A method comprising: receiving signals, in a receiver from one or more transmitters, and recording corresponding observations associated with the received signals and recording corresponding locations associated with the receiver, wherein the observations include power levels of the corresponding signal, and wherein the signals propagate from the one or more transmitters through an environment to the receiver; receiving geometry data that includes two-dimensional or three-dimensional data describing objects (104, 105) in the environment, wherein the environment includes the locations associated with the received signals; determining expected observations of the signals, corresponding to the recorded observations and locations, wherein determining the expected observations of the signals includes: determining a bias describing gain or attenuation of a transmitter-receiver pair associated with the recorded observations, wherein determining the bias includes: (i) calculating (702, 704), for each of a plurality of sets of values for characteristics of objects (104, 105) in the environment, expected observations corresponding to the recorded observations and locations, (ii) calculating a difference, for each set of values, between the expected observations and the corresponding recorded observations, (iii) determining the set of values with best fit to the recorded observations accounting for the corresponding difference, and (iv) determining the bias based on the set of values with the best fit, and determining expected observations of the signals based on the determined bias and the geometry data; comparing (306, 808) the expected observations with the recorded observations; and estimating (306, 812, and 816) values of characteristics of the objects (104, 105) in the environment based on the comparing, wherein the estimated values of the characteristics of the objects (104, 105) include data describing a height of at least one of the objects (104, 105) in the environment. receiving signals, in a receiver from one or more transmitters, and recording corresponding observations associated with the received signals and recording corresponding locations associated with the receiver, wherein the observations include power levels of the corresponding signal, and wherein the signals propagate from the one or more transmitters through an environment to the receiver; wherein the observations include power levels of the corresponding signal, and wherein the signals propagate from the one or more transmitters through an environment to the receiver; receiving geometry data that includes two-dimensional or three-dimensional data describing objects (104, 105) in the environment, wherein the environment includes the locations associated with the received signals; determining expected observations of the signals, corresponding to the recorded observations and locations, wherein determining the expected observations of the signals includes: determining a bias describing gain or attenuation of a transmitter-receiver pair associated with the recorded observations, wherein determining the bias includes: (i) calculating (702, 704), for each of a plurality of sets of values for characteristics of objects (104, 105) in the environment, expected observations corresponding to the recorded observations and locations, (ii) calculating a difference, for each set of values, between the expected observations and the corresponding recorded observations, (iii) determining the set of values with best fit to the recorded observations accounting for the corresponding difference, and (iv) determining the bias based on the set of values with the best fit, and determining expected observations of the signals based on the determined bias and the geometry data; determining a bias describing gain or attenuation of a transmitter-receiver pair associated with the recorded observations, wherein determining the bias includes: (i) calculating (702, 704), for each of a plurality of sets of values for characteristics of objects (104, 105) in the environment, expected observations corresponding to the recorded observations and locations, (ii) calculating a difference, for each set of values, between the expected observations and the corresponding recorded observations, (iii) determining the set of values with best fit to the recorded observations accounting for the corresponding difference, and (iv) determining the bias based on the set of values with the best fit, and (i) calculating (702, 704), for each of a plurality of sets of values for characteristics of objects (104, 105) in the environment, expected observations corresponding to the recorded observations and locations, (ii) calculating a difference, for each set of values, between the expected observations and the corresponding recorded observations, (iii) determining the set of values with best fit to the recorded observations accounting for the corresponding difference, and (iv) determining the bias based on the set of values with the best fit, and determining expected observations of the signals based on the determined bias and the geometry data; comparing (306, 808) the expected observations with the recorded observations; and estimating (306, 812, and 816) values of characteristics of the objects (104, 105) in the environment based on the comparing, wherein the estimated values of the characteristics of the objects (104, 105) include data describing a height of at least one of the objects (104, 105) in the environment.