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A rectangular projection is a relatively simple map-making exercise. It involves a grid of equal-sized rectangular cells. This, of course, is not a perfect square, but is a very close approximation. The scale of the map is a convenient unit of measure: one plot-unit per degree. However, this does not include the finer points of sizing the individual cells, or determining the relative size of the grid. Luckily, the software makes this a painless process.
There are many different types of projections, each aiming to preserve some geometric property. A good rule of thumb is to avoid wasting time on a particular one if you can use a more accurate and efficient method. Choosing a better-suited type of projection for your specific needs can help keep your cartography looking clean and crisp. One example is a polyconic or pseudocylindrical projection, which is best used to compare the sizes of different areas on a map.
Cylindrical projections are often used in world maps. These outlines are easily identifiable due to their straight meridians and parallels. They are also handy if you need to make airline distances from a central point. Also, they are fairly accurate for their intended purpose. If you don’t know what you are doing, you could end up displaying the wrong airline miles or kilometres from your destination.
Pseudocylindrical projections are similar to cylindrical ones, but tend to fill up the whole of the rectangle instead of just the center. Pseudocylindrical outlines are generally barrel-shaped. They can also have equally spaced meridians. Using a pseudocylindrical projection for your next map project can save you from having to do it all over again.
A conic projection is similar in that it is based on the idea of a rolled piece of paper touching the Earth. However, unlike a cylinder, a conic has a standard parallel for the true scale. With the right set of parameters, you can create your own projected coordinate systems with the best of both worlds. As a bonus, conic projections are not as prone to the worst of polar regions. In the real world, they can also be used to create a map of the United States in a single click.
Depending on your requirements, you may also want to consider using the equirectangular projection. Even though it is not as smooth as the conic, it still produces a useful and elegant map. To achieve this, you’ll need to be able to distinguish the two hemispheres. You’ll also need to calculate the centroid of your area of interest.
The best way to tell which of these projections is best for your needs is to figure out what you intend to do with the map. Once you have the answer to that question, you can use the information to pick the best of the bunch. Alternatively, you can take a cue from the best of the worlds to develop your own custom coordinate system, which can be an invaluable tool when attempting to locate a missing family member or snag a flight.
