a watershed management program is usually based on the results of watershed modeling. accurate modeling results are decided by the appropriate parameters and input data. precipitation is the most important input for watershed modeling. precipitation characteristics usually exhibit significant spatial variation, even within small watersheds. therefore, properly describing the spatial variation o...

A four-parameter kinematic model for the position of a fluid parcel in a time-varying ellipse is introduced. For any ellipse advected by an arbitrary linear two-dimensional flow, the rates of change of the ellipse parameters are uniquely determined by the four parameters of the velocity gradient matrix, and vice versa. This result, termed ellipse/flow equivalence, provides a stronger version of...

When faced with an ellipse fitting problem, practitioners frequently resort to algebraic ellipse fitting methods due to their simplicity and efficiency. Currently, practitioners must choose between algebraic methods that guarantee an ellipse fit but exhibit high bias, and geometric methods that are less biased but may no longer guarantee an ellipse solution. We address this limitation by propos...

This paper presents a new approach for precision estimation for algebraic ellipse fitting based on combined least squares method. Our approach is based on coordinate description of the ellipse geometry to determine the error distances of the fitting method. Since it is an effective fitting algorithm the well-known Direct Ellipse Fitting method was selected as an algebraic method for precision e...

In this note we prove that if a convex body in the three dimensional Euclidean space has the pedal property of the ellipse, then it is an ellipsoid of revolution. We also give a family of curves in the plane with exactly one point which behaves, in some sense, like a focus on an ellipse. Finally, we study another property of the ellipse which we name the harmonic property and prove that a conve...

In this paper we proposes a new method t o detect a slanted ellipse using Hough transform with 5 parameters effectively. The procedure is as follows: First, a pair of arcs are detected as a part of the slanted ellipse using a circle detecting Hough transform with 3 parameters; the central point (xc,yc) and the slanted angle 9 can be obtained. Second, the slanted ellipse is transformed into a no...

Ellipse fitting for iris boundary is an important step in eye gaze estimation and iris recognition applications. In most of the proposed algorithms only the edge image is used for ellipse fitting. In these algorithms, the undesired edges may lead to erroneous iris ellipse. In this paper, we propose a novel algorithm to ellipse fitting for iris boundary which uses gray and edge images simultaneo...