Introduction to Raster Data
Raster Data is the type of geospatial data that is used to geocode maps and fill in the information related to surface features. It can be a pixel, matrix or even collection of cell forming a picture in general term. The Satellite imagery and the layers are classified into Raster Data. Unlike Vector Data, this form of data represents the interior part of the feature. Vector Data forms the boundary of any geo feature, and Raster Data fills the feature with specific pixelation. Raster Data are more into storing temperature, elevation, depth and soil pH value related data. The colour contrast varies from. Location to location and also depends on various geographical features covering the area. Two types of Raster data are Discrete Raster Data and Continuous Raster Data.
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How does Raster Data Work?
- As given in the above definition, each cell or the matrix act as a data container. They can be called the variables that store colour-specific information depending on the classification and nature of the geographic feature. In the Raster form of data, the map area is divided into several cells and a matrix. The area is equally distributed with the help of Rows and Columns. Each cell of the row and the column has some unique attributes that define the value.
- Most of the raster data pixels are in a square or rectangular format, but other shapes like triangular or hexagonal are also possible. The whole imagery or datasheet contains all these uniquely filled cells and forms the Raster data. Raster spatial data structures are two-dimensional arrays; this means that the area that each cell grid represents can both be used to define map resolution and the number of cell grids to describe the spatial distribution. Single-pixel or a cell in the layer can only have one attribute being mapped to it. To handle more than one attribute, more data layers need to be created. These layers can be visualized as stacked, one on top of the other.
- While working on any project, GIS Analysts and Technicians load the Raster data models from the serving source and then work on the geocoding and referencing part. Based on the Raster data’s reference, they further create the vector map objects that consist of point, line, and polygon. The data is stored in various file formats like Images (.IMG, .JPG, and . PNG file extensions), ESRI uses bit maps (.BMP, .BPW) and many more customized formats.
- The Raster Data is the imagery form of the surface area where each pixel in the data describes the surface area.Camera Sensors are used to capture the features with the help of electromagnetic waves generated through the sensors. The data collected from these sensors are the measurements that are reflected using electromagnetic waves.
- There are primarily two types of sensors, Active Sensors and Passive Sensors.Passive Sensorsin the satellite sensors that detect only the data emitted from the landscape or reflected from any other light source. Active Sensors emits their signal, and the sensors in the satellite measures what is reflected. SONAR and RADAR are perfect examples of this type of sensor.
Passive Sensor Active Sensor
Types of Raster Data
Raster Data is further classified into various types; they are:
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- Satellite Imagery
- Digital Elevation Model(DEM)
- Digital Orthophotos
- Binary Scanned Files
- Graphic Files
Let us study the above-mentioned types in details:
1. Satellite Imagery
The imagery is remotely sensed and collected data in the raster format. The image value in the pixel represents the light or energy that is emitted and reflected from the earth back to the satellite sensors, which collects the data. Various types of land use and hydrography features can be classified during image processing. The imagery generated through this method can be either in RGB format or in traditional black & white format.
2. Digital Elevation Model (DEM)
Digital Elevation Model is the computer graphic representation of any terrain surface. This can be of a Mountain, Plateau or even a Planet. The models that are generated with the help of the Digital Elevation Model technique are mainly 2 dimensional and 3-dimensional array of data. The information equipped in Digital Elevation Model is by using remote sensing techniques like photogrammetry (a type of collecting images of physical objects), LIDAR (With the help of laser technique), IfSAR (a type of RADAR technique) and land surveying (With the help of field workers). The data collected in the Digital Elevation Model can be point-based, but it can be converted into the raster format.
DEM of Snow covered mountains
Source Link: https://nsidc.org/data/highmountainasia
3. Digital Orthophotos
Digital Orthophoto is a type of aerial imagery or satellite imagery that is extracted using remote sensing techniques. It is said to the corrected and processed imagery where the camera tilts and terrain relief is removed. This imagery form is geometrically correct and used for the digitization of 2D models. The collection of these Orthophotos form a large sheet of imagery, also known as Google Earthimagery is the perfect example of this orthophoto.
4. Binary Scanned Files
As the name states, the data in these type of files are stored in binary format (value of 0 and 1). These type of image files are mostly monochromatic, i.e. they are only available in black and white. The images, in general terms, are also known as grayscale images. Due to less utilization of pixels of different values, the data and the file are easy to handle because of their low bit and byte size.
Binary Images Showing the presence in black, grey and white
5. Graphic Files
In this format, the Maps, Photographs and Images can be stored as digital graphic files. The popular graphic files that we come across in our daily life are GIF (Graphic Interchange Format), TIFF (Tagged Image File Format), JPEG (Joint Photographic Experts Group) and PNG (Portable Network Graphics)
Advantages of Raster Data
Below are the advantages mentioned:
- Raster Datais the simplest form of data structures, and hence they are easy to use and understand by the Geographic Information Systems Workforce.
- This data form can be used to do various spatial analysis.
- The model maintains uniformity when it comes to size and shape due to matrix and multi-array like structure.
