Geospacial Technology

Geospatial Technology

REMOTE SENSING

Remote sensing can be defined as human’s ability to study objects without being in direct physical contact with them. So for example, your eyes are a form of passive remote sensing because they are “passively” absorbing electromagnetic energy within the visible spectrum from distant objects and your brain is processing that energy into information. There are a variety of remote sensing platforms or devices, but they can basically be categorized into the following that we will look at throughout the course.

GLOBAL POSITIONING SYSTEMS

Another type of geospatial technology is global positioning systems (GPS) and a key technology for acquiring accurate control points on Earth’s surface. Now to determine the location of that GPS receiver on Earth’s surface, a minimum of four satellites are required using a mathematical process called triangulation. Normally the process of triangulation requires a minimum of three transmitters, but because the energy sent from the satellite is traveling at the speed of light, minor errors in calculation could result in large location errors on the ground. Thus, a minimum of four satellites is often used to reduce this error. This process using the geometry of triangles to determine location is used not only in GPS, but a variety of other location needs like finding the epicenter of earthquakes.

A user can use a GPS receiver to determine their location on Earth through a dynamic conversation with satellites in space. Each satellite transmits orbital information called the ephemeris using a highly accurate atomic clock along with its orbital position called the almanac. The receiver will use this information to determine its distance from a single satellite using the equation D = rt, where D = distance, r = rate or the speed of light (299,792,458 meters per second), and t = time using the atomic clock. The atomic clock is required because the receiver is trying to calculate distance, using energy that is transmitted at the speed of light. Time will be fractions of a second and requires a “time clock” up the upmost accuracy.

GEOGRAPHIC INFORMATION SYSTEMS

There is a technology that exists that can bring together remote sensing data, GPS data points, spatial and non-spatial data, and spatial statistics into a single, dynamic system for analysis and that is a geographic information system (GIS). A GIS is a powerful database system that allows users to acquire, organize, store, and most importantly analyze information about the physical and cultural environments. A GIS views the world as overlaying physical or cultural layers, each with quantifiable data that can be analyzed. A single GIS map of a national forest could have layers such as elevation, deciduous trees, evergreens, soil type, soil erosion rates, rivers and tributaries, major and minor roads, forest health, burn areas, regrowth, restoration, animal species type, trails, and more. Each of these layers would contain a database of information specific to that layer.

Nearly every discipline, career path, or academic pursuit uses geographic information systems because of the vast amount of data and information about the physical and cultural world. Disciplines and career paths that use GIS include: conservation, ecology, disaster response and mitigation, business, marketing, engineering, sociology, demography, astronomy, transportation, health, criminal justice and law enforcement, travel and tourism, news media, and the list could endlessly go on.

Now, GIS primarily works from two different spatial models: raster and vector. Raster based GIS models are images much like a digital picture. Each image is broken down into a series of columns and rows of pixels and each pixel is georeferenced to somewhere on Earth's surface is represents a specific numeric value - usually a specific color or wavelength within the electromagnetic spectrum. Most remote sensing images come into a GIS as a raster layer. The other type of GIS model is called a vector model. Vector based GIS models are based on the concept of points that are again georeferenced (i.e. given an x-, y-, and possibly z- location) to somewhere specific on the ground. From points, lines can be created by connecting a series of points and areas can be created by closing loops of vector lines. For each of these vector layers, a database of information can be attributed to it. So for example, a vector line of rivers could have a database associated with it such as length, width, stream flow, government agencies responsible for it, and anything else the GIS user wants tied to it. What these vector models represent is also a matter of scale. For example, a city can be represented as a point or a polygon depending on how zoomed in you are to the location. A map of the world would show cities as points, whereas a map of a single county may show the city as a polygon with roads, populations, pipes, or grid systems within it.

Now more then ever society has access to spatial information through the use of geospatial technology, which is directly influencing how we understand the physical and cultural environments we live in. Recently the Washington Post had two articles on how maps help us understand our world titled 40 Maps That Explain Our World and 40 More Maps That Explain Our World. The images below are satellite images from NASA and proved by NASA's Earth Observatory. Click on the thumbnails to see a large image and click on the those to get detailed information for each satellite image. All of the images in this eTextbook are free and licensed as Creative Commons. By clicking on any image, you will be directed to the original source.

Summary

Geography is a unifying discipline of research that helps us understand the physical, environmental, and cultural environments with an emphasis in interconnections and spatial dynamics between these environments. The discipline of geography has had a long history starting back to the time of the earliest explorers, through the colonial era of power, territory, and domination, and today as a scientific discipline based on empirical evidence using the scientific method. Because geographers look at the physical and cultural world, most geographers are trained in both physical, natural, and social sciences in order to understand how each influences the other. Geography is also an important spatial science and uses geospatial technology to understand the various environments spatially and over time. This is done by using technologies such as satellite imagery, aerial photography, global positioning systems and geographic information systems to name a few. It also requires geographers to have a strong background in spatial thinking and analysis to understand patterns, connects, and pathways between the

SOURCE: http://www.opengeography.org/ch-1-intro-to-geographic-science1.html