# GPS track editing software?



## Speedub.Nate (Dec 31, 2003)

I'm curious if a GPS track editor exists with the following features:

- Averaging of track: Ability to overlay multiple tracks recorded over the same trail, and average the results in order to discard obviously erroneous points.

- Manual track correction: Ability to manually select two points (A & Z) which are accurate (clearly on the trail when viewed on a Google Earth overlay), then "drag" the remaining inaccurate points (B through Y) back into the correct location, like a rubber band effect.

- Track Optimization: Automatically discard redundant points, for instance if the trail continues in a nearly straight line, discard any unnecessary points recorded before or after that straight line section.

Does this exist?


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## Nathan Cloud (Jul 18, 2005)

Speedub.Nate said:


> I'm curious if a GPS track editor exists with the following features:
> 
> - Averaging of track: Ability to overlay multiple tracks recorded over the same trail, and average the results in order to discard obviously erroneous points.
> 
> ...


Topofusion has their "trail network" feature which covers your averaging track request.

It also has a simplify track feature which trims down the number of points for track optimization, does a great job if you ask me


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## Speedub.Nate (Dec 31, 2003)

Nathan Cloud said:


> Topofusion ...does a great job if you ask me


Most excellent! Free demo, too. Thanks, I'll check it out.


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## heatstroke (Jul 1, 2003)

have you tried mapedit ? 
It does not have an automatic averaging but you can draw your own polyline. Most functionality is available in the trial version


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## jcbikeski (Nov 26, 2005)

I use expertgps for editing. For some other automated edits like reducing points (to fit in a gps) I also use the free gpsbabel software.

btw, another cool feature I found in expertgps is the ability to automatically geotag your .jpg files.


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## Krein (Jul 3, 2004)

Speedub.Nate said:


> I'm curious if a GPS track editor exists with the following features:
> 
> - Averaging of track: Ability to overlay multiple tracks recorded over the same trail, and average the results in order to discard obviously erroneous points.
> 
> ...


Hi,

Disclaimer: I write/sell TF.

For averaging, try the network feature as suggested. It's not really designed to be a general purpose track averaging tool, but you get that for free when you create a network out of a number of tracks.

Re: manual correct, you can draw a box around a group of points and move them all together to get them back on the correct trail. Not sure exactly what you're after, but if TF doesn't do it, I'd like to hear what you'd like to be able to do so I can think about adding it.

You'd be amazed how few points you can simplify a GPS track down to without losing much detail. I simplified my 140,000 point track of the Great Divide down to 10k and only lost a few miles in overall length. Just right click on the track in the map window to get the "simplify/spline/split track" option.

Hope that helps.


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## Speedub.Nate (Dec 31, 2003)

Krein said:


> Re: manual correct, you can draw a box around a group of points and move them all together to get them back on the correct trail. Not sure exactly what you're after, but if TF doesn't do it, I'd like to hear what you'd like to be able to do so I can think about adding it.


Thanks for the pointers. I downloaded the evaluation version and have played with it a little, but I wasn't finding some of the stuff I wanted and have to spend a few minutes reading your instructions. From what I've seen so far, it's very nice!

As for manual correction, I'm noticing that for the most part my Vista HCx is on the money. However, it appears that at certain points, when I get in the "shadow" of a hill, I get sort sections of errors that diverge widely, then make their way back to the trail.

So what I'm looking for is a feature where I can identify a start point and an end point that are both "on trail"/accurate, but where the points in between gradually increase in error, then decrease in error. I'd like to "rubber band" these intermediate points back into place. I would "grab" the most erroneous point, and move it back to where it should be, and the points on either side would also move, but by a lesser and lesser amount.

Kind of like a "curve" function on a drawing / drafting program, where I might start with a straight line, but create an arc out of it by grabbing any point along the line and dragging it.


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## fishbum (Aug 8, 2007)

DeLorme's TOPO USA lets you read in a track, convert it to a draw layer, and edit any of the points as needed rubber-band style or delete points. Plus it has the TOPO detail underneath. Plus you can overlay the track on imagery and georeference the points. Just a suggestion.


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## socalenduro (Nov 1, 2006)

so once you have edited and changed everything, can you then move the edited track back to the Garmin unit?


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## fishbum (Aug 8, 2007)

Yup. You can move Tracks and waypoints from/to the Garmin device with TOPO, just no maps.


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## Krein (Jul 3, 2004)

Speedub.Nate said:


> As for manual correction, I'm noticing that for the most part my Vista HCx is on the money. However, it appears that at certain points, when I get in the "shadow" of a hill, I get sort sections of errors that diverge widely, then make their way back to the trail.
> 
> So what I'm looking for is a feature where I can identify a start point and an end point that are both "on trail"/accurate, but where the points in between gradually increase in error, then decrease in error. I'd like to "rubber band" these intermediate points back into place. I would "grab" the most erroneous point, and move it back to where it should be, and the points on either side would also move, but by a lesser and lesser amount.


That's interesting. I guess I've seen some similar errors, but not frequent enough that I thought about adding a feature like you are describing. In my experience most errors are pretty random, without too much of a pattern. But then, I do live in AZ, land of plentiful GPS signals.

