GPS speedometer DIY

[Neilm]

Hi there and thank you for taking time to read this.

I have a pair of electronic marine speedometers (paddle wheel) that I'd like to convert to GPS. I'm keeping the original gauges, but the plug-n-play conversion kits I've seen on the market are way too expensive. I see all kinds of gps modules and other peripherals online and wonder if they can be combined to drive an electronic analog speedometer; or is not that simple and requires advanced knowledge?
I have zero expertise in electronics so forgive me if it's a ridiculous question
Thanks !

 

[Nuvi-Nebie]

I don't think it is practical to drive your paddle driven guages from a GPS, for a start they are measuring different things, a paddle or pitometer is measuring how fast water is going past your boat, if your boat is traveling forward at 10mph against a current / tide of 10 mph then water is going past the boat at 20 mph, a GPS will measure how fast you are travelling in space in the example just given the travelling forward at 10mph would be cancelled out by the current pushing you backwards at 10mph, so your GPS speed is zero, you are not moving through space, you are standing still