Setting "Map Offset" on HB units....

"Map Offset" is a feature in the HB units that has always piqued my interest but I've never actually used it or even knew if I needed to use it...

Does anyone have experience with this feature....??

How does one accurately check if their unit even needs the "Map Offset"...??

How does one then use this feature to adjust their map accurately...??

If I have waypoints saved in my unit that were saved while the map was possibly off...will my saved waypoints be inaccurate after setting the "Map Offset"...??

Rickie

I've been interested in this feature too. I'm not even sure what it does. Our electronic charts on our towboats are pretty accurate. When my chart shows me in the channel I'm in the channel.

Maybe 1 of the HB guys will chime in.

It is used to recalibrate your map. I tried it, didn't do crap. My map is off by at least 50 feet.

Maybe Greg will chime in and offer some info on this

Rickie

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Originally Posted by rnvinc

Maybe Greg will chime in and offer some info on this

Rickie

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He and Joby probably remember me whining about this about 3 years ago.Devil Icon

If the donut gets fixed you can beat it with a ball bat.

I was under the impression that it was for the depth contours, not for an adjustment to your coordinates but I was wrong. I did a search and here's what I found:How to set a Map Offset on Humminbird unit - Video by eddie Kendrick

I used the TVA high voltage transmission pylon near Mansard Island in the water as the known position. I marked the spot and the HB program did just like the video clip showed. No improvement. I tried it several times.

I really don't know how HB can calibrate a map using 1 waypoint. ??????????? I use map calibration on several mapping programs. They require at least 2 or more waypoints to calibrate the map. I usually use 3.

That's what I was thinking also. We call it "translate and rotate".

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Originally Posted by Cane Pole

I really don't know how HB can calibrate a map using 1 waypoint. ???????????

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The HB Donut is probably used to calibrate it from running a circle around the waypoint.... Rofl Rofl Hands Clapping

“How does one accurately check if their unit even needs the "Map Offset"...??”
About the only way to do this is if you observe that your boat’s position is shown in one location yet some fixed structure is shown in another. The example of the bridge is a good one to use as these usually don’t move around a lot.

“How does one then use this feature to adjust their map accurately...??”
I think that Eddie did a good job of explaining this.

“If I have waypoints saved in my unit that were saved while the map was possibly off...will my saved waypoints be inaccurate after setting the "Map Offset"...??”
No they will not as the coordinates will be the same. They will appear in a different location on the map though. Think of it this way: the map is just a background picture that can be moved around. Setting the Map Offset feature effectively moves the background map around. It does not change the coordinates of your waypoints.

One thing that was not mentioned is that on some of the lakes and rivers on the mapping cards we think of these as a single big map. They are not always one map and can be several combined together. This means that the map offset may not be needed on all areas of a lake and setting it for one area of the lake may make it off on another.

Hey Greg, with only one waypoint required, how do you know which way to "rotate" the map? I like this feature, but it didn't help me out any.

We don’t rotate the map CP. It is just a simple Lat/Lon adjustment. If the maps are rotated it will only work to improve the accuracy in the spot you offset it at.

The pylon is about 5 miles up stream from where I was expecting some correction. Was this too far a distance from where I was expecting some correction? Book didn't give much info. I can go try a recalibrate. I verified my calibrate waypoint with Google Earth. Pretty accurate.

With no rotation, I would expect the farther you get from your control point, the less accurate the map will be.

CP, did your map show you were right on your spot before you calibrated, or could you see a little difference there? (your boat icon I mean)

I had a donut. I was tied off at the pylon, so I wasn't moving anywhere. Been a while(bout 2 years) so I don't remember the details. I like the feature, but maybe I was expecting too much.

I marked the waypoint and calibrated the map while tied off. You don't have to be on the spot to calibrate using the cursor.

Has anyone else tried the Map Offset besides me??????????

I'm still trying to find a good activation spot close to where I normally fish so that I can check my map to see if it even needs calibrating.

Rickie

Maybe Greg Humminbird will give us a "effective" distance the calibrate will affect. I may have been too far away from the calibrate point. This is not documented. I verified my point by going to Google and uploaded my waypoint. It was right there by the pylon where I marked it. Did this just to verify my mark.

CP,
It is my understanding (and what I have done) that you have to be on the spot that you are using to ‘calibrate’ or use the Map Offset feature. Not being on the same exact spot would through the offset off a bit. I’ve always used a boat ramp myself.

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Originally Posted by Humminbird_Greg

CP,
It is my understanding (and what I have done) that you have to be on the spot that you are using to ‘calibrate’ or use the Map Offset feature. Not being on the same exact spot would through the offset off a bit. I’ve always used a boat ramp myself.

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I did calibrate at the pylon. Drove back to my fishing spot and saw no change (about 5 miles down stream). Tried to recalibrate at my fishing spot by moving cursor to pylon. No change.

The screen showed it to be calibrated though. Maybe it is map error. I dunno. At least I tried. ha

I was still fishing on the bank. Didn't catch any grass carp though.