Yet Another Cycling Forum

General Category => The Knowledge => GPS => Topic started by: TPMB12 on July 24, 2018, 11:19:25 pm

Title: Garmin etrex models - what's the difference and what's important?
Post by: TPMB12 on July 24, 2018, 11:19:25 pm
Garmin etrex 20, 30, etrex touch 25 and 35. What's the difference? What's important? What's good for cycle touring especially with limited charging opportunities? Can you use them like cycling GPS unit to track route and log it (strava or Garmin connect linkage possible?).

Are the touch internal battery and the 20/30x are external? Are the 20/touch 25 basically very similar and 30/ touch 35 are similar?

Any come with bike mounts?

Just seen etrex 30 for £19 0 at cotswolds. A good price?
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 24, 2018, 11:57:53 pm
The Etrex touch are touch screen, the others have a wiggly button to press. A joystick type thing. I think all the etrexes use AA batteries. I don't think any of them come with a bike mount, as they're primarily intended for hiking. Handlebar mounts are readily available from Garmin for IIRC £14 or on ebay from a tenth of that including postage.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: TPMB12 on July 25, 2018, 12:06:27 am
Is there anything better for £190?
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 25, 2018, 12:28:06 am
Difference between a 20 and a 30 is that the 30 can speak to some[1] Ant+ sensors (chiefly heart-rate monitors); that it has a barometric altimeter to reduce the error inherent in reading elevation from GPS; and a magnetic compass so the map/arrow always points the right way[2], even when you're not moving.

I expect the difference between a 25 and a 35 is similar.  IIRC the 'x' models are just a minor improvement to the screen.

The little joystick thing is often infuriating (particularly for text input) if you're used to modern touchscreen devices, but it has the substantial advantage that it can be operated while wearing thick gloves.

All eTrex units are excellent at recording a track of where you've been - unlike the cycling-specific Edge units, they'll quietly get on with it in the background at all times, rather than expecting you to press a button to start and stop the recording, so you don't end up with the problem of it not recording your ride because you've forgotten to press something.  They're less good for racing/training analysis for the same reason.

The navigation features are broadly similar, and work best if you're prepared to put a bit of time and effort in, both learning how best to use it to suit your style of navigation (do you want it to tell you what to do, display a line to follow, or just be a waterproof backlit map with a 'you are here' arrow that you never have to turn over?), and at your computer creating the relevant routes/tracks to upload to the unit before you set off.

Anything AA-powered is a no-brainer for touring.  Expect to get 2-3 days of use from a decent set of NiMH batteries, slightly less from alkalines.

The handlebar mounts for the modern eTrex units are often referred to by retailers as the Oregon/Dakota mounts, as they fit those units as well.  It's not as compact as the Edge series brackets, but it's designed so that the back of the unit is more comfortable in your hand, without sticky-outy bits to click into the mount.  They work well, although the cheap eBay copies can sometimes be too loose.


[1] Conspicuous omissions (compared to the Edge) are wheel speed sensors[3], and cadence sensors that aren't combined with a speed sensor.  Yes, this is ridiculous.
[2] This doesn't work very well when it's attached to a bike on account of the metal, but it's a welcome improvement if you use it for walking.
[3] Much like having a barometric altimeter, the logic behind this is that it gives a more accurate measurement of speed/distance than GPS alone.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: TPMB12 on July 25, 2018, 08:34:22 am
Thank you for the summary.

One by product of the smartphone take up is the almost common conductive material in gloves to allow touch screen use. In walking brands it's been around a few years now. I wonder if the joystick will survive for many more GPS generations. Looking into satmap units it's part of their big idea based on the founder's experience of military electronics as used by squaddies. Touch screen supposedly a bad idea for durability. Gorilla glass 6 out now and I suspect durability will become a non issue for touchscreens.

With these GPS units do you need a computer to upload routes? Is there anyway of linking with your phone? I'm thinking if I decide to get one it'll be to put our proposed route on it (website for route gives gpx and other format route files out for download). If we change very loose plans because of what we find there we'll be without computer wanting to re-route. It's going to be a case of Internet cafe I guess or manual entering. No new gpx download to phone then sync across somehow? Would he difficult getting usb-c cable to GPS unit and no BTLE on the gps.

