wave velocity profile for the soil. Full waveform inversion Full-waveform-inversion (FWI) methods are among the most recent techniques for geotechnical site characterization, and are still under continuous development. The method is fairly general, and is capable of imaging the arbitrarily heterogeneous compressional and shear wave velocity profiles of the soil. Elastic waves are used to probe the site under investigation, by placing seismic vibrators on the ground surface. These waves propagate through the soil, and due to the heterogeneous geological structure of the site under investigation, multiple reflections and refractions occur. The response of the site to the seismic vibrator is measured by sensors (geophones), also placed on the ground surface. Two key-components are required for the profiling based on full-waveform inversion. These components are: a) a computer model for the simulation of elastic waves in semi-infinite domains; and b) an optimization framework, through which the computed response is matched to the measured response by iteratively updating an initially assumed material distribution for the soil. Other techniques Civil engineering can also use remote sensing information for topographical mapping, planning, and environmental impact assessment. Airborne electromagnetic surveys are also used to characterize soft sediments in planning and engineering roads, dams, and other structures. Magnetotellurics has proven useful for delineating groundwater reservoirs, mapping faults around areas where hazardous substances are stored (e.g. nuclear power stations and nuclear waste storage facilities), and earthquake precursor monitoring in areas with major structures such as hydro-electric dams subject to high levels of seismic activity. BS 5930 is the standard used in the UK as a code of practice for site investigations. Archaeology Ground penetrating radar can be used to map buried artifacts, such as graves, mortuaries, wreck sites, and other shallowly buried archaeological sites. Ground magnetometric surveys can be used for detecting buried ferrous metals, useful in surveying shipwrecks, modern battlefields strewn with metal debris, and even subtle disturbances such as large-scale ancient ruins. Sonar systems can be used to detect shipwrecks. Forensics Ground penetrating radar can be used to detect grave sites. This detection is of both legal and cultural importance, providing an opportunity for the affected families to pursue justice through legal punishment of those responsible, as well as allowing families to experience closure over the loss of a loved one. Unexploded ordnance detection Magnetic and electromagnetic surveys can be used to locate unexploded ordnance. See also Archaeological geophysics Hydrocarbon exploration Kola Superdeep Borehole