A fisheye lens can see wider than any other type of lens. Lens designers spend much of their time ensuring that the natural tendency in optical lens combinations to exhibit geometric distortion like barrel distortion (where vertical and horizontal lines curve outwards) or pincushion distortion (where the lines curve inwards) is minimised. Such lens designs are rectilinear; straight lines are reproduced as straight lines. A fisheye lens is completely the opposite and known as curvilinear.
Why are they called fisheye? Curvilinear lenses typically comprise a large dome-shaped front element, which resembles an eye of a fish. More importantly, a fisheye lens usually has a very wide angle of view. The most definitive form of fisheye lens can record detail from a 360° view of 180°. That view is recorded as a circular projection onto the frame, and a lens that manages this is called a circular fisheye. These are relatively rare and most fisheye lenses are of the full frame variety.
So-called true fisheye lenses have a 180° angle of view, while many fisheye conversion lenses that fit onto the end of normal rectilinear lenses see a less wide field of view and retain curvilinear distortion. Some fisheye lenses, like the rare Nikkor 6mm f/2.8 built in small numbers in 1972, have a field of view exceeding 180°, meaning the lens can see behind itself. In the case of the Nikkor, the angle of view recorded is 220°.
With digital post-processing it’s now possible to convert curvilinear images to rectilinear with ease. The rise of the action camera has popularised fisheye lens use and a new generation of fisheye cameras is emerging, producing rectilinearly corrected images and video in real time.

If astronauts reach the moon according to NASA’s Artemis project plan, one of their main goals is to mine ice in the crater near the moon’s South Pole. However, they will need to accurately navigate to the site. They already have equipment such as landing ships, lunar vehicles, drilling equipment, and supply vehicles. However, on the moon’s orbit or on a very strange surface of the moon, they need to know their position in real-time and accurately. Of course, they will need a GPS for this. Nevertheless, will a GPS work accurately? 


On Earth, global positioning systems (GPS) have changed our lives. A number of countries operate a large number of satellites that help people navigate in many ways. On Earth, GPS can pinpoint locations in centimeters. Can it help astronauts land on the moon?

YES – GPS WILL WORK ON THE MOON

Zhang Jiaming and Li Charles of the NASA Jet Propulsion Laboratory performed some mathematical calculations on the possibility. Mathematically and theoretically, YES, a GPS will work accurately in the moon. Signals from existing global navigation satellites near Earth can be used to navigate astronauts on the moon 385,000 kilometers away.


They mapped the orbits of navigation satellites from the US Global Positioning System and Galileo in Europe and GLONASS in Russia, for a total of 81 satellites. Most of them have directional antennas pointing to the surface of the earth, but their signals also radiate into space. The researchers said the signals were strong enough to be read by a spacecraft with a fairly compact receiver near the moon. They calculated that the spacecraft in lunar orbit would be able to “see” the signals of 5 to 13 satellites at any given time. At this distance, the positioning accuracy is about 200 to 300 meters. In computer simulation, they can continue to implement various methods to improve accuracy. NASA scientists believe that relay satellites in the lunar orbit as a positioning beacon.


Metal drums are common containers used to ship oil and many other materials. A metal drum is essentially a cylinder. A simple formula can allow you to calculate the volume of a cylinder from a few simple measurements.
The volume of a 3 -dimensional solid is the amount of space it occupies. 
Volume is measured in cubic units ( in³,ft³,cm³,m³,etc). 
Be sure that all of the measurements are in the same unit before computing the volume.
To Find the volume of the cylinder shown. Round to the nearest cubic centimeter.

Let’s begin,
A drum measures 83 cm high.
The diameter measures 56 cm. this is the distance across a circular end.
Divide the diameter in half. This gives you the radius.
half of 56 cm is 28 cm.
The formula for the volume of a cylinder is 

V= π (28)² (83)
π = 3.14
V=3.14 x 784 x 83 = 204326
Therefore, the volume of the cylinder is 204326 cubic centimeters.
Now Convert cubic centimeters to liters. To do this, use the conversion rate 
Dividing the volume (in cubic centimeters) of the cylinder by 1,000 will give you the volume in liters (L).

