Landitude Incorporated provides a wide range of geophysical services using state-of-the-art equipment and software. Whether your organization needs underground utilities located and mapped or you are an archeologist that wants to determine if a potential dig site is worth further investigation, we can help.

Ground Penetrating Radar was developed in the early 1970s by the US military to identify underground caves where the Vietcong were hiding during the Vietnam War. Since the 1970s this technology has been refined and de-militarized so that it can be used for a variety of civilian applications. Today GPR is used for many diverse applications:

• Cement inspection (rebar, chairs, cracks, faults, sag, encased utilities, etc)
• Utility location (metallic and non-metallic subsurface location and mapping)
• Wildlife Applications (location and mapping of wildlife dens)
• Search and Rescue (finding people trapped under debris, snow and ice)
• Geologic Applications (location and mapping of groundwater and mineral deposits)
• Environmental Monitoring (location and mapping of saline and petroleum spills)
• Soil Moisture Mapping (Conductivity)

GPR works by sensing a difference in radio-wave propagation (dielectric). As a result, if the target object has the same conductivity as the overlying soils it will be invisible to GPR (i.e. a clay pipe in a clay soil). The larger the difference in conductivity between a target object and the surrounding soil, the easier it can be identified with GPR. This technology works very well for mapping and locating underground utilities if the following assumptions are met:

• Conductivity (dielectric constant) between soil substrate and target objects are different
• PVC pipe filled with air/gas will be harder to identify than a PVC pipe filled with liquid
• Metallic objects will be easier to identify than non-metallic objects
• Low conductivity Soils (Sandy to Sandy Loam Soils)
• Low levels of soil moisture (moisture increases conductivity and reduces dielectric contrast)
• Low amounts of radio-reflective substrate overlaying the target objects
• Rocks, pieces of metal, etc can mask target objects
• Non-metallic target objects must be at least one inch in diameter for every foot of overlying soil (general rule of thumb)
• 2-inch diameter PVC pipe will be almost invisible at > 2 foot of depth
• Soil disturbance of trench lines can aid in identifying deeper utilities

Electromagnetic location equipment is useful for locating and mapping metallic objects (ferrous and non-ferrous). This technology was developed to locate and map unexploded ordinance. EM generates an energy field that is directed down into the earth by a coil. This EM field will energize metallic objects and cause them to create eddies in the energy field which are detected and measured by the EM device. This technology works very well for identifying and mapping shallow (< 6 feet) metallic objects. Since this technology generates its own energy field it is not sensitive to surrounding metallic noise (buildings, operator, vehicles, etc.)

Magnetometers are extremely sensitive pieces of equipment that detect differences in magnetic field. Due to their sensitivity, they are not suitable for use in urban environments or areas that have a large amount of metallic noise (buildings, vehicles, etc). These devices work very well for locating and mapping ferrous objects (pipelines, barrels, etc) in addition to detecting differences in gravitational fields (soil compaction, soil disturbance, etc). Magnetometers can detect very small magnetic field differences at extreme soil depths.

Each of these geophysical technologies are powerful tools that are intended for a specific purpose. If possible, it is best to conduct a survey using multiple sensors so that the results obtained from one instrument can be cross-validated with the results of another instrument. Unfortunately, GPR is the only type of equipment that can be used reliably for conducting non-metallic surveys.

Call us today to discuss your geophysical needs