Abstract: The limited density data sampling is analyzed. A method of enhancing the precision of linear borderline measurement is proposed, and the highest precision that the limited density data sampling can reach is discussed. The resolving spectrum map and resolving map are established. The effect of limited density sampling interval on the resolving power is explained. Some useful advices to avoid resolving blind area in the map and then reach a high precise measurement are also given. At last, how to improve the precision of other types of borderline measurements are discussed.