- Comparatively to its vector counterpart, the technology is far cheaper and affordable.
- This makes the data livelier and presentable due to the involvement of colour codes, and hence when pairing with vector models, it gives proper relatable information.
With the help of Raster data form, spatial data becomes valuable. Most of the organization that is into GIS domain refer to external raster data forms. Raster data is simple yet heavy to handle due to toa large amount of imagery related files. Unlike earlier days, RDMS and Systems have become robust to handle these large and heavy data models. Both the data types are crucial in the world of GIS, but Raster data is the most preferred one.
This is a guide to Raster Data. Here we discuss Introduction to Raster Data along with the working and 5 different types and the advantages. You can also go through our other related articles to learn more –
- GIS Components
- Impala Database
- Data Quality Tools
- What is Data Engineering?
- What is Spatial Data?
In its simplest form, a raster consists of a matrix of cells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information, such as temperature. Rasters are digital aerial photographs, imagery from satellites, digital pictures, or even scanned maps.What are the different types of raster data? ›
raster data types. There are three types of raster data that can be stored in a geodatabase: raster datasets, raster catalogs, and raster as attributes. Raster datasets are single images that are stored in the database.Which are the 4 types of raster resolution? ›
When working with imaged raster data, there are four types of resolution you might be concerned with: spatial resolution, spectral resolution, temporal resolution, and radiometric resolution.What are the elements of raster data? ›
A raster represents a continuous surface, but for data storage and analysis, a raster is divided into rows, columns, and cells. Raster data represent points by single cells, lines by sequences of neighboring cells, and areas by collections of contiguous cells.What are 4 common raster file types? ›
A raster graphic is made up of a collection of tiny, uniformly sized pixels, which are arranged in a two-dimensional grid made up of columns and rows. Each pixel contains one or more bits of information, depending on the degree of detail in the image.What are two types of raster data? ›
There are two types of raster data: continuous and discrete. An example of discrete raster data is population density. Continuous data examples are temperature and elevation measurements. There are also three types of raster datasets: thematic data, spectral data, and pictures (imagery).What is raster best used for? ›
Raster images are best for digital photos and print materials. 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.What is the difference between raster data? ›
Raster data and vector data are two types of spatial data in GIS. The main difference between Raster and Vector Data is that the raster data represents data as a cell or a grid matrix while vector data represents data using sequential points or vertices.Which is raster format? ›
Popular types of raster files include JPEG, PNG and GIF images.
Examples of raster image file types are: BMP, TIFF, GIF, and JPEG files.How many cells are in a raster? ›
By default, the size of a raster attribute table is limited to 65,535 unique values.What are the 5 main components of GIS? ›
A working GIS integrates five key components: hardware, software, data, people, and methods. Hardware is the computer on which a GIS operates. Today, GIS software runs on a wide range of hardware types, from centralized computer servers to desktop computers used in stand-alone or networked configurations.What are the properties of raster? ›
Raster products include the Raster Metadata section, which lists the sensor and product information. Properties in this section include sensor name, product level, imagery acquisition date, sun and sensor elevation and azimuth angle, and the off-nadir angle.What are the characteristics of raster image? ›
These are the types of images that are produced when scanning or photographing an object. Raster images are compiled using pixels, or tiny dots, containing unique color and tonal information that come together to create the image. Since raster images are pixel based, they are resolution dependent.
The 5 Types of Digital Image Files: TIFF, JPEG, GIF, PNG, and Raw Image Files, and When to Use Each One. There are 5 main formats in which to store images.What are the 3 types of files? ›
The types of files recognized by the system are either regular, directory, or special. However, the operating system uses many variations of these basic types. All file types recognized by the system fall into one of these categories. However, the operating system uses many variations of these basic types.Why is it called raster? ›
The word "raster" has its origins in the Latin rastrum (a rake), which is derived from radere (to scrape). It originates from the raster scan of cathode ray tube (CRT) video monitors, which paint the image line by line by magnetically or electrostatically steering a focused electron beam.What is raster process? ›
Raster functions are operations that apply processing directly to the pixels of imagery and raster datasets in the map display, as opposed to geoprocessing tools, which write a new raster output to disk.Why is it called raster image? ›
The name derives from the early CRT video technology, which would “paint” an image on a screen line by line by magnetically steering a focused electron beam across a fluorescent viewing surface. This process of building an image was known as a Raster Scan, and the resulting pattern — or picture — was known as a Raster.
Raster data is stored as a grid of values which are rendered on a map as pixels. Each pixel value represents an area on the Earth's surface. Vector data structures represent specific features on the Earth's surface, and assign attributes to those features.How do you create a vector PDF? ›
First, open the image you want to save as a PDF in Photoshop. Then, go to File > Save As and select “PDF” from the drop-down menu. In the next window, select “Vector” from the “Format” options and click “Save.” That's it! Your image is now saved as a vector PDF.What are the advantages of raster data? ›
Raster data is more suited to mathematical modelling and analyses. Due to the fact that raster surfaces represent one attribute or value, calculations, algorithms and quantitative processing can be very quick and simple to run. The grid surface is ideally suited for presenting and storing continuous values.What are the types of raster images? ›
- JPG — compressed raster format, often used for photos. Best for web use. ...
