Grayscale depth finders (fishfinder)
Posted: Tue Mar 24, 2009 3:59 pm
Read a great article by Mark on a color finder and the thermocline,,, now what about a grayscale unit and how does the same info show up on these.
Well, that is a very good question and I will try to answer it the best I can, not knowing what unit you have, and based on my experiences.
I owned an older Eagle Fish I.D. before I got my current color screen unit. While out on Amber Lake, going down the middle of the lake, I would notice light gray pixels showing up about 15 feet off the bottom. At the time, I thought they were weeds, but also thought that 15' high weeds in a lake like that is unusual. When I got my new color unit, it dawned on me that the gray pixels were not weeds, but the thermocline. I confirmed that by asking Dennis who has a gray scale unit. He told me he was seeing tall weeds off the bottom. I looked at his unit and then mine. The images were at the same depth. What was gray on his screen, was blue on mine.
So, a gray scale does pick up the thermocline, but it shows up like weeds do, but less dense. You can confirm a thermocline by dropping down a Depth-o-therm to the depth just above where the gray pixels start. Take two reading, above the line and below. You should show a significant drop in temperature. Sportsman's Warehouse has the Depth-O-Therm. Make up a unit like I mentioned in the article.
Return images on a screen is based on density. Cold water is denser than warm. The higher end units will now discriminate between cold water and vegetation.
Hope that helps.