River Mileage Help

[JB]

I am making a water trail map for a park and I have traced the river using the measurement tools in mileage. When I handed in a rough copy of the map someone from the office insisted it was incorrect because they drove close by the river and their odometer said it was closer to 5 miles and I have 3.9. I guess my silly question is how accurate are the measurement tools and how accurate is measuring the river by road? If someone could please answer it would be greatly appreciated. Thank you in advance.

[ChristineDartiguenave]

It depends on the shape of the river versus the road, but still 1 mile is still quite large even in this case. I would double-check the projection and make sure you are using a projection that provides a good representation of the true length.

Christine Dartiguenave
Esri Water Resources Team