What is Aerial Surveying?
What is Aerial Surveying?
Aerial surveying is a geomatics way of gathering information that uses aerial photography or remote sensing imaging from various bands of the electromagnetic spectrum, such as infrared, gamma, or ultraviolet.
It may also refer to a chart or map created by flying over a region and analyzing it. This is normally accomplished with the use of planes, helicopters, and, in the past, balloons.
Because of its superior resolution, clarity, and atmospheric circumstances, aerial surveys should be distinguished by satellite imagery technology.
Today, aerial survey is sometimes used interchangeably with aero photogrammetry, a type of photogrammetry in which the camera is mounted in the air. Photogrammetric technology and methodologies give measurements on aerial photographs.
Aerial Surveying Techniques
In an aerial survey, the goal is to obtain a complete and accurate representation of the world below. There are two main methods for obtaining this information:
- Aerial photography- This is the most popular method used. It involves taking pictures with a camera and analyzing that data later.
- Remote sensing- This involves using sensors to collect data through radio waves, infrared, or ultraviolet wavelengths of light.
- Multispectral– This type of data enables the analyst to see all wavelengths of light at once. They have many advantages, such as being able to see through clouds and other obstructions that would otherwise hide information from the eye.
- LiDAR- LiDAR is a form of mapping that uses light pulses in order to collect 3D data.
The types of data collected by aerial surveys can vary based on the needs of the person who commissions the survey. In general, aerial surveying collects data regarding topography, land use, and engineering structures.
Aerial Surveying History
The history of aerial surveying refers to the times when images were primarily viewed through the use of cameras. Cameras were used as early as the 1920s, and they were first used in aerial photography in 1938.
For most of its history, aerial surveying required a large investment. Therefore, it was mostly used by businesses and governments.
In recent years, however, there has been an increase in personal use of remote sensing technologies to gather data for personal, recreational, and hobbyist purposes.
Aerial Surveying Methods
There are four main methods used to fly in aerial survey.
- Fixed Wing- This is the most common type of aircraft used for aerial surveying. It involves flying an airplane of fixed wings, which allows the operator to generate a lot of lift with their wings at different speeds, thus allowing them to gain height very quickly and accurately.
- Rotary Wing- Rotary wing aircraft are machines that combine the vertical lift capabilities of a helicopter with the horizontal speed capabilities of an airplane. They are used to take a lot of pictures over a large area, and they have a lot more range than fixed wing aircraft.
- Satellites- Satellites, or Remote Sensing satellites, are in space and take pictures from above the atmosphere. These images are not as detailed as aerial photos. However, they can provide incredible clarity and resolution.
- Balloons- Balloons are the least used method of aerial surveying. They are harder to control, and often require the use of a parachute for safety. However, they provide valuable information by taking pictures from a large height above the ground
Aerial Surveying Examples
One example of aerial surveying is the use of airplanes during World War II. Pilots would travel close to enemy lines, taking pictures as they flew overhead. These photos were then used to create maps and visuals of enemy troop movements.
In modern times, aerial surveying is used to make plans for infrastructure. For example, business will take pictures of the terrain in order to plan out where to put their factories.
Aerial Surveying Ethics
There are a lot of ethical issues around the use of aerial surveying. These include:
- Privacy: For example, it is unethical to distract or invade privacy of an individual without consent or permission from them. This is known as “spying.”
- Security: The security of people on the ground should also be considered. For instance, if a controlled detonation is planned, there must be privacy for all involved.
- Human Rights: It’s important to consider the people who live in an area that aerial surveying is being done over. For example, if a government is planning to build a new city over an old population’s lands, they should notify them and give them the opportunity to move elsewhere.
Aerial Surveying Equipment
Aerial surveying tools can be broken into two main categories:
The first category is that of the hand-held aerial surveyor’s toolbox; this consists of:
- Camera- Typically, a small hand-held digital camera. The data will then be analyzed later through the use of a computer and an image processing software package. A more popular piece of technology is the GPS camera which collects large amounts of data at once and then transfers it to a small satellite that can transmit the information back to a central computer.
- Tripod- tripods are typically used in low light situations, such as early in the morning or late in the evening, when hand held units are difficult to see and utilize. Temporary tripods are used to obtain measurements of a structure, such as a foundry or blast furnace.
- GPS- GPS is used in most aerial surveys to obtain position information; in order to map lines accurately, geodesists need to know the precise location of the surveyor at all times. GPS has become an essential tool for aerial surveying and has helped propel it into new technological advancements, such as multi-sensor data transfer and a proprietary software called YRI which is becoming more common.
