1. A method of detecting the presence of at least one threadlike object suspended in the detection field of a telemeter on board a vehicle, the method comprising the following steps of mounting the telemeter on board the vehicle, and: i) calculating the terrestrial coordinates (x, y, z) of points ( 30 ) corresponding to echoes delivered by the telemeter and from these points selecting candidate points; ii) in a horizontal plane, searching for straight line segments that are close to vertical projections of the candidate points; and iii) in each vertical plane containing a straight line segment found in step ii), searching for catenary portions that are close to the candidate points; wherein: in step iii), for each vertical plane taken into consideration, and for each set of at least four candidate points close to the vertical plane in question, using the least squares method to calculate the values of three parameters a, b, and c of a catenary having an equation of the form: 
 y=a cos h[ ( x−b )/ a]+c the catenary containing the projections on the vertical plane of the points in the set under consideration; and determining that at least one suspended threadlike object is present as a function of the value of the correlation coefficient associated with said least squares method for all of the sets of at least four candidate points close to the vertical plane under consideration.