to any editor (like me, could be you) who comes along, and sees tracks without matching dotted lines on the map.  The editor usually does any necessary cleanup (removing cache breaks etc.) before adding to the map.  Then after a delay (a few months?), those trails even show up on the cache page map; zoom in one notch to see.  (Changes show up sooner on other OSM-based maps.)

</aside>

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2 hours ago, Atlas Cached said:

There are a great many software options for cleaning up and editing tracks in post processing. Many of them are listed in the Software page at GPSrChive. I have spent much time using BaseCamp, and it is not the most friendly, but once you learn how it works, can be pretty efficient. I have Folders for each GPSr I use, so I can import raw tracks to one location then save edited tracks in another folder. Be careful with any of the 'Track Simplifier' options, as taking the easy way out is not always the easiest way out...

Always keep an archival copy of the original track log that is never touched with any editing software, so you can reverse any mistakes you may make in post processing. 

 

I use BaseCamp and can't even guess how many times I have been frustrated trying to figure something out.  It is definitely not intuitive.  Or I should say, whenever you feel you are about to do something correctly because if feels so intuitive, BaseCamp requires you to do something else entirely which is anything but easy and intuitive. But what else is there that really does what you can do in BaseCamp? It is especially hard to learn and remember for those of us that are not tech/coding/engineer types in the first place, but just want a GUI interface that allows us to do what the tech/coding/engineer types can do. I get the feeling if I had a local friend who was really good in BaseCamp I would be all set.  For me the biggest problem is not actually doing something in BaseCamp once you , but figuring out first how to get to the tool/procedure/steps that allow you to do what you want.

 

 

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4 minutes ago, Viajero Perdido said:

 

<aside>

Documenting trails, you say?  I'm not sure how you plan to do this, but I'd like to put in a plug for OpenStreetMap, in case you're not already familiar.

 

OSM gratefully accepts GPS tracks, trails especially.  In their lingo, tracks are called "traces", and there's an upload a trace option.  This doesn't put them on the map directly, but makes them available to any editor (like me, could be you) who comes along, and sees tracks without matching dotted lines on the map.  The editor usually does any necessary cleanup (removing cache breaks etc.) before adding to the map.  Then after a delay (a few months?), those trails even show up on the cache page map; zoom in one notch to see.  (Changes show up sooner on other OSM-based maps.)

</aside>

 

I may just have to look closer at OSM but a while ago I looked and could not find a good topo option? I like NW Trails and NW Topo at switchbacks.com.  If there was an OSM map the overlaid NW Topos, OR an OSM map that you could use and overlay NW Trails on, that would be worth exploring.  Any way to make either of those work?  If yes, maybe we can take it to another thread to discuss and not get this one off its OP topic. 

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On 12/8/2018 at 10:08 AM, Viajero Perdido said:

I'm pretty sure the answer is yes, for Garmin I'm assuming.  If you fire up another thread, we can get into specifics.

 

OK - I will do that now.  Thanks.

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On 12/8/2018 at 2:10 AM, Cheminer Will said:

Thanks Robert - I am hoping the new 66 series is able to somewhat reduce the mess of points caused by water breaks and such with its feature to stop recording points when you stop moving. So far I have fixed that issue only after the fact in Basecamp.  I have shied away from directly using tools like GPSBabel because I am not as technically proficient as many of you. But maybe it is not as hard to use as I think and I should be brave!  I hope the track simplifier can be used with the GUI version?


You got lots of good answers below (thanx, gang!) but I'll come back to this.

The track simplifier can sort of be used with the GUI. There are a bunch of options about exactly how you can choose to simplify (by count, by keeping the maximum overall fidelity of the original, by removing points that change the traveled distance the least, etc. These are covered in the doc.  As is often the case with GUIs, in order to keep complexity manageable, the GUI makes some of these choices and forces you to just use the 'count' option. It's about as easy as this sort of thing gets. (The screenshot is an older version that's known to be ugly in my configuration - the current version has the layouts fixed...)

If you want to pick out individual trackpoints one by one, we're the wrong tool and plucking them in Basecamp or such will be more to your liking.
 

Screen Shot 2018-12-09 at 10.34.57 PM.png

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My wife and I hike up to caches and many hikes up to 13 miles or so and we never have the same results. Sometimes were real close but I don't count on it. Been this way for years. Her's is the Oregon 700T mine the Montana 680T. We bought have the track log set for once every 3 seconds and auto pause off. Gps settings the same as well.WAAS ,etc. And load it into Basecamp to compare tracks as well as MapSource. 

Go figure.. different internal computing. It doesn't take much to make them different.. just carrying ways or how one hikes would effect it as well over a day.  

 And since it's a phone I wouldn't count of great results in the data transfer,etc like a dedicated Garmin and Basecamp would give. 

Edited by capt caper

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