A navigation data source stored on a computer-readable storage medium, said navigation data source comprising: - multiple navigation data sets (101, 102, 103, 104), - each of said multiple navigation data sets (101, 102, 103, 104) being independently updatable, - each of said navigation data sets (101, 102, 103, 104) representing a map (M101, M102, M103, M104) of a geographic region (R101, R102, R103, R104) and defining a plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400), wherein each of said gateways of said plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400) is associated with a position at a border of said geographic region (R101, R102, R103, R104) and being associable with a gateway (G1, G2, G3, G4, G100, G200, G300, G400) of a further navigation data set (101, 102, 103, 104) representing a map (M101, M102, M103, M104) of a further geographic region (R101, R102, R103, R104), and - multiple pre-computed cost data sets (CT101, CT102, CT103, CT104), - each of said cost data sets (CT101, CT102, CT103, CT104) being associated with a navigation data set of said multiple navigation data sets (101, 102, 103, 104), - wherein each of said cost data sets (CT101, CT102, CT103, CT104) comprises cost data (CD101, CD102, CD103, CD104), said cost data (CD101, CD102, CD103, CD104) defining for at least a part of possible gateway pairs of said plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400) at least a cost value each, said cost value indicating a cost for a route (150,152, 160, 161, 161a, 161b, 162, 163) between gateways (G1, G2, G3, G4, G100, G200, G300, G400) of a respective gateway pair. - multiple navigation data sets (101, 102, 103, 104), - each of said multiple navigation data sets (101, 102, 103, 104) being independently updatable, - each of said navigation data sets (101, 102, 103, 104) representing a map (M101, M102, M103, M104) of a geographic region (R101, R102, R103, R104) and defining a plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400), wherein each of said gateways of said plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400) is associated with a position at a border of said geographic region (R101, R102, R103, R104) and being associable with a gateway (G1, G2, G3, G4, G100, G200, G300, G400) of a further navigation data set (101, 102, 103, 104) representing a map (M101, M102, M103, M104) of a further geographic region (R101, R102, R103, R104), and - each of said multiple navigation data sets (101, 102, 103, 104) being independently updatable, - each of said navigation data sets (101, 102, 103, 104) representing a map (M101, M102, M103, M104) of a geographic region (R101, R102, R103, R104) and defining a plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400), wherein each of said gateways of said plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400) is associated with a position at a border of said geographic region (R101, R102, R103, R104) and being associable with a gateway (G1, G2, G3, G4, G100, G200, G300, G400) of a further navigation data set (101, 102, 103, 104) representing a map (M101, M102, M103, M104) of a further geographic region (R101, R102, R103, R104), and - multiple pre-computed cost data sets (CT101, CT102, CT103, CT104), - each of said cost data sets (CT101, CT102, CT103, CT104) being associated with a navigation data set of said multiple navigation data sets (101, 102, 103, 104), - wherein each of said cost data sets (CT101, CT102, CT103, CT104) comprises cost data (CD101, CD102, CD103, CD104), said cost data (CD101, CD102, CD103, CD104) defining for at least a part of possible gateway pairs of said plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400) at least a cost value each, said cost value indicating a cost for a route (150,152, 160, 161, 161a, 161b, 162, 163) between gateways (G1, G2, G3, G4, G100, G200, G300, G400) of a respective gateway pair. - each of said cost data sets (CT101, CT102, CT103, CT104) being associated with a navigation data set of said multiple navigation data sets (101, 102, 103, 104), - wherein each of said cost data sets (CT101, CT102, CT103, CT104) comprises cost data (CD101, CD102, CD103, CD104), said cost data (CD101, CD102, CD103, CD104) defining for at least a part of possible gateway pairs of said plurality of gateways (G1, G2, G3, G4, G100, G200, G300, G400) at least a cost value each, said cost value indicating a cost for a route (150,152, 160, 161, 161a, 161b, 162, 163) between gateways (G1, G2, G3, G4, G100, G200, G300, G400) of a respective gateway pair.