GPSMap 66st

 

I have enabled the US Satellite system and GLONASS as well as WAAS/EGNOS.

Should I concerned with using all 3 or will this allow for more accuracy?

Thank you,

No

Although I've never seen any real accuracy increase when using WAAS/EGNOS. Having GLONASS and GPS helps with faster satellite lock, as you're using more satellites, and helps in potentially poor signal areas for same reason.

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Where there's a will ... there's a way ... DriveSmart50LMT-D, Nuvi 2508LMT-D, 1490LMT, 1310, Montana 650T, Etrex 20

Battery Life?

You will most certainly get better position accuracy using all three navigational platforms.
I can't speak specifically for the GPSMap 66st but on other GPS units I've used, enabling WAAS & GLONASS can shorten battery life. If this is a concern, you might consider turning them off in areas with good GPS coverage. I believe this is one of the reasons for providing the on / off option.

Wide Area Augmentation System

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Charlie. Nuvi 265 WT and Nuvi 2597 LMT. Android Here WeGo - Offline Maps & GPS.