- Compass- compasses are utilized to obtain bearing information and allow a surveyor to make a visual representation of the map. The most common types are the baseplate compass, which is easily transferable from one place to another, and the transit compass, which is used for high accuracy work done in one location.
The second category consists of the Field mounted toolboxes; these have been developed by companies that have found success in the photogrammetric marketplace. This category consists of:
- Cameras- there are many different types of cameras that can be mounted in the air. The type of camera used will depend on the surveyor and their needs.
- Heads- this is the body that houses and protects the camera, and in some cases, the gimbal stabilizer when a picture is taken.
- Software- software is used to process the data and aid in the quality of the information that is collected.
- GPS- GPS is used in most aerial surveys to obtain position information, it helps with accuracy and allows the surveyor to transfer their hard work onto a map later on.
- Electronic level- these are used, like a transit level, to measure up or down inclines and hills with extreme accuracy; they are also used in multi-sensor applications because they do not require calibration.
- Temporary tripod/monopod- temporary tripods and monopods are used to obtain measurements of a structure, such as a foundry or blast furnace.
Aerial Surveying Usage
Aerial photography is used for surveyors to create an image of the land. This helps determine any topographical features that may alter the route of a proposed development. Images are used for other purposes as well, such as to determine any cultural features or structures that may be present that would inhibit the construction. These images can also be used to provide information about any nearby rivers, roads, or cities where the construction will take place and how it will affect these areas during construction.
The images collected are then processed through a computer and used to create maps of the area. The maps can be used to determine the topography, land use, and engineering structures. In some cases these images may also be used to create an elevation model in order to aid in determining how construction will affect the surrounding areas.
Aerial photography is also helpful for environmental surveys as well as general development planning efforts. Aerial photography is used in areas that do not have sufficient ground resources to sample with traditional methods, such as remote rural areas, forested areas, and wetlands. Images are also collected for environmental studies, such as to determine whether there are any endangered species that may be present.
Aerial photography can be used to create maps of any subject matter; it can be used to create a road map of a country or even just a street map of a city. Images are also taken of buildings, commercial areas and sometimes even individual buildings.
- Asset Mapping
Aerial imagery can be used to create many different types of maps, but mostly it is used to map and assess objects in an asset management light; this is especially useful in areas where there are a lot of natural assets that should be kept protected, such as a national park or wilderness area. The images are then combined with a lot of other data such as satellite imagery, ground control, etc. to create a three-dimensional map of the area.
- Cadastral/Boundary Mapping
Aerial surveys are used to collect data regarding topography, land use and engineering structures in support of cadastral surveying and mapping.
Aerial surveys are used to identify and establish the presence of property boundaries; they are also used to develop owner information, land use designations, individual crop acreages, and a variety of other statistical data that can be used for land management purposes.
- Remote Sensing
Aerial surveys can also be used for remote sensing to create maps and information about a specific area.
The imagery is often combined with satellite imagery, aero metrics as well as ground control to create the final product. Remote sensing can also be used for coastal zone monitoring; this is especially important in areas prone to flooding and erosion from high winds, storms and water level changes.
Aerial surveys are used to collect data in support of climatic surveys, especially when the area is at risk from snow or ice drifting. These images are often taken during the winter months to determine ice-influenced land cover, ice cover as well as snow cover quality to determine if there are any issues that need to be addressed.
Aerial Survey procedure
- To begin the survey, a surveyor will determine where they are going to start the project and set up temporary facilities. Surveyors must be aware of their surroundings and take the necessary precautions such as identifying their location on a map and having detailed maps of the area.
- Surveyors will then begin taking photographs at regular intervals so that they can create a map that uses all of the information gathered throughout the process.
- Once the survey is complete, surveyors will then use a computer to prepare the data for review and/or for further processing.
- Once the data has been processed, it will be uploaded to a computer where additional information can be added or modified if necessary.
- Finally, the surveyor will print out a copy of the information that they have collected and use it as a baseline for any future studies/projects that may need aerial photos as a part-time method.
The major steps in an aerial survey thus are;
1) Surveyor sets up temporary equipment and facilities. Note the location on a map.
2) Begin photography at regular intervals.
3) Processing. The surveyor will have to lay out the various features on the photos, scale them and position point with reference to known features on the ground, or in some other way mark them.
4) The processed original photos are edited to remove unwanted marks and retouching is done where necessary.
5) The compiled information is then transferred to a computer map, along with any other information gathered.
6) Further work can be done by the surveyor; this includes the printing of the information on paper or to an electronic format.
7) The final product can be used for a number of purposes including engineering and land use planning.
