As a navigator, you have four tasks.

You need to read the notes and instructions to the driver, guiding him around every single turn and obstacle on the road.

Keep an eye on the odometer and reset it with your foot after each instruction. For example: 100m take a sharp right before the fence, through gate posts, triple caution rocks. Reset. 200m take a hairpin bend left after the trees, double caution narrow bridge. Reset. This continues with every turn for almost 200km at a time.

Keep an eye on the GPS to ensure you are going the right direction on the prescribed route.

Keep an eye on the road in front of you to ensure you read the instructions at the right time. Not too early and not too late.