# Pixels and image resolution their relationship moved

blur size increases, the resolution of the moving object can be enhanced by a tional pixel samples to reconstruct the object at a higher res- olution? Unfortunately We analyze the relationship between the blur size and parameters of the images into a single high resolution image have been pro- posed in literature [ Create a blank image, x pixels with RGB color PImage img . Before we move on, I should stress that this example works because the display area . In previous examples, we've seen a one-to-one relationship between source pixels . If you've bought a digital camera at a big box retail store, you've probably been sold on the features of the digital cameras they're trying to move. Perhaps no feature is Regardless of format, the image has pixel dimensions.

We can resample the raster as well to adjust the resolution. If we want a higher resolution raster, we will apply a grid with more pixels within the same extent. If we want a lower resolution raster, we will apply a grid with fewer pixels within the same extent.

One way to do this is to create a raster of the resolution you want and then resample your original raster. The resampling will be done for either nearest neighbor assignments for categorical data or bilinear interpolation for numerical data.

Notice that each raster has the same extent but each a different resolution because it has a different number of pixels spread out over the same extent. This is not an new concept by any means, however we need to remember this when we talk about coordinate reference systems associated with spatial data. When we make maps on paper or on a computer screen, we are moving from a 3 dimensional space the globe to 2 dimensions our computer screens or a piece of paper.

To keep this short, the projection of a dataset relates to how the data are "flattened" in geographic space so our human eyes and brains can make sense of the information in 2 dimensions.

The projection refers to the mathematical calculations performed to "flatten the data" in into 2D space. The coordinate system references to the x and y coordinate space that is associated with the projection used to flatten the data.

If you have the same dataset saved in two different projections, these two files won't line up correctly when rendered together. Maps of the United States in different projections. Notice the differences in shape associated with each different projection.

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These differences are a direct result of the calculations used to "flatten" the data onto a 2 dimensional map.

How Map Projections Can Fool the Eye Check out this short video, by Buzzfeedhighlighting how map projections can make continents seems proportionally larger or smaller than they actually are! There are lots of great resources that describe coordinate reference systems and projections in greater detail. However, for the purposes of this activity, what is important to understand is that data from the same location but saved in different projections will not line up in any GIS or other program.

For a library of CRS information: A great online library of CRS information.

## Understanding Image Resolution: Pixels, Inches, and DPI for Both Print and Web

We can define the exact extent that we need to use too. Let's create a new raster with the same projection as our original DEM. We know that our data are in UTM zone 11N.

For the sake of this exercise, let say we want to create a raster with the left hand corner coordinate at: First, let's set up the raster. Define the xmin and ymin the lower left hand corner of the raster 1. Resample Rasters Now apply your skills in a new way! Resample rasterNoProj from 1 meter to 10 meter resolution. Plot it next to the 1 m resolution raster. What happens to the extent if you change the resolution to 1. Sometimes we download data that have projection information associated with them but the CRS is not defined either in the GeoTIFF tags or in the raster itself.

If this is the case, we can simply assign the raster the correct projection. Be careful doing this - it is not the same thing as reprojecting your data. If you want to actually change the CRS of a raster, you need to use the projectRaster function.

## The Relationship Between Raster Resolution, Spatial Extent & Number of Pixels

You could consider looking at it in QGIS first to compare it to the other rasters. Does it line up with our DEM? Look closely at the extent and pixel size. Does anything look off? A Measurement of Image Detail DPI stands for dots per inch, and is an easy way to tell how detailed an image can be without actually seeing the image. But what is a "dot"? A dot can be anything: Heck, if you're in a sports arena and you look across the stadium, each of the people in those seats can be considered a "dot".

The two most common types of "dots" are pixels when looking at a computer screenand droplets of ink when printing something out. If you have 1 DPI, then you have a 1 x 1 grid and you're just going to have a solid color in a single square inch. If you have DPI, that means there are both horizontal dots and vertical dots, which gives you a x grid in a single square inch. You can see that the more dots you have, the more detail you can cram into an image. For Computers Only Your monitor is made up of "dots" called pixels.

You may have heard that monitors display images at 72 or 96 DPI. This may have been true at one point, but not anymore. If you're creating a design for on-screen display only, you can forget that DPI and inches even exist, because they're irrelevant.

If you're creating a design that is going to be printed, then you'll have to understand the relationship between pixels, inches, and DPI, which I'll talk about later. For Print Only An inch is an inch right?

That's true when you're measuring printed items, but since the pixel density — or DPI — between computer monitors can vary, inches have little to no bearing on a design when you're viewing it on a computer. We all know how to use a ruler, so I don't really need to explain inches in depth I hopebut how do you know how many pixels something should be if you know the size in inches, or how many inches something should be if you know the size in pixels?

How Pixels, Inches, and DPI Relate to Eachother The confusion between how it all works has a lot to do with the fact that even when you're designing something strictly for print, you're obviously going to be looking at it on a computer display.

So how do pixels, inches, and DPI fit together? How do I know what size it should be in pixels?