Garmin eTrex - Creating a trail map using track recordings

xarielle

Hi, I am completely new to the world of handheld GPS devices. I am looking into the Garmin eTrex line of GPS devices. Let me first explain my goal. I have a private land where my family and I have made several trails, which are not mapped. I would like to use a GPS device to record my tracks in as much detail as possible (the terrain is quite difficult to navigate) as I travel along all of the different trails that we have made. I would then like to export and compile them to create a complete map of our trails, preferably colour-coded and including points of interest (waypoints), which I could then import back onto the GPS. Then a newcomer would be able to follow these trails with the GPS and always know where they are relative to all the trails and waypoints. Is this doable with the eTrex devices? What would be the best way to do this? Thank you!!

Boyd

Yes, that's certainly possible and I have done something similar using a variety of devices over the years (eTrex Legend C, GPSMap 60csx, Oregon 400 and Montana 600). I actually got the best results with a Garmin GLO, which is a stadalone GPS device that broadcasts your position over Bluetooth, where you can then use it with the Android or iOS app of your choice. See this thread:


http://forums.gpsreview.net/discussion/30108/what-is-gps-accuracy-testing-the-garmin-glo-in-the-forest

However, there's no reason why you couldn't do this with one of the new eTrex devices. Where it gets more complicated is turning the data into a map. I have been making maps for a long time and have professional software for this, but that won't be a good option for you. The simplest approach is to simply record a track on the eTrex and then import it into Garmin's free Basecamp software. You can edit it there and export it to a .gpx file. The .gpx file should be usable by others with Garmin handhelds as well as most smartphone apps. But the downside is that you will have very little control over the appearance and it won't be like a real "map" that also has other features.

You could convert the .gpx file to a Garmin format map, but this gets rather involved and also has a limitation when it comes to mapping relatively small areas. Garmin's map format is limited to about +/- 2.5 meters accuracy (about +/- 8 feet). This might not be an issue for you, but I found it did not properly capture all the winds and turns of the little trails on my own property. So I used Garmin's "custom map" format (.kmz files) which is what we call "raster imagery". This kind of map is really just a "picture" and is much more accurate than Garmin's standard vector-based maps.

Now this all gets rather technical, so I won't go into further details. But if you have specific questions, I'll try to help.

xarielle

Boyd said:

Thanks a lot for your prompt and helpful reply!

sussamb

You may find this useful https://www.javawa.nl/imgfromgpx_en.html

xarielle

sussamb said:

You may find this useful https://www.javawa.nl/imgfromgpx_en.html

That looks like a great tool thanks a lot!

Boyd

Javawa's tools are great, but if you convert your track to an .img file, it will suffer from the loss of accuracy I described above. Again, that might not matter to you but I was not happy with this for the map I made.

xarielle

Boyd said:

Javawa's tools are great, but if you convert your track to an .img file, it will suffer from the loss of accuracy I described above. Again, that might not matter to you but I was not happy with this for the map I made.

I see, that is an important point as I would like the trail map to be precise.

Boyd

I made an old post about this issue at GPSFileDepot, including some screenshots

https://forums.gpsfiledepot.com/index.php?topic=1335.msg8387#msg8387

The pink lines in this image are the high resolution trails. The blue lines are the result of converting them to a Garmin .img file. To be fair, these have been zoomed in extemely close, but that is what I wanted for my map

xarielle

Boyd said:

The pink lines in this image are the high resolution trails. The blue lines are the result of converting them to a Garmin .img file./>

Yeah that does look pretty bad

Boyd

I think will need to learn a lot more before you have the proper frame of reference to really understand this kind of issue. If you just record a track on the eTrex, it will be a big mess, zig-zagging all over the place - would look much worse than the blue line above. You need to walk the trails a number of times, then overlay all the tracks on each other to get an idea of where the trail really is. Then, if you want a "pretty" map you will need to draw your own smooth line over what you recorded. I think you could do all of this in Basecamp, although it's not what I use.

Also, if making a trail map is the main use for the GPS then I would not get an etrex or any other Garmin handheld. They are just not intended for that usage, they are primarily designed for hiking and design trade-offs have been made to make the batteries last a long time while still providing a screen that is readable in sunlight.

See the thread I linked to in my first post about the Garmin GLO and accuracy. I also reviewed the GLO here in 2013:

gpstracklog.com/2013/04/garmin-glo-review.html

It will be cheaper than an eTrex and should be much more accurate. The big advantage is that it updates your position 10 times per second while Garmin handhelds only update once per second, so you get a lot more data to work with. And it will be compatible with (literally) hundreds of apps for your iPhone or Android phone. There are also apps that allow you to make maps right on the phone.

xarielle

Boyd said:

See the thread I linked to in my first post about the Garmin GLO and accuracy. I also reviewed the GLO here in 2013:

gpstracklog.com/2013/04/garmin-glo-review.html

It will be cheaper than an eTrex and should be much more accurate. The big advantage is that it updates your position 10 times per second while Garmin handhelds only update once per second, so you get a lot more data to work with. And it will be compatible with (literally) hundreds of apps for your iPhone or Android phone. There are also apps that allow you to make maps right on the phone.

Thanks for the advice, I will be looking into the Garmin GLO then.

