Frequently Asked Questions

Geophysical

What does a geophysical survey cost?


There is no method to estimate what a geophysical survey will cost without knowing site conditions and the reason(s) for the survey. Depending on the geology and the depth of the survey, different technologies might be utilized, such as GPR (ground penetrating radar), EM (electromagnetic Induction), ERI (electrical resistivity), or seismic.




What can you do with Geophysics data?


You can search for underground features, such as utilities, sinkholes, groundwater, underground storage tanks, or buried munitions.




Can geophysical surveys be used for groundwater exploration?


Yes, geophysical surveys can use it for identifying zones of permeability capable of providing maximum extraction rates and ultimately reducing drilling costs.




How does SurvTech help with Geophysical prospecting?


SurvTech has professional geologists and geophysicists on staff trained at collecting, processing, and interpreting geophysical data. From which we can produce a CAD or GIS map or professional report outlining our findings.




What is a Geophysical Survey?


The measuring of geological, structural, and physical characteristics of the foundation soil to be properly planned.




How do you read a geophysics map?


Geophysical image maps can be shown as black and white or color. Warm colors can represent high values such as magnetic intensity, and cooler colors like blues and greens can represent lesser values. Our team can apply different filters to make results easier to see.




What is the field of Geophysics?


The definition of geophysics is geology that uses physical principles to study properties of the earth, including conductivity, soil composition, fluid dynamics, gravity, magnetism, minerals, and radioactivity.




What are some geophysical testing methods?


Some common methods for geophysical exploration are cone penetrometer testing, ground-penetrating radar, gamma spectrometry, magnetometry, resistivity, and seismic reflection/refraction.




In what environments can geophysical mapping be performed?


Many geophysical methods can be performed on the ground, in the air, and on the water.




What is GPR used for?


GPR can be used to locate utilities and buried storage tanks, the depth of the water table, characterize stratigraphy and find void spaces and unmarked graves.




What is a cone penetrometer test?


A CPT is done to characterize soil stratigraphy, measure soil compaction, and bearing capacity.




What is gamma spectrometry, and what is it used for?


All elements on earth are radioactive to some capacity. A gamma spectrometer (GRS) fingerprints elements by their energy signature. The signatures can be quantified, and the sources can be traced, making GRS a useful tool in locating rare-earth elements.




What is Electrical Resistivity Imaging (ERI)?


ERI is a non-destructive method of imaging the subsurface. It involves passing an electrical current into the earth and measuring the voltage potential between pair of electrodes along a survey line. Materials such as sand and water have drastically different conductive properties that can be observed using the method. Sinkholes are just one anomaly that can be seen using ERI.




What applications does geophysics have for mining?


Using geophysical mapping techniques can focus mining efforts more effectively. See case example.





UAV/Drone Surveying

What is the accuracy of LiDAR?


LiDAR accuracy is different depending on the platform and sensor. For example, terrestrial LiDAR (on a static tripod) has accuracy in the millimeter range. In comparison, LiDAR on a moving vehicle, such as an airplane or UAV, may result in inaccuracy in the tenths of a foot range.




When would you use LiDAR on a UAV?


UAV LiDAR is collected from a much lower flying height than an airplane to achieve high accuracy and a much denser point cloud. For example, UAV LiDAR can get upwards of 150 PPSM (points per square meter) compared to airplane LiDAR, which is typically less than 40 PPSM. So, LiDAR on UAV would be used on smaller areas with a need for higher point density.




What is UAV?


A UAV is an acronym for Unmanned Aerial Vehicle. It is commonly referred to as a drone.




What is a UAS?


A UAS stands for Unmanned Aerial System; it is the totality of everything that makes a UAV work, including its GPS module, ground control module, transmission systems, camera, software, and the person on the ground controlling the drone.




When do I need UAS Services?


UAS services are used to supplement Ground Survey Topo. When very dense LiDAR data is required, this is another tool to provide LiDAR.




Why do I need UAS Surveying?


