Optical Surveying Equipment & New GPS Technology for Buyers

By accentu8

Top FAQs about Construction Laser Levels

New or inexperienced users and buyers should have a basic understanding of surveying equipment types (laser, optical surveying, GPS for surveying) as a starting point for additional learning that is often necessary.  Common questions are answered below.

1. What are the technologies behind the main types of land and construction surveying instruments?  The types can be broadly categorized as laser, optical and satellite positioning (GNSS– GPS is one system).  These technologies are increasingly combined in newer surveying instruments.  While optics were used in all surveying instruments up until about four decades ago (sighting was the only way to measure or project horizontal/vertical angles and grades), precision optical lenses are still used today for sighting instruments and, with the advent of lasers for surveying, ultra-precise optics are integral to most laser surveying instruments.  The emergence of GPS for surveying a decade ago can facilitate precise positioning without optical and laser surveying instruments.

2. How is laser technology used in surveying instruments, and what are the types? Laser instruments are extensively used in construction surveying and layout to set elevation, grade or to plumb, and also used for 3D imaging to support engineering work, and laser energy is the dominant technology for distance meters.   Lasers are often used in machine control for vertical precision.

  • Construction Laser levels point or rotate to create a reference point, line or plane. For outside construction work, they are almost always used with a receiver attached to a grade rod, or mounted on heavy equipment for laser machine control.  Inside, activity is usually guided by a visible beam (but sometimes a receiver is used for larger areas).  Some units have the ability to slope the plane on one or two axes and do steep slopes.  Most have auto-leveling capability.  Some models offer vertical and horizontal capability.  Small laser tools like multi-plane generators are used for interior work.
  • Laser receivers can attach to grade rods with sliding brackets, and larger receivers are mounted on heavy equipment for machine control
  • Pipe lasers are used with targets to set the precise elevation of grade-sensitive pipes like drains or sewers.
  • 3D scanners use multipoint scanning to produce a 3D model of any indoor or outdoor man-made or natural structure, mostly for project design support.
  • Distance meters (EDM) can be a handheld device or part of a total station or other type of instrument, and typically reflect infrared laser energy off a surface to measure distances.
  • Laser guided machine control uses receivers and sensors (depending on system and configuration) to either “indicate” by annunciation, thus directing the operator to perform certain actions until the target grade is reached, or “automate” thus controlling the machine hydraulics to achieve the desired grade.   Lasers are sometimes used in precise machine control applications to provide greater vertical precision when used with GNSS.

3. How are optics used in surveying instruments, and what are the instrument types?   While laser and GNSS technologies have had a major impact on surveying instruments, precision optics are still used for sighting instruments used in optical surveying and in lasers (as previously noted).

  • Sight levels (often automatic, digital)are common optical surveyinginstruments that use an optical telescope to view a line of sight along a level  plane (sometimes sloped if grade set with digital level).
  • Transits are a basic type of theodolite that projects vertical and horizontal angles by optical sighting.
  • Theodolites measure both horizontal and vertical angles.  Most made today are digital.  When an object is sighted through a telescope, the angle of each axis (vertical, horizontal) is measured or set with precision.
  • Total Stations are fully integrated electro-optical instruments, with models for land and construction surveying, the latter having less features, precision, and greater simplicity.  In basic form it combines an electronic theodolite and an EDM, with integral software. Units may use reflecting targets or may be reflector-less. There are also ATS-enabled total station units with the capability to provide positioning without GNSS and also to support 3D machine control.

4. How is GPS for surveying used in construction and land surveying? GNSS/GPS technology is applied to traditional surveying functions as well as earthwork machine control. Primary GPS for surveying system components include base station (containing radio, receiver and antenna), radio modem, rover receiver, data collector and software.  There are a number of possible system configurations depending on the equipment age and manufacturer.

  • Static Surveying – Total stations with integrated GNSS bring a dramatic change to surveying activity over total stations without the capability.  As long as the worksite sky is unobstructed, surveying activity using GNSS can be utilized for land survey work (existing boundaries, land subdivision), or providing location guidance for new construction activity.
  • Machine Control GNSS-based machine control is a 3D solution that may be utilize GNSS individually or in combination with laser or sonic to control heavy construction or agricultural equipment.

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