The Humminbird 587ci HD DI is a combination GPS and fishfinder that includes Humminbird’s trademark Switchfire and Dual Beam Plus sonar technologies as well as their Down-Imaging system all displayed on a high definition 256 color 4.5 inch 640×480 resolution screen that has brightness levels that can be adjusted to read clearly even under direct sunlight. Switchfire brings to the user two modes of sonar viewing. The first is a maximum mode that brings incredible detail of the world below to the screen. Not only the expected cover and bottom, but also water current as well as thermoclines. The second is a clear mode which is for those times when the water is shallow, murky, or filed with sediment. These are times when getting every detail simply fills the screen. Clear mode filters out the unnecessary noise and gives you a clear picture under these challenging situations. Switchfire technology gives th