You can get Survey Grade Accuracy on open terrain to supplement the Ground Survey effort to save time and be more efficient. You can map features that are above ground level.




What is the accuracy of UAS?


You can achieve 2-5cm RMSE. Sometimes it is better, depending on how accurate your control is.




What is the difference between UAV and UAS?


A UAS is the totality of everything that makes a UAV work, including its GPS module, ground control module, transmission systems, camera, software, and the person on the ground controlling the drone. To put it simply, a UAV is simply a component of a UAS.





Subsurface Utility Engineering (SUE)

How accurate is GPR?


GPR, which stands for Ground Penetrating Radar, is the industry standard to see through concrete and soil. It depends on the type of soil, operator experience, noise levels, moisture content, and equipment capabilities. Our team is considerably more accurate than the industry standard.




How does Ground Penetrating Radar work?


A high-frequency radio signal is transmitted into the ground. The time it takes for reflected signals to return is measured and collected to give a digital picture of what is below, like a sonogram.




Can you give us depths via the GPR?


GPR measures the time it takes for its signal to return to it to determine the depth of an anomaly. Because soils are not cohesive, an accurate depth from a GPR is not obtainable. The velocity of the signal can change drastically from one soil to the next.




Can you measure the thickness of a pipe without shutting the pipe off?


Yes, SurvTech utilizes the 38DL PLUS® Ultrasonic Thickness Gauge.




How do you find and map rebar and post-tension cables?


Using a high-frequency Ground Penetrating Radar (GPR), SurvTech can map Rebar, PT cables, pipes, voids, and more. SurvTech even can map the lines in 3D utilizing AR technology.




What is the difference between SUE Quality Levels A, B, C, and D services?


Utility quality level A: Includes the precise horizontal and vertical location of utilities obtained by the actual exposure (or verification of previously exposed and surveyed utilities) and subsequent measurement of subsurface utilities, usually at a specific point. Minimally intrusive excavation equipment is used to minimize the potential for utility damage. A precise horizontal and vertical location and other utility attributes are shown on plan documents. Accuracy is typically set to 15-mm vertical and to applicable horizontal survey and mapping accuracy as defined or expected by the project owner. Utility quality level B: Includes information obtained by applying appropriate surface geophysical methods to determine the existence and approximate horizontal position of subsurface utilities. Quality level B data should be reproducible by surface geophysics at any point of their depiction. This information is surveyed to applicable tolerances defined by the project and reduced onto plan documents. Utility quality level C: Includes information obtained by surveying and plotting visible above-ground utility features and by using professional judgment in correlating this information to quality level D information. Utility quality level D: Information derived from existing records or oral recollections. On average, how much money is saved in the form of preventing damage and production delays can you expect for every dollar spent on SUE services? The Federal Highway Administration (FHWA) wanted to know this answer as well, so they teamed up with the University of Purdue and did a study to find out. What they found was that for every one dollar spent on SUE, there was a quantified savings of $4.62.




How deep can you see with a GPR?


It depends on the frequency of the antenna and the dielectric constant of the soils that are being scanned. Now with that said, on average, in Florida, utilizing a 250MHz, you can see down 6-12 ft.




Do you rent GPR equipment?


We don’t rent GPR equipment unless there is a need for a very specialized frequency. When you hire SurvTech Solutions, you get the equipment with a trained technician who specializes in underground utility locations to make your project go smoothly.




What if Level A SUE data is required at a location beneath a public roadway


Our Crew Chiefs hold Maintenance of Traffic (MOT) certifications and are experienced at deploying MOT to route traffic around our work zones safely. We also have senior staff members who hold Advanced MOT certifications capable of planning complex MOT designs when necessary.




What type of reporting can I expect after hiring you for SUE services?


Our Deliverable Reports are customized for each project, but, in general, you can expect a Field Sketch of utilities detected within our scope of work, Test Hole Data Reports for each Level A SUE test hole conducted, and thorough photographic documentation of our findings. We can also collect our results in the field with traditional surveying equipment so that the data can be drafted into a CAD Exhibit.





Aerial Surveying

What is aerial LiDAR Survey?


When we use a plane or drone to collect aerial LiDAR data. It allows for 3D spatial data to be collected in the air that can be acquired day or night and can penetrate vegetation if it is not too dense.




What is Aerial photogrammetry surveying?


The process of collecting high altitude overlapping photos with a plane or drone to create stereo imagery, then utilizing software to create a digital elevation model or an ortho-image.




What pixel resolution do I need for my aerial imagery project?


The ground sample distance, or GSD, of your aerial imagery, is the resolution of your imagery. GSD will determine how much detail you can see in your imagery and may also impact the cost of your project. Higher resolution imagery correlates to a smaller GSD. A typical high-resolution GSD maybe 1-inch to 6-inch pixel resolution, and lower resolution imagery may be 1-foot to 1 meter GSD.




Do I need RGB or CIR imagery?


RGB, or color, imagery is used for most aerial imagery projects. Color-Infrared (CIR) imagery aids in the analysis of vegetation. Typically, healthy vegetation will show up bright red in color-infrared imagery.




What is an orthophotograph?


An orthophotograph is an aerial imagery that has been orthorectified. This process drapes the imagery over a surface model of the terrain. Once aerial imagery has been orthorectified, any distortions due to terrain relief are removed.




Why do I need my aerial imagery orthorectified?


Aerial imagery may include distortions due to terrain relief that produce errors in measurements. Orthorectification removes these distortions so that the imagery can be used to make accurate measurements.




Why is new aerial imagery better than available satellite imagery?


Existing satellite imagery is acquired at regular intervals and is subject to the path and schedule of the satellite’s orbit. Satellite imagery may include clouds or other anomalies and is usually of a lower resolution than aerial imagery. Aerial imagery can be acquired when atmospheric conditions are ideal for producing high-quality imagery of your specific project area.




When/Why do I need ground control for my aerial imagery/LiDAR?


When aerial images are going to be used for measuring or are going to be mosaicked together, ground control may be required depending on the accuracies desired. Having quality ground control points aids in aerotriangulation when creating the mathematical model used to stitch overlapping images together.





3D Scanning Department

What are the differences between photogrammetry versus 3D Scanning (terrestrial LiDAR)?


3D canning uses lasers to measure distance, while imagery uses overlapping (stereo) imagery to create a 3D point cloud. LiDAR is more accurate because it utilizes direct measurements of an object, while imagery utilizes a mathematical equation to generate the distance.




How much does 3D Laser scanning cost?


3D scanning pricing can only be estimated after knowing the site parameters (size, structures, equipment), required accuracy, and required deliverables. There are numerous types of laser scanning (LiDAR), including terrestrial (static tripod), SLAM (simultaneous localization and mapping) utilizing a backpack, UAV, or handheld unit, mobile, utilizing a truck, boat, or ATV.




What is 3D scanning (terrestrial LiDAR)?


3D scanning uses light/lasers to measure the size and shape of physical objects by obtaining millions and billions of 3D points on the visible faces of the object.




What is LiDAR?


Light Intensity Distance and Ranging. It uses light/lasers to measure distances to a physical object.




How does LiDAR work?


A sensor emits pulsed light waves into an area. The device measures the time it takes to bounce off surrounding objects and return. The measured time is used to calculate the distance between objects. This process is repeated millions of times to create a precise 3D map.




What is the difference between mobile and terrestrial LiDAR?


Terrestrial LiDAR (3D Scanning) is when the LiDAR sensor (scanner) is set stationary on a tripod. It collects data at 360°, and the scans from each tripod setup have to be referenced together using a process called registration. Mobile LiDAR is the collection of data from a moving platform, such as an airplane, automobile, UAS, boat, or ATV. Since the sensor (scanner) is continuously moving, the position and orientation of the sensor have to be updated thousands of times per section. On exterior mobile scanning, the position of the sensor is obtained through the use of GPS and an inertial measurement unit (IMU). The IMU measures subtle changes in acceleration to obtain x,y,z differences, and the GPS corrects the IMU position up so that “drift” in position doesn’t occur.




