Our scientific echosounders for fisheries and aquatic habitat assessment include everything you need to explore aquatic ecosystems using hydroacoustics. Our proven single and split beam sonar echosounder system are versatile, optimized for flexibility, reliability and ease of operation and include the data acquisition, real-time analysis, data visualization and post-processing software you need to get results.
DT-X Extreme Autonomous Portable Scientific Echosounder – This versatile echosounder is ideal for mobile surveys, or as a fully autonomous system for ASV/AUV surveys, surface buoys and other unmanned or fixed location monitoring applications for aquatic ecosystem research and management.
DT-X SUB Autonomous Submersible Echosounder – Our autonomous, fully submersible echosounder, for marine envoriments, optimized for ocean observatories and long-term AUV or ASV missions.
DT-X AMS Automated Monitoring Systems – Designed for fixed location, long-term or permanent deployments to monitor passage, migration and entrainment of fish and marine life or debris.
MX Aquatic Habitat Echosounder – A low cost, turn-key solution for rapid assessment and mapping of aquatic vegetation, substrate and bathymetry.
What is EM Locator Technology?
Electromagnetic (EM) Locator technology relies upon the detection of an alternating magnetic field. This magnetic field is created by the flow of current through a conductor, whether a wire, cable, pipe, or other conductive material. Often, additional ‘tracer wires’ are run in parallel to non-conductive pipes such as gas lines expressively for the purpose of facilitation such detection. AC power utilities, as long as current is flowing in the form of power usage, usually radiate a very detectable magnetic field as a side-effect of normal operation. It is also possible to intentionally induce a ‘tracer’ current (by inductive clamp or direct attachment) onto otherwise passive conductors in order to create a detectable field that can be followed.
LineTrac technology is a multi-sensor fashion technology that combines the power and advantage of GPR with the specific target-identifying capabilities of EM location. Linetrac operates in both “Power” (50 or 60 HZ Utility Power) and in arbitrary “Frequency Mode” up to 50KHz, using a customer-supplied transmitter.
We provide two models of EM locator technology. The LineTrac system for our UtilityScan series and the LineTrac XT for our StructureScan Mini XT system.
Seismic refraction maps contrasts in seismic velocity – the speed at which seismic energy travels through soil and rock. This parameter typically correlates well with rock hardness and density, which in turn tend to correlate with changes in lithology, degree of fracturing, water content, and weathering.
There are two basic approaches to seismic refraction data analysis: layer-cake and tomographic inversion. The former is the more traditional approach, although tomography has become more popular as faster computers have made it much more feasible than in the past.
Especially in the near-surface, it is not always the case that seismic velocities are divided into high-contrast, discrete layers. Nor is it the case that velocities are constant horizontally. Conventional layer-cake inversion techniques, such as the delay-time method, assume both, and require the geophysicist to provide layer assignments before the data inversion can be completed.
Tomography is less constrained in this sense; it does not “think” in terms of layers, and it better accommodates horizontal velocity variations. If discrete layering is not apparent in the raw data, the tomographic approach is generally more appropriate. As such, Geometrics’ SeisImager Refraction Analysis software offers both options.
The depth of penetration in a seismic refraction survey is approximately 1/5th of the length of the geophone spread, including offset shots. So if you need to see 10m deep, you will need room to lay out a (minimum) 50m seismic spread, as measured from offset shot to offset shot.
For most engineering refraction work, the best possible source is a 14 or 16lb sledgehammer. A downhole seisgun is not a good refraction source in general, except in cases where the surface is too soft to use a hammer effectively. An accelerated weight drop can be a good source, but is not portable and requires vehicle access to the shot points. Small explosives, such as Kinepak, are ideal when portability is required and the depth of interest is greater than what can be reached with a hammer.
Seismic refraction requires that velocities increase with depth. A lower velocity layer beneath a higher velocity layer will not be detected by seismic refraction, and will lead to errors in depth calculations. Fortunately, this is a fairly uncommon occurrence in the shallow subsurface.
The seismic source employed must match the desired depth of penetration. For hammer and plate work, the maximum depth you can expect to explore to is about 15-20m; however, this can vary significantly depending on geology, surface conditions, cultural noise, and the person swinging the hammer. Refraction is a relatively broad-brush technique – it looks at gross velocity differences, and you should not expect to be able to map more than 3-4 individual velocity layers.
