![]() The SRTM project yielded publically available, high resolution DEMs at 1 arc-second (~30 m) resolution in the United States and 3 arc-second (~90 m) worldwide. In 2000, the shuttle radar topography mission (SRTM) collected rasterized elevation data across 80% of the globe, generating a DEM covering the Earth's surface from 60°N to 60°S latitude. The collection methods for the data researchers want to compare to digital topography and the importance of boundaries plays a significant role in the decision to represent topography as a TIN or DEM.Ī case study from the Annapurna Range of Central Nepal More qualitative cultural data, such as population, employment, election results, etc are usually collected by state or county agencies and are visualized in vector format. ![]() Examples of satellite derived gridded data are precipitation data, landcover, or vegetation type. Often, digital data acquired from satellites are collected in a gridded fashion. The DEM type decision depends on the analysis of interestĭigital vector topography can clearly define boundaries, such as valley floors or ridge lines. Choosing to represent digital topography in either vector or raster (TIN or DEM) format depends on the type of GIS analysis a user wants to perform. Raster format divides the topographic surface into equally spaced intervals or a gridded array and then displays the elevation value for each grid cell (called a digital elevation model or DEM). Vector format uses a series of irregularly spaced elevation points connected by lines into a triangulated irregular network (TIN). Digital topography can be represented in either vector or raster format. If your project requires scalable shapes and solid colors, vector is the best choice, but if your project requires complex color blends, raster is the preferred format.The recent explosion of Geographic Information System (GIS) tools enable geoscientists to visualize the Earth's surface in three dimensions using digital topography. Raster images are best for digital photos and print materials. Their native files are needed for coin designs, laser engraving, t-shirts, patches, etc. They're also used in lower thirds for videos, web-based objects and rendering 2D or 3D computer animation. Raster-based software (e.g., Adobe Photoshop)Ī vector graphic's small file size and scalability make it uniquely suitable for use in digital printing from business cards to billboards.Vector-based software (e.g., Adobe Illustrator).Digital printing (e.g., business cards, billboards).However, a high resolution image printed at a small size will cause the pixels to "cram" together and will make the image look as unprofessional as not having enough pixels in a large image. Resolution limits the size the image can be scaled up without being able to see pixels. The lower the number of pixels, the lower the resolution. More pixels result in better quality at the same or larger sizes as the original, but this also increases the size of the file and the amount of space it takes to store the file. Each image can only contain a fixed number of pixels the amount of pixels determines the quality of the image. These images are created by digital cameras, by scanning images into a computer or with raster-based software. Pixels appear like little squares on graph paper when the image is zoomed in or enlarged. Raster images are made of pixels or tiny dots that use color and tone to produce the image. Because they consist of lines and anchor points, the size of the file is relatively small. These graphics are also device-independent, which means their quality doesn't depend on the number of dots available on a printer or the number of pixels on a screen. ![]() ![]() Their lines are sharp, without any loss in quality or detail, no matter what their size. Because these graphics are not based on pixels, they are known as resolution independent, which makes them infinitely scalable. These graphics consist of anchored dots and are connected by lines and curves, similar to the connect-the-dot activities you may have done as a kid. Vector graphics are also known as scalable vector graphics (SVG).
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