What is mobile scanning using SLAM?


SLAM stands for simultaneous localization and mapping. The position of the scanner is generated by constantly comparing what is being currently scanned vs. what was just previously scanned. For example, when a room is being scanned, the initial scan goes out at 360°, and when the SLAM scan sensor moves forward and scans, there is overlap between the two scan locations. So, by comparing what was scanned moments before to what is being scanned now, the scan data can be positioned correctly in reference to the previous data.




What is a digital twin?


Most people know what an Avatar is due to the movie. A digital twin is much less exciting. Instead of being a graphical/virtual representation of you that is based on whatever you decide. A digital twin is the exact representation of the physical object from the real world, in the virtual world. The digital twin is the same size, shape, color and has the same orientation and position as in the real world.




What kind of deliverables can 3D scanning produce?


All types of deliverables can be produced from 3D scanning, including the point cloud, 360° imagery, CADD models, BIM Models, renderings, animation, and 3D printed objects.




When is scanning useful?


Scanning is useful where there are no other methods of measuring objects due to the amount of data, such as industrial plants, power plants, oil rigs, multiple story buildings, electric substations, or positions that a surveyor can’t occupy.




What are real-world 3D scanning applications?


Real-world applications are traditionally any object or site that is difficult to measure with standard surveying methodologies, such as buildings, power plants, chemical plants, industrial plants, bridges, or odd-shaped structures, such as artwork or statues. 3D scanning is the foundation of reality capture to create virtual reality, such as “digital twins” and “BIMs” (building information models).





Surveying

What is a Topographic Survey?


A Topographic Survey shows all the improvements on the property, with elevations that show the contour of the land. Typically, a topographic survey is used by engineers to help them with the design of new improvements, including, but not limited to parking lots, sidewalks, drainage features, and buildings.




What is an ALTA Survey?


An ALTA Survey is typically used to transfer or refinance commercial property. This type of survey depicts the property boundary and all of the improvements on the property. The survey will also depict easements of record that are included in a title commitment or report.




Why do I need a Survey?


Different surveys are used for various reasons. Typically, a Boundary / Mortgage Survey is ordered when you buy or sell a house. The bank/lender usually requires a survey to make sure that there are not any encroachments on the property or that any improvements on the property do not encroach onto adjoining lands. An ALTA Survey is required for the sale of commercial real estate for similar reasons. A Design, Tree, and/or Topographic Survey is typically used by engineers for the design of new improvements or retrofitting existing features. These are a few of the more common types of Land Surveys ordered. There are various other types of Surveys that are used for different industries for numerous reasons.




How much does land surveying cost?


Even though many members of the public try to treat land surveying as a commodity, it is NOT. Land survey is a profession, and the cost of any survey must be based on on-site parameters (size, improvements, and vegetation) and the type of survey (Boundary, Topographic, Tree, or Wetland).




How much does surveying cost?


Every survey is different, based on site conditions, site location, site improvements, site vegetation, and the type of survey that is required. All these conditions can change and determine the price. Instead of looking for the price of the survey, owners and consultants should be looking for the best VALUE of the survey services. An individual or company purchasing surveying services should have a defined and detailed scope that accomplishes everything that the entity needs to fulfill its project requirements. As surveyors, we should ask the right questions to determine this scope of work and then tailor a solution to meet those project requirements at the best price and best value to our clients.




What is topographic surveying?


Typically, a 3D representation or map of the terrain. The survey locates changes in grade, brake lines (curbs, banks, ditches, etc.), and general (spot) elevations and creates a digital terrain model (DTM) that is used to generate contours. Topographic surveys typically always show planimetric improvements, such as buildings, roads, fences, and visible utilities.




What is cadastral surveying?


It is the field of locating boundaries of properties, including easements and other encumbrances of title.





