A method comprising, performed by at least one apparatus: obtaining results of measurements for a plurality of communication nodes, the measurements performed by a mobile device (300, 411, 412) at a particular position on signals of the communication nodes and the measurement results for each of the communication nodes including at least a signal strength related value and an identification of the communication node; obtaining for at least one of the plurality of communication nodes a stored indication of a location and a stored signal strength related value associated with the stored indication of a location, and determining for the at least one communication node a difference between the signal strength related value included in the results of measurements for the at least one communication node and the stored signal strength related value obtained for the at least one communication node; obtaining (203, 503) for at least a part of the plurality of communication nodes stored radio model data, and estimating (203, 503) the particular position of the mobile device (300, 411, 412) based on the obtained results of measurements for at least a part of the plurality of communication nodes and on the obtained stored radio model data; and in the case that the determined difference between the signal strength related value included in the results of measurements for the at least one communication node and the stored signal strength related value obtained for the at least one communication node falls short of a predetermined threshold, determining (204, 504) a distance between the estimated particular position of the mobile device and a location indicated by the obtained stored indication of a location for the at least one communication node, as an indication of a health state of stored radio model data. obtaining results of measurements for a plurality of communication nodes, the measurements performed by a mobile device (300, 411, 412) at a particular position on signals of the communication nodes and the measurement results for each of the communication nodes including at least a signal strength related value and an identification of the communication node; obtaining for at least one of the plurality of communication nodes a stored indication of a location and a stored signal strength related value associated with the stored indication of a location, and determining for the at least one communication node a difference between the signal strength related value included in the results of measurements for the at least one communication node and the stored signal strength related value obtained for the at least one communication node; obtaining (203, 503) for at least a part of the plurality of communication nodes stored radio model data, and estimating (203, 503) the particular position of the mobile device (300, 411, 412) based on the obtained results of measurements for at least a part of the plurality of communication nodes and on the obtained stored radio model data; and in the case that the determined difference between the signal strength related value included in the results of measurements for the at least one communication node and the stored signal strength related value obtained for the at least one communication node falls short of a predetermined threshold, determining (204, 504) a distance between the estimated particular position of the mobile device and a location indicated by the obtained stored indication of a location for the at least one communication node, as an indication of a health state of stored radio model data.