Cultural noise can be a problem – it is more difficult to conduct a seismic survey in an urban environment than in a rural one. Surveying along busy roadways should be avoided when possible. Shooting at night is sometimes necessary in order to achieve acceptable signal-to-noise ratio in busy areas.
The final product of a refraction survey is a velocity model, such as the layer-cake inversion shown on the left, or a tomographic inversion as shown below
To give an idea, the rule of thumb is that 1 ton of steel will give 1nT at 100 ft. The distortion caused by the steel in the earth’s field falls off as the cube with distance and is linear with mass. Therefore, at 50 ft, 250 lbs will give 1nT, at 25 ft 30 lbs will give 1nT, at 12 ft 4 lbs will give 1nT. Cables and pipelines fall of at somewhat a different rate (inverse square) so can be seen further for a given mass.
Ultra-wideband (UWB) signals have been used for decades in geophysical applications. When UWB signals are used in geophysical instruments, the sensor is moved to detect and map underground objects. When used in GSSI’s LifeLocator®, the sensor is stationary to detect motion and breathing characteristics.
UWB signals are generally defined as electromagnetic transmitters whose bandwidth is at least 25% of the nominal center frequency. UWB operates in the time domain; almost all other transmitters operate in the frequency domain.
Geophysical instruments are moved across a surface and transmit very short bursts of electromagnetic energy into the ground. Reflections from buried objects are received at another antenna. This technology can detect targets such as plastic pipes and voids underground, and inside walls and floors. Any change in dielectric property of materials will cause a reflection. Reflections from targets will arrive at different times depending on their distance from the antenna (and will also vary depending on the type of material through which the signal passes).
For LifeLocator®, the transmitted and reflected signals are primarily passing through debris and air. The sensor is stationary and detects moving objects. As with geophysical analysis, the approximate distance of the object causing the reflected signal can be determined by the particular time delay in the signal return. The monitored area may approximate a cone with a beam width of 120 degrees and a range as large as 30 feet. There may be concrete walls or other structures and obstacles in the radiation path.
Total average power is transmitted is ~1% of a cell phone
Working in the time domain, distance to the motion can be measured
The reason for using a UWB signal instead of a single frequency transmitter is improved motion resolution, distance measurement and obstacle penetration. Lower frequencies within the transmitted pulse carry further, especially when looking through walls and floors; however, resolution is coarser with lower frequencies. Since the resolution is a function the wavelength of the transmitted signal, higher frequencies will provide finer resolution. In the simplest terms, the wide spectrum of the transmitted signal accommodates most motion and obstacle types. In essence, a maximum number of frequencies are transmitted (both low and high frequencies) with the notion that some frequency will be reflected and sent back to the receiver.
The depth of exploration is determined by the spatial wave-length of the magnetic anomalies revealed during the survey. It is important to understand that the measurement of the magnetic field at a single point does do provide any depth information. A single measurement includes the contribution of the magnetic field from many sources and so it is necessary to measure the variation in magnetic field strength at many different locations in order to determine the location of the objects that are causing the magnetic field variation.
Magnetic field surveys are used during exploration for almost all types of minerals. Magnetic survey data are usually interpreted in an effort to gain a better understanding of the geologic structure beneath the survey area and this understanding is used as a guide for conducting follow-up surveys using different techniques or for choosing the optimum placement of exploratory drill holes. In addition to this, magnetometer surveys are commonly used as a means of direct detection of iron and nickel ore and also for gold exploration. In the case of gold exploration, the target mineral is magnetite which, because of its density, is used as an indicator in locating gold in fluvial deposits. Similarly, an absence of magnetite is used as indicator of possible gold deposition in epithermal conditions.
When surveying a large area or when conducting the survey of a small area over a long period of time, it is necessary to remove the back-ground variation of the Earth's magnetic field. Your engineer is correct in being concerned about the effects of magnetic storms and these are the more extreme examples of the diurnal magnetic field variation that is always present. It is customary to use a base station magnetometer to recognize and remove this variation component. We recommend our model G-856AX proton precession magnetometer for use in this role. The G-856AX is a very stable, relatively inexpensive magnetometer and includes a very stable and accurate clock, as do our models G-858 and G-859. When used as a base station, the G-856AX clock is synchronized with the survey magnetometer's clock and it is set up on a tripod and configured to run automatically in a fixed location. Each of the measurements that the G-856AX records will be automatically recorded, along with the date and time of the measurement. The same thing happens automatically for each measurement made with the roving (survey) magnetometer. Then, when the data are down-loaded to the processing computer, our MagMap2000 software can be used to process these data sets to remove the diurnal variation from the survey data and perform other data processing and analysis functions. Attached, please also find a quotation for our G-856AX with base station accessories.