The new OS GPS units have BTLE on them so they might be heading that way.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 25, 2018, 08:51:32 am
I think I've heard some people say that when cycling, the touchscreen can be randomly activated by heavy rain. Possible I misheard that, but I do know my phone's touchscreen doesn't always respond properly when it's wet.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: frankly frankie on July 25, 2018, 09:29:38 am
Personally I think touchscreen devices are a safety issue for road users, at least in towns - you can't operate a touchscreen without looking at it, and you can't look at it and concentrate on the road ahead at the same time. 
Regardless, I would certainly avoid the Etrex Touch devices - everything I've read about them suggests they are little more than a rebadged Dakota, I used to have a Dakota for a while and it was awful.

Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: fuaran on July 25, 2018, 09:36:22 am
The Etrex Touch 35 has Bluetooth. Though not sure what you can actually do with it. It should work with the Garmin Connect app, which will let you upload your tracks (and automatically sync to Strava etc). So saves you having to plug in a cable for that.
Not sure if there's any way of downloading routes over Bluetooth.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: frankly frankie on July 25, 2018, 09:43:16 am
Ah yes I have successfully connected an Etrex30 and an Android phone, OTG-stylee, and transferred files both ways.  But it depends on the phone, and on the whole it's such a faff I would rather just build a new Route on the GPS itself (which most people seem to think is beyond the pale but I find it reasonably workable).  Anyway, I'm one of those outliers who doesn't normally carry a phone.  :thumbsup:
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: fhills on July 25, 2018, 01:13:20 pm
Re connecting stuff to the Etrex 20/30. It have found it a bit hit and miss connecting my android tab to the Garmin, even using an OTG lead and a powerbank to try to overcome apparent power issues. Problem solved now for touring as have just got myself an 11.6 inch chromebook for £99. A route can be obtained from cycle.travel with a few seconds internet access. IF (and I stress IF) want to finesse it I can do that with more internet access via wifi (spoons recommended in the UK) and the numbering of the points and other file editing can be done offline with the caret chrome extension. Best if it is then briefly checked online for syntax - that takes second
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Ian H on July 25, 2018, 01:46:38 pm
OTG connection was initially a faff, but with the latest Android update it seems to just work.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: fhills on July 25, 2018, 01:50:50 pm
OTG connection was initially a faff, but with the latest Android update it seems to just work.
which version of android are you using?

Mine is 6.0

Had the imporession the issue had more to do with my hardware (a Lenovo 7 inch Tab 3) than op system - the Lenovo sometimes tells me there is a power/potential overheat problem and urges me to shut down promptly.

I have managed to connect the Etrex 20 and the Lenovo but it is a bit hit and miss/unnerving. No probs - now have the mini chromebook.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Ian H on July 25, 2018, 02:00:04 pm
OTG connection was initially a faff, but with the latest Android update it seems to just work.
which version of android are you using?

Mine is 6.0

Had the imporession the issue had more to do with my hardware (a Lenovo 7 inch Tab 3) than op system - the Lenovo sometimes tells me there is a power/potential overheat problem and urges me to shut down promptly.

I have managed to connect the Etrex 20 and the Lenovo but it is a bit hit and miss/unnerving. No probs - now have the mini chromebook.

7.0.  Moving from 6 apparently made a difference.  I can also now see both the Etrex and its SD card.

Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: vorsprung on July 26, 2018, 04:38:24 pm
I have a 20x and it will run indefinitely off a B&M Luxos USB charging port.   When it is running off external power like this the back light is on all the time at night.  The Luxos light and the rear generator powered light and the Etrex20x all work at the same time.  The only annoying feature of this is that if you forget to turn it off when you stop then it will beep when the cache battery in the Luxos USB circuit runs out (after a few minutes) and then ask if you want to switch to batteries.  The default is "no, switch off"

The Openstreet map maps work well but you need a sd card to put them on.  I have a 4GB one that is far too big.  I suppose if I ever get OS maps or something it will come in handy
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Ian H on July 26, 2018, 06:55:39 pm
I have a 20x and it will run indefinitely off a B&M Luxos USB charging port.   When it is running off external power like this the back light is on all the time at night.  The Luxos light and the rear generator powered light and the Etrex20x all work at the same time.  The only annoying feature of this is that if you forget to turn it off when you stop then it will beep when the cache battery in the Luxos USB circuit runs out (after a few minutes) and then ask if you want to switch to batteries.  The default is "no, switch off"

The Openstreet map maps work well but you need a sd card to put them on.  I have a 4GB one that is far too big.  I suppose if I ever get OS maps or something it will come in handy

I think Francis explained somewhere why OS maps on an Etrex would be a bad idea (raster graphics, too much detail/clutter, etc).
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 26, 2018, 07:08:09 pm
I think Francis explained somewhere why OS maps on an Etrex would be a bad idea (raster graphics, too much detail/clutter, etc).

I tried a pirate copy to see how well it worked.  Raster graphics mean it's slower than usual, but that's only a problem if you're trying to do the big-picture stuff that's a world of pain on an eTrex anyway.  It also means you have to embrace 'north up', otherwise all the labels spend most of their time upside-down.  Unintuitively, it's the lack of detail that's the real problem: A 1:50k OS map is actually quite coarse compared to a vector map at the 200-80m zoom level that works best for understanding road junctions, and you're liable to overshoot if you try to use it to navigate in urban areas (for values of urban that include every little village with a couple of ambiguous side-roads).

I concluded that it might be useful for hill walking, but it's rubbish for cycling.  And I say that as someone who paid for the full set of OS maps in Viewranger - an Android (tablet by preference) being a much better platform for the sort of bigger-picture planning that OS maps are really good for.

The main appeal of OS maps for a road cyclist is the contours, and you can get those as part of an OSM map, or as an overlay to use with eg. the Garmin road maps.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: andrew_s on July 26, 2018, 11:41:06 pm
I've found that OS mapping works well, but you need OpenStreetmap as well for the more zoomed in scales where OS goes blocky. That generally means I use OS in rural areas, and switch to OSM for towns.

That's using a GPSMap 64s (much the same as an eTrex 30, but more buttons). The OS maps are above the OSM, so I leave OSM on permanently, and show OS over the top as desired.

OS includes 1:250k as well as 1:50k. The problem with pure OSM is that all the minor roads turn off if you try to view too large an area, which I commonly do, mostly just using the GPS as a map and making the route up as I go along.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 27, 2018, 08:57:39 am
Note about the handlebar mounts: At the bottom of the Etrexes is a little hole thing for threading a lanyard through. Use it and loop the lanyard round your bars, stem or whatever fixed point is handy, otherwise you might find your Garmin bouncing on to the road.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 27, 2018, 02:48:48 pm
Note about the handlebar mounts: At the bottom of the Etrexes is a little hole thing for threading a lanyard through. Use it and loop the lanyard round your bars, stem or whatever fixed point is handy, otherwise you might find your Garmin bouncing on to the road.

Which isn't to say the handlebar mounts (at least the proper ones) don't hold it securely[1], but it's a small amount of effort to prevent it going flying if something untoward does happen.  A minor off that hurts nothing but your pride and bar tape would be significantly worse if it culminated in your GPS being crushed by a taxi.


[1] The exception is when it's bashed from below by Brompton-stem-mounted water bottles, or kicked by a weary rider mounting or dismounting a recumbent.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 27, 2018, 05:44:21 pm
Another exception is when in a dark pub garden you put the Garmin on the mount upside down (and don't notice because it's off – you don't need it now, you're going home and know the way, but it's handier to put it on the mount than anywhere else).
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: fhills on July 27, 2018, 05:54:45 pm
Note about the handlebar mounts: At the bottom of the Etrexes is a little hole thing for threading a lanyard through. Use it and loop the lanyard round your bars, stem or whatever fixed point is handy, otherwise you might find your Garmin bouncing on to the road.

