Remote Sensing

Acquisition of information about a certain phenomenon or an object without making any physical contact with it is called remote sensing. It generally refers to the use of aerial sensor technologies that do detect and also classify objects in the atmosphere, earth surface and also in the oceans through some propagated signals, for example satellites or electromagnetic radiation that is emitted from an aircraft.

Passive Remote Sensing

When passive sensors are used to detect natural radiation that is reflected or emitted by an object or the surrounding area is called passive remote sensing. Sunlight that is reflected by objects or surrounding areas is the most common source of radiation that is measured by the passive sensors. Infrared, photography, charge-coupled devices and radiometers are examples of passive remote sensors.

Active Remote Sensing

Active remote sensing is where some energy is emitted in order to scan objects and areas. The sensor then detects and also measures the radiation that is back-scattered or reflected from the target.

The LiDAR and the RADAR are examples of active remote sensing where the time delay between emission and the return is measured, the location, height, speed and the direction of the object are also established.

Advantages of Remote Sensing

One of the advantages of remote sensing is that it’s possible to collect data in dangerous and inaccessible areas.
There are various applications of remote sensing that includes monitoring deforestation in areas like the Amazon Basin, depth sounding of coastal  and ocean depths, and glacial features in Antarctic and the Arctic regions.

The military use remote sensing in times of war to collect data in dangerous areas. It also replaces slow and costly data collection on the ground and it ensures that objects or areas are not disturbed in the process. Data collected is used to analyze and compare things like pollution, forestry, erosion, land use and weather among other uses.

Digital Photogrammetry - A Brief Overview

Photogrammetry is the study of overhead images to determine topographical properties.  Digital Photogrammetry is the use of computers to ascertain the measurements of objects in these overhead images.  The images are carried out primarily from airplanes that can take overlapping photographs or videos of a given area to get full coverage of what is required.  Satellites can also be used to produce the images.

What is Digital Photogrammetry?

Digital Photogrammetry is used with photogrammetric software to calculate spatial relationships.  Most commonly used for the creation of topographical maps, it is also used in architecture, plastic surgery, manufacturing, forensic investigation and by the military forces.  The military make great use of digital photogrammetry to plan missions, track fugitives and direct missiles.

Important Variables to Digital Photogrammetry

In digital photogrammetry there are several variables that are of importance.  The first point is the necessity of the photogrammetrist to have a full working knowledge of the camera or video involved.  This is important as the type of camera, the focal length of the lens and/or the distance from the camera to the point of interest is critical.  Often a special type of camera, called a metric camera is used to take these photographs as it is calibrated to be able to take images with very minimal lens distortion.

The second point to note well when working with digital photogrammetry is the desired result that is required of the images.  Two dimensional (2D) measurements such as the height of a mountain or the width of estuary may be all that is required many projects and can be determined from single images.  However, if a three dimensional (3D) measurement is required such as the width, length and height of a building, then the process becomes a lot more detailed as it requires information from a lot more photographs.

Stereophotogrammetry - 3d Modeling

The procedure of creating 3D models is another field again, known as stereophotogrammetry.   Stereophotogrammatetrists are able to analyze several photographs taken of the same object from a variety of angles.  Common points of reference shared by the photographs or where they overlap allow them to create a digital 3D model.  These images can then be mapped together, megapixel by megapixel to create an image of measurable space in each of the three dimensions.

The third critical variable to take into account is the type of photographs used.  These are usually video or still digital camera photographs.  Videos need to be uploaded into computers to allow them to be used in digital photogrammetry.


Types of Photographs Used in Digital Photogrammetry

Two main types of photographs used are aerial and close- range photography.  Obviously aerial images are taken from a fixed video or digital camera mounted underneath an airplane.  Topographical mapping is done by using this technique.  The airplane flies over a given area of coordinates on a meandering flight path so as to enable the images to be overlapped.

Close- range or terrestrial digital photogrammetry uses images taken from closer proximity with hand held or tripod mounted cameras.  This is what allows the third dimension to be utilized- giving the means whereby 3D laser modeling of items such as buildings can be used portraying designs in development proposals.  This method is also used on movie sets when creating scenes.

In general, digital photogrammetry is a very important field to determine many factors in varied areas of applications.  Without it, it would be very difficult to create architectural images, create accurate maps, create movie scenes, direct armed warfare and to observe global changes as they occur.

3D GIS Software: Mapping The Future

3D GIS software has been shown in fancy science fiction movies for the past few years. However, what once was a fragment of our imaginations is already here. Technology has made it possible to utilize it for the advancement of our society. Geographic information systems now give us prized information about areas around us and even the whole world.

What is 3D GIS (Geographic Information Systems)?

Geographic information system technology has long been used for developing and planning cities, building various infrastructures, strengthening national defense, and many more uses both for public and private companies. Information gotten from these systems offer valuable data to help improve our community and our society today. As early software might display their scans in 2D, 3D nowadays is beginning to be the standard.

Technology has introduced these three-dimensional systems to both public agencies and private companies. Their choice of software typically is influenced by two important things such as budget and usability. Such software may prove to be a bit expensive, but the information is deemed to be very crucial. However, it doesn't stop other agencies to find the best possible deal in sourcing such software to use with their own systems.

Usability has also become quite important. Software which is too complicated can prove to be very confusing especially for those who are not quite trained to use such software. A lot of systems nowadays tend to simplify their software so more people can easily learn to use it and thereby apply it to their own advantage. Simple, yet effective software should be kept in mind.

How can 3D GIS software help us to change the world?

Answers typically given include the valuable information that they can give which is near-perfect just like what you see in real life. Scans of the insides of infrastructures, the whole plan of the city and how you can plan a certain area by taking into consideration the earth's crust is definitely important data.

As an example of its importance, urban planning can never be the same once you've got a 3D model of the city. You get to actually see what is inside, what is in a particular place, what lacks in a particular area and many more. Engineers, city planners, architects and other people can then suggest the best possible solutions to existing problems.

All in all, 3D GIS software can be the start of a great change for us to see our world in a whole different way.

Aerial Photography: Choosing The Proper Company

Aerial photography has a lot of different types and functions. Knowing specifically what you need will help you to determine what a company can provide the best services to you.

You will need to know what you require photography of. Some frequently requested services include real estate photography, records of weddings and special events, and surveying data collection. Once you have determined what you need the photographs for, you can start looking into the platform to be used (where the picture will be taken from). Some of the best methods are from kites, balloons, remote controlled helicopters, and manned aircraft.

Real Estate Aerial Photography

The best way to take pictures of real estate is from remote controlled helicopters. They can fly around the property providing different angles and views. If the wind permits, kite and balloon pictures may also be beneficial, but may not produce the desired results. If a lot of properties are being photographed, manned aircraft might be a better choice.

Aerial Photography for Weddings and Special Events

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Some people desire aerial photography of a wedding or special event. Kite and balloons can provide very good photographs, but they require that the wind cooperate. They are strongly recommended because they can remain stationary and are silent. Remote controlled helicopters are also used, but they can be distracting.

Aerial Photography for Land Surveying

High altitude is usually required for surveying, so manned aircraft are almost always used. Some companies are now providing GPS stabilized remote controlled helicopters that can reach higher altitudes for more affordable rates.

Once you have chosen a platform to be used, you will need to decide what type of photographs you desire. There are three types of photograph styles: vertical, oblique, and panoramic.

Vertical

These photographs are straight down shots and are primary used when being able to plot and calculate distances is very important. Photographs are typically considered bad if the angle of the photo exceeds three or more degrees. Real estate and survey companies usually get the best results from vertical photographs because they can use them to plot specific points against maps of an area of interest.

Oblique

Oblique photographs are taken at an angle and can either be high angle or low angle. The only difference between the two is that high angle includes the horizon and low angle does not. These types of photographs are of particular interest during special events and to real estate companies.

Panoramic

Panoramic shots incorporate multiple photographs that are taken in rapid sequence and are joined together to make one wide image. Survey companies usually benefit the most from these photographs.

Choosing the right types and platforms form aerial photography will help ensure that you select the right company to do the job for you.

How to Evaluate Good Photogrammetry Companies

Photogrammetry is a term used to describe the science of measuring land reliably via photographs. This is usually done using aerial photos for purposes of land surveys. Land surveying is an extremely complex and painstaking task that should only be done by professional surveyors.

The best time to look for good photogrammetry companies is when you don’t actually need one. It’s good to have an established relationship with a company so that you can call on them with confidence when you have a land surveying project that needs attention.

The first thing you should do is check out the company history to be sure that the company you are considering is established, experienced and competent. Talk with some of their former clients and look at some of their projects. If this all checks out, go on to look at the services they provide and the technology they use.

When undertaking aerial surveying, it is absolutely essential to use the most up-to-date equipment possible. Here is the equipment you should expect a good photogrammetry company to have on hand:

They should have equipment for low altitude mapping photography (LAMP) which is a technology that is conducted with digital cameras used to take images of land and structures at an altitude of about three hundred feet. The main uses of LAMP are park planning, road planning, patrolling pipelines and power lines, aerial mapping and assessments conducted by real estate representatives.

A good photogrammetry company should also have light detection and ranging technology (LiDAR). This equipment is used for measuring the properties of scattered light. This allows collection of information on properties and objects that are quite far away. It works by utilizing laser pulses that can measure the distance to a surface or an object. It does this by keeping track of the time that transpires between broadcasting a signal and detecting its reflected signal.

LIDAR can be used in conjunction with a global positioning system (GPS) to gather information about elevation and location. This information is used to create topographical maps that are useful to law enforcement personnel, military personnel, people interested in conservation projects, astronomers, biologists, physicists, meteorologists and geologists.

LIDAR and GPS can also be used in conjunction with topographic maps, stereo photogrammetry, Doppler radar, inertial surveys and digital terrain modeling (aka: digital elevation modeling) in a number of applications. These include: engineering, farming, creating relief maps, base mapping, infrastructure design, precision forestry, geographic and geometric terrain analyses.

It can be hard to find a good surveying company, but it is absolutely essential if you want to get a proper, usable survey. If you don’t invest in a good surveyor, you may end up wasting a lot of time, energy and money in the long run. If you make all your calculations based on faulty data, you are bound to end up in trouble.

By becoming familiar with a company in advance and ensuring that they have all of the equipment and expertise necessary to deliver competent, accurate services, you can feel confident you are hiring just the right photogrammetry company for your project.