Which Projection Is Best
The mathematics of projection do not permit any particular map projection to be best for everything. Something will always be distorted. Thus, many projections exist to serve the many uses of maps and their vast range of scales.
Modern national mapping systems typically employ a transverse Mercator or close variant for large-scale maps in order to preserve conformality and low variation in scale over small areas. For smaller-scale maps, such as those spanning continents or the entire world, many projections are in common use according to their fitness for the purpose, such as Winkel tripel, Robinson and Mollweide. Reference maps of the world often appear on compromise projections. Due to distortions inherent in any map of the world, the choice of projection becomes largely one of aesthetics.
Thematic maps normally require an equal area projection so that phenomena per unit area are shown in correct proportion.However, representing area ratios correctly necessarily distorts shapes more than many maps that are not equal-area.
The Mercator projection, developed for navigational purposes, has often been used in world maps where other projections would have been more appropriate. This problem has long been recognized even outside professional circles. For example, a 1943 New York Times editorial states:
What Is Area Distortion In Human Geography
An area can appear more elongated or squat. May be altered One area may appear larger than another on a map, but in reality is smaller. Direction. From place to place can be distorted.
What is the closest meaning of distorted?
Some common synonyms of distort are contort, deform, and warp. While all these words mean to mar or spoil by or as if by twisting, distort and contort both imply a wrenching from the natural or normal, but contort suggests a more involved twisting and a more grotesque and painful result.
What is an example of distortion in human geography?
There are four main types of distortion that come from map projections: distance, direction, shape and area. The Mercator projection, for example, distorts Greenland because of its high latitude, in the sense that its shape and size are not the same as those on a globe. Another example is in cylindrical projections.
Examples Of Map Projections
Throughout human history, people have used map projections for a wide range of uses. Explorers use Mercator maps for rhumb lines to accurately travel in a constant track direction. Actually, the first known map originated in Greece and perceived the world as cylindrical.
There are thousands of map projections that are in existence today!
Some map projections are useful for some things and other map projections are good for other things.
Two of the most common map projections used in North America are the Lambert conformal conic and the Transverse Mercator.
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Evaluation Of Map Projection Distortion
Figure 1. Elementary circle in the tangent plane on the sphere , and corresponding ellipse of distortion in the mapping plane .
10Acknowledging that map projection distortion can present itself in many different ways , some authors have also proposed the use of combined distortion measures, which provide a general assessment of the combined impact of two, three or even more different aspects of distortion. Some of these measures, especially those referring to various aspects of distortion at the local scale, already have a long history , others have been proposed more recently . One of the major difficulties in the definition of combined distortion measures is that not all aspects of distortion are expressed in the same units, and therefore cannot be directly compared. Overcoming this problem requires that measurements of different aspects of distortion are properly calibrated. Only recently Laskowski proposed a method for the standardisation of different distortion measurements that offers a partial solution to the problem of unlike units. However, the more fundamental problem of weighting different aspects of distortion equally is far from solved and remains an interesting area for future research.
Metric Properties Of Maps
Many properties can be measured on the Earth’s surface independently of its geography:
Map projections can be constructed to preserve some of these properties at the expense of others. Because the Earth’s curved surface is not isometric to a plane, preservation of shapes inevitably requires a variable scale and, consequently, non-proportional presentation of areas. Similarly, an area-preserving projection can not be conformal, resulting in shapes and bearings distorted in most places of the map. Each projection preserves, compromises, or approximates basic metric properties in different ways. The purpose of the map determines which projection should form the base for the map. Because maps have many different purposes, a diversity of projections have been created to suit those purposes.
Another consideration in the configuration of a projection is its compatibility with data sets to be used on the map. Data sets are geographic information their collection depends on the chosen datum of the Earth. Different datums assign slightly different coordinates to the same location, so in large scale maps, such as those from national mapping systems, it is important to match the datum to the projection. The slight differences in coordinate assignation between different datums is not a concern for world maps or those of large regions, where such differences are reduced to imperceptibility.
Other distortion metrics
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What Four Things Do Map Projections Distort
There are four basic characteristics of a map that are distorted to some degree, depending on the map projection used. These characteristics include distance, direction, shape, and area.
My article is not to discuss the benefits of map projections but to look at how technology is contributing to skills and knowledge being lost.
What four things do map projections distort?
As a cartographer with over 25 years experience in the GeoSpatial Industry, I guess I have a slightly more critical eye when I see maps that are produced these days. It makes me cringe when I see maps that are missing some essential items like a scale, north point, legends, projection information or title. It is so easy these days to just press the print button and have the software spit out the map. It may portray the data in the way the cartographer indented but it looses basic usability outside the original production when it does not have these basic elements.
