You could buy Raymarine's gps sensor with NMEA output, but it will set you back around $300. I have installed several of them (they mount like an antenna) and they are excellent.
I plan to use something cheaper: Maybe Garmin's GPS - 18x OEM USB - GPS receiver module, which is a waterproof gps with a usb cable to the computer. Unfortunately, it has a magnet built into the base, not so useful on an aluminum boat and I have banned magnets from mine.
There are a couple of suitable units available at
Buy GPS Now I think that
This one looks pretty good. for under $30 bux.
If the sensor puts out NMEA 0183 via usb, then any charting software that I have seen will read it.
I have gps serial output from my alarm system and I have used it successfully with laptops. But laptops are not so convenient when they belong to someone else, and I plan to put a cheap, dedicated computer on board for tasks like navigation. I would like to buy a real plotter from Raymarine, but I just will not have thousands for it. When I get thousands, I will spend a year in the Bahamas, forget plotting.
1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida