ESRI has defined three projections especially for the contiguos United states.Custom book review ghostwriting site for college
These are included in QGIS as well:. So it is up to you which projection characteristics you need: equal area, equal distance or conformal. If shape is important, consider a Lambert conic conformal projection, with two standard latitudes. Distances will be consistent in the vicinity of each of the standard parallels. You could also consider some sort of "equidistant" projection.
However, distance scale will never be true everywhere; only true from one or two points in all directions or from one line in a single direction. Sign up to join this community. The best answers are voted up and rise to the top. Which projection is best for mapping the contiguous United States?
Ask Question. Asked 5 years, 8 months ago. Active 5 years, 8 months ago. Viewed 35k times. DenaliHardtail DenaliHardtail 2, 3 3 gold badges 23 23 silver badges 57 57 bronze badges.Why America still uses Fahrenheit
What is more important: shapes, distances, or cardinal directions? Related: gis. Active Oldest Votes. Albers, pg 37 Lambert, pg 66 equidistant conic, pg MC5 MC5 1, 12 12 silver badges 23 23 bronze badges.
Good direction indeed! AndreJ AndreJ It's not clear what you mean by "equal distance. Other projections may have relevant properties not shared by these, such as being cylindrical, minimizing the grid convergence, etc. The wide variety of possible choices is what led mr.
What Is a Map Projection?
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Top 10 World Map Projections
Hat season is on its way!It is impossible to accurately represent the spherical surface of the earth on a flat piece of paper. Also, imagine peeling an orange and pressing the orange peel flat on a table—the peel would crack and break as it was flattened because it can't easily transform from a sphere to a plane.
The same is true for the surface of the earth and that's why we use map projections. The term map projection can be thought of literally as a projection.
If we were to place a light bulb inside a translucent globe and project the image onto a wall—we'd have a map projection. However, instead of projecting a light, cartographers use mathematical formulas to create projections. Depending on the purpose of a map, the cartographer will attempt to eliminate distortion in one or several aspects of the map. Remember that not all aspects can be accurate so the map maker must choose which distortions are less important than the others.
The mapmaker may also choose to allow a little distortion in all four of these aspects to produce the right type of map. Gerardus Mercator invented his famous projection in as an aid to navigators. On his map, lines of latitude and longitude intersect at right angles and thus the direction of travel—the rhumb line—is consistent.
The distortion of the Mercator Map increases as you move north and south from the equator. On Mercator's map, Antarctica appears to be a huge continent that wraps around the earth and Greenland appears to be just as large as South America although Greenland is merely one-eighth the size of South America.
Investigating Map Projections
Mercator never intended his map to be used for purposes other than navigation although it became one of the most popular world map projections.
During the 20th century, the National Geographic Society, various atlases, and classroom wall cartographers switched to the rounded Robinson Projection. The Robinson Projection is a projection that purposely makes various aspects of the map slightly distorted to produce an attractive world map.
Share Flipboard Email. Matt Rosenberg. Geography Expert. Updated September 03, In cartographya map projection is a way to flatten a globe 's surface into a plane in order to make a map.
This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane. Depending on the purpose of the map, some distortions are acceptable and others are not; therefore, different map projections exist in order to preserve some properties of the sphere-like body at the expense of other properties.
The study of map projections is the characterization of the distortions. There is no limit to the number of possible map projections. However, "map projection" refers specifically to a cartographic projection. Despite the name's literal meaning, projection is not limited to perspective projections, such as those resulting from casting a shadow on a screen, or the rectilinear image produced by a pinhole camera on a flat film plate.
Rather, any mathematical function that transforms coordinates from the curved surface distinctly and smoothly to the plane is a projection. Few projections in practical use are perspective. Most of this article assumes that the surface to be mapped is that of a sphere. The Earth and other large celestial bodies are generally better modeled as oblate spheroidswhereas small objects such as asteroids often have irregular shapes.
The surfaces of planetary bodies can be mapped even if they are too irregular to be modeled well with a sphere or ellipsoid. A model globe does not distort surface relationships the way maps do, but maps can be more useful in many situations: they are more compact and easier to store; they readily accommodate an enormous range of scales; they are viewed easily on computer displays; they can be measured to find properties of the region being mapped; they can show larger portions of the Earth's surface at once; and they are cheaper to produce and transport.
These useful traits of maps motivate the development of map projections. Map projections can be constructed to preserve some of these properties at the expense of others. Because the curved Earth's surface is not isometric to a plane, preservation of shapes inevitably leads to a variable scale and, consequently, non-proportional presentation of areas. Vice versa, an area-preserving projection can not be conformalresulting 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 many purposes exist for maps, 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 model 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 other vast territories, where such differences get shrunk to imperceptibility.The video above is from the September iPad edition of National Geographic magazine.
Choosing a map projection is a major challenge for cartographers. Features such as size, shape, distance, or scale can be measured accurately on Earth. Once projected on a flat surface, however, only some of these qualities can be accurately represented.
Every map has some sort of distortion. The larger the area covered by a map, the greater the distortion. Depending on the map's purpose, cartographer s must decide what elements of accuracy are most important to preserve. This determines which projection to use. For example, conformal map s show true shapes of small areas but distort size.One paragraph easy essay
Equal area map s distort shape and direction but display the true relative sizes of all areas. There are three basic kinds of projections: planar, conical, and cylindrical. Each is useful in different situations. Cartographers at National Geographic chose to use a version of the Mollweide projection for their map highlighting ocean floors, published as the map supplement in the September issue of National Geographic magazine. This Mollweide projection is referred to as a pseudocylindrical projection.
The specific version of the Mollweide projection used is called an interrupted Mollweide, because lines of longitudeor meridian s, are interrupted. The map is pulled apart at specific meridians to minimize distortion in areas where the cartographer would like the map reader to focus their attention.
Find more interactive content, photos, and videos in the iPad version of National Geographic magazine.
When did Flemish cartographer Gerardus Mercator first design the famous projection named after him? The projection was first designed and used by Gerardus Mercator induring the 16th century. According to the video, Africa is fourteen times larger than Greenland. Even though Greenland appears to be larger in maps projected in the Mercator projection, this is just a distortion introduced by the projection.
What map projection was chosen for the National Geographic Magazine September map supplement and which ocean was chosen as the center point of the map? An interrupted Mollweide projection was chosen, and cartographers chose to have the map centered on the Pacific Ocean. They chose the interrupted Mollweide projection because it shows all three oceans with the least distortion possible.
The emphasis in this map is meant to be on ocean floors rather than land areas. What are two characteristics of the Mollweide map projection that a cartographer would consider when creating a map?
The Mollweide projection is not appropriate for use in navigation, but you can use it to compare the size and shape of land areas. An interrupted version of the map projection can also be used to minimize distortion in important areas.
Also called an orange-peel map. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Sean P. For information on user permissions, please read our Terms of Service.
Each state is an independent shapefile and I need to merge them all at the end to generate the final product. I'm wondering which projected coordinate system should I use in this case? Or it doesn't matter at all since it won't affect the result of geoprocessing?
For my past work, I only mapped small area so I chose state plane NAD 83 of specific area as projected system. They also indicate to what extend they preserve size, shape or direction. Depending on you application a different priority might be set. For instance if I had to map an areal phenomenon like e. There are projections that make a good compromise of all three aspects. Used for many thematic maps, especially choropleth and dot density maps.
All areas on the map are proportional to the same areas on the Earth.Speech recognition systems future research project
Directions are reasonably accurate in limited regions. Distances are true on both standard parallels. If you are making a map of conterminous States, use the standard parallels of Scale true only along standard parallels.
Sign up to join this community. The best answers are voted up and rise to the top. Choosing projected coordinate system for mapping all US states?This projection was developed by Gerardus Mercator back in for navigational purposes.
Its popularity was so great that it became used as a geographic teaching aid even though the projection grossly distorts countries sizes. This is at its worst the closer you are to the poles. Arthur Robinson developed it in using a more visual trial and error development. The curved meridians, give it a nice spherical look. Image - Daniel R Strebe.Bruges political research papers
This projection was released by R Buckminster Fuller in after several decades working on it. The world is projected onto the surface of a icosahedron, allowjng it to be unfolded and flattened in two dimensions.
This is a cylindrical world map projection, that regains accuracy in surface area. It is named after James Gall and Arno Peters. These are then projected into a tetrahedron that can be unfolded into a rectangle. What this allows you to do is to retain the correct proportional sizes of the continents and oceans. Something never achieved before. Whilst the shapes of the continents are recognisable the layout certainly is not! Image - AuthoGraph. The Winkel Tripel projection is a modified azmiuthal projection.
This is, in essence, a globe that is projected onto a flat surface giving it curved lines of latitude and curved meridians. The projection, by Oswald Winkel in was developed with the goal of minimizing the three kinds of distortion: area, direction and distance.How to write a business email in french
Thus it became the Tripel Projection German for triple. The projection is neither equal-area nor conformal, its main feature is that all of the parallels are curved except for the straight poles and equator.
This gives a lovely spherical feeling to this two dimensional map. Close menu. Corporate Gifts. Log in. Christmas Gift Guide Read Now. It may come as a surprise to hear that there is no truly correct way of representing the earth as a flat image.
A world map projection is a visual representation of this challenge using a grid composed of lines of longitude and latitude. This transference has been subject to interpretation and choice since the earliest days of world mapping. In no particular order we give you our top 10 world map projections.
Mercator This projection was developed by Gerardus Mercator back in for navigational purposes. Image - Daniel R Strebe 2. Image - Daniel R Strebe Our Classic world map uses the Robinson projection and is a contemporary tribute to the familiar schoolroom map and is perfect for map-lovers of all ages. Available in a choice of 3 different colourways you can buy one here.
Dymaxion Map This projection was released by R Buckminster Fuller in after several decades working on it. Gall-Peters This is a cylindrical world map projection, that regains accuracy in surface area. Sinu-Mollweide Developed in by Allen K Philbrick, this projection fuses the Sinusoidal projectionwhich was first used in the 16th Century, with Karl Brandan Mollweide's map of and challenges our assumption of how the flattened globe should look.Demonstrate the challenge of transferring a spherical surface to a flat surface.
Explain that cartographers and others needing flat maps for practical uses have long been challenged to show Earth, a three-dimensional sphere, on a flat, two-dimensional plane. To demonstrate the challenge of moving from 3-D to 2-D with a sphere, invite volunteers to the front of the room and give each a navel orange or other type of orange that is easily peeled. Ask them to peel the orange, trying as best they can to keep the peel in one piece. One at a time, place the peels on an overhead projector and discuss the shapes as a whole class.
Have them imagine this is the surface of Earth or a globe.Custom essay writers sites uk
Show the video, The Cartographer's Dilemma, to introduce the challenges that cartographers face with representing Earth on a flat surface. Tell students they will next test the reverse, changing from a flat map to 3-D. Divide students into small groups of three. Give each group one copy of the 3-page worksheet Map to Globe: 2-D to 3-D Models, scissors, and transparent tape.
Have groups study these versions of the globe. Ask: What is the relationship between lines of longitude and the black lines cuts on the map? The cuts are all made along lines of longitude. What is the relationship to the Equator? Cutlines stop at the Equator. Have each member of each group work with one page to cut and tape together a model, attempting to make a globe from the maps.
Project the three maps Mercator, Mollweide, and Robinson showing different map projections that have been developed by cartographers. Read the captions for each. Ask: What do you observe about the lines of longitude in each of these map projections?
Some have lines of longitude meeting at the poles; some have parallel lines of longitude; some have curved lines of longitude but do not meet at north and south poles. Have students analyze the three projections and the globe to note the distortions found. Have students also compare the size that area is proportional and the shapes of land and water on the maps with what they see on the globe.
You may want to show this short video more than once. Allow students to revise their findings based on this information. Have students refer to the Map Projections handout, and use the provided answer key to have a whole class discussion about their answers in the chart. Next, project the upside-down map of the world and the Pacific-centered world map. Does it matter if a continent is larger or smaller in relation to other continents and on the map and on the globe?
Have them debate what they believe is the best map for use in classrooms and the general media, such as news reporting. What recommendations do you have for school settings?
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