Optical digital odometer for trekker

Hello to all, I have to create a 11dof platform with gps and IMU solution for gps outages period. Now I'm thinking to use also an odometer, to increase stability of positioning. If I wanted to install it on a car it should be easy: I can link it to a wheel, counting wheel cycle. But I have to install this system for trekking: a solution can be a pedometer, but it isn't too accurate. Another solution is "reading" the ground to calculate distance and velocity, as a mouse of a pc. There are 2 possibilities: 1) with the same principle of a optical mouse, interpreting the light reflected from the ground 2) with the same principle of a modern optical mouse, interpreting the image captured by the camera, correlating it with the distance traveled Do you think can it be possible? Does exist already something for this? Thanks Stiv

But it would be a project that has to be developed. I want to try if I can increase the precision of my IMU with a odometer. The odometer can be a pedometer (I think a bit inaccurate), a cycle wheel or a camera. Then, if the precision increase significantly, I will develop a better odometer. But first of all I want to test my IMU with this "self made" odometer, that can be a pedometer, a cycle wheel or a camera. The best it would be to actualize an odometer with a camera, as newer optical mouses. I have two possibilities: or I make the software myself or I can take the system of a mouse, but I don't know how to realize it. Do you know where I can find the software of an optical mouse. Or do you have other suggestions? To answer to you: I would attach it to the belt of a person, triyng to be quite stable. I would use a small netbook to process all. Thanks Stiv