So far, several methods for the estimation of directional spectra have been proposed and improved. However, in general, to obtain the accurate estimate of a directional spectrum by using those methods, a set of simultaneous records from the large number of wave sensors are needed. Practically, onyl a limited number of wave sensors can be mobilized in the field observation. Therefore, it is of great importance to enable an accurate estimate of a directional spectrum from the records of small number of wave sensors.
　In this report, the methods for estimating directional spectra from simultaneous measurement of three-quantities related to radom wave motions are discussed, and a new method with the use of maximum entropy principle is proposed. The proposed method is exanmined for numerical model and field wave data, and validity of the method is also discussed in this report with the following conclusions.
1) The proposed method can be applied for thee-element wave records.
2) It yields a better estimate than others.
3) it cvan recognize well not only a unimodel anglular distribution but also bimodal one.
4) It can be applied for various sea conditions of wind waves alone and combinations of wind waves and swell, except the case that the anglular spreading is very narrow such as in the case of long-traveled swell.