Mn / Cu / Mg are not ferromagnetic and also none of the common mineral sources of these elements are ferromagnetic. So direct detection of Mn / Cu / Mg is highly unlikely. I would recommend that you retain the services of an economic geologist familiar with your prospect area to see if a magnetic survey useful in gaining understanding for the geologic structures that may be important for locating concentrations of minerals that include these elements.
GPR works by sending a tiny pulse of energy into a material and recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area make up what is called a scan. Reflections are produced whenever the energy pulse enters into a material with different electrical conduction properties or dielectric permittivity from the material it left. The strength, or amplitude, of the reflection is determined by the contrast in the dielectric constants and conductivities of the two materials. This means that a pulse which moves from dry sand (dielectric of 5) to wet sand (dielectric of 30) will produce a very strong reflection, while moving from dry sand (5) to limestone (7) will produce a relatively weak reflection.
While some of the GPR energy pulse is reflected back to the antenna, energy also keeps traveling through the material until it either dissipates (attenuates) or the GPR control unit has closed its time window. The rate of signal attenuation varies widely and is dependent on the properties of the material through which the pulse is passing.
Materials with a high dielectric will slow the radar wave and it will not be able to penetrate as far. Materials with high conductivity will attenuate the signal rapidly. Water saturation dramatically raises the dielectric of a material, so a survey area should be carefully inspected for signs of water penetration.
Metals are considered to be a complete reflector and do not allow any amount of signal to pass through. Materials beneath a metal sheet, fine metal mesh, or pan decking will not be visible.
Radar energy is not emitted from the antenna in a straight line. It is emitted in a cone shape (picture on left). The two-way travel time for energy at the leading edge of the cone is longer than for energy directly beneath the antenna. This is because that leading edge of the cone represents the hypotenuse of a right triangle.
Since it takes longer for that energy to be received, it is recorded farther down in the profile. As the antenna is moved over a target, the distance between the two decreases until the antenna is over the target and increases as the antenna is moved away. It is for this reason that a single target will appear in the data as a hyperbola, or inverted “U.” The target is actually at the peak amplitude of the positive wavelet.
1. There are basically three types of "gold": low concentration disseminated gold in ore, placer gold deposits and solid gold such as that associated with treasure. Magnetometers are used to find disseminated gold by its association with mineralized zones which also contain magnetite or other magnetic minerals. Magnetometers are often used in conjunction with airborne Electro-Magnetic surveys to find the conductive ore bodies. Placer gold is the type found in buried stream channels such as the gold which sparked the California gold-rush in 1849. Gold dust and magnetic minerals have been concentrated in river banks over thousands of years. Where there is gold there is often magnetite and therefore the magnetometer can be used to locate placer gold deposits. Gold treasure is a different story and being non-magnetic gold, silver, and other precious minerals are not directly detectable by the magnetometer.
2. The magnetometer can only detect ferrous (iron or steel) objects. If the gold is stored in an iron box or has iron materials next to the gold (such as colonial ship ballast stones in the marine environment), there is the possibility of detecting the iron material. This is true for land and marine (sunken galleon) gold bullion. The vast majority of target search surveys are performed on a grid in a "lawn mower" back and forth manner to cover the area of interest. Lane spacing is dependent on target size (magnetic mass).
3. At a sensor to target distance of 2 to 3 meters there will need to be at least 1-2 kilograms of iron. This can produce a 1-2 nT anomaly that is detectable in a magnetically clean environment. The ideal environment would be in a plowed farm field or the bottom of the ocean away from human activity i.e., away from a port or harbor. You will probably not be able to detect this small of an anomaly in a city or port location. The more iron mass there is, the better the detectability.
4. Training to use the magnetometer can take 1-2 days depending on experience with setting up computerized survey equipment and a GPS.
5. Processing the magnetic data requires several days of training and would require a geophysical background to interpret the final maps. We provide free software to make maps and estimate the target depth of burial (inversion). If you are unfamiliar with this procedure, we would recommend that you find a local geotechnical firm to look at the data to determine if there are anomalies that should be investigated further. Remembering that non-ferrous materials do not cause anomalies (gold, silver, copper, brass, aluminum, gems) you will be looking for anomalies either associated with the container OR associated with ground disturbance (i.e., gravesite). In this way some anomalies can be detected where there has been an excavation such as a gravesite.
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