Assuming you have a dyno, charger, and a smartphone, are there significant reasons to use some other gps device for navigation on long distance tours?

I gather that the dyno cannot keep the phone charged in continual display mode, but should be ok if the phone is typically not displaying? Perhaps cellar service with maps are an issue, but it appears all maps can be downloaded in free wifi areas.

I used my iPhone with a cycling app for over 4 years and never had any issues. I did, however, have a Wahoo RFLKT connected to the phone to display my ride data so I could keep the phone's screen turned off. When my RFLKT died, I went with a Wahoo Bolt and found that the battery drain, per ride, is the same as that of the phone. If you are charging the phone while riding, I don't see why you should have any issues. You may have to do some research on things that you can do to increase your phone's battery life, which should help.

I use an external battery to power my phone. It has enough capacity that I can keep the phone's display on all day and keep the battery topped up.

The downsides to using a phone are:

1. You need a really good mount. Don't cheap out. I use a Quad Lock.
2. Accuracy is not as good unless you use speed (and cadence?) sensors. I don't use them, because the GPS accuracy is good enough for me, but it's not for everyone.
3. Using a phone's screen is not always possible, even when it's right there, because fingers bounce, and I can't look at the phone for more than a second. A bike computer has tactile buttons.

You could use a dynamo-powered charger to charge a cache battery and run the phone off that battery. I haven't tried that, because I have a power outlet at the beginning and end of every ride. A good such charger is about $120.

It's a personal preference thing. It matters not one bit which one you want to use as long as it works for you.

From what I've read on other forums, phones might be a little better for use in cities with tall buildings. The idea being that the cell tower connectivity gives them a quicker recovery from signal interruption. Some say that in areas far from cell tower reception, that dedicated GPS cyclometers fair better.

So if you are like most and not hampered by very tall buildings or out in the middle of nowhere, then it boils down again to just personal preference.

I sometimes use my phone to navigate when I am driving my truck. Use Maps.Me app for android. They recently added a bicycle routing ability to it, but the few times I tried that routing it did not work so well. Load maps ahead of time when you have wifi access.
https://play.google.com/store/apps/d...maps.pro&hl=en

That app is getting better every year, when I first started using it (at that time it was called MapsWithMe, I paid for the Pro version) it did not offer routing, just maps, I think I first started using it in 2012 or so.

But, I have been using a Garmin GPS on my bike for so many years, I see no reason to change. For one thing, I can read it in direct sunlight, can't see my phone that way. I used to use a Garmin Legend or Vista (the old black and white screen ones) where I loaded the maps into the GPS at home on my computer. Recently bought a Garmin 64 and use that now. The 64 I can plug it into a USB charger and charge a pair of NiMH batteries in it (there is a trick to doing this, if you are interested let me know). But the 64 will only work with a USB charger that has a pass through cache battery, it will not charge batteries when I plug it into my Sinewave charger without a pass thru cache battery.

If you are not familiar with pass through cache batteries, this explains it.
https://www.cyclingabout.com/best-dy...fer-batteries/

The downside to the Garmin is that I have to use my computer to load maps into it. It does not have any wifi or internet access by itself. I do not mind planning a trip on my computer, so that is not that much of a down side to me, but if you want to do it all on your phone then that is a huge downside.

I have a very minimal data plan with my phone, I try to only use it on wifi.

In my experience, the one advantage of dedicated bike computers is their ruggedness. A phone is more likely to be damaged (although it never happened to me), and driving rain will make it next to impossible to interact with a phone (the tactile screen confuses raindrops with gestures).

Other than that, phones are superior on all features.

It is fairly easy to keep a phone fully charged. Turn the screen off when you don't need turn by turn directions. A battery pack may also be a useful addition to your kit.

As others have indicated, phones can be used offline. I use an old S5, without SIM. Occasional WiFi access may be useful, but rarely necessary.

Phones are hard to see in bright sunlight. Bike GPS computers are waterproof, viewable in full sun, and the battery lasts a long time.

Phones are way better at browsing around the map. I have the very low cost osmand+ app. It downloads maps in advance, so no cell signal is needed, and the maps display very fast. You can try out the free version, with a limited number of map downloads.
osmand: free, a limited number of state or country downloads.

I reviewed osmand+ in this post. It's $9 for an unlimited amount of map downloads. Contour lines are an additional plugin.

Now, the newer version of osmand has an icon to switch between driving, bicycle, or walking, with different views shown.

Thanks to all for the range of well considered information. It appears from the comments that the gps screens are easier to see, which is surprising given that the screen technology is the same. Perhaps the gps has less detail and therefore easier to see?

I have used the Maps.me app and played a bit with Osmand, but I am used to google maps which can now be downloaded for offline use, so I don't see an obvious benefit for these other apps. Perhaps google maps does not allow uploading of pre-generated routes from computer?

Certainly important to have a robust mount, wouldn't care to see device being launched off the bike while moving down the road.

