if you are designing a robot that will follow a defined path providing a reference on the ground may work well. this can be done many ways including a contrasting line, barcodes at specific locations, or a buried wire. given your reference to a frequency of movement i assume you will want an absolute position reference at at least one location to reduce accumulated error/drift that can result from localization using encoders or other integration methods. You can also combine several localization methods to improve accuracy.
describing what application, environment, size, complexity, accuracy, and any other details about you robot would help people provide more meaningful recommendations.