Build a gps speedometer

I want to replace the paddle well of my jet ski, simply a Hall sensor that send a 12V signal directly to the speedometer, with a gps sensor. Now I have some spare parts from my rc multicopter, in particular one ATmega328P chip (Arduino Uno bootloader) and one Ublox 7 gps. Anybody can help me with a schematic and a sketch?

Start by connecting power and grounds, then connect TX on the GPS to RX on the Arduino and verify NMEA serial data.

Ok, but what I have to flash on my ATmega?

Are you hoping the forum will write the entire program for you?

See the TinyGPS++ programming examples.

...or the NeoGPS examples... It's a library I wrote that is smaller, faster and fully configurable. Be sure to read the Troubleshooting section. It describes some common problems, especially when you try to modify the TinyGPS and TinyGPS++ examples.

There's also a diagnostic program that may come in handy.

Cheers, /dev