+1 learned my lesson the hard way. The mount had proved very good over some very bumpy ground. Then once it fell off. Appeared undamaged when I retrieved it (Etrex 20) from the road but it turned out the linkage with one of the buttons had been spoiled. Sent it back to Garmin and for a very reasonable amount they sent me back a reconditioned basically as new one.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Oxford_Guy on July 27, 2018, 06:03:41 pm

Anything AA-powered is a no-brainer for touring.


Unless you have a dynamo that can charge an external battery pack (i.e. I charge that when riding usually, rather than the GPS unit, which I then plug into the external battery at rest stops)... Which is what I do. Possibly only problematic if cycling very long night time audax rides, where you also need to run the lights at full power, so can't charge the battery.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 27, 2018, 06:09:45 pm

Anything AA-powered is a no-brainer for touring.

Unless you have a dynamo that can charge an external battery pack (i.e. I charge that when riding usually, rather than the GPS unit, which I then plug into the external battery at rest stops)... Which is what I do. Possibly only problematic if cycling very long night time audax rides, where you also need to run the lights at full power, so can't charge the battery.

I have one of those.  It mostly powers my phone/tablet.  Sometimes charges AAs for the Garmin on longer tours.  Sometimes charges my torch.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 27, 2018, 06:28:50 pm
I run my Etrex on rechargeable batteries. I don't have a way of charging it off the dynamo – heard various reports good and bad of a number of devices for this, but general consensus seems to be that it's best to charge a cache battery or power bank thing while riding and then charge devices off that – but I have noticed that when I connect it to my computer to install or download tracks, it appears to be charging the batteries. I've never left it plugged in to see how effective this is but it seems to suggest you can charge NiMHs in the device.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 27, 2018, 10:38:31 pm
Nahh, the eTrex won't actually charge its batteries, it'll just use power from the USB port instead of them.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Phil W on July 28, 2018, 02:27:56 pm
Be wary of powering an Etrex on the go. I did that on rattly / rough roads and it trashed the usb socket necessitating me getting a reconditioned unit as replacement.  Only just managed to get my track logs off the device on the dodgy connection.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 28, 2018, 02:32:15 pm
Yes, the design of the mini-USB socket is such that the delicate springy part is in the socket on the device, rather than the plug on the cable, which limits its lifetime.  Micro-USB is much better in this respect (it's still quite delicate, but it's much more likely to be the easily-replaced cable end that gets damaged).

Garmin have stuck with mini-USB for far too long.  I assume because it's easier to waterproof[1].


[1] In the sense of water not getting into the device via the socket, not the sense of the socket being usable in the wet.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: fhills on July 28, 2018, 02:32:26 pm
good tip phil

sounds sensible to me.

USB ports are pretty delicate stationary inside.

Seems the top tips to me are:

get an Etrex 20/30
use a lanyard
Don't connect external power on the move.

For anyone wanting to recharge their two AAs on the road (ie stopped in a tent) from a powerbank, I can recommend this.

https://www.ikea.com/gb/en/products/smart-home-appliances/cables-chargers/vinninge-battery-charger-art-40303632/

A mere £1.80

Remarkably it seems to work fine.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 28, 2018, 02:36:57 pm
For anyone wanting to recharge their two AAs on the road (ie stopped in a tent) from a powerbank, I can recommend this.

https://www.ikea.com/gb/en/products/smart-home-appliances/cables-chargers/vinninge-battery-charger-art-40303632/

A mere £1.80

Remarkably it seems to work fine.

Separate channels, nice.  That should avoid cell balancing issues if you use it long-term, and means that you can deal with odd numbers of cells (eg. head torches with 3 AAAs).

(I've got a cheap and lightweight two-cell USB charger that I use for touring which charges them in series.  Fine for occasional use, but not ideal.)
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Phil W on July 28, 2018, 02:47:32 pm
[1] In the sense of water not getting into the device via the socket, not the sense of the socket being usable in the wet.

The Etrex USB socket works very well in heavy rain. The rubber cover ends up facing forward keeping rain off from the front. The socket it below the unit stopping heavy rain from above getting in. So provided you have good mudguards using in rain on handlebars not an issue other than it breaking under vibration.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Phil W on July 28, 2018, 02:49:33 pm
good tip phil

sounds sensible to me.

USB ports are pretty delicate stationary inside.

Seems the top tips to me are:

get an Etrex 20/30
use a lanyard
Don't connect external power on the move.

For anyone wanting to recharge their two AAs on the road (ie stopped in a tent) from a powerbank, I can recommend this.

https://www.ikea.com/gb/en/products/smart-home-appliances/cables-chargers/vinninge-battery-charger-art-40303632/

A mere £1.80

Remarkably it seems to work fine.

I use a lanyard taken from a camera that does not really need the security in the places I use it.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 28, 2018, 02:52:56 pm
[1] In the sense of water not getting into the device via the socket, not the sense of the socket being usable in the wet.

The Etrex USB socket works very well in heavy rain. The rubber cover ends up facing forward keeping rain off from the front. The socket it below the unit stopping heavy rain from above getting in. So provided you have good mudguards using in rain on handlebars not an issue other than it breaking under vibration.

Depends on your riding position.  On my recumbents the eTrex faces backwards rather than upwards, so the socket it quite exposed.  On the Brompton it's at about a 45 degree angle, although well out of spash range.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: aidan.f on July 29, 2018, 12:32:49 pm
I'm struggling to  get my new  Etrex30 to alarm on waypoints. - As  you approach  a  junction Ping and  display  'R-SP-York'- Can anyone give tips please? I have gone through this guide http://www.aukadia.net/gps/lwg_20.htm (http://www.aukadia.net/gps/lwg_20.htm)
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 29, 2018, 12:39:46 pm
Nahh, the eTrex won't actually charge its batteries, it'll just use power from the USB port instead of them.
Ahh, that makes more sense.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Ian H on July 29, 2018, 02:42:28 pm
I'm struggling to  get my new  Etrex30 to alarm on waypoints. - As  you approach  a  junction Ping and  display  'R-SP-York'- Can anyone give tips please? I have gone through this guide http://www.aukadia.net/gps/lwg_20.htm (http://www.aukadia.net/gps/lwg_20.htm)

I think you have to set the proximity alarm for each waypoint.  I do that in a mapping program prior to uploading to the Etrex.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: frankly frankie on July 29, 2018, 04:08:16 pm
I think you only have a max of 10 proximity points unfortunately.  Best reserved for info controls.  (If you create more than 10, any extra ones are just downgraded to ordinary waypoints during import.)

I haven't noticed my E30 bleeping during Track-with-Waypoints navigation, but displaying the Waypoint name and Distance-to-next works well** (although on the E20/30 the font is very small for the waypoint name, really poor compared with the older models).

** fairly well - the interspersed 'high point' and 'low point' flags do mess it up a bit in typical undulating UK lanes, and there doesn't seem to be any reasonable way to switch these off.  They work better in the Alps of course!

If following a Route it will bleep for an upcoming Waypoint though not loud enough for my likeing, haven't really explored the pop-up options if any.

Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 29, 2018, 05:02:09 pm
I haven't noticed my E30 bleeping during Track-with-Waypoints navigation

Me neither.  I suspect this is one of the useful things that vanished in the upgrade from the HCx models.

If I want beeps, I put the effort in and coax auto-routing to do the right thing.

Otherwise, proximity alarms for (info) controls only.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Ian H on July 29, 2018, 11:15:44 pm
I haven't noticed my E30 bleeping during Track-with-Waypoints navigation

Me neither.  I suspect this is one of the useful things that vanished in the upgrade from the HCx models.

If I want beeps, I put the effort in and coax auto-routing to do the right thing.

Otherwise, proximity alarms for (info) controls only.

I've only used it for controls (so limited numbers).
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Cudzoziemiec on July 30, 2018, 09:09:16 am
I think you only have a max of 10 proximity points unfortunately.  Best reserved for info controls.  (If you create more than 10, any extra ones are just downgraded to ordinary waypoints during import.)

I haven't noticed my E30 bleeping during Track-with-Waypoints navigation, but displaying the Waypoint name and Distance-to-next works well** (although on the E20/30 the font is very small for the waypoint name, really poor compared with the older models).
I thought you could alter the font size.

Quote
** fairly well - the interspersed 'high point' and 'low point' flags do mess it up a bit in typical undulating UK lanes, and there doesn't seem to be any reasonable way to switch these off.  They work better in the Alps of course!