The reason I mention the mounts is that I tried to find the sweet spot between price and quality. That was a mistake. I almost lost a phone, but there was also a lot of inconvenience and frustration. And I spent more than I needed to, trying to save money. Just buy a Quad Lock system and be done. You need a mount and a case, minimally.

Unless things have changed recently, gmaps is unreliable for offline navigation. It requires connectivity to compute a route, and if you deviate from a route set while you were connected, you'll loose navigation.

There are several great offline navigation apps. I use Locus pro / Android.

Phones are large, gps are smaller; this makes a difference to me with a smaller frame size. I already am limited to 20-21 oz water bottles :-/ I like monitoring my live stats and progress as I ride and the gps allows me to do this. I don't require maps. For hiking, I use Strava on my phone in airplane mode to conserve battery life.

YMMV

I think it is just brighter backlight on GPS, they were made for outdoor use (more rugged, waterproof, no need to buy a seperate case for protection, etc.) and phones are generally designed for indoor use. My phone in direct sun is almost impossible to see. But my phone cost $105 USD, so maybe your phone has a more expensive backlight if you can see it with the sun shining directly on it.

The larger screen on a larger phone or small tablet I think is better for planning a route. I usually bring a 7 inch tablet to use in the campsite for route planning, etc. The dedicated GPS units have much smaller screens that are best for figuring out where the next turn is, if it is close.

The Garmin GPS units use a different kind of screen called "transreflective".

Transreflective screens can use a backlight (illumination from behind) AND they can use sunlight (illumination from the front). Transreflective screens avoid needing to use the backlight (which reduces power consumption).

The backlights in the GPS units aren't brighter (they probably are less bright).

Transreflective screens are dimmer indoors (which is why they aren't used on smartphones).

It's a compromise.

thanks for this important piece of information.

I'd like to add that I stopped using the Edge Touring because it was essentially useless in bright light, under some conditions (i.e. sun's angle -- even trying to shade with the hand didn't really work. Had to stop to look at the map. OTOH, my phone was perfectly legible). Might be that Garmin's screen have been improved (my VivoActive is very legible under the brightest sun). Or that some models use a different tech.

The Touring has the same screen as the 800. The transreflective screen works well in the sun but it's fairly angle-dependent (you really need to be able to adjust the angle). I've gotten used to it.

Shading it really isn't what you want to do since that reduces the light hitting the screen.

My iPhone is very dark in direct sunlight.

Nothing is perfect and everything is a compromise.

The Garmins have an engineering goal of being small with a long runtime.

Using a backlight (one brighter than they already have) all the time works against those goals.

An alternative would be to use a black and white LCD screen (losing the advantages color provides). Black and white LCD screens are more legible in sunlight than transreflective screens.

One thing the OP may want to consider is the use of sensors when using a phone. While the sensors may connect to the phone, not all mapping apps will support them. You may need to use cycling specific apps if you are going to use external sensors.

You can, in theory, download and cache Google map segments on the phone. So no data required as along as you are riding in the area the cached map covers. Never done it, I just use a Garmin.

Yes yes. Maps can be used offline. And they are getting better - it is now possible to generate a car route offline. Caveats are that routes cannot be modified. Nor can you generate a course for bicycle or pedestrian travel.

It's 2018. Amazing that things aren't easier by now.

Seattle Forest,
Buying a new bike from R&E in May and then touring for a few weeks. I've never been to the area. Is the attached approximate route relatively ok for lower car density? Thanks, always helps to have more information.

https://goo.gl/maps/eoc1LncAGCN2

When I use Maps.Me on my Android phone, it is off line as I always load the maps on wifi due to my tiny data plan. It does the routing off line and if I leave the route, it recalculates.

That app has bicycle routing too, but the few times I tried it, it did not pick very good routing. The bicycle routing is a pretty new feature.

I do not know if it has pedestrian routing or not, never looked for it.

The ride out of Seattle will have a lot of traffic but it will drop off pretty quickly once you get out of the metropolis. I'd recommend taking the Chief Sealth Trail instead of Marginal Way for mile ~2 to ~10 because it will get you off a 45 mph road (where everybody does 60) and put you on a scenic MUP. Otherwise, I'm jealous.

Yes. I was referring to gmaps. Until recently you could download areas and see where you were, offline. They've now added offline routing.

Regarding offline apps (typically using OSM cartography), I'd say that car routing is usually good, albeit not as good as gmaps as far as driving is concerned. Bike routing is probably better than gmaps, but finicky because of strict adherence to routing rules. (Such as avoiding divided highways, even when you can legally ride them, whatever the cost in extra distance).

I typically use bRouter (Locus pro companion app) double checking routing and quite frequently fighting the algorithm tendency to get off a side track just because it is there, having you ride off and then on the main road.

Well, that's dumb.

Some phones are too power hungry to run off a dyno. On all but the flattest ground, with my Samsung Galaxy S5 connected to my SON28 + USB-Werk it bounces in and out of charge mode and quickly loses power even with the display off.

It charges OK in "low power mode" with no apps, black and white display, and dimmed screen although that's not useful for navigation.