A mobile device comprising: - one or more digital image sensors; - a radio receiver; - one or more memories storing: o a set of visual words; o a set of radio words, a radio word being defined at least by an identifier of a radio transmitter; ∘ a set of reference locations, each reference location having associated therewith a reference location vector comprising binary values defining respectively the presence or absence, at the corresponding reference location, of visual words and radio words; - a communication link to said one or more memories; - a processing logic comprising: ∘ an adaptation to acquire an image of an environment of the mobile device from said one or more digital image sensors; ∘ an adaptation to detect receivable radio transmitters using said radio receiver; - a communication link to said processing logic; the mobile device being characterized in that said processing logic further comprises: ∘ an adaptation to create an observation vector comprising binary values defining the presence or absence of visual words in the image, and binary values defining the presence or absence of radio words in receivable radio transmitters; ∘ an adaptation (244, 344) to determine a current location of the mobile device at least among the set of reference locations based on said observation vector and said reference locations vectors. - one or more digital image sensors; - a radio receiver; - one or more memories storing: o a set of visual words; o a set of radio words, a radio word being defined at least by an identifier of a radio transmitter; ∘ a set of reference locations, each reference location having associated therewith a reference location vector comprising binary values defining respectively the presence or absence, at the corresponding reference location, of visual words and radio words; o a set of visual words; o a set of radio words, a radio word being defined at least by an identifier of a radio transmitter; ∘ a set of reference locations, each reference location having associated therewith a reference location vector comprising binary values defining respectively the presence or absence, at the corresponding reference location, of visual words and radio words; - a communication link to said one or more memories; - a processing logic comprising: ∘ an adaptation to acquire an image of an environment of the mobile device from said one or more digital image sensors; ∘ an adaptation to detect receivable radio transmitters using said radio receiver; ∘ an adaptation to acquire an image of an environment of the mobile device from said one or more digital image sensors; ∘ an adaptation to detect receivable radio transmitters using said radio receiver; - a communication link to said processing logic; the mobile device being characterized in that said processing logic further comprises: ∘ an adaptation to create an observation vector comprising binary values defining the presence or absence of visual words in the image, and binary values defining the presence or absence of radio words in receivable radio transmitters; ∘ an adaptation (244, 344) to determine a current location of the mobile device at least among the set of reference locations based on said observation vector and said reference locations vectors. ∘ an adaptation to create an observation vector comprising binary values defining the presence or absence of visual words in the image, and binary values defining the presence or absence of radio words in receivable radio transmitters; ∘ an adaptation (244, 344) to determine a current location of the mobile device at least among the set of reference locations based on said observation vector and said reference locations vectors.