Challenges of Aerial Surveying
- Even though aerial photography is now a very common method for survey, it still has its challenges. One of the larger issues is dealing with uncooperative terrain. This includes tall vegetation, heavy tree limbs as well as dense undergrowth that can make it difficult for the aircraft to see certain areas.
- Another issue that is being faced today is dealing with modern changing weather conditions that include man-made pressures such as aircraft and infrastructure obstructions that create blind spots where natural terrain was obscured by the surveyor’s vision.
- The last issue that surveyors must deal with is privacy. Most aerial surveys have to have permission from the land owner to take photographs on their property.
If the surveyor is taking photographs of private property, they may have to take special steps to ensure that they do not invade the privacy of individuals in their area of interest; this includes trying to stay at least 100 feet away from any residential areas and being sure not to take pictures of anybody without their permission.
- The other main issue with aerial photography is the cost. The price of the photos and data that are collected during an aerial survey can easily cost between $500 – $10,000 US dollars or an average of $15 per acre (depending on the area).
The costs that are involved in aerial surveying vary quite a bit depending on who is performing the work and what level of service they choose to provide.
- Aerial surveys can also pose a lot of hazards to surveyors, especially those that do not have much experience with them.
The most common issues that arise include;
1) Terrain obstruction – this is the biggest issue with aerial surveying as any change in terrain can hinder the surveyor’s line of vision and affect the quality of their photographs.
2) Logging and construction – Often times, these projects make it difficult for surveyors to get the adequate coverage that they need in order to get all of their data; this can also make it difficult for them to ensure the accuracy of their final product.
3) Animals/Deer/Bird – These animals can distract the pilot causing a loss of control of the equipment; this can result in accidents that could have been prevented if they had been paying close enough attention to their surroundings.
- Finally, a good surveyor needs to be able to stay on schedule and meet the deadline. If certain factors begin to slow the project down, it could end up costing the surveyor more time and money in order to meet those deadlines.
How much does an aerial survey cost?
The cost of the aerial survey will depend on factors that include the size of the area and the number of photos that are needed.
How long does it take for an aerial survey to be performed?
This really depends on a number of factors that involve the terrain, how cooperative it is, weather complications, etc. It also depends on how much information needs to be gathered from the photographs; this mostly affects how long it takes to set up camp and get everything set up.
Where do these photos come from and why are they called “satellite” photos?
Aerial photography is a very common method that is used in many cases. Photos of this type are usually taken from aircraft that are made to travel very high in the air. There are many different types of aerial photography systems, but most of them use satellites as their main source of information.
What are the key challenges facing modern day Aerial surveying?
This really depends on who you ask and what they are trying to use aerial photos for. Most of the issues that arise depend on terrain obstruction and weather conditions.
Why is it important to get permission before taking aerial photographs on private property?
Aerial surveying is by no means illegal, but it is important to get authorization from the owner of any property that you want to take photos of. If you do not have permission, then some people may question the legality or validity of your survey.
How are aerial surveys done?
During an aviation survey, a plane employs LiDAR technology and GPS data to swiftly scan an area as it flies overhead. Airplanes offer a better method to swiftly scan huge regions, such as when doing exploratory surveys before deciding on a location.
What are the technical terms used in aerial surveying?
Other key ideas in aerial photography include stereoscopic coverage, fiducial markers, focal length, roll and frame numbers, and flight lines and index maps.
Why are aerial photographs important?
Aerial photographs provide a large amount of valuable information that people can use to make decisions. Images can be used to show the areas of a particular township, land or city as well as any structures built on it.
Aerial photographs can also help surveyors see the effects changes in area conditions will have on any constructed structures, and they can be used to show the locations of any risks or issues that an area may contain.
What does an aerial survey encompass?
An aerial survey is an act of gathering data from an aircraft. This data can be used for a number of purposes including engineering and land use planning.
The most common types of aerial surveys include:
1) Topographic surveys – these types of surveys are used to create maps that can help engineers and other professionals to create calculated layouts for roads, bridges, buildings and other potential infrastructure projects.
2) Cadastral surveys – these are also land-use types of surveys that are used to determine the boundaries of a certain area. These areas can range from a small piece of land to an entire county or state.
3) Aerial Photography – this type of survey is used to take photographs from an aircraft in order to get a better aerial view of the area. These photos are then turned into data that can be used by other professionals.
4. Is topographic data the same as aerial photography?
No. Topographic data is the process and analysis of preparing maps that are used for the purpose of engineering and land use planning. Aerial photography is one type of survey that can be used to create these maps.
However, it is not a requirement for a surveyor to be able to take photographs in order to create topographical maps or products as they could purchase them instead from satellite imagery or other sources with aerial photography capabilities.