204326 / 1000 = 204.3 L

So, a Drum that is 83 cm height, 56 cm wide, has a volume of 204.3 L

Understanding the difference between watts and volts, as well as amperes (amps) and ohms, is crucial when working with any type of electrical system. Repairing household wiring requires a solid understanding of electrical terms, and it is even a helpful knowledge base to have for everyday living. How many times have you seen a lightbulb printed with "100W/120V" and wondered how the two units of electricity relate? Can the two be used interchangeably? Before looking at differences, it helps to start with basic definitions.
Watts, Volts, Amps, and Ohms Defined
Electrical terms and definitions such as watts and volts are set by a system called SI (International System of Units). An intergovernmental, international agency called BIPM (Bureau International des Poids et Mesures) sets terms and definitions for weights and measures under this system. Over a hundred countries are members or associates of BIPM.
The hydraulic (water) analogy is a common method of explaining electrical terms. Water flow within a closed-system pipe, or circuit, is compared to electrical flow. As with the closed-system pipes, electricity must move in a continuous circuit (or circular fashion) to work.
Volts
A volt represents the "potential difference between two points of a conducting wire carrying a constant current of 1 ampere when the power dissipated between these points is equal to 1 watt." The symbol for volt is "V."
Simplified, this means that voltage, compared to water pressure through pipes, is the speed of the electrons as they pass a point within the circuit.
Amps
With amps (short for amperes), the SI official definition is not only unwieldy but ever-changing. Its general thrust, though, never changes. Amps are the base unit that measure the volume of the electrons in the electrical circuit. The letter "A" capitalized is the symbol for amperes or amps.
With the hydraulic comparison, amps would be a unit of measure indicating the volume of water moving past a certain point. Volume is quantity, not speed. A lightning strike is about 20,000 amps. A watch may draw one-millionth of an amp. Household electrical cables typically are rated for 15 amps or 20 amps.
Watts
A watt expresses the rate of power flow. When one amp flows through an electrical difference of one volt, its result is expressed in terms of watts. "W" is the symbol for watt or watts.
Watts are derived from the formula V x A = W.
Ohms
The base unit ohm is the SI term indicating electrical resistance. Ohm is a measurement of the resistance that a device or material placed within the electrical circuit resists or reduces the electrical flow. The Greek symbol for omega, resembling a downward horseshoe, is also the symbol that denotes ohms.
The Difference Between Watts and Volts

Watts and volts are not independent of each other. Watts cannot exist without volts since they are the product of a combination of volts and amps. In basic terms and using the hydraulic analogy, volts are similar to pressure and watts are similar to rate.
Understanding the concept of rate is key to understanding watts vs. volts. When traveling in a car, it is possible to say that the vehicle covered 65 miles. While this is useful information, it doesn't give us a good picture of exactly what just happened. Did the car do those 65 miles in one hour, as one might reasonably expect, or did it take three months to cover that distance?
Or if you were to tell a friend that you drove for ten hours, she might follow up by asking where you drove or how far you drove. Discussing the length of a car trip is far less meaningful than if you said that you covered 800 miles during those ten hours.
One set of data deals with distance in the physical world; another set deals with time. Instead of juggling two sets of data back and forth, it is much more helpful and convenient to come up with a single number that combines the two. That number is rate.
So, the formula V x A = W is similar to the car trip example; both indicate rate. With the car, that rate is the familiar designation MPH (miles per hour): rate is equal to distance divided by time.
In electrical systems, amperage and voltage are useful sets of information. But wattage is an additional usual body of data because it combines the two to produce an indicator similar to rate or speed.

   Though the machine design procedure is not standard, there are some common steps to be followed; these can be followed as per the requirements wherever and whenever necessary. Here are some guidelines as to how the machine design engineer can proceed with the design:


●      1) Making the written statement: Make the written statement of what exactly is the problem for which the machine design has to be done. This statement should be very clear and as detailed as possible. If you want to develop the new produce write down the details about the project. This statement is sort of the list of the aims that are to be achieved from machine design.
●      2) Consider the possible mechanisms: When you designing the machine consider all the possible mechanisms which help desired motion or the group of motions in your proposed machine. From the various options the best can be selected whenever required.
●      3) Transmitted forces: Machine is made up of various machine elements on which various forces are applied. Calculate the forces acting on each of the element and energy transmitted by them.
●      4) Material selection: Select the appropriate materials for each element of the machine so that they can sustain all the forces and at the same time they have least possible cost.
●      5) Find allowable stress: All the machine elements are subjected to stress whether small or large. Considering the various forces acting on the machine elements, their material and other factors that affect the strength of the machine calculate the allowable or design stress for the machine elements.
●      6) Dimensions of the machine elements: Find out the appropriate dimensions for the machine elements considering the forces acting on it, its material, and design stress. The size of the machine elements should be such that they should not distort or break when loads are applied.
●      7) Consider the past experience: If you have the past experience of designing the machine element or the previous records of the company, consider them and make the necessary changes in the design. Further, designer can also consider the personal judgment so as to facilitate the production of the machine and machine elements.
●      8) Make drawings: After designing the machine and machine elements make the assembly drawings of the whole machines and detailed drawings of all the elements of the machine. In the drawings clearly specify the dimensions of the assembly and the machine elements, their total number required, their material and method of their production. The designer should also specify the accuracy, surface finish and other related parameters for the machine elements.

Whether you get on a plane once a year or once a week, there are probably still a few things you don’t know about flying.

Here are a few secrets you never know about taking to the skies, according to flight attendants, pilots, and industry experts.
The chimes you hear during a flight are actually a secret code.
Notably, they’re not usually conveying anything too exciting.
According to a blog post by Qantas Airlines, flight crews usually use a system of chimes and bells to communicate across the cabin.
These chime messages could be about anything from the number of remaining snacks to turbulence detected on the flight path.
On rarer occasions, the chimes could be a signal from the cockpit conveying an emergency or change of route.
Airplane lavatories can unlock from the outside.
You can actually unlock the lavatory from the outside via an external lock mechanism, which is usually hidden beneath the “no smoking” sign on the door, according to LifeHacker.
Though it might seem invasive, the lavatories unlock from the outside for safety reasons.
You may not want to drink the water on a plane.
Even if you’re not a germaphobe, you might want to think twice about ordering tea or coffee on a plane.
According to testing conducted by the Environmental Protection Agency in 2004 and 2012, the drinking water on more than one out of every 10 planes tested positive for “high” levels of coliform, which are potentially harmful bacteria found in human feces.
Though coliform by itself is not a serious hazard, it usually signals the presence of other dangerous microorganisms like E. coli.
While the EPA now requires planes to have their water supply tested once a year, most flight attendants will tell you to avoid the onboard water supply at all costs.
Generally, dimming the lights is meant to prepare your eyes for a potential evacuation.
No, the crew isn’t trying to lull you to sleep when they dim the lights for takeoff. Turning down the interior lights is actually done so that passengers’ eyes are already adjusted to the darkness, just in case something goes wrong during takeoff or landing, according to Conde Nast Traveler.
Flight attendants don’t get paid until the plane doors close.
Flight attendants who earn an hourly wage don’t actually start getting paid until the aircraft doors close.
Similarly, they stop getting paid after the doors open, according to The Points Guy.
That’s right – all that time flight attendants spend getting the plane ready, boarding passengers, doing safety inspections, and getting everyone off the plane is unpaid.
Many European airlines use a salary system for compensating their flight attendants, and most crew members on both sides of the pond receive a tax-free allowance to help them cover expenses like food during their layovers.
That emergency oxygen mask only lasts about 15 minutes.
In what probably sounds like a terrifying revelation, the drop-down emergency oxygen masks on the plane are usually only equipped to pump out oxygen for about 12 to 15 minutes, according to HuffPost.
But don’t freak out. It normally takes a pilot far less time to drop the plane to a safe altitude than it does for those masks to run dry of oxygen.
The important thing is to get your mask on over your nose and mouth as soon as you can, as you risk passing out just 30 seconds after cabin pressure drops to unsafe levels.
A plane captain has some serious authority.
Federal regulations give the PIC, or “pilot in command,” a lot of authority while the plane doors are closed, according to Think Aviation.
A PIC can put a passenger in restraints, take a will, write fines, and refuse entry to a passenger who looks sick. A PIC is the ultimate authority on an airplane – what they say goes.
Your boarding pass has a lot of hidden information.
Much of the text on your boarding pass probably doesn’t make a lot of sense to you at first glance, but it actually includes a wealth of interesting – and potentially sensitive – information.
The first two letters before the flight number refer to the airline. The numerical portion of your flight number is actually a clue as to what direction you’ll be flying in — odd-numbered flights fly south while even numbers fly west, according to Gizmodo.
Meanwhile, the six-character segment of text on your boarding pass is your booking reference or passenger name record. This little code actually can be used online to look up everything from your destination to your age and credit card information.
The tray tables are oftentimes the dirtiest things on an airplane.
The tray table at your plane seat is probably one of the dirtiest things on your flight. They’re only cleaned “about once a day, usually when the aircraft RONs (remains overnight,” active flight attendant Sara Keagle told HuffPost.
Flight attendants recommend bringing sanitizing wipes with you to wipe down your space, as passengers do everything from drool to change dirty diapers on those tables.  
 
