accuracy is also affected by the accuracy of the map you are using. All maps are geo-referenced to fixed points on earth. How accurately that is done greatly affects what you see on Google Earth
or any of the ENC
or Vector charts commercially available.
You will often see a chart plotter representation of your boat that has you sailing across the beach instead of your actual position safely within the channel. Is this due to GPS inaccuracy or poor map geo-reference? The answer is YES.
GPS accuracy and how well the company's mapset have been 'tied' to the earth all affect the representation of where the GPS "thinks you are." To be safe, assume that the GPS gets you close - the rest is up to your good old MK 1 Mod 0 eyeball. If you are standing in the parking lot, yet Google Maps shows you on the boat ramp
, which one of your sensory inputs will you believe?
That is a key phrase with GPS - where it "thinks you are." One or 2 groundings is all it takes for you to remember this fact...