Thanks for the idea. I'll think about how best to implement it, and also check out the latest TopoUSA. I need to check in with their latest developments.


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## Harold (Dec 23, 2003)

I know the feature speedhub.nate is after. It's a feature I use with GIS software (ESRI's ArcGIS 8.0 or the opensource QGIS). It occasionally happens where I'll get some really bizarre outlyer point that just needs to go away. I've not used any other programs that allow me to simply edit the relevant file, view ALL trackpoints, and click on the points that need to be deleted. From there, I can then move the points around, add new points to smooth out a curve, cut the track into pieces at a specific point, merge two or more tracks into one, add on...the list goes on.


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## fishbum (Aug 8, 2007)

Here is an example of DeLorme's TOPO USA track editing.

First image is raw track data imported from the GPS to TOPO and overlayed onto TOPO data.








Second image is raw track data overlayed onto hires imagery. Note how the raw GPS track is off the actual trail. Also note the curved monument in the lower right corner.








Third image is optimized track data - I've removed the unneeded datapoints and rectified the data to the imagery.








Piece of cake!


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## presslab (Jan 5, 2007)

I use GPSMapEdit. I just import a bunch of GPX files and you can easily see the trend of the tracks. Mine usually lay right on top but where it deviates I just move the points.


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## presslab (Jan 5, 2007)

fishbum said:


> Here is an example of DeLorme's TOPO USA track editing.
> 
> First image is raw track data imported from the GPS to TOPO and overlayed onto TOPO data.
> View attachment 318637
> ...


Are you sure the aerial image is really accurate? I would guess your GPS signal would have less error, especially in that kind of terrain.


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## fishbum (Aug 8, 2007)

Track data was collected when the foliage was present, and the imagery is about 5 yrs old before the tree growth expanded... I have to assume the imagery is precisely aligned and it's better than the accuracy of the GPS, it's just an example anyway. The reality I've come to believe when collecting trail track data is that the EXACT position of the trail track is not as important as the exact location of the the start finish of the trail (intersections).


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## Speedub.Nate (Dec 31, 2003)

fishbum said:


> Track data was collected when the foliage was present, and the imagery is about 5 yrs old before the tree growth expanded... I have to assume the imagery is precisely aligned and it's better than the accuracy of the GPS, it's just an example anyway. The reality I've come to believe when collecting trail track data is that the EXACT position of the trail track is not as important as the exact location of the the start finish of the trail (intersections).


Here's a quick example.

Most of this track is "right on" on the Google Earth overlay.

The trail picks up from the left, pretty much on track, then diverges slightly (but acceptably) after the first little bend.

But after heading "southwest" and, presumably, being blocked by rising terrain, my electronic breadcrumbs have been dropped onto the neighboring golf course, instead of along the trail which is clearly visible.

I'd like to anchor a point at that last 90° jog, and again further up the trail where everything is back on track, then select the portion along the golf course (inbetween the anchors) to nudge the points back on track.


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## presslab (Jan 5, 2007)

Speedub.Nate said:


> Here's a quick example.
> 
> Most of this track is "right on" on the Google Earth overlay.
> 
> ...


That's interesting. I would be curious to see your satellite reception screen before that bend and after. I would guess you are losing a satellite or two which causes a shift in the data. Do you have WAAS enabled, and were you receiving the satellite? Did you update the firmware so WAAS does not turn off every time you turn the GPS off?


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## fishbum (Aug 8, 2007)

WAAS does help improve accuracy, but not as much as everyone thinks (roughly 10-40%, or 2 to 8 feet improvement out of 20 feet of error).

I'd suggest that the foliage is affecting the accuracy there more than anything. And if there is a hill there may be additional multipath error added as well...


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## presslab (Jan 5, 2007)

I would guess multi-path error is more likely in urban areas with buildings, etc. I doubt that the little signal left after passing through those trees bounces off the hill and reaches the receiver.

Wikipedia shows that WAAS accuracy is typically better than 1-1.5 meters overall.
http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System


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## Speedub.Nate (Dec 31, 2003)

presslab said:


> That's interesting. I would be curious to see your satellite reception screen before that bend and after. I would guess you are losing a satellite or two which causes a shift in the data. Do you have WAAS enabled, and were you receiving the satellite? Did you update the firmware so WAAS does not turn off every time you turn the GPS off?


I posed this question in a recent thread. By carrying my GPSr in my backpack, I'm excluding half of my visible horizon. Add terrain to the mix, and I've got maybe 1/4 or 1/3 of the horizon in view. I believe that is my problem.

I relented and bought a handlebar mount, but haven't put it into use yet. I'm expecting to see somewhat improved results.

Even stashed in the pack, the vast majority of my tracks are recorded accurately.


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## presslab (Jan 5, 2007)

Ah, the bar mount will help for sure. That's what I use on my Vista HCx. With this GPSr I get great results. I've been mapping a lot of trails here in the north bay and creating Garmin topo maps with the data.


