INTRODUCTION TO GEOGRAPHIC INFORMATION SYSTEMS
Q1.
GIS has been given several meanings over the years in various disciplines and areas of study. Interestingly, all these definitions of GIS attest to the uniqueness of spatial data since geographic locale is an essential peculiarity of strategies, plans, policies, and activities. Below is a sum up definition: GIS can be defined as a computer-based methodology and technology used to collect, analyze, model, manage, and present geographical information or data for a vast dimension of applications (Tyler pg. 210)
Components of GIS
People- Individuals are by far the most fundamental part of a GIS. The procedures and task definitions that are to be performed by the GIS must be developed and outlined by people. Human beings can, again and again, blow-away shortfalls emerging from other GIS components while the vice versa is impossible. Even the high-end computers and application software around the globe can never counterbalance incompetence.
Data- It is also another critical aspect of GIS, which carries both attributed and geographical information. Data accuracy and availability affects the outcomes of analysis and queries. Therefore, data collection methods and people collecting data need to be properly aligned to avoid instance inviting errors that can later lead to misinterpretation.
Hardware- GIS hardware devices or components such as plotters, computers, and digitizers provide the user with an interface to interact and carry out operations of the GIS. Such hardware components link both the software and people interactions using the outlined methods to perform GIS activities.
Software- GIS software components include the primary GIS software itself alongside other imaging, statistical, database, and drawing software programs. These software programs provide a platform for human and hardware interactions to design, operate and generate results of the GIS operations. Therefore, the software to be used should be as comprehensive as possible to enable all GIS operations to be conducted with a lot of ease, but generating the desired or expected outcomes.
Procedures or Methods- To generate reproducible and correct results, GIS analysis will demand a consistent and straightforward methods and procedures. The methodology employed in GIS operations should be simple to understand, implement and use. This will also enable the other components of GIS to operate efficiently.
Network- It allows the GIS to rapidly communicate and share digital data. The Internet phenomenon has proved to be a very reliable tool for enabling GIS application deliveries. The internet makes this relation and relies on data as quick and accurate as possible, thus, becoming an integral instrument for the machine and human communication channel.
A GIS example could be in instances where the supermarket management would want to carry out research on how many customers from the neighborhood do visit their store. The method could be by distributing flyers with the neighborhood customers targeted. The movement of people could be monitored and recorded. This data could be analyzed to give an insight of what is happening in that locale
Q2.
Data Sources
Primary data sources refer to the data gathered in digital format to be mainly used in a GIS venture or project. Secondary sources, on the other hand, are analog and digital datasets which were initially collected for other purposes, and, therefore, need to be transformed into an acceptable digital format for a GIS project use (Longley pgs 107-108), i.e., they are data reused from initial studies or research.
Primary vector source
The two commonly and popularly used data capture sources under this category are ground surveying and Global Positioning System, GPS. Ground surveying focuses on the basis that the three dimension of a point may be identified by taking angular or distance measurements from any known points. Hence, survey starts from a laid point or benchmark. GPS satellites on the other hand, continually send coded radio frequency signals that show the exact positioning of objects within time and space (Longley pgs 109-110).
Primary raster source
The most commonly and popularly used primary raster data source is the Remote sensing. It is a technique deployed in extracting information concerning the biological, the physical and also the chemical compositions of objects, but not physically engaging in direct contact. From the measurements of the quantity emitted, scattered or reflected electromagnetic radiation of objects, information can then be derived. These measurements are obtained through sensors that are deployed throughout the spectrum of electromagnetic field (Longley pg. 111).
Secondary vector source
Secondary vector source entails digitizing objects of the vector dimensions from geographic sources of data such as maps. The commonly and popularly used methods include manual digitizing, photogrammetric, heads-up digitizing and COGO data capture (Longley pg 112).
Secondary raster source
The most commonly used secondary raster source is the scanner. It is a device used in converting the analog hardcopy media into equivalent digital images. This is achieved by performing successive line scanning a document or map and then taking recordings of light reflections from local sources of data (Longley pg.113).
Q3.
Spatial data- These are data which are having geographical or structural component (Shekhar pg. 20), implying that the data is linked to some place or point on the Earth’s surface. A good example is evident in a road pictorial or map. A road map is a two-dimensional object containing lines, polygons and points representing roads, cities and political boundaries like provinces or states. The road map is geographical information that can be visualized. Locations of such places as roads, cities existing on the Earth’s surface are translated into the two-dimensional piece of paper or display, retaining the respective positions and distances for the object formerly rendered.
Attribute Data- These are measurements, classifications and or descriptions of geographical objects in a pictorial representation such as a map. They can be categorized into four classes of measures: ordinal, ratio, nominal and interval. Again, attribute data gives features of spatial data (Shekhar pg. 21). Examples may include the name of the owner, phone number and address for an existing spatial data parcels.
Spatial Referencing-This is a series of variables or parameters used to define coordinates and other related spatial objects or features for every dataset found in the Geo datasheet (Shekhar pg. 22). It has been commonly taken that all datasets for a particular region use a typical definition for the spatial reference. Spatial references make it possible for spatial data on different sources or layers can be incorporated into reliable or accurate analysis or viewing. Examples include using line data in representing linear objects such as streets, trails or rivers.
Spatial Entities-The spatial entities are elements that are used to create a data model which can now be used in representing real world (Shekhar pg. 23). These spatial entities include the point, the area, the line and the surface. Drawing an example from a telecommunication GIS, a line can represent cable section, a point to show where the junction box is located, and the surface may indicate the land through which the cables should be laid while the area can represent the building to be powered.
Q4.
Projections are essential elements of map designing. It is a scientific way of transferring data and information to a two-dimensional platform such as computer screen or piece of paper, from the Earth’s model, which is represented as a curved surface with the three-dimensional layout (Maling pg. 139). Various projections are applied to separate kinds of maps since every prediction precisely matches certain applications or uses. Therefore, a reliable projection method needs to be used for the relevant application to avoid situations where errors appear or transformation become out of context.
Main types of projection
Analytical transformation
This seems to be the easiest, direct and obvious solution to the task of relating the coordinates of the Cartesian on a map with the geographical coordinates available on the surface of the earth. This type of projection approximates to the classical cartography method where points are located and plotted on their respective geographic coordinates. GIS automated applications convert the object coordinates for the digitized points on the map source into their natural geographical coordinate layouts (Maling pg. 140). This is finally used to establish the original coordinates to be used by GIS framework in creating a new map. It is referred as the forward solution since it employs the standard practice of converting from geographical to plane coordinates to construct map projections. It also uses the inverse solution method to arrive at the objects in situations where the imagery is available. All these transformations are done about the x-y coordinates of the Cartesian plane.
Grid-on-grid or direct transformation
This method never requires the inverse solution but is based on the relationship between same points existing on the coordinates of the rectangular shaped object available in two projects (Maling pg. 141). It is essential in mappings generated by remote sensing. Also, it is the method deployed in latest analytical plotters to be supplemented with normal aerial photography. This process is considered to be modern, accurate and aerially-oriented thus makes it easy to be used in remote sensing aerial photographic views.
Polynomial transformation
This projection type is sometimes referred to as the numerical change. This coordinates correlation involves constructing polynomial expressions for fitting information and data with the aim of using the resulting coefficients for transforming coordinates of the point left of the map elements or details (Maling pg. 145). It is primary essential in numerical analysis with vast applications. The scenario of numerical changes present a complicated data handling cases that require a deeply analytical method that can exhaust all the necessary data analysis to generate polynomial expressions for fixing data in establishing the coefficients for coordinate transformations.
Q5.
Coordinate systems are means through which determination of where locations or points fall in space are done. Geographical coordinate, most often referred to as latitude-longitude, are the three-dimensional location systems whereas rectangular coordinates are interested in the two-dimensional space (Maling pg. 135). Furthermore, it requires two and three numbers to locate points in two-dimensional and three-dimensional spaces respectively. For instance, to be able to determines a point on the earth’s surface say equator, using latitude-longitude system, one will not only require both the latitude and longitude distances with respect to northern or southern polarities, but will also need to know the height difference from the earth’s surface. Thus, making it to be a total of three-pointers in point location. These coordinate systems are thought of to be providing indices to points location in space, thus to the characteristics of objects that the points indicate.
Advantages of the geographical coordinate system-With this system, one can accurately represent any area or point on the surface of the earth as can be allowed by the used measurement methods. It is pretty simple to locate the points using taken or established measurements in locating such definite points on the earth’s surface. The only sources of error could result in the initial stages of measurement exercise; otherwise, the process would, therefore, be as accurate as the measurements were taken.
Disadvantages of the geographic coordinates-This type of coordinate representation are barred by complicated and time is wasting calculations in the process of distance determination between the area or two locations enclosed by a polygon established through sets of locations or points. It might not only be tedious to calculate these distances but the arithmetic calculations involved might at times not give the exact distance measurements. Alternatively, doing every measurement practically from the ground might be close to impossible considering the fact that reference points for every location can vary from one benchmark to the other depending on the personnel collecting data.
Advantages of rectangular coordinate system- Distance calculations between points located on the surface of the Cartesian plane are always trivial. Area determinations are simple. Graphical depictions are genuine given that that the area coverage is sizeable. Not unless a colossal sectional area is considered then the process might be a little bit complicated, otherwise it is the simplest way one can decide to use for small areas. With accuracy involved in this process, the pictorials generated are the exact representations of the features available in the examined locale.
Disadvantages of rectangular coordinates- With this system, it at times appear that nearly each point on the Cartesian surface is out of place even though not very much. Each projection has the tenancy of inviting errors regarding shapes, distances, directions or sizes about the projection done. The system is quite delicate as on the face value points appear to be misaligned with their real locations though in a slight variance. Accumulation of such variances not only invites errors but also tend to change the reality of object projection as they would otherwise appear if such variances were not encountered or omitted.
Work cited
Tyler, