Unit 5 – geodesy as a career

There are many different types of careers that fall into the category of environmental sciences. Geodesy is one of them. Geodesy is the scientific discipline that deals with the measurement and representation of the Earth, including itsgravitational field, ina three-dimensional time-varying space¹ as well as with location of fixed points on the Earth. At one time, all work done in the field of geodesy was based on land surveys. Now, land surveys are done in conjunction with the use of satellites.

Surveying or land surveying is the technique and science of accurately determining the terrestrial or three-dimensional space positionof points and the distances and angles between them. These points are usually associated with positions on the surface of theEarth, and are often used to establish landmapsandboundariesforownershipor governmental purposes. In order to accomplish their objective, surveyors use elements ofgeometry,engineering,trigonometry,mathematics,physics, andlaw. Furthermore, a particular type of surveying known as "land surveying" is the detailed study or inspection, as by gathering information through observations, measurements in the field,research of legal instruments², and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, judicial surveys, and space delineation³. Land surveying can include associated services⁴ such as mapping and related data accumulation, construction layout surveys⁵, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys⁶, and the analysis and utilization of land survey data.

Surveying has been an essential element in the development of the human environment since the beginning of recorded history (ca. 5000 years ago) and it is a requirement in the planning and execution of nearly every form of construction. Its most familiar modern uses are in the fields oftransport,buildingand construction,communications, mapping, and the definition of legal boundaries for land ownership.

Surveying equipment. As late as the 1990s the basic tools used in planar surveying⁷ were a tape measure for determining shorter distances, a level for determining height or elevation differences, and a theodolite, set on atripod, with which one can measure angles (horizontal and vertical), combined withtriangulation. Starting from a position with known location and elevation, the distance and angles to the unknown point are measured. Electronic distance-measuring devices had made field surveys easier and more accurate, while much improved circle graduation has made theodolites (transists) lighter as well as more precise. A more modern instrument is atotal station, which is a theodolite with an electronic distance measurement device (EDM) and can also be used for leveling when set to the horizontal plane. Since their introduction, total stations have made the technological shift from being optical-mechanical devices to being fully electronic with an onboard computer and software. Moderntop-of-the-line total stations⁸ are fully robotic, and can even e-mail point data to the office computer and connect to satellite positioning systems, such as aGlobal Positioning System(GPS), a device used to help define a location and map it in relation to other spots on the planet. This is something that can be quite useful to geodesists who use GPS in their field of work. With the use of a GPS device, geodesists can locate the exact position of any object on the surface of Earth which gives them valuable information without the need to physically travel to locate or chart specific things. Though real-time kinematic GPS systems have increased the speed of surveying, they are still only horizontally accurate to about 20mm and vertically accurate to about 30-40mm. However, GPS systems do not work well in areas with dense tree cover or constructions. Total stations are still used widely, along with other types of surveying instruments.One-person robotic-guided total stations⁹ allow surveyors to gather precise measurements without extra workers to look through and turn the telescope or record data. A faster way to measure large areas (not details, and no obstacles) is with a helicopter, equipped with a laser scanner, combined with a GPS to determine the position and elevation of the helicopter. To increase precision, beaconsare placed on the ground (about 20km apart). This method reaches precisions between 5-40cm (depending on the flight height).

Satellite navigation

Surveying as a career. The basic principles of surveying have changed little over the ages, but the tools used by surveyors have evolved tremendously. Engineering, especially civil engineering, depends heavily on surveyors. Whenever there areroads,railways,reservoir,dams,bridgesor residential areas to be built, surveyors are involved. They establish the boundaries of legal descriptions and the boundaries of various lines of political divisions. They also provide advice and data forgeographical information systems(GIS), computer databases that contain data onland features¹⁰ and boundaries. A geographic information system (GIS) is any system that captures, stores, analyzes, manages, and presents data that are linked to location. In the simplest terms, GIS is the merging of cartography and database technology. GIS systems are used in cartography,remote sensing,land surveying,photogrammetry,geography,urban planning,emergency management¹¹, navigation, andlocalized search engines¹². In the strictest sense, the term describes any information systemthat integrates, stores, edits, analyzes, shares, and displaysgeographicinformation. In a more generic sense, GIS applications are tools that allow users to createinteractive queries (user-created searches)¹³, analyze spatialinformation, edit data, maps, and present the results of all these operations. Surveyors must have a thorough knowledge ofalgebra, basiccalculus,geometry, andtrigonometry. They must also know the laws that deal withsurveys,property, andcontracts. In addition, they must be able to usedelicate instruments with accuracy and precision¹⁴.

What does a geodesist do? A geodesist measures the Earth's surface. He studies the science and shape of our planet as well as its gravitational field. A geodesist measures the size of the Earth on a global scale and also specific regions of land known as fixed points. By doing so, crustal shifts and polar movement can be detected. Measurements can determine rate of movement and other pertinent information. A geodesist assigns 3 dimensional points on, above and below the surface of the Earth to measure the average depths of oceans, mountain peaks and also abnormalities in the surface of the Earth. The field of geodesy also includes the study of tides as well as crustal and polar motion¹⁵. The field of geodesy developed from the human need to understand the world in which we live. As it was once believed that our world was flat, we now know much more about our planet through specialized fields such as geodesy.

Notes:

1. …in a three-dimensional time-varying space… 2. …research of legal instruments… 3. …space delineation 4. …associated services… 5. …construction layout surveys… 6. …horizontal and vertical control surveys… 7. …planar surveying… 8. …top-of-the-line total stations… 9. one-person robotic-guided total stations… 10. …land features… 11. …emergency management… 12. …localized search engines 13. …interactive queries (user-created searches)… 14. …delicate instruments with accuracy and precision 15. …crustal and polar motion

– в постоянно изменяющемся во времени трехмерном пространстве – изучение юридической документации – обозначение границ – сопутствующие виды деятельности – геодезические разбивочные работы – съемки планового и высотного обоснований – плановая съемка – новейшие (самые современные) тахеометры – автоматизированные электронные тахеометры, управляемые одним оператором – особенности рельефа – служба скорой помощи – местные системы поиска – интерактивное общение с пользователем – высокоточные приборы, требующие аккуратного (острожного) обращения – движение земной коры и полюсов