(1) uncertainty as to the true boundary line.
This isn't the case with mous931's property. The line CAN be established with a proper survey. If the adjoining neighbors had a survey that proves where the line is; then it is not uncertain.
Maybe the above would apply to someone in the ozarks where they can't get a proper survey.
Sounds good...I'd like to bank on it.
However, from the same case there is also this note, which sounds to me like in some obscure special cases, it doesn't matter if the boundary could be surveyed:
*FN 1. It has been stated in some cases that a boundary is considered definite and certain when it can be made certain from the deed. (E.g., Kraus v. Griswold (1965) 232 Cal.App.2d 698, 706-707 [43 Cal.Rptr. 139]; Meacci v. Kochergen (1956) 141 Cal.App.2d 207, 212 [296 P.2d 573]; Williams v. Barnett (1955) 135 Cal.App.2d 607, 612 [287 P.2d 789].) Since the decisions of the Supreme Court and a majority of the Courts of Appeal adhere to the rule that the possibility of accurately surveying the true line is immaterial, however, these cases have been regarded as departures from the established rule. (Humphrey v. Futter, supra, 169 Cal.App.3d at p. 340; 3 Miller & Starr, Current Law of Cal. Real Estate (1977) § 21.27, p. 557, fn. 11; Annot. (1989) 72 A.L.R.4th 132, § 13(b), p. 174, fn. 13, § 20, p. 182, fns. 16-18.)