Part of the landscape photography challenge is researching locations. I happen to enjoy it and the more time you spend the better prepared you are when you arrive on location.
In this section I will discuss some of the websites and apps I utilise in planning photography trips.
Google Maps I'm sure everyone has used before including Street View.
I subscribe to OS Premium, primarily for the ability to download maps on to my phone and tablet for offline use.
Sunrise & Sunset
To understand where the sun will rise and set I use The Photographer's Ephemeris (Website | iOS | Android). It's good to be able to save locations for future use, and if you choose an applicable map, can be viewed offline.
I also use TPE 3D (iOS) when I want to understand how the sun will hit different points of my intended scene and at what time, particularly useful if shooting a mountainous landscape.