A method for detecting human entry into a container using electromagnetic imaging to generate image maps of the container, comprising: generating a baseline image map of the container; detecting an entry door open event with a door monitor associated with the container; generating a post entry door open event image map of the container; and comparing the baseline image map generated before the entry door open event with image map generated after the entry door open event, characterised in that the generating the baseline image map comprises in one or more processors: receiving uncalibrated first data corresponding to signals of a first plurality of different frequencies associated with an antenna array residing in a container having contents; estimating second data based on a computer model and simulation of signals of a second plurality of different frequencies associated with the antenna array, the second plurality of different frequencies comprising a subset of the first plurality of different frequencies, wherein estimating comprises estimating one or more parameters of the contents in the container, wherein the one or more parameters comprises one or more geometric parameters that describe one or more interfaces between various contents of the container; comparing magnitudes, without corresponding phase comparisons, of the first and second data at each frequency of the second plurality of different frequencies; updating the second data based on the comparing, wherein updating comprises using an optimization algorithm iteratively; and providing information about the contents within the container based on the updated second data. generating a baseline image map of the container; detecting an entry door open event with a door monitor associated with the container; generating a post entry door open event image map of the container; and comparing the baseline image map generated before the entry door open event with image map generated after the entry door open event, characterised in that the generating the baseline image map comprises in one or more processors: receiving uncalibrated first data corresponding to signals of a first plurality of different frequencies associated with an antenna array residing in a container having contents; estimating second data based on a computer model and simulation of signals of a second plurality of different frequencies associated with the antenna array, the second plurality of different frequencies comprising a subset of the first plurality of different frequencies, wherein estimating comprises estimating one or more parameters of the contents in the container, wherein the one or more parameters comprises one or more geometric parameters that describe one or more interfaces between various contents of the container; comparing magnitudes, without corresponding phase comparisons, of the first and second data at each frequency of the second plurality of different frequencies; updating the second data based on the comparing, wherein updating comprises using an optimization algorithm iteratively; and providing information about the contents within the container based on the updated second data. receiving uncalibrated first data corresponding to signals of a first plurality of different frequencies associated with an antenna array residing in a container having contents; estimating second data based on a computer model and simulation of signals of a second plurality of different frequencies associated with the antenna array, the second plurality of different frequencies comprising a subset of the first plurality of different frequencies, wherein estimating comprises estimating one or more parameters of the contents in the container, wherein the one or more parameters comprises one or more geometric parameters that describe one or more interfaces between various contents of the container; comparing magnitudes, without corresponding phase comparisons, of the first and second data at each frequency of the second plurality of different frequencies; updating the second data based on the comparing, wherein updating comprises using an optimization algorithm iteratively; and providing information about the contents within the container based on the updated second data.