 
Your flight attendant could probably deliver your baby.
Flight attendants aren’t just waiters in the sky – they have some serious credentials. Training to be a flight attendant involves a host of technical and safety know-how.  
As flight attendant Carrie A. Trey told The Points Guy, “practical tests can include learning how to put out fires via simulators, diagnosing various conditions, splinting broken limbs, stopping nosebleeds, administering CPR, and yes, even baby delivery.”

LiDAR, or light detection and ranging, is a popular remote sensing method used for measuring the exact distance of an object on the earth’s surface. Even though it was first used in the 1960s when laser scanners were mounted to aeroplanes, LiDAR didn’t get the popularity it deserved until twenty years later. It was only during the 1980s after the introduction of GPS that it became a popular method for calculating accurate geospatial measurements.



Now that its scope has spread across numerous fields, we should know more about LiDAR mapping technology and how it works. Here are a few insights about it that are good to know.
LiDAR Technology
According to the American Geoscience Institute, LiDAR uses a pulsed laser to calculate an object’s variable distances from the earth surface. These light pulses — put together with the information collected by the airborne system — generate accurate 3D information about the earth surface and the target object.
There are three primary components of a LiDAR instrument — the scanner, laser and GPS receiver. Other elements that play a vital role in the data collection and analysis are the photodetector and optics. Most government and private organizations use helicopters, drones and airplanes for acquiring LiDAR data.
Types of LiDAR Systems
LiDAR systems are divided into two types based on its functionality — Airborne LiDAR & Terrestrial LiDAR.
Airborne LiDAR
Airborne LiDAR is installed on a helicopter or drone for collecting data. As soon as it’s activated, Airborne LiDAR emits light towards the ground surface, which returns to the sensor immediately after hitting the object, giving an exact measurement of its distance. Airborne LiDAR is further divided into two types — Topological LiDAR and Bathymetric LiDAR.
Terrestrial LiDAR
Unlike Airborne, Terrestrial LiDAR systems are installed on moving vehicles or tripods on the earth surface for collecting accurate data points. These are quite common for observing highways, analysing infrastructure or even collecting point clouds from the inside and outside of buildings. Terrestrial LiDAR systems have two types — Mobile LiDAR and Static LiDAR.
How Does LiDAR Work?
LiDAR follows a simple principle — throw laser light at an object on the earth surface and calculate the time it takes to return to the LiDAR source. Given the speed at which the light travels (approximately 186,000 miles per second), the process of measuring the exact distance through LiDAR appears to be incredibly fast. However, it’s very technical. The formula that analysts use to arrive at the precise distance of the object is as follows:
The distance of the object = (Speed of Light x Time of Flight) / 2
LiDAR can be used to accomplish many developmental objectives, some of which are:
Oceanography
When the authorities want to know the exact depth of the ocean’s surface to locate any object in the case of a maritime accident or for research purposes, they use LiDAR technology to accomplish their mission. Other than locating objects, LiDAR is also used for calculating phytoplankton fluorescence and biomass in the ocean surface, which otherwise is very challenging.
Digital Elevation or Terrain Model
Terrain elevations play a crucial role during the construction of roads, large buildings and bridges. LiDAR technology has x, y and z coordinates, which makes it incredibly easy to produce the 3D representation of elevations to ensure that concerned parties can draw necessary conclusions more easily.
Agriculture & Archaeology
Typical applications of LiDAR technology in the agriculture sector include analysis of yield rates, crop scouting and seed dispersions. Besides this, it is also used for campaign planning, mapping under the forest canopy, and more.
Apart from the applications mentioned above, LiDAR is used by geoscientists for unearthing geomorphology related secrets, as well as by military for carrying out various security operations near the national borders.
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