แสดงบทความที่มีป้ายกำกับ Surveys แสดงบทความทั้งหมด
แสดงบทความที่มีป้ายกำกับ Surveys แสดงบทความทั้งหมด

วันอังคารที่ 20 ธันวาคม พ.ศ. 2554

The Different Types of Land Surveys

While most people think of land surveys in the most basic sense, the drawing of the boundaries of a property, in actuality there are many varied and different ways of surveying that service many different industries. Property surveys are a large part of the business, but there are also surveys and surveyors that service the construction industry, the environmental sector, and many others. The kinds of surveys that are conducted would surprise most people, and some things that you might think are surveys aren't surveys at all. Instead of the standard two-dimensional measuring from one point to another, today's surveys not only measure the land, but also the air and water above and below us.

The most common and well-known surveys conducted today are boundary surveys, mortgage surveys, and topographic surveys. An ALTA survey, which is actually a shortened title for ATLA/ACSM, combines elements of all three, with a set of standards put forth jointly by the American Land Title Association and the American Congress on Surveying and Mapping. ALTA surveys are most commonly used for commercial properties; by having a universal standard, companies can assure themselves of the level of thoroughness and be confident when the results are guaranteed by an ALTA survey.

Boundary Surveys are exactly what the name describes: a survey to establish the true boundaries of a given property. Through previously recorded markers and the establishment of new landmarks, a surveyor will establish the true boundaries of a property and then mark the corners and lines of the plot, using markers such as iron rods, pipes or concrete monuments in the ground, or nails set in concrete or asphalt. In the past, piles of stones, trees or other, less permanent markers were used, which led to confusion when the markers were either destroyed or changed.

Mortgage Surveys are simple surveys that, for the most part, determine land boundaries and building locations. They are usually required by title companies and lending institutions when they provide financing to show that there are no structures encroaching on the property and that any structures on the property meet current zoning and building codes. It is important to ensure that you are getting an officially licensed mortgage survey performed by a licensed land surveyor, and not a mortgage inspection, which is a substandard survey which does not adhere to any set standards and is not regulated or accepted as an official land survey.

Topographic Surveys are land surveys which locate natural and man-made features. For example, buildings, improvements, fences, elevations, land contours, trees and streams. These are then measured for their elevation on a particular piece of land, and presented as contour lines on a plot. Topographical surveys are sometimes required by the government. Engineers and architects also use topographical surveys to aid in the design of improvements or developments on a site.

One of the largest and most rapidly growing segments of land surveys are in the construction industry. Surveys are crucial tools from inception and planning, to actual construction and maintenance afterwards. Most construction surveys fall under the discipline of civil engineering, which may require additional degrees and certifications in order to conduct. All construction projects begin with the Plot Plan or Site Plan, which sets out the plan for the entire project, including all existing and proposed conditions on a given site. As-Built Surveys are conducted several times during a construction project to verify for local and state boards that the work authorized was completed to the specifications set on the plot plan. Foundation Surveys are a type of as-built survey which collects the positional data on a foundation that has been poured and is now cured. Foundation surveys are done to ensure that the foundation has both been constructed in the proper location and has been built in the proper manner according to the plan.

For existing structures, a Deformation Survey determines if a structure or object is changing shape or moving. By the taking of three-dimensional positions on specific points on an object, then letting a period of time pass before retaking and measuring the points, a determination of whether a structure is moving can be made.

Although it may seem counter-intuitive, land surveyors are also responsible for performing Hydrographic and Bathymetric Surveys. Hydrographic surveys collect data relating to any body of water, and the data collected may include the water depth, bottom contours, the direction of the current, observing and recording high water marks and water levels, as well as location of fixed objects and landmarks for navigational purposes. They can also be conducted to gather information for engineering or resource management purposes, such as hydro power plants. Bathymetric surveys deal exclusively underwater, and map the seabed profile.

Geodetic surveys fall under both the land and water category, as they map out the shoreline. Thomas Jefferson commissioned a geodetic survey in 1807 as the Survey of the Coast. Progress on the survey moved slowly at first, as they did not even have the proper instruments to perform the survey until 1815. It still exists today as the National Geodetic Survey and its responsibilities now include the interior lands of the United States as well as its coasts.

Wetlands Delineation and Location Surveys belong in a category all on their own; they are performed when construction work that is being planned on or near a site containing defined wetlands. Local, state, or federal regulations vary, but wetlands are usually classified as areas that are completely inundated with water more than two weeks during the growing season. Boundaries of wetlands are determined by observing the soil colors, vegetation, erosion patterns or scour marks, hydrology, and morphology of the land in question. Data is then collected on the locations of the placed flags and a plan is drawn to reference the boundary of the wetlands and compare it to the proposed boundaries of the surrounding plots or parcels of land and the construction work proposed within.

While there are many more forms of land surveys, to list them all and their attributes would result in a very long article. The options presented above are simply the most common forms of land surveys, and the ones that the general public is most likely to encounter.

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วันอังคารที่ 25 มกราคม พ.ศ. 2554

Engineering Surveys

Engineering surveys are those that are associated with all aspects of engineering design, such as topographic, as-built and layout. Engineering surveys are usually much more advanced than those created by civil engineers and serve additional purposes.

They must be conducted by licensed surveyors. There are several exams and qualifications that a surveyor must attain before being able to practice engineering surveying in the USA.

What are they used for?

The main purpose of is to assess and determine the conditions of a building site either pre or post construction. They can also help assist builders, architects and civil engineers in preparing base plans.

Engineering and building surveys are an essential part of all large building constructions including roads, railways, dams, bridges and residential areas. Civil engineers in particular rely heavily on them.

Types

Engineering surveys are a very broad category and include a range of different types to suit different purposes.

Typically they can be divided into three survey categories: planning, design and construction.

Planning surveys are completed prior to construction work at a particular site. Within planning surveys there are also investigation and channel alignment surveys. Investigation surveys can include such elements as: vertical control, gully, valley and channel cross-section surveys, and reservoir area surveys. In many cases all these different types of engineering surveys will be required to get a full picture of the site situation.

Design surveys are a group of surveys that are done during the design phase of construction - after the planning have been completed. Types nclude: structure site and channel surveys.

Finally, construction surveys are a very important category of engineering surveys. These can be done both during and after construction has been completed. Their purpose is both to keep a check over the construction process as well as to maintain the buildings once they are complete. Embankment, principal spillway, existing channel and emergency spillways surveys are just some examples of construction surveys that may be required.

Methods

A variety of methods are used for conducting these surveys - and the methods will change depending on the particular job at hand.

One of the most modern and cost-effective methods of conducting engineering surveys is using a method called lidar surveying.

Lidar surveying uses three-dimensional scanners to provide high definition measurements for use. They provide the highest possible level of detail for both interior and exterior buildings. This method, however, is only suitable for use with already-built buildings, not prior to construction.

Engineering surveys can cover a wide range of features relating to a building or construction site, even including the underground waterways. The types of features they are required to add to their survey will influence what apparatus and tools they use.

There are a range of apparatus used by professional surveyors, including theodolites, total stations, dopplers and GPS.

Some of the methods engineering surveyors may use include: differential leveling, which uses a tripod and mounted telescope to measure angles and lengths; and trigonometric leveling, using the mathematics of trigonometry.

There are also usually several people involved in the surveying process. Engineering and building surveys are very complex and cannot be completed alone. Some of the workers that may be involved include: field engineers, hydrologists and planning engineers.

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