Polyconic can refer either to a class of map projections or to a specific projection known less ambiguously as the American polyconic projection. Polyconic as a class refers to those projections whose parallels are all non-concentric circular arcs, except for a straight equator, and the centers of these circles lie along a central axis.
What is the American polyconic map projection?
The American polyconic map projection is a map projection used for maps of the United States and regions of the United States beginning early in the 19th century. It belongs to the polyconic projection class, which consists of map projections whose parallels are non-concentric circular arcs except for the equator, which is straight.
What is the shape of a polyconic map?
Most polyconic projections, when used to map the entire sphere, produce an "apple-shaped" map of the world. There are many "apple-shaped" projections, almost all of them obscure. ^ An Album of Map Projections (US Geological Survey Professional Paper 1453), John P. Snyder & Philip M. Voxland, 1989, p.
Is the polyconic map projection available in ArcGIS?
It is available in ArcGIS Pro 1.0 and later and in ArcGIS Desktop 8.0 and later. The polyconic map projection is shown centered on Greenwich. The subsections below describe the polyconic projection properties. This is a polyconic projection. The equator and the central meridian are projected as two perpendicular straight lines.
What is the difference between compression and polyconic projections?
Tearing: Polyconic projections produce maps with an unusual, butterfly-like shape. The outer edges of the map are curved lines of longitude 180 degrees from the map's central meridian . Tearing occurs along these edges. The polyconic projection is not used to build interrupted maps . Compression : The polyconic projection is not equivalent .
What is polyconic map projection?
: a map projection consisting of a composite series of concentric cones each of which before being unrolled has been placed over a sphere so as to be tangent to a different parallel of latitude.
What is the purpose of polyconic projection?
Uses: The polyconic is a somewhat unusual projection that produces maps with a unique set of qualities. In the past, the projection was more highly regarded than it is today. Currently, the polyconic is considered suitable only for mapping relatively small areas near the projection's central meridian.
What is the meaning of polyconic?
: relating to or based on many cones.
How is a polyconic projection made?
The polyconic projection is also known as American polyconic or ordinary polyconic projection. The name translates into "many cones," and it is created by lining up an infinite number of cones along the central meridian. This affects the shape of the meridians.
What is the advantage of the Gnomonic projection?
It projects great circles as straight lines, regardless of the aspect. The projection is not conformal nor is it equal-area. This is a useful projection for navigation because great circles highlight routes with the shortest distance.
What are the advantages and disadvantages of a conic map projection?
Conical Projections: Pros: These maps are very good for mapping regions that are primarily West-East in dimension like the United States. That is because a cone, when developed, is itself wider than tall. Cons: The basic con is that a single cone cannot show the entire globe.
What is a Mollweide map?
The Mollweide projection is an equal-area pseudocylindrical map projection displaying the world in a form of an ellipse with axes in a 2:1 ratio. It is also known as Babinet, elliptical, homolographic, or homalographic projection. The projection is appropriate for thematic and other world maps requiring accurate areas.
What type of projection is commonly used in North America?
Two of the most common map projections used in North America are the Lambert conformal conic and the Transverse Mercator.
What is Gnomonic chart?
Gnomonic Charts are used in passage planning to plot great circle routes as a straight line. They are useful for devising composite rhumb line courses.
What is meant by aniconic in art?
Definition of aniconic 1 : symbolic or suggestive rather than literally representational : not made or designed as a likeness trees, boulders, and other aniconic objects of primitive worship an aniconic image. 2 : without idols or images : opposed to the use of idols or images an aniconic religion.
What does anionic mean?
a negatively charged ionAnionic refers to chemical substances that possess a negatively charged ion. Anionic substances and solutions do not ionize in aqueous solutions; as such, they are effectively used to create corrosion-inhibiting surfactants.
What is meant by anechoic?
Definition of anechoic : free from echoes and reverberations an anechoic chamber.
What is polyconic projection?
The polyconic projection is also known as American polyconic or ordinary polyconic projection. The name translates into "many cones," and it is created by lining up an infinite number of cones along the central meridian. This affects the shape of the meridians. Unlike other conic projections, the meridians are curved rather than straight. The projection is neither conformal nor equal-area. It is appropriate for regions of predominant north-south extent.
Who developed the projection?
The projection was developed by Ferdinand R. Hassler in 1820. It is available in ArcGIS Pro 1.0 and later and in ArcGIS Desktop 8.0 and later.
Is polyconic projection good for regional maps?
The polyconic projection is not recommended for regional maps. Because there is no distortion along the central meridian, the projection is appropriate for regions of predominant north-south extent. It was used for topographic USGS quad sheets from 1886 until approximately 1957.
Is polyconic projection conformal?
The polyconic projection is neither conformal nor equal-area. It generally distorts shapes, areas, distances, directions, and angles. The central meridian is free of distortion. The scale along each parallel and along the central meridian of the projection is accurate. Distortion increases with distance from the central meridian. The east-west distortion is greater than north-south distortion. The projection produces considerable distortion toward the edge of the map. Distortion values are symmetric across the equator and the central meridian.
Description
The name of this projection translates into "many cones". This refers to the projection methodology. This affects the shape of the meridians. Unlike other conic projections, the meridians are curved rather than linear.
Projection method
More complex than the regular conic projections, but still a simple construction. This projection is created by lining up an infinite number of cones along the central meridian. This projection yields parallels that are not concentric. Each line of latitude represents the base of its tangential cone.
Properties
No local shape distortion along the central meridian. Distortion increases with distance from the central meridian; thus, east–west distortion is greater than north–south distortion.
Limitations
Distortion is minimized on large-scale maps, such as topographic quadrangles, where meridians and parallels can be drawn in practice as straight-line segments. Producing a map library with this kind of map sheet is not advisable because errors accumulate and become visible when joining sheets in multiple directions.
Uses and applications
Used for 7 1/2 and 15 minute topographic USGS quad sheets, from 1886 until approximately 1957.
Which projections fall into the polyconic class?
Some of the projections that fall into the polyconic class are: Van der Grinten projection -- projects entire earth into one circle; all meridians and parallels are arcs of circles. Nicolosi globular projection -- typically used to project a hemisphere into a circle; all meridians and parallels are arcs of circles.
What is the name of the projection called the Van der Grinten projection?
For the specific projection called "polyconic", see American polyconic projection. Van der Grinten projection of the world. Polyconic can refer either to a class of map projections or to a specific projection known less ambiguously as the American polyconic projection.
When did Ginzburg make the apple shaped map?
Another series by Georgiy Aleksandrovich Ginzburg appeared starting in 1949. Most polyconic projections, when used to map the entire sphere, produce an "apple-shaped" map of the world. There are many "apple-shaped" projections, almost all of them obscure.
What projections project the Earth into a circle?
Van der Grinten projection -- projects entire earth into one circle; all meridians and parallels are arcs of circles. Nicolosi globular projection -- typically used to project a hemisphere into a circle; all meridians and parallels are arcs of circles.
What is the American polyconic projection?
The American polyconic map projection is a map projection used for maps of the United States and regions of the United States beginning early in the 19th century. It belongs to the polyconic projection class, which consists of map projections whose parallels are non-concentric ...
When was polyconic projection invented?
The American polyconic projection was probably invented by Ferdinand Rudolph Hassler around 1825 . It was commonly used by many map-making agencies of the United States from the time of its proposal until the middle of the 20th century.
What is the shape of a polyconic projection?
Tearing: Polyconic projections produce maps with an unusual, butterfly-like shape. The outer edges of the map are curved lines of longitude 180 degrees from the map's central meridian . Tearing occurs along these edges. The polyconic projection is not used to build interrupted maps .
What is the variation within polyconic projections?
Variation Within Polyconic Projections : Polyconic projections differ in the location of their central meridians .
How many lines of tangency does a polyconic projection have?
Case : The polyconic projection is tangent , with each of its infinite number of cones having a single line of tangency . Thus, the projection as a whole has an infinite number of lines of tangency .
Is polyconic projection equivalent to compression?
Compression : The polyconic projection is not equivalent . There is little area distortion along the map's central meridian ; but the distortion increases as you move to the east or west of the central meridian .
Is polyconic projection conformal?
Conformality: The polyconic projection is not conformal . There is little shape distortion along the map's central meridian ; but the distortion increases as you move to the east or west of the central meridian.
