GPX elevation clean-up program recs?

[sprengers4jc]

I am using Backcountry Navigator on a Galaxy S3 mini. As with most non-dedicated GPS units, the tracks leave a bit to be be desired as far as accuracy. Another user suggested GPS airtime monitoring and using that in airplane mode, the accuracy of my tracks have increased dramatically. Thanks to that user (whom I cannot remember his/her name right now). But the elevation gain still has issues since there is no built-in altimeter. This results in many spikes and artificially-inflated EG readouts on the final gpx. Even GPSfly cannot correct them.

On a thread a few months back, Koda had recommended GPX creator and GPS merge as great opensource programs and these have been invaluable to me over the past six months. I would just pop the gpx into GPXcreator, correct the elevation and kick out a new, more accurate track. Thanks, Koda! My problem, though, is that beginning last week, GPX creator can no longer correct elevation. I get an error every time I try to use it for that purpose. I uninstalled, reinstalled, rebooted. No go. I updated my Java, thinking that might be part of the issue. But the program has an expired security certificate and I have to manually override my Java settings to go forward and I am not comfortable with doing that, as it's possible that the program has been compromised at this point.

So my question for all of those who use their phone as a gps unit, are there any other programs out there that can do what I am wanting? Here is an example: we walked a loop at Lewisville Park last night in Battle Ground. I know this loop is no more than 150 feet or so of EG but my gpx track records it as 880 feet. I need a program that can correct the spikes automatically using either an existing database of the routes or something else that doesn't require me to meticulously delete point by point.

Thanks in advance for any help you all can provide .

[adamschneider]

GPS Visualizer can quickly replace the elevations in your file with data from a USGS or NASA database. Just enable the "Add DEM elevation data" option in the conversion form: http://www.gpsvisualizer.com/convert_input

One caveat is that in canyon-ish areas, your GPS signal can get wonky, and sometimes the recorded latitude and longitude will correspond to a point halfway up a cliff! When that sort of thing is happening, I bring my track into Google Earth (again, using GPS Visualizer), and edit the stray points in the GE application -- then save it as .kmz and convert it back to GPX using GPS Visualizer's converter.

[miah66]

Kerri-Tracy (which one am I talking to? ),

I do the same as you. I use Viewranger to record my gps track on my Samsung S4. I never use the elevation data as it's always WAY off. Even the distance seems to be understated, as I get about 10% less mileage than when hiking w/ someone using a dedicated Garmin or similar. I used the gps visualizer program that Adam recommended to add DEM elevation data (I chose USGS NED1) and uploaded my tracks from last weekends Falls Creek Falls hike to GPSfly.org.

Results from raw track:

http://gpsfly.org/a/4305

Results from converted track w/ DEM data:

http://gpsfly.org/a/4304

Almost 500' eg difference, negligible mileage difference. I think I will continue to experiment and see what I get. The Field Guide shows this hike as 6.2 miles, 1250' eg, though I added some distance w/ a few side trip explorations on mostly level terrain, so eg should've been about the same.

[adamschneider]

By the way, you can also make use of the smoothing filters in the "advanced options" in GPS Visualizer's converter. For my own purposes, I almost always set the "trackpoint distance threshold" to at least 4m; this means that wandering points recorded while I was standing still get eliminated from the output.

More info about smoothing/simplifying: http://www.gpsvisualizer.com/tutorials/ ... lters.html

[aiwetir]

I use RideWithGPS for cycling, it records a track very well, but the moving vs stopped time is all wrong for hiking so I don't recommend it for recording your track. I'm not sure if running your GPX through that would mess up the moving/stopped time, but it would probably smooth the elevations.

I do recommend it for route planning as it will follow trails on whichever basemap you choose OSM, Google, etc. I mostly use it to record tracks for updating OSM as it has a preference for how often a point gets recorded.

On their website, it has elevation corrections which seem to work very well for me.

My experience with Java certificates usually is a problem with Java and not the certificate.

I didn't know you could use Google Earth to edit GPX files, I'll have to give that a go, I use Garmin Basecamp.

I use GaiaGPS on the iPhone which is a very good product IMO, I use it for hiking as well as wildlife biology and the elevation is usually within 1-2% of what the field guide says things are.

[sprengers4jc]

Thanks everyone, I will try these ideas and report back.

Adam, I had stumbled upon gps visualizer but couldn't seem to figure out how to smooth out the track to improve upon my initial recording at all. What you suggested makes more sense than what I was doing. Hopefully, that will work for me.

Miah, this is Keri, btw . I think that FCF loop is about 1,100 feet of EG from what the field guide says so still quite a bit off. I don't mind a little off but hundreds of feet is frustrating, isn't it? The upside is, my friends think I am in amazing shape when I post my tracks because I look like I can climb 7,900 feet on the Hardy Ridge loop .

[kepPNW]

Almost 500' eg difference, negligible mileage difference. I think I will continue to experiment and see what I get. The Field Guide shows this hike as 6.2 miles, 1250' eg, though I added some distance w/ a few side trip explorations on mostly level terrain, so eg should've been about the same.

Fwiw, my track (http://gpsfly.org/a/3277) was about 7 miles and 1300', but we didn't do that upper segment you did.

By the way, you can also make use of the smoothing filters in the "advanced options" in GPS Visualizer's converter. For my own purposes, I almost always set the "trackpoint distance threshold" to at least 4m; this means that wandering points recorded while I was standing still get eliminated from the output.[/url]

That's a nice looking filter. May have to give it a shot.

Btw, I noticed in miah's example that the filter seems to have removed the timestamps as well?

I think that FCF loop is about 1,100 feet of EG from what the field guide says

Probably doesn't include the climb up to the upper viewpoint?

I can climb 7,900 feet on the Hardy Ridge loop .

Reminds me of the time I accumulated 2200' at Ridgefield Wildlife Refuge!

[adamschneider]

Btw, I noticed in miah's example that the filter seems to have removed the timestamps as well?

I don't know what Miah did, but GPS Visualizer's filters and elevation routines should leave the timestamps in place. Editing in Google Earth usually kills timestamps though.

[aiwetir]

Don't wanna hijack your thread, but is there a smoothing filter for the trackpoints anywhere?

[miah66]

Btw, I noticed in miah's example that the filter seems to have removed the timestamps as well?

I noticed that after you mentioned it! However, on my next example of Tumala Mtn the data is definitely still there. Weird. Notice that the elevation difference is even more profound here.

Viewranger from phone gps:

http://gpsfly.org/a/4306

GPS Visualizer elevation correction:

http://gpsfly.org/a/4307