Are these basic elements being lost because it does not matter anymore or is it too easy to just rely on the technology and therefore too easy to overlook the basic elements. I feel it is more about the technology, although I do see there appears to be less importance placed on some of these at some levels of education.
The Distribution of the total number of Tweets in 2013
The Distribution of the total number of Tweets consists of the word birthday in 2013
What Causes A Distortion In A Map
- Representing the earth’s surface in two dimensions causes distortion in the shape, area, distance, or direction of the data. A map projection uses mathematical formulas to relate spherical coordinates on the globe to flat, planar coordinates. Different projections cause different types of distortions.
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Projections By Preservation Of A Metric Property
Conformal, or orthomorphic, map projections preserve angles locally, implying that they map infinitesimal circles of constant size anywhere on the Earth to infinitesimal circles of varying sizes on the map. In contrast, mappings that are not conformal distort most such small circles into ellipses of distortion. An important consequence of conformalityis that relative angles at each point of the map are correct, and the local scale in every direction around any one point is constant. These are some conformal projections:
If the length of the line segment connecting two projected points on the plane is proportional to the geodesic distance between the two unprojected points on the globe, then we say that distance has been preserved between those two points. An equidistant projection preserves distances from one or two special points to all other points. The special point or points may get stretched into a line or curve segment when projected. In that case, the point on the line or curve segment closest to the point being measured to must be used to measure the distance.
- : Distances from the two poles are preserved, in equatorial aspect.
- Azimuthal equidistant: Distances from the center and edge are preserved.
- Equidistant conic: Distances from the two poles are preserved, in equatorial aspect.
Why Do Maps Have Distortion
Because you can’t display 3D surfaces perfectly in two dimensions, distortions always occur. For example, map projections distort distance, direction, scale, and area. Every projection has strengths and weaknesses. All in all, it is up to the cartographer to determine what projection is most favorable for its purpose.Oct 29, 2021
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Directions Sometimes A Straight Line Isnt The Shortest Path
New York City and Istanbul are on nearly the same line of latitude, about 41ÂºN. That means that if you head due east on a straight line from New York, youâll reach Istanbul. But that doesnât mean that this is the shortest distance between the two cities.
In this image, thereâs a line which shows the straightest, simplest path between New York and Istanbul, which is simply to point yourself east and start flying. But the curved line above it shows the way you should go if youâd like to travel the least distance while getting there. Because the Earthâs surface is curved, the shortest paths around it are curved, too. This can be a bit confusing, but makes more sense if you try it yourself: find a globe and place a piece of string on it. Pin one end to New York and one to Istanbul, and pull the string taut. Youâll notice that the string covers the exact same path as the curved route in the map above. We call these curved shortest-distance paths great circle routes. On the other hand, a path like the straight line, where you keep yourself pointed in the exact same compass direction the whole time, is called a rhumb line or a loxodrome.
Now the straight line is the great circle, and the curved one is the loxodrome. These lines are the same as in the Mercator above, but the projection changes their appearance.
Distance Most Projections Distort Distances
A trip from Madison to Buenos Aires is much farther than a trip from Madison to Madrid. But on an Equirectangular projection, both of those trips looks like theyâre the same length, because this is a projection that does not preserve distance. On the other hand, the Azimuthal Equidistant projection shows distances in the correct proportion.
Thereâs a catch, though. While we have map projections that can preserve areas or form everywhere on the map, there isnât one that can preserve distances everywhere. There are only projections that let you preserve distances relative to just one or two points on the map. Distances to and from the center of an Azimuthal Equidistant map are shown correctly, but distances between any other two points are distorted. When a projection preserves distance, we call it equidistant.
The properties of area, distance, and form are mutually exclusive. If you have a map projection that preserves one, it will distort the other two
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Choosing A Projection Surface
A surface that can be unfolded or unrolled into a plane or sheet without stretching, tearing or shrinking is called a developable surface. The cylinder, cone and the plane are all developable surfaces. The sphere and ellipsoid do not have developable surfaces, so any projection of them onto a plane will have to distort the image.
One way of describing a projection is first to project from the Earth’s surface to a developable surface such as a cylinder or cone, and then to unroll the surface into a plane. While the first step inevitably distorts some properties of the globe, the developable surface can then be unfolded without further distortion.
Geometric Distortion In Imagery
Any remote sensing image, regardless of whether it is acquired by a multispectral scanner on board a satellite, a photographic system in an aircraft, or any other platform/sensor combination, will have various geometric distortions. This problem is inherent in remote sensing, as we attempt to accurately represent the three-dimensional surface of the Earth as a two-dimensional image. All remote sensing images are subject to some form of geometric distortions, depending on the manner in which the data are acquired. These errors may be due to a variety of factors, including one or more of the following, to name only a few:
- the perspective of the sensor optics,
- the motion of the scanning system,
- the motion and stability of the platform,
- the platform altitude, attitude, and velocity,
- the terrain relief, and
- the curvature and rotation of the Earth.
Framing systems, such as cameras used for aerial photography, provide an instantaneous “snapshot” view of the Earth from directly overhead. The primary geometric distortion in vertical aerial photographs is due to relief displacement. Objects directly below the centre of the camera lens will have only their tops visible, while all other objects will appear to lean away from the centre of the photo such that their tops and sides are visible. If the objects are tall or are far away from the centre of the photo, the distortion and positional error will be larger.
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What Is Distortion And How Does It Affect Maps
Because you can’t display 3D surfaces perfectly in two dimensions, distortions always occur. For example, map projections distort distance, direction, scale, and area. Every projection has strengths and weaknesses. All in all, it is up to the cartographer to determine what projection is most favorable for its purpose.
Where Does The Least Distortion Occur On Any Map Projection
Distortion is not constant across the map, as distortion may take different forms in different parts of the map. There are few points were distortions are going to be zero, however, distortion is usually less near the points or lines of intersection where the developable surface intersects the globe.
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Map Projections And Coordinate Systems
Remember that with a sphere, we use latitude and longitude to pinpoint our position. This is our geographic coordinate system. For example, New Yorks position is .
But when the Earth has a map projection, this means that it has projected coordinates. For example, the Universal Transverse Mercator system splits the Earth into 60 sections by lines of longitude. If you can imagine you are cutting an orange into 60 wedges, this is how the UTM system works.
From here, it assigns the central meridian a value of 500,000 meters.
The key takeaway is this:
When we locate positions on a sphere, we use decimal degrees. But when we use map projections, we locate positions in meters or feet.
It uses an equation to transform Earths angular geographic coordinates to XY Cartesian coordinates using developable surfaces. A developable surface is a geometric shape that a map projection can be built on.
Actually, some map projections dont use developable surfaces at all such as the Goode and Bonne projections.
What Are Map Projections
Earth is a big blue marble thats the shape of a sphere . This is why a globe is the best way to represent the Earth.
But globes are hard to carry in your suitcase and you can only see one side of the globe. On top of that, its hard to measure distances and theyre just not as convenient as paper maps.
This is why we use map projections on globes and flatten them out in two dimensions. But as youre about to find out, you cant represent Earths surface in two dimensions without distortion.
On top of that, all types of map projections have strengths and weaknesses preserving different attributes.
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What Is Distorted On A Map
In cartography a distortion is the misrepresentation of the area or shape of a feature. The Mercator projection for example distorts Greenland because of its high latitude in the sense that its shape and size are not the same as those on a globe.
What Is A Word For Distorting The Truth
2 bias, colour, falsify, garble, misrepresent, pervert, slant, twist. put smb. off the scent exp. mislead someone deliberately provide wrong information to forbid someone from knowing the truth.
What causes the distortion of the message?
Message distortion occurs whenever a message sent by one communicator is interpreted differently by the person receiving the message. Complex and costly examples of message distortion often occur on the job when someone misinterprets instructions about completing a task.
Which is the best definition of the word distortion?
Definition of distortion. 1: the act of twisting or altering something out of its true, natural, or original state: the act of distorting a distortion of the facts.
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Choosing A Model For The Shape Of The Body
Projection construction is also affected by how the shape of the Earth or planetary body is approximated. In the following section on projection categories, the earth is taken as a sphere in order to simplify the discussion. However, the Earth’s actual shape is closer to an oblate ellipsoid. Whether spherical or ellipsoidal, the principles discussed hold without loss of generality.
Selecting a model for a shape of the Earth involves choosing between the advantages and disadvantages of a sphere versus an ellipsoid. Spherical models are useful for small-scale maps such as world atlases and globes, since the error at that scale is not usually noticeable or important enough to justify using the more complicated ellipsoid. The ellipsoidal model is commonly used to construct topographic maps and for other large- and medium-scale maps that need to accurately depict the land surface. Auxiliary latitudes are often employed in projecting the ellipsoid.
Other regular solids are sometimes used as generalizations for smaller bodies’ geoidal equivalent. For example, Io is better modeled by triaxial ellipsoid or prolated spheroid with small eccentricities. Haumea‘s shape is a Jacobi ellipsoid, with its major axis twice as long as its minor and with its middle axis one and half times as long as its minor.See map projection of the triaxial ellipsoid for further information.