- PNG — raster format good for illustrations or icons. supports transparency, unlike JPG. ...
- TIFF — raster format that is best for high-resolution printing.
Raster graphics are made up of orderly arranged colored pixels to display any image whereas, vector graphics are composed of paths using a mathematical formula that is a vector that directs the route and shape. Raster images are more capable of rendering complex, soft-colored, vibrant multi-colored visuals.What is raster data model? ›
The raster data model is a widely used method of storing geographic data. The model most commonly takes the form of a grid-like structure that holds values at regularly spaced intervals over the extent of the raster.What is raster size? ›
Raster Resolution or "Cell Size"
The pixels within a raster are also referred to as "Cells" and so the resolution of a raster may also be referred to as "cell size". Cell size = Spatial Resolution: the dimension of the area covered on the ground and represented by a single pixel (e.g., 10m).
A raster layer consists of one or more raster bands — referred to as single band and multi band rasters. One band represents a matrix of values. A color image (e.g. aerial photo) is a raster consisting of red, blue and green bands.What is raster map? ›
A raster map is basically a 'dumb' electronic map image made up of a set number of pixels. You can't manipulate the information, move a place name around for example, and when you zoom into the map, it quickly becomes pixellated and unreadable, just like a photo taken on a digital camera.What is a raster vector? ›
Raster (or bitmap) images are described by an array or map of bits within a rectangular grid of pixels or dots. Vector images are described by lines, shapes, and other graphic image components stored in a format that incorporates geometric formulas for rendering the image elements.
There are three methods to store image and raster data: as files in a file system, in a geodatabase, or managed from the geodatabase but stored in a file system. This decision also involves determining whether to store all the data in a single dataset or in a catalog of potentially many datasets.What is an open raster image? ›
OpenRaster is a file format proposed for the common exchange of layered images between raster graphics editors. It is meant as a replacement for later versions of the Adobe PSD format. OpenRaster is still in development and so far is supported by a few programs. The default file extension for OpenRaster files is ".What is a raster made of? ›
Raster files are images built from pixels — tiny color squares that, in great quantity, can form highly detailed images such as photographs. The more pixels an image has, the higher quality it will be, and vice versa. The number of pixels in an image depends on the file type (for example, JPEG, GIF, or PNG).Where is raster cell size? ›
To find out the cell size of a raster layer, right-click the raster layer in the table of contents, click Properties, then click the Source tab.Is raster data stored as a cell? ›
Recall that the basic unit of the raster data model is the cell. Cells store information about what things are like at a particular location on the earth's surface. Depending on the type of data being stored, cell values can be either integers (whole numbers) or floating points (numbers with decimals).What are the 5 benefits of GIS? ›
- Make Better Business Decisions. ...
- Improve Functional Performance & Reduce Cost. ...
- Enhance Customer Service and Increase Sales. ...
- Better & More Cost-effective Plan Citizens.
A map is a symbolic representation of selected characteristics of a place, usually drawn on a flat surface. Maps present information about the world in a simple, visual way. They teach about the world by showing sizes and shapes of countries, locations of features, and distances between places.How does raster image processing work? ›
In handling raster images, a raster image processor works with sets of pixels or bits that are programmed for monochrome or color display. This type of tool often sends the processed image to a printer or handles the transfer between various types of hardware.How is data stored in the raster data? ›
Raster data is stored as a grid of values which are rendered on a map as pixels. Each pixel value represents an area on the Earth's surface. Vector data structures represent specific features on the Earth's surface, and assign attributes to those features.What is raster data processing? ›
Common raster data processing tasks include cropping and reprojecting raster data, using raster math to derive new rasters, and reclassifying rasters using a set of values.
The raster GIS data capture technique involves capturing of attributes and other data without physical contact. This is usually done with the help of satellite imaging techniques such as aerial photography.What is raster image used for? ›
Raster images are often used for digital photographs, but they can also be used for illustrations, logos, and any other type of image. Raster images are made up of pixels, which are tiny dots of colour.Why do we use raster? ›
Raster graphics are best used for non-line art images; specifically digitized photographs, scanned artwork or detailed graphics. Non-line art images are best represented in raster form because these typically include subtle chromatic gradations, undefined lines and shapes, and complex composition.How is raster data structure stored? ›
There are three methods to store image and raster data: as files in a file system, within a geodatabase, or managed from within the geodatabase but stored in a file system. This decision also involves determining whether to store all the data in a single dataset or in a catalog of potentially many datasets.What are the properties of raster data? ›
Raster products include the Raster Metadata section, which lists the sensor and product information. Properties in this section include sensor name, product level, imagery acquisition date, sun and sensor elevation and azimuth angle, and the off-nadir angle.What is raster data analysis? ›
Raster data analysis is based on cells and rasters. ● Raster data analysis can be performed at the level of individual cells, or groups of cells, or cells within an entire raster. ● Some raster data operations use a single raster; others use two or more rasters.