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## Harold (Dec 23, 2003)

Are you 100% sure your software and GPS are using exactly the same datum? That's the kind of error you'd expect to see if you weren't using the same datum, say NAD27 instead of NAD83 or something. And sometimes, depending on the source, the imagery IS just plain off, while the gps was correct. Try overlaying onto imagery from a different source to see what happens.



fishbum said:


> Here is an example of DeLorme's TOPO USA track editing.
> 
> First image is raw track data imported from the GPS to TOPO and overlayed onto TOPO data.
> View attachment 318637
> ...


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## fishbum (Aug 8, 2007)

Datums are correct, both WGS84. With other data that I have access to the track lies a little closer to the actual trail. I also have other track data in this area that is off to the other side of the trail slightly.

Guys - It's only 20 feet off even with the first image I've shown!!!! At any given moment in time I would expect the error to be off consistently in the same direction, and in this case it is. Thats pretty dang good in my opinion and it could be entirely attributed to the GPS accuracy. 

Its possible that the imagery could be aligned a little more precisely, but the point I was trying to show is that you can edit the tracks, delete points, and move tracks completely.


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## fishbum (Aug 8, 2007)

Speedub.Nate said:


> By carrying my GPSr in my backpack, I'm excluding half of my visible horizon.


Hmmm... the pack isn't actually physically blocking the view to the sats, the pack materials (and your body) are absorbing some of the RF energy so the receiver isn't able to detect the weaker signals if some of the sat signals were already marginal... So you are effectively determining a solution with fewer sats...

BUT as you mention, even with fewer sats your tracks are pretty accurate. Cool stuff. :thumbsup:


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## Speedub.Nate (Dec 31, 2003)

fishbum said:


> Hmmm... the pack isn't actually physically blocking the view to the sats, the pack materials (and your body) are absorbing some of the RF energy so the receiver isn't able to detect the weaker signals if some of the sat signals were already marginal... So you are effectively determining a solution with fewer sats...
> 
> BUT as you mention, even with fewer sats your tracks are pretty accurate. Cool stuff. :thumbsup:


I've ridden with the receiver in the side pockets and in the top flap pocket. All leave the antenna facing more in the horizontal direction, weakening the strongest signals from above and "behind" the antenna.

I live on a fairly unobstructed hill. A quick test outside gives me nearly all full bars with the receiver facing straight up. Rotating the receiver vertical, two or three satellites drop significantly. Holding the receiver in this vertical orientation, and turning to face each of the cardinal directions, sees weaker satellites pick back up, and others drop off.

Hiding in the shadow of a house or car yields similar, but more significant, degradation.

All interesting stuff.

In the overhead I posted, besides the terrain visible to the south, there is also a 500' ridge (out of view) extending along the east.

I'll have to do a couple of loops, first with the bar mount, then with the Vista tucked into a pocket.


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## fishbum (Aug 8, 2007)

Depending on the antenna design there is a pattern of energy produced, the pattern may have 'blind spots' in certain places depending on whether it's a ceramic patch or helix or...? Your GPS probably has a patch so when you lay it flat/horizontal you get the best performance, stand it vertically and point it north and you may not be able to see southern sats, for instance.

Overall if we assume consumer GPS devices can provide TYPICAL accuracy of anywhere from 20-100 feet thats pretty good. Add foliage, hills, backpack fabric and this can degrade. Handlebar mount with clear sky view probably gives the best accuracy. The accuracy your GPS reports is a position error estimate - it's just an estimate and there is no standard and each vendor has their own algorithm, some are conservative and some optimistic! Even if the accuracy is not perfect a GPS is a damn good tool to have!


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## BigLarry (Jul 30, 2004)

*Garmin MapSource Edits Tracks*

The Garmin MapSource software that should have come with your GPS can edit tracks, but not average.

First make sure you have the latest version. Mine is 6.13.2. You can download Mapsource updates free from Garmin.com. The Help menu automtacially connects.

Then right click anywhere on your menu bar and make sure the "Track Edit" buttons are checked. You can join, remove, or move track points as you wish.

Alternatively, I can double click on any track to get it's properties, and edit the waypoints in the list. This is really only good for eliminating points, but you can cut and paste track sections too. The advantage of this method is that you can select a few points, then hit the "Center map on selected items" check box, and the map will zoom in to the points you want to work with as your moving through the list.


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## chri123 (Jun 29, 2011)

stumbled over this post a few days back. 
In the meantime I have found *GoBreadcrumbs* on the web. Is a free GPS track web app that comes with a built in GPS track editor and you can split and extract your imported tracks as well. Something I need often, when I forget to turn off my GPS after a ride.


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## Harold (Dec 23, 2003)

chri123 said:


> stumbled over this post a few days back.
> In the meantime I have found *GoBreadcrumbs* on the web. Is a free GPS track web app that comes with a built in GPS track editor and you can split and extract your imported tracks as well. Something I need often, when I forget to turn off my GPS after a ride.


I much prefer to do such editing on my home computer. There are several websites that allow trackpoint editing - runningfree and mapmyride being a couple other options. Since I store backups of all my data files on my computer, it just makes sense to do my editing there, too.


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