Positioning of mobile phone on handlebar

I use osmand for navigation and much prefer the portrait orientation. Can’t really say why since I always have the map aligned northwards, so it’s not about being able to look farther ahead. I guess it’s just because I’m used to it and all apps work in portrait mode but some do not work in landscape mode.

The Topeak Ridecase Mount (+Omni Ridecase silicon straps to attach the phone) I use can easily be turned 180° though. I can highly recommend osmand and the Topeak mount.

Bicycle-oriented navigation devices tend to use the portrait orientation. Net searching for images of e.g. Garmin bicycle computer, Wahoo bicycle computer, and basically any other minor brand gives you devices with their screen exclusively in the portrait orientation, both those that can show a map and those which cannot. There are also smaller square-shaped devices, and it obviously makes no difference to rotate them.

I failed to find a single bicycle navigation device that is offered in the landscape orientation configuration as a default. On the contrary, car GPS-navigation systems from e.g. the same Garmin are predominantly in landscape.

A smartphone is often used to navigate on the go, when a user holds it in one hand. The landscape orientation is more comfortable when two hands are used to hold a phone, and that is not always optimal when one is walking. As such, it makes sense that navigation applications are focused on single hand operation and related experience.

It is not exactly clear to me why there is such a uniformity in the designs, except for a slightly (possibly undetectable in practice) more aerodynamic configuration the portrait mode offers. Another thing is that handlebars have limited width (especially drop bars which are typically no wider than 48 cm), and everything that is placed on them or near them takes space from hand positions. The landscape orientation is clearly disadvantageous in this case, as the portrait configuration is "narrower".

I use Topeak F55 mount with Smartphone Drybag which allows you to click the case in place in either portrait or landscape orientation.

Personally I'm not that interested what's to the sides of the path I follow, I'd rather see further ahead, so I use portrait mode and have the map orientation set to the direction of movement. I suppose the landscape orientation of the phone can be useful when you want to watch Calvin Jones showing you how to fix your bike.

I use the Quad-Lock system. As the name implies, you can position the phone at any 90 degree point you want. You have to rotate the phone to snap it in, which can cause interference with other things on your handlebars like lights.

Consider the zero case - stick your phone in your pocket instead of on the bars.

Most smartphones shut their screen off fairly quickly - if you force the screen to stay on, it eats battery and produces heat.

The phone is exposed and vulnerable to rain and damage from impact.

The phone can be relatively easily snatched and stolen.

Many smartphone screens are hard to read in full sunlight and require extra attention from the rider, when they should be focusing on the road and traffic.

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Upshot - consider storing your phone safely in a pocket while riding. If you really need to interact with your phone, pull over safely. At that point you can use Portrait or Landscape as you see fit.