by James Caviness
Land surveying is the process of measuring the elevation, angles, and boundaries of natural and man-made structures and mapping their relative locations to accomplish one of many different objectives. Land surveys are necessary for providing information to homeowners, city planners, conservation projects, municipalities, or countless other people and organizations who work within a geospatial world.
Surveyors use sensitive instruments to perform precise measurements of different features of the environment around them. With a wide range of uses for this type of data, there are myriad types of surveys to accomplish different objectives. A real-estate agent may need to see the boundaries of the property, but the changes in elevation may be of little concern. Likewise, a crew looking to break ground on a large building may be very concerned with even slight changes in elevation, but not as much as the perimeter of the property itself. Different tools are used to achieve different results, and there is a potential solution for just about any geospatial problem.
7 Different Types of Land Surveying
1. Boundary Surveys
Boundary surveys will show the perimeter of the parcel of land being surveyed. This type of survey is performed first by obtaining a map of the approximate property boundaries from a town hall. This map will show you the approximate borders, but more importantly, the corners and the distance between markers. Keep in mind some of these may be long distances, yet precise measurement and accurate measurement are needed. Next, using a metal detector and a long measurement tape, start at one corner and walk the distance shown on the map. Once you've reached the approximate distance, you can use your metal detector to locate the actual property marker. It is wise to trace back and mark off the border with tape, stakes, or paint. If you are searching through some tougher terrain or brush, a magnetic locator might be helpful, as magnetic locators will have better range and sensitivity to the long iron property markers.
2. Construction Surveys
A construction survey is conducted within a construction site. This type of survey will use stakes to mark off roadways, underground utilities, walls, and buildings on the site. In general, this type of survey is used to provide construction workers direction when working on developmental plans. This technique is also used to mark off horizontal or vertical grading along with the slope in addition to an as-built survey.
3. ALTA/ACSM Surveys
Typically used in commercial real estate, the objective of an ALTA/ACSM survey is to show existing improvements on a specific site. This type of survey will also show any easements, zoning classifications, and any other notable features. Ultimately, the information from this survey will be by a title holder to obtain an American Land Title Association or Extended Title Coverage insurance policy, so it must be thorough. In general, this category of the survey is used for commercial real estate for improvements and zoning. This type of survey can take weeks to several months.
4. Location Surveys
A location survey is similar to a boundary survey but will also include information from within the structure or home. This survey is generally provided to fulfill zoning requirements or for a loan application.
5. Site Planning Surveys
A Site Planning survey will combine the benefits of the boundary survey as well as a topographic survey. This will give representation to the outer perimeter of the parcel, as well as any topographical changes on the surface that may be relevant before beginning a project. Site planning surveys are used in commercial and residential projects and provide great general information before breaking ground.
6. Topographic Surveys
Topographical surveys are some of the most significant and are only performed by civil engineers. A topographical survey will aim to locate roads, ditches, waterways, embankments, utilities, contours, or any other improvements like walls or fences. The resulting map will include all natural and man-made features in the area. A topographical survey aims to be comprehensive and can be used to fulfill requirements for local or state governments.
7. Subdivision Surveys
Subdivision surveys are used to divide one larger parcel of land into several smaller units. These types of surveys are used by local government agencies for long-term planning. These subdivisions go hand-in-hand with proper zoning when used for city planning.
Land surveys are creating maps of land boundaries. Population surveys are used to understand the demographics of an area, such as age and gender breakdowns. For surveys on commercial buildings, a building surveyor inspects the property for damage and anomalies before purchase.
The main system used in the United States today is called the public land survey system (PLSS). The PLSS is used to determine the boundaries of property ownership. Interestingly Thomas Jefferson was the first to use the PLSS in the 1700's.
Types of Survey Applications
Surveying can be broken down into different areas such as structural engineering, environmental engineering, landscaping, and civil engineering. Structural engineers might survey to check for cracks in bridges or create plans for new buildings' foundations, or survey locations for utility lines.
A land surveyor will use a range of land survey equipment and tools, from simple handheld tools like a compass to computers and more complicated machinery. Some common land survey tools include:
(EDM): EDMs are surveying instruments used for measuring horizontal and vertical angles. The most basic type is a laser which emits a single point on the target object and is read by another device with an eyepiece, but accurate measurements depend on the person's sight.
Measuring wheels are one surveying tool nearly everyone has noticed when driving by a land survey. Think of a measuring wheel as a rolling tape measure that a surveyor pushes as they walk. A simple yet needed survey instrument.
Theodolites are survey instruments that measure horizontal and vertical angles and distance. This is achieved by rotating sighting tubes called alidades over 360 degrees with the help of a calibrated scale inside. It also includes a compass that can measure magnetic bearings relative to the true north.
The most accurate land surveying equipment, a robotic total station, is used in difficult terrain where a human cannot move easily. Total stations allow for accuracy in these situations. This surveying instrument achieves distance measurement and is a staple in the land survey equipment market.
A surveying tripod is used for measuring the angles and heights of objects.
Typically, a surveyor's level is used to transfer the sightline or cannot be set on surfaces that are not flat. Some popular choices are laser levels and other equipment from Leica geosystems. These include a GPS (Global Positioning System) receiver and software that gives the current position of the user, as well as other data such as elevation. The information about the position is compared to the known positions of latitude and longitude to make it possible for users to map and record their surroundings.
Unmanned aerial vehicles - While land surveyors surveying Global navigation satellite systems (GNSS) such as North America's Global Positioning System, Russia's GLONASS, or China's BeiDou are global navigation systems that rely on satellites to give accurate positioning data. Google Earth is an excellent example of a system that uses satellite imagery and maps to allow users to view different geographical locations from above.
Survey Data Collection
Survey data includes 3d model surveys, laser scanning, 3d scanners, and drones. 3d model surveys consist of using a three-dimensional scale to determine the size and shape of an area. Laser scanners are used similarly to measure overall dimensions along with individual objects such as trees or buildings. Drones allow users to take aerial photos for mapping purposes. With the help of a 3D scanner, quick and easy data collection is possible.
Data collectors collect information in different ways for different purposes. Some survey data collection terms include:
- Vertical datums are chosen depending on the area being surveyed. They may be chosen from a local level, ellipsoid height, mean sea level, or another plane. A plane is the most common type of vertical datum.
- A horizontal reference system is used for projects that require measurements in horizontal angles, such as building construction, mining, etc.
- A vertical reference system is used for projects that require measurements in vertical angle or angles, such as the construction of dams and roads.
- Inclination measures how far off a horizontal line on a map is relative to an established datum plane, horizontally if using a horizontal datum, or vertically if using a vertical datum.
- The term derives from the practice of leveling a region to compensate for the curvature of the earth's surface.
Copyright 2021 Detector Electronics Corp. - Revised August 2022