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 corresponding to echoes delivered by the telemeter and selecting candidate points from the points; ii) searching in a horizontal plane for straight line segments that are close to vertical projections of the candidate points; and iii) searching in each vertical plane containing a straight line segment found in step ii) for catenary portions that are close to the candidate points; wherein in step iii), for each vertical plane under consideration, and for each set of at least four candidate points close to the vertical plane under consideration, 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 the least squares method for all of the sets of at least four candidate points close to the vertical plane under consideration, wherein in order to calculate the three parameters a, b, and c of the catenary, an initial calculation is performed of each of these parameters, and wherein, after this initial calculation, a respective difference value as calculated using the least squares method is added to each of the calculated parameters in an iterative manner.