Boyd

What kind of phone do you have? With an iPhone, it will automatically recognize the GLO and use it instead of the built-in GPS. Not sure about the current version of Android but AFAIK, you need to install this free app and set it up in order to use an external bluetooth receiver

https://play.google.com/store/apps/details?id=googoo.android.btgps&hl=en_US

If you want to use the GLO, before you purchase, I suggest you play around with some of the apps on your phone. There are literally hundreds, and most have free trials. They will work fine on the phone without the GLO, so you can field test them. Only difference will be that your tracks will be less accurate (although, depending on your expectations, they might actually be good enough).

xarielle

Boyd said:

What kind of phone do you have?

I have an android phone. So if I understand correctly, what you are suggesting is that before getting the GLO, I test apps to make trail maps and just using the phone GPS? Then when I find a good one I would generate more accurate tracks using the GLO and import the tracks into that app to make the map?

Boyd

Yes! But, just to be clear, all the GLO does is provide more accurate data to the phone. Once you set it up then everything will continue working just the same, but you will have more accurate data.

Looking at the thread I linked to about accuracy, the white lines are tracks I recorded by walking my trails many times. The red lines are the actual positions of the trails, as traced from aerial imagery. Like I said, you cannot really use the the tracks directly if you want an accurate map, you have to draw your own smooth line based on the tracks.

sussamb

You don't say where you are, I assume in the US, but in UK I find tracks created by my Etrex 20, which uses both the GPS and GLONASS system, rarely vary over repeated tracks and certainly would enable anyone else following them to pretty much walk in my footsteps.

Boyd

I would be very interested to see some examples of this, overlaid on aerial imagery. But I'm sure that GLONASS helps much more in the UK than it does here in the US.

There is certainly nothing wrong with the eTrex line if you want a general purpose GPS for hiking. But the OP seems pretty clear that he just wants it for this project. The GLO will be cheaper, provide 10x more track data and give you the choice of hundreds of apps.

But if you think you might also want to use it on long hikes, and if you want to use Garmin maps then an eTrex will be a good choice.

xarielle

Boyd said:

Looking at the thread I linked to about accuracy, the white lines are tracks I recorded by walking my trails many times. The red lines are the actual positions of the trails, as traced from aerial imagery. Like I said, you cannot really use the the tracks directly if you want an accurate map, you have to draw your own smooth line based on the tracks.

Thanks for pointing that out, that's good to know. It seems a bit strange to me that it cannot be more accurate though! Like you mentioned the purpose of the GPS would really be just for this project, but precision is one of my main goals. If that's as good as it can get, it will have to do!

sussamb

Boyd said:

I would be very interested to see some examples of this, overlaid on aerial imagery. But I'm sure that GLONASS helps much more in the UK than it does here in the US.

Here are links to a track taken recently when I walked the Coast to Coast route in the UK. It will give you an idea of the accuracy: (sorry, failing to post them correctly), one shows the track overlaid on imagery and the other the imagery without the track

https://i.postimg.cc/X77dQLNQ/Map-1.jpg
https://i.postimg.cc/tCSPf6Yy/Map-2.jpg

Boyd

Thanks, those look fine. However, this is not at all comparable to the examples I gave. The aerial image is zoomed way out. Look at the distance scale in the example I posted above - click on it to see full size. If you zoom in that far on your track, I'm sure you will see very noticeable variations between tracks recorded at different times.

I certainly agree that the tracks in your example are more than adequate for someone who wants to follow a road on a hike. That is not the same as making an accurate map of a small area that looks good when zoomed way in.

Again, nothing against the eTrex. I just think there are better tools for the project that @xarielle wants to undertake.

Boyd

xarielle said:

It seems a bit strange to me that it cannot be more accurate though!

It will not seem strange if you become more familiar with the technology. Garmin's handheld devices are accurate to within about +/- 5 meters (16 feet). And Garmin claims +/- 3 meter (10 foot) accuracy for the GLO. Think about what these numbers mean. If you go to a marked location and record your position two times, those points will (theoretically) be within 5 meters of the true location. However, one of the points could be 5 meters north of the actual location, and another could be 5 meters South. So, the distance between two points recorded at the exact same location could be 10 meters (33 feet) and the GPS would be within its specifications. You can see this graphically in the image I posted (and the thread about accuracy I linked to).

If you are trying to map a trail that is only 1 meter wide, that is a huge error. But, such are the limits of consumer devices. None of them (including the GLO) were designed for making precise maps of small areas. Want more accuracy, no problem. SXblue makes some nice bluetooth receivers with sub-meter - or even centimeter - accuracy. Cost is in the $3000 to $7000 range

https://sxbluegps.com

Trimble is considered the "gold standard" for highly accurate GPS receivers. Expect to pay in the same range, although you may find some in the $2000 range.

https://geospatial.trimble.com/GIS

These are professional tools where no trade-offs have been made to keep the price low enough to appeal to a mass audience. There are other bluetooth receivers in the consumer space you might consider however, such as Bad Elf

https://bad-elf.com/collections/bluetooth-gps

and Dual

https://gps.dualav.com/explore-by-product?category=GPS

I considered these two companies when I got my glo a number of years ago, but felt they did not offer any advantages at that time. Things may have changed today, so you might want to do your own research.

xarielle

Boyd said:

It will not seem strange if you become more familiar with the technology.

Yes, I am researching more on the topic to gain a better understanding, thanks a lot for taking the time to give me all this detailed information, it is very much appreciated! :)

Boyd

You're welcome!