GIS & Remote Sensing
Coastal Environments, Inc. has provided a variety of GIS services over the past decade and has been active in the evolution of data translation and automation. Our multidisciplinary GIS team link databases and maps as well as provide tools to visualize and query. We provide you with a cost-saving dynamic and informative display for your project needs. Our GIS staff is uniquely qualified to assist clients in both the public and private sectors to develop and implement GIS technology for the solution of a wide range of data-intensive technical problems. We have the equipment and the expertise to collect, analyze, and present spatial informaiton to meet the needs of your project.
We offer full Terrestrial and Underwater GIS and Remote Sensing services from data collection to analysis to presentation:
Magnetic gradiometers are passive instruments that measure the gradient of the magnetic field strength at a point on the Earth’s surface. Archaeological features exhibit either permanent or induced types of magnetism. Permanent magnetization, also called remnant magnetism, is created when hearths, perishable structures, and other features are burned. Induced magnetism, or magnetic susceptibility, is increased by the organic content of pits and middens in the presence of the magnetic field of the Earth. Iron targets also produce strong magnetic gradients and these can obscure the relatively subtle archaeological targets.
Ground Penetrating Radar (GPR)
GPR operates by propagating a radar pulse into the ground from an antenna. Based on contrasts in certain electrical properties of the soil and ground targets, the radar wave will reflect back to the antenna. By estimating the velocity of the soil, the approximate depth of the target can be determined and the spatial extent of each target can be determined in three dimensions.
Electrical resistivity instruments measure the of subsurface resistivity variation using probes placed on the surface. One advantage of the technique is that the approximate depth of maximum sensitivity is equal to the separation distance of the probes. Archaeological applications often use profiling type surveys, where a fixed probe separation distance is used to create a plan view map of anomalies at a chosen depth. Generally the resistivity distribution is closely related to the amount of moisture contained in the subsurface material. Archaeological features that may produce resistivity contrasts include buried stone architecture, tombs, and compacted floors. CEI owns a TR/CIA resistivity meter.
Electromagnetic Induction (Conductivity and Magnetic Susceptibility)
Electromagnetic induction consists of a transmitter that creates an electromagnetic field and a receiver that measures its response as the instrument is carried over the survey area. Based on the phase of wave, two properties are simultaneously measured: conductivity and magnetic susceptibility. Conductivity responds to similar features as electrical resistivity, while magnetic susceptibility responds to pits and midden deposits.
Metal detectors are a type of electromagnetic induction device that detect metal targets at shallow depths. Instruments are composed of a control box, a coil, and a cable that connects the two other parts. When metal is encountered, the greater conductivity causes a phase shift that is received by the control box that results in a change in the tone or value. Discriminating between various types of metal can be accomplished by narrowing to certain ranges of phase shift that correspond to known average values.