Remote Sensing
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Geophysical, Underwater & Airborne Remote Sensing

CEI’s remote-sensing capabilities encompass a wide array of terrestrial, underwater, and airborne methods. Remote-sensing applications are aligned with CEI’s applied science, environmental, and cultural resources services, as well as other industries that benefit from remotely sensed data. CEI’s terrestrial remote-sensing expertise centers on near-surface geophysical methods, which employ sensors positioned on the ground surface to map buried targets. Similarly, CEI uses underwater remote sensing to characterize the bed of waterways and to locate marine targets. CEI’s airborne remote sensing capabilities include unmanned aircraft systems (drones) and the latest photogrammetry software, which are used to create high-resolution aerial photographs and 3D models. CEI also uses a range of data from aircraft and satellite platforms housed in data warehouses. The spatial data produced by CEI’s remote-sensing specialists are closely integrated with our GIS and survey capabilities
We offer full Geophysical and Underwater GIS and Remote Sensing services from data collection to analysis to presentation:

GEOPHYSICAL Remote Sensing

Our geophysical remote-sensing staff has extensive experience in the use of near-surface geophysical techniques on a wide range of site types and geographic settings. We are ready to collaborate on both cultural-resource and academic research archaeological projects, as well as environmental, geological, forensics, concrete, utility mapping, and other applications.

MAGNETIC GRADIOMETERS

Magnetic gradiometers, a type of magnetometer, 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 enhanced 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. Because of its rapid collection speed and its response to a wide array of targets, magnetic gradiometry is an excellent archaeological prospection technique.

Magnetic Gradiometer Survey, Henderson Yoakum House, Walker County, Texas

Ground Penetrating Radar (GPR)

GPR operates by propagating a radar pulse into the ground, which responds to certain electrical properties of the soil and subsurface targets. By recording reflections along multiple transects, the three-dimensional extent of buried targets can be determined. GPR can be used to map burials, pits, trenches, hearths, stone foundations, kilns, buried living surfaces, metal objects, voids, tunnels, and other features. GPR also has an array of applications outside archaeology. CEI offers advanced GPR processing, analysis, and visualization using the software package GPR Slice.

3D visualization of ground penetrating radar (GPR) results, Levi Jordan Plantation, Brazoria County, Texas

Electrical Resistivity

Electrical-resistivity instruments respond to archaeological features through changes in soil type, moisture, and other properties, which affect the flow of an electrical current introduced into the ground. Archaeological features that may produce resistivity contrasts include ditches, pits, shell deposits, stone architecture, compacted floors, and a variety of other features. 

Electromagnetic Induction (Conductivity and Magnetic Susceptibility)

Electromagnetic induction (EMI) instruments measure the interaction of an electromagnetic field with subsurface targets. One property measured by EMI, conductivity, responds to similar features as electrical resistivity. EMI also can be used to measure magnetic susceptibility, which responds to pits, midden deposits, and other type of soil disturbance.

Metal Detectors

Metal detectors are a special type of electromagnetic induction device that respond to respond to shallowly buried metal targets. The latest metal detectors provide enhanced information on target composition and depth. Metal detectors are important tools for investigating battlefields and other types of historic sites.

Ground penetrating Radar (GPR) Survey, Temple of The Masonry Altars (Structure B4), Altun Ha, Belize

Underwater Remote Sensing

CEI’s Marine Archaeology Division has been involved in marine geophysical studies in a variety of environments since 1977. Many of these projects have involved intensive remote-sensing and cultural resource investigations of marine and riverine environments in Louisiana, Texas, Mississippi, Alabama, Arkansas, Florida, as well as in the waters of the Gulf of Mexico. These studies have included remote-sensing surveys, processing of geophysical datasets, and archaeological interpretation of remote-sensing data. In addition, we conduct hydrographic surveys, remote-sensing surveys designed to specifically identify underwater hazards, such as pipelines and well heads, and remote-sensing surveys to collect information on the natural environment, including seabed classification and identification of oyster reefs and sea grass beds.

Magnetometer
Magnetometers measure the Earth’s ambient magnetic field. Deviations from the ambient background are called anomalies, which typically are generated by the presence of ferrous objects. Each anomaly recorded by the magnetometer is measured, and the magnetic intensity, signature, and persistence of each anomaly is used to make inferences about the identity of the source object. For marine survey projects, magnetometers are used to locate metallic objects that might represent submerged cultural resources (e.g., shipwrecks or anchors), as well as hazards or impediments to planned activities (e.g., pipelines).
Side-Scan Sonar
Side-scan sonar is an instrument that, through the transmission of dual fan-shaped pulses of sound and reception of reflected sound pulses, produces an acoustic image of the bottom. The side-scan sonar data are used to map bottom conditions within the project area and identify features of interest.
Sub-Bottom Sonar
Sub-bottom profilers use low-frequency acoustic waves to collect information on subsurface features and shallow subsurface stratigraphy in the survey area. These returns are received by hydrophones in the tow fish. The data sets are computer processed and reproduced as a cross-section scaled in two-way travel time (the time taken for the pulse to travel from the source to the reflector and back to the receiver). Using estimates of the velocity of sound through the water and the seabed, this travel time can then be converted to depth in the sediment column.

Fathometer

Echo sounders are used to obtain information on bathymetry in the surveyed area. In addition, it also can be used to identify objects that extend above the seabed.

Side-scan Sonar — Underwater Reefs in Baton Rouge, LA

Deploying the magnetometer sensor.

The sensor was floated at the surface 60 feet behind the survey vessel.

AIRBORNE REMOTE SENSING


CEI employs airborne remote-sensing data from a variety of sources, including from drone / Unmanned Aerial Systems (UAS) platforms. We operate a DJI Phantom 4 Pro V2.0 UAS and Pix4D Mapper software, which allow us to create a variety of 2D and 3D spatial products for many applications. The data can be enhanced with ground control points in order improve the spatial accuracy. CEI operates using FAA Part 107 guidelines for commercial drone / UAS operation.” 



CEI UAS LiDAR surveys produce elevation data at extremely high resolutions. LiDAR sensors can penetrate tree canopy, revealing archaeological features and many other types of targets. CEI staff can process and classify LiDAR data, creating bare-earth digital

GIF Imagery location)


Implementing GIS technology

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 information to meet the needs of your project. 
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