Hydrographic

What is a bathymetric survey?


It measures the subaqueous ground surface of any water body, such as a ditch, canal, stream, river, pond, lake, or ocean.




What does a bathymetric survey cost?


There is no way to estimate the cost of a bathymetric survey without knowing site parameters (size, depth of water, access, and obstructions) and the required type of survey (single beam, single beam dual-frequency, or multi-beam).




What is Hydrographic Survey?


Hydrographic survey is the science of mapping underwater. Some examples of Hydrographic Survey include bathymetric survey, or water depth measurements, volume calculations for dredging, and seafloor feature mapping. Hydrographic survey has a long history of ingenuity and was originally done with poles or by dragging chains from a vessel. Today, it can take the form of high powered sonar or LiDAR, able to map minute details of the water bottom in great detail. Some other examples of a hydrographic survey are side scan, sub-bottom profiling, seismic, pinger, and magnetometer surveys. These surveys are not measuring depth but collecting other data of the subaqueous bottom or subsurface bottom.




What type of technology is used for Hydrographic Survey?


Hydrographic survey is typically accomplished with sonar, where sound attenuation through the water allows the measurement of distance, depth, and features. Examples of the types of sonar used in hydrographic surveys are single beam echo sounders, multi-beam echo sounders, and side-scan sonar. This type of survey is conducted from a survey vessel. Some hydrographic survey is accomplished through bathymetric LiDAR, which uses high-powered lasers and can be conducted from a plane or UAV.




What kind of data products can I get from a Hydrographic survey?


Hydrographic data products are digital representations of underwater features and are often represented as a point cloud, and 3D surface model, and contours. Data can be delivered in CAD, GIS, and ASCII formats. Results from hydrographic surveys are typically incorporated into maps and charts or are used in calculations.





Metrology

What is Metrology?


In its simplest form, the definition of Metrology is the scientific study of measurement. In a broader sense, it is the application and use of precise methods, procedures, and equipment to produce the most accurate measurement achievable in each situation.




What is Industrial surveying?


Industrial surveying is the use of accurate and repeatable tools (such as trackers) to conduct inspections, alignments, and existing condition surveys on large-scale objects and structures. These structures typically include aircrafts, metro trains, bascule bridges, rockets, etc.




What is a laser tracker?


A laser tracker is an extremely accurate laser-based instrument used to measure objects (both large and small) using optical targets (typically referred to as SMR’s; spherically mounted retroreflectors) to determine distances, measurements, volumes, and deviations from nominal.




What is the accuracy of SurvTech’s laser tracker?


SurvTech measures to 0.001” using a Leica AT-403 in most cases. However, in a climate-controlled environment and proper techniques applied, the Leica AT-960 is capable of measurements up to 0.0001”.




What services does SurvTech provide in Metrology?


SurvTech provides precision steel alignment, part inspection, 3d precision laser scanning, deviation to nominal analysis, bridge settlement analysis, reverse engineering, and many more.




How is 3D scanning incorporated with Metrology?


SurvTech uses metrology drift nests incorporated with scan targets to vastly improve the accuracy of scan data. This can be used with targets valued from the tracker that coincide with the scan targets in order to georeference individual scans. Also, precision small volume scanners such as the Handyscan can be used to precisely model smaller based objects and parts. Scanners such as the Hemispherical Surphaser can be used for larger volume precision scans and modeling. Lastly, the Leica ATS-600 combines both tracker-based accuracy and 3D laser scanning in one solution. This allows SurvTech to utilize 3D scanning in a multitude of ways, using the right tool for the right job.




What is Metrology?


Metrology is the field of precision measurement. It is much higher precision than what can be obtained from traditional surveying methodology and instrumentation. Today’s metrologists typically utilize laser trackers to perform measurements in 3D space that are accurate to as much as 1/10,000th of an inch. Metrology is used in industrial plants, ships, moving bridges (draw bridges) to perform precision placement and alignment of moving parts.