In this paper, we describe an instrument system for performing continuous resistivity profiling in shallow freshwater and marine environments. Using a streamer cable containing 9 electrodes, the system continuously samples the dipole-dipole resistivity at n-spacings 1 through 6. The system can be installed aboard a variety of small inboard or outboard powered vessels in a few hours. Hand-held or marine GPS units provide location information that is recorded by a laptop computer. With this system, up to 40 line-km/day of dipole-dipole data have been collected. The resistivity data are merged with the GPS positions as a post-processing step. The final step in the post-processing is the inversion of overlapping segments of each profile using a 2-D smooth model. The inversions provide high resolution images of the geoelectric cross-section. The depth of investigation ranges from 20-30 m, with a 10 m dipole spacing. Over the last 4-years, we have performed surveys on the Ohio River, near Louisville, KY, on tidal estuaries and bays along the Atlantic coast in Delaware, Maryland, Virginia, and North Carolina, and in Tampa Bay, Florida. Data from these surveys will be used to illustrate the final deliverable from a survey.

Electromagnetic induction methods are effective in locating unexploded ordnance (UXO). However, the induction EM instruments that are used for UXO detection generally have limited bandwidths and provide little, if any, information for UXO classification. It is well known that the broadband induction EM response from confined conductors (such as UXO) can be parameterized in the time-domain as a series of damped exponential decay curves, and in the frequency domain as a set of discrete real first order poles and their residues. Characteristic decay time or its equivalent real pole has been shown to be a function of characteristic target dimensions, target conductivity, and relative magnetic permeability. Therefore, parameterization of the broadband EM response in terms of these characteristic modes provides a basis for the classification of UXO anomalies.In this paper we have used a numerical method (Prony) to analyze TEM decay curves to obtain a set of exponential decay time-constants and their corresponding residues. Using a commercially available field data acquisition system, we have acquired fast transient TEM data from UXO. We show that these data can be analyzed and displayed in a way that is simple to understand and useful for classifying the TEM response.