Marking accuracy with active cursor?

I've been doing a lot of researching into the new Helix SI/GPS units and I'm gaining a fair understanding of what I'm looking at and the functions of the unit. One of the tasks I'm still pondering on is how do the following variables affect the ability of the unit to accurately mark an object with the active cursor in the side imaging view?:
-distance of the unit from transducer
(They could be anywhere from 5' to 18' away from each other)
-chart speed
-boat speed

Or am I just nuts and none of these variables have a factor?
Thanks in advance for any insight! Stay warm as well.

only distance from TD to unit will matter. when you mark something the pic. freezes so speed doesn't come into play. I think?

like said,only distant,when marking make sure u are not marking shadow,even at long distant you will be near enough to see it and can make new wp if needed

I really don't think any of those are going to affect accuracy enough to not be able to go to an waypoint. The unit tracks boat speed, so that only plays into getting a good image recorded. Chart speed isn't going to change accuracy. Distance to the object probably has the biggest potential error because small errors in angle become large linear errors over longer distances.

The distance between the unit and transducer will play a part but how much so depends on how far apart they are and how accurate the civilian GPS system is at that time. The GPS Receiver is built into the control head on the HELIX 5ci SI-GPS units.

Example: the distance between the unit and transducer is 8 feet. You are traveling due north and see some structure off to one side and mark it with a waypoint, the unit thinks that the GPS Receiver (inside the control head) and transducer are at the same location. If you come back to that waypoint also heading due north, there would be no additional inaccuracy introduced by the unit to transducer distance. The additional inaccuracy starts adding up if you come back to that waypoint from any other direction other than due north, with heading south being the worst case. Although the GPS may show that you are on top of the waypoint you will be up to an additional 16 feet off from the actual structure that you marked. Remember that this is in addition to any inaccuracy within the civilian GPS system. Most of the time though you should be within 2D sonar range though and you should be able to find that same structure again.

Thanks a bunch for the explanations and responses. I never thought about distance or direction having an influence, but i will be sure to keep an eye out for those things. Stay safe and thanks again!