If following a Route it will bleep for an upcoming Waypoint though not loud enough for my likeing, haven't really explored the pop-up options if any.


Those high point and low point markers are mostly somewhat useless. It's not really terribly interesting to know that you're at a high point if the difference is only a couple of metres.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: aidan.f on July 30, 2018, 10:18:06 am
Oh, that sounds as if it will never do exactly  what I want it to..
Sleep with the screen off until 30m before turn points and then wake up for 60 seconds.
But there is workaround (that I have yet to find ) involving auto routing. Does that need additional routable mapping?
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: frankly frankie on July 30, 2018, 11:42:50 am
Currently Etrexes are normally sold with 'Garmin Topoactive' map pre-installed.  That is routable (though I wouldn't want to rely on it too much) and covers UK and nearby Europe.
But having the screen backlight come on before a turn should work with direct Routes (non-autorouting) as well.  Just not with navigating-by-Track.  The real advantage of autorouting is that it requres a bit less prep (but NB not no prep).

Those high point and low point markers are mostly somewhat useless. It's not really terribly interesting to know that you're at a high point if the difference is only a couple of metres.

If you have a waymarked turn and a high/low point gets inserted shortly before it, it really messes up your valuable 'Distance-to-next' information.  I would be tempted to remove whatever base map is being used to supply this information, but I'm not sure which one it is.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 30, 2018, 11:51:10 am
The real advantage of autorouting is that it requres a bit less prep (but NB not no prep).

I'd say it involves more prep, but that's because I don't usually want it to send me on a magical mystery tour.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: aidan.f on July 30, 2018, 02:05:34 pm
Confused! I don't want to randomly autoroute. If I have enough defined waypoints will that nail it down?
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 30, 2018, 02:21:53 pm
Confused! I don't want to randomly autoroute. If I have enough defined waypoints will that nail it down?

Nearly always yes, for extremely variable values of 'enough'.  Therein lies the rub.  Every now and then you come across some section of road that the algorithm will - for no obvious reason - go to extreme lengths to avoid.  Usually you can lay down enough routepoints to persuade it, but there are occasional exceptions.

Similarly, auto-routing is much more sensitive to gaps in the map.  If a section of road is missing (eg, because it's technically two dead-end roads joined by a footpath, or a road that's just randomly absent from the map), you can hand-wave over it in an off-road Route or Track, as they're not tied to the map.  But auto-routing has no allowance for that sort of thing.  You can bung a routepoint at your dead end, and another on the other side, but you can't stop it from leading you round the houses to get from one to the other.  My preferred approach is to add a waypoint (with proximity alarm if needed) reminding me to ignore the auto-routing for a bit.

The pragmatic approach to using auto-routing for audax type rides is to back it up with a visible Track.  That way you get the convenience of reminder beeps and highly visible instructions, but if it does something suspicious (eg. leading you downhill  :)) you have an easy way to quickly confirm whether or not it's talking bollocks.


I appreciate that it's a hard problem, but it shouldn't be this hard.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Ian H on July 30, 2018, 07:16:10 pm
I have got into the habit of glancing at the screen whenever a junction looms.  So just a dumb track works fine for me.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: aidan.f on July 30, 2018, 08:48:13 pm
Thanks Kim and  Ian .. .I shall practice navigation on some familiar routes.. 
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: Kim on July 30, 2018, 09:15:08 pm
Thanks Kim and  Ian .. .I shall practice navigation on some familiar routes..

That's the key: Practice.  Like everything else in cycling, what works best for you isn't always what works best for other people, and the best way to work out what doesn't is when it's just a bike ride.
Title: Re: Garmin etrex models - what's the difference and what's important?
Post by: andyoxon on August 01, 2018, 08:35:20 am
I also just use a simple gpx track and check screen as a junction approaches, with my old Etrex Vista HCx.  To improve the thin track line visibility on screen, I often overlay two tracks which have been reduced to max 500 points, using two different websites/ programs*, and so are slightly 'mismatched'.

*e.g. ridewithgps/winGDB3/basecamp