Investigations of radioactivity

A method of measuring activity of radioactive material at one or more source locations within an environment, the method including:

• measuring emissions using an instrument at a measurement location, which instrument includes a detector, the instrument considering a first detector field of view of the environment and considering a second detector field of view of the environment which is different from the first field of view, which fields of view include a source location;
• providing an indication of detected emissions for each field of view;
• correcting the detected emissions to give emitted emissions in respect of the first field of view, the correction being achieved by using a correction factor specific for the first field of view;
• and
• correcting the detected emissions to give emitted emissions in respect of the second field of view, the correction being achieved by using a correction factor specific for the second field of view,
• the correction factors accounting for one or more of:
• the field of view format by applying to the detected emissions for a field of view a weighting which accounts for the degree of sampling of that field of view relative to a normal level of sampling of that field of view;
• and/or the attenuation between the source location and the detector by changing the correction factor between fields of view to account for the presence of different materials between the source location and the detector;
• and/or the distance between the source location and the detector by determining the distance between the detector and two or more potential source locations, establishing an actual source location from amongst the potential source locations and using the distance between the actual source location and the detector in the correction factor,
• the emitted emissions being indicative of the activity.