Gps Technique
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GPS VS CONVENTIONAL SURVEY Like a surveyor’s Total Station, an instrument that measures horizontal and vertical distances, Global Positioning System (GPS) surveying equipment is a state of the art measuring tool. It’s a modern device that provides land surveyors with an alternate method to determine distances. That’s what surveyors do!
elevation for that position. This method requires a line of sight and due to the change in terrain, it also requires the establishment of many set-ups throughout the project area.
With the advent of Real Time Kinematic (RTK) GPS survey techniques, crew chiefs are utilizing both RTK GPS and conventional methods on the same site to complete projects in less time.
With GPS, the same results are achieved, but the base station (GPS receiver) can be located at one nearby position, on- or off- site, and the roving receiver roams the satellites entire area without regard to line of sight. Landfills are a classic application for GPS over conventional methods because they have extreme terrain and are entirely open GPS rover to the sky.
What is GPS? GPS is a system of 24 orbiting satellites continuously transmitting positioning information to observers on the ground. For surveying, a base station (set at a known position) and a roving receiver collects GPS data from the satellites. base station The unknown x, y and z coordinates are then calculated and identified by the GPS receiver through a rigorous triangulation process. The objective is to obtain a horizontal and vertical location of a position or series of positions to produce accurate coordinates (x, y and z values).
The conventional survey method is limited to line of sight, where GPS is not. Conventional survey methods confine surveyors to existing terrain and conditions. GPS survey only needs a clear window to four or more satellites. When using conventional survey methods, such as a Total Station, the instrument is set at a known position then angles and distance are measured by sending an electronic signal to a roving target prism. The prism reflects a signal back to the station. This will determine the coordinates and
Our field crews have consisted of three people surveying on-site at one time. A two-person crew was collecting data using the conventional method, while the third person was acquiring additional data with a GPS backpack unit. As time goes on, GPS equipment and software prices will decrease and more surveyors will have access to this technology. This will result in additional applications for GPS survey techniques to be found and put to use.
Not all projects can solely rely on GPS. Some project areas will require survey by conventional methods to obtain highly accurate positions and elevations under vegetation cover; for instance, property line control base lines. Whereas open areas (parking lot limits, curb lines, parking striping, and light poles) can be collected easier and more cost effectively with a roving GPS unit and a known base station.
One unique application for employing GPS is to scale and level aerial photography. SELLS places the roving unit in an aircraft that takes precision aerial photography and captures the position of each exposure. This is known as Airborne GPS. Truly a state of the art measuring tool!
ADVANTAGES OF GPS OVER CONVENTIONAL SURVEY APPROACHES: ○
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➛ RTK GPS provides the unknown ➛ values instantaneously. ➛ Does not require line of sight. ➛ between basestation and rover. ➛ Allows navigation to a ➛ known position. ➛ Fieldwork can be completed at night. ➛ Not as sensitive to inclement weather.
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Some applications only require one person to complete the project. Airborne GPS to scale & level Aerial Photography The most notable advantage is an expanded geographical area can be surveyed much more cost effectively.
SELLS specializes in Survey & Photogrammetry. For more information, contact an office near you or visit us at http://www.chashsells.com PM07NC
elevation for that position. This method requires a line of sight and due to the change in terrain, it also requires the establishment of many set-ups throughout the project area.
With the advent of Real Time Kinematic (RTK) GPS survey techniques, crew chiefs are utilizing both RTK GPS and conventional methods on the same site to complete projects in less time.
With GPS, the same results are achieved, but the base station (GPS receiver) can be located at one nearby position, on- or off- site, and the roving receiver roams the satellites entire area without regard to line of sight. Landfills are a classic application for GPS over conventional methods because they have extreme terrain and are entirely open GPS rover to the sky.
What is GPS? GPS is a system of 24 orbiting satellites continuously transmitting positioning information to observers on the ground. For surveying, a base station (set at a known position) and a roving receiver collects GPS data from the satellites. base station The unknown x, y and z coordinates are then calculated and identified by the GPS receiver through a rigorous triangulation process. The objective is to obtain a horizontal and vertical location of a position or series of positions to produce accurate coordinates (x, y and z values).
The conventional survey method is limited to line of sight, where GPS is not. Conventional survey methods confine surveyors to existing terrain and conditions. GPS survey only needs a clear window to four or more satellites. When using conventional survey methods, such as a Total Station, the instrument is set at a known position then angles and distance are measured by sending an electronic signal to a roving target prism. The prism reflects a signal back to the station. This will determine the coordinates and
Our field crews have consisted of three people surveying on-site at one time. A two-person crew was collecting data using the conventional method, while the third person was acquiring additional data with a GPS backpack unit. As time goes on, GPS equipment and software prices will decrease and more surveyors will have access to this technology. This will result in additional applications for GPS survey techniques to be found and put to use.
Not all projects can solely rely on GPS. Some project areas will require survey by conventional methods to obtain highly accurate positions and elevations under vegetation cover; for instance, property line control base lines. Whereas open areas (parking lot limits, curb lines, parking striping, and light poles) can be collected easier and more cost effectively with a roving GPS unit and a known base station.
One unique application for employing GPS is to scale and level aerial photography. SELLS places the roving unit in an aircraft that takes precision aerial photography and captures the position of each exposure. This is known as Airborne GPS. Truly a state of the art measuring tool!
ADVANTAGES OF GPS OVER CONVENTIONAL SURVEY APPROACHES: ○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
➛ RTK GPS provides the unknown ➛ values instantaneously. ➛ Does not require line of sight. ➛ between basestation and rover. ➛ Allows navigation to a ➛ known position. ➛ Fieldwork can be completed at night. ➛ Not as sensitive to inclement weather.
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
○
Some applications only require one person to complete the project. Airborne GPS to scale & level Aerial Photography The most notable advantage is an expanded geographical area can be surveyed much more cost effectively.
SELLS specializes in Survey & Photogrammetry. For more information, contact an office near you or visit us at http://www.chashsells.com PM07NC
