The Study provides the technical background and calculation method f3r the long wave track defect. On high speed railway, It is necessary to manage the long wave band up to 80m track defect fur improving a riding quality. For this reason, Track recording methods for highspeed railway are used 10m and 30m recording bases, these are covered middle wave band and long wave band successfully. Extended base recording data is calculated by geometrical model and this data provides a good result for KTX riding index.