Method of localising a device, carried by a user, inside a space in which a plurality of sources (2a...2n) of coded visible light are located, the method including the steps of: - modulating each source (2a...2n) with a different periodic signal (5a...5n) or a different combination of periodic signals (5a...5n) and assigning an identification code related to the frequency of each periodic signal (5a...5n) or to the frequencies of each combination of periodic signals (5a...5n) to said source (2a...2n); - acquiring images of a scene in which one or more sources (2a...2n) of said plurality of sources (2a...2n) of coded visible light are present by means of a camera of the device, the camera including a matrix of pixels sequentially read according to the rolling shutter technique; - processing (104, 105) an image in order to recognise the identification code of the or each source (2a...2n) present in the image through the steps of: - identifying (104, 202 - 204) in the image one or more regions of interest, each substantially comprising the only block of pixels containing a source (2a...2n); - checking (104, 205 - 211) the compatibility of the source or sources present in the or each region of interest with the characteristics of a system implementing the method; and, for each system-compatible region of interest, - extracting a brightness profile of the region of interest in the reading direction of the matrix of pixels; and - determining (305, 306) the indices of the non-zero coefficients, in the wave number domain, characterising the brightness profile, and obtaining therefrom the identification code of the source (2a...2n) corresponding to the region being processed; - and accessing, by using the identification code recognised, information associating the codes with the sources (2a...2n) and their positions in the space; characterised in that the processing step (104, 105) is performed on a single image and performs the extraction of the brightness profile along a single line, in the reading direction, of the matrix of pixels, such that the brightness value for each row of the matrix of pixels is the sum or average of the brightness values of all pixels in the row, or alternatively the sum or average of the brightness values of part of the pixels in the row, or yet the brightness value of a single column, in the middle of the matrix, and in that the identification (202 - 204) of a region of interest includes the steps of: - performing a sparse sampling of the image by taking only one every K pixels; - building a reduced matrix including the pixels resulting from the sampling; - analysing the brightness of the pixels in the reduced matrix in order to determine an average brightness of the image background; and - calculating a brightness threshold exceeding of which identifies the boundaries of the region of interest. - modulating each source (2a...2n) with a different periodic signal (5a...5n) or a different combination of periodic signals (5a...5n) and assigning an identification code related to the frequency of each periodic signal (5a...5n) or to the frequencies of each combination of periodic signals (5a...5n) to said source (2a...2n); - acquiring images of a scene in which one or more sources (2a...2n) of said plurality of sources (2a...2n) of coded visible light are present by means of a camera of the device, the camera including a matrix of pixels sequentially read according to the rolling shutter technique; - processing (104, 105) an image in order to recognise the identification code of the or each source (2a...2n) present in the image through the steps of: - identifying (104, 202 - 204) in the image one or more regions of interest, each substantially comprising the only block of pixels containing a source (2a...2n); - checking (104, 205 - 211) the compatibility of the source or sources present in the or each region of interest with the characteristics of a system implementing the method; and, for each system-compatible region of interest, - extracting a brightness profile of the region of interest in the reading direction of the matrix of pixels; and - determining (305, 306) the indices of the non-zero coefficients, in the wave number domain, characterising the brightness profile, and obtaining therefrom the identification code of the source (2a...2n) corresponding to the region being processed; - identifying (104, 202 - 204) in the image one or more regions of interest, each substantially comprising the only block of pixels containing a source (2a...2n); - checking (104, 205 - 211) the compatibility of the source or sources present in the or each region of interest with the characteristics of a system implementing the method; and, for each system-compatible region of interest, - extracting a brightness profile of the region of interest in the reading direction of the matrix of pixels; and - determining (305, 306) the indices of the non-zero coefficients, in the wave number domain, characterising the brightness profile, and obtaining therefrom the identification code of the source (2a...2n) corresponding to the region being processed; - and accessing, by using the identification code recognised, information associating the codes with the sources (2a...2n) and their positions in the space; - performing a sparse sampling of the image by taking only one every K pixels; - building a reduced matrix including the pixels resulting from the sampling; - analysing the brightness of the pixels in the reduced matrix in order to determine an average brightness of the image background; and - calculating a brightness threshold exceeding of which identifies the boundaries of the region of interest.