1. A method of constructing a digital model of a road, said method comprising: using an implementation device comprised of a differential global positioning system device and a hybridised inertial unit with a global positioning system (GPS) to execute the steps of acquiring, with the differential global positioning system device at a first refresh frequency, a first set of data relating to the geometry of the road, the differential global positioning system device (DGPS) being relatively precise as compared to the hybridised inertial unit in absolute terms as to a specific point, acquiring, with the hybridised inertial unit at a second refresh frequency which is greater than the first refresh frequency, a second set of data relating to the geometry of the road, the hybridised inertial unit being relatively precise as compared to the differential global positioning system device in relative terms between two consecutive points, indexing values of said first and second sets of data by determining their confidence level, eliminating the values of said first and second sets of data below a predefined confidence threshold in order to obtain a first set and second set of corrected data, and aggregating data of said first and second sets of corrected data in order to obtain the digital model of the road whose data refresh frequency is equal to the second refresh frequency.