I used it for the foundation of a wooden house with ground screws. It is visible outdoors in daylight up to about 5-6 meters, but in the early morning, on cloudy days, or at dusk, it can be seen much further away. I definitely recommend using the sensor for outdoor use as well. I've seen many bad tests about these DIY home (non-professional) levels, so I had my doubts, but I checked it, and no matter how I turned it, it worked well. Maybe I was just lucky. :)