![]() ![]() Polygons also have one unique feature - they could have holes.Ī polygon hole represents an area inside of the polygon but does not belong to it.įor example, a lake with an island can be depicted as a polygon with a hole. The polygon representation is used to represent shapes and locations of different objects, from a lake or a patch of vegetation, through a building or a city block, to some administrative units. Its only difference from the line is that the first and the last point in a polygon has the same coordinates, and thus close the object. In this case, we can express line features’ attributes using either lines’ color or their widths.Ī polygon is again a set of ordered points (vertices) connected by straight lines. Lines are used to representing linear features, such as roads, rivers, boundaries, footpaths, etc. It gives the illusion that the line is curved. Therefore, a straight spatial line consists of two points (two pairs of coordinates), while complex spatial lines could be created based on a large number of points. It consists of several points with coordinates (called vertices) that are arranged in some order.Ĭonsecutive points are connected by straight lines. Properties of points can be expressed on maps by different point sizes, colors, or shapes. They are also used to express abstract features, such as locations of map labels. Points can represent features on different spatial scales, from a GPS position, location of a bench in a park, to a city on a small scale map. X and Y could be unitless, in degrees, or in some measure units, such as meters (extended discussion on coordinates and related topics is in section 2.4). There are three basic types of geometries: points, lines, and polygons, all of them are made up of coordinates (left part of Figure 2.1).Ī point is represented by a pair of coordinates, usually described as X and Y, allowing for locating this point in some space. ![]() The role of geometry is to describe the location and shape of spatial objects.Īttributes, on the other hand, are used to store the properties of the data. The vector data model represent the world as a set of spatial geometries with non-spatial attributes (Figure 2.1). tmap: elegant and effective thematic maps in R.Our raster and vector maps can be found on this part of the website. If you feel like experimenting with raster and vector maps, you can download them here for free. ![]() For now, hopefully you have become a bit wiser about the use and the advantages and disadvantages of raster maps and vector maps. If we want to dive deeper into this we will do that in a next blog post. This is where the possibilities really become interesting. This way, even loose data can be placed on a piece of vector file. Something grid has a very difficult time with. Vector is flexible and can easily be transformed into other forms. It is therefore essential for us to be able to work with vectors in order to preserve the quality of our material. Don't look now but maps and also atlases, there it reigns supreme! However, the number of images, illustrations and photographs that are taken made from vector, are vastly limited. There is an area where they flourish the most. This type of structure contrasts with the pixels of the raster layout. It can not be stretched, twisted or inflated without losing any quality. Vector maps are made up of points, lines and surfaces. To be blunt, where vector will always win over raster is the preservation of quality. Yet there is one aspect where gridmaps loses out to vector maps, and that is quality. Seems almost too good to be true doesn't it? It is not for nothing the most commonly used format. If you would print a photo or the like, then you can also see on the print that loose dots are visible. All computers, telephones, digital boards and other carriers of media can handle this type. Everything that is graphically visible really. Raster is the leader in the field of file formats in terms of photos, images, maps, icons. The thing that makes a grid layout so strong and accessible, for example, is the following. Some more useful and accessible than the other. Grid maps and vector maps both have separate properties. A raster file is characterized by the use of pixels. As you zoom in more, more blocks appear, or pixels. ![]() Pixels we know are the blocks that we see when we zoom in on a photo. It's not, and we'll clarify through this blogpost. So, where to start? What is the difference between these two, and what does it mean? Let's start with the most known of the two.Īny photo or image as you know it, from any webpage is almost always made up of pixels. It is not unusual if these two terms sound at all strange to you. Two terms that we come into contact with as makers of maps. ![]()
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