GPS vs Depth Raider speed disparity problem solved!!!

[Dukdog]

When trolling at my favorite speed, 2.1 on GPS, My depth raider always read 1.3 !!

I knew there would be some disparity due to current etc but I discovered yesterday just where most of that speed differential was coming from.

The UPS man delivered a pair of 15 pound Shark cannonballs yesterday and I couldn't get to the lake here in Maine fast enough to try them out. There are slick but the best part is they led me to discover where the lion's share of that speed differential was coming from.

I had been running 8 and 12 pound round balls which resulted in quite a bit of blowback when going over 2 MPH. The 15# sharks cut that blowback to almost nothing and I immediately noticed that my Depth Raider was now indicating 1.8 when I was doing 2.1 on GPS.

I believe that the previous angle on the cable and subsequently on the Depth raider probe caused the pinwheel to not turn as smoothly and resulted in a lower indicated speed than it does now that the cable is more vertical with the sharks.

Not Rocket science but an interesting observation and kind of answers my question about there being so much difference in the past.

[Mickey Finn]

Most of us notice that the depth raider and sub-troll both will indicate .5 MPH slower than GPS. You can check this by putting your probe in the water just a foot or two and compare them when trolling on a calm day. It's not that important that they match. It's more important to be able to get your speed the same using the probe. I just keep it in the back of my mind that the probe reads about .5 slower.

[LongLine]

Yep, agree thast your cable is more vertical and your probe is also more vertical. Too much blowback & you'll probably loose speed at the probe altogether.

Tom B.

(LongLine)