Gall-Peters projection wraps a cylinder around the earth and maps each point on the earth to the nearest point on the cylinder. Cordiform projection designates a pole and a meridian; distances from the pole are preserved, as are distances from the meridian which is straight along the parallels.
What is GIS? What is a Map Projection? Creation of a Map Projection The creation of a map projection involves three steps in which information is lost in each step: selection of a model for the shape of the earth or round body choosing between a sphere or ellipsoid transform geographic coordinates longitude and latitude to plane coordinates eastings and northings.
The metric properties or a map are area shape direction distance scale Choosing a projection surface If a surface can be transformed onto another surface without stretching, tearing, or shrinking, then the surface is said to be an applicable surface. Using globes vs. Choosing a model for the shape of the Earth The projection is also affected by how the shape of the earth is approximated. Categories Projection classification is based on type of projection surface that is used.
Area preserving projection — equal area or equivalent projection Shape preserving — conformal, orthomorphic Direction preserving — conformal, orthomorphic, azimuthal only from a the central point Distance preserving — equidistant shows the true distance between one or two points and every other point NOTE: It is impossible to construct a map projection that is both equal area and conformal. Azimuthal projections Azimuthal projections touch the earth to a plane at one tangent point; angles from that tangent point are preserved, and distances from that point are computed by a function independent of the angle.
Azimuthal conformal projection is the same as stereographic projection. Conformal projections Conformal map projections preserve angles. Despite how the Tissot indicatrix changes from a circle to an ellipse, an equal-area projection retains relative size. So now you have an idea how equal area projections work, we have a section entirely dedicated to the types of distortions found in maps. What are some of your favorite types of equal-area projections?
Please let us know with a comment below. I am facing difficulty in remotely selecting a few equal-area projections to choose for my study area.
Could you recommend an equal-area cylindrical projection that covers the extent of Southeast Asia In GIS operations this projection is commonly referred to as Geographicals. This is a cylindrical projection, with the Equator as its Standard Parallel. The difference with this projection is that the latitude and longitude lines intersect to form regularly sized squares.
By way of comparison, in the Mercator and Robinson projections they form irregularly sized rectangles. Refer to the section on Projections for more information about distortions generated by projections.
Enter your Keywords. Commonly Used Map Projections. Breadcrumb Home Fundamentals of Mapping Projections. These are two examples of maps using Stereographic projection over polar areas. In these the radiating lines are Great Circles. Produced Using G. In this the Great Circles are not as obvious as with the two Polar maps above, but the same principle applies: any straight line which runs through the centre point is a Great Circle.
This is an example of how a Great Circle does not have to be a set line of Longitude of Latitude. These two maps highlight the importance of selecting your Standard Parallel s carefully. For the first one the Standard Parallels are in the North and for the second they are in the South.
The Lambert Conformal Conic is the preferred projection for regional maps in mid-latitudes. Compare this to the Mercator projection map above. This is not commonly appreciated and UTM is often wrongly described as a projection in its own right — it is not — it is a projection system. Created in Best Used in mid-latitudes — e. USA, Europe and Australia. Created in Best Used in areas around the Equator and for marine navigation. Other meridians are curved lines, while other parallels are straight lines.
This map projection was initiated by Karl B. Mollweide in However, there is more scale accuracy in the equatorial regions. The projection is ideal for making global maps. All the parallels are straight lines perpendicular to a central meridian, while other lines are curved like those in the Mollweide projection. The values of sine curves are used to create meridians, making the meridian spacing wider than that of the Mollweide projection.
The Sinusoidal projection is typically used for map making of the equatorial regions such as in South America and Africa. This type of equal-area projection is a combination of the Homolographic and the Sinusoidal. Normally, the Sinusoidal projection is applied between the 40 degrees south and 40 degrees north latitudes, grafted to the Homolographic in the areas out of the above mentioned range. As the two projections can not match perfectly, small kinks are seen on the meridians where the two projections match.
Skip to main content. You are here Home. Planar, Azimuthal or Zenithal projection This type of map projection allows a flat sheet to touch with the globe, with the light being cast from certain positions, including the centre of the Earth, opposite to the tangent area, and from infinite distance. This group of map projections can be classified into three types: Gnomonic projection, Stereographic projection and Orthographic projection.
Gnomonic projection The Gnomonic projection has its origin of light at the center of the globe. Stereographic projection The Stereographic projection has its origin of light on the globe surface opposite to the tangent point. Conic projection This type of projection uses a conic surface to touch the globe when light is cast.
When the cone is unrolled, the meridians will be in semicircle like the ribs of a fan. The tangent areas of conic projection can be classified as central conical projection or tangent cone, secant conical projection, and polyconic projection. Central conical projection This simple map projection seats a cone over the globe then casts the light with the axis of the cone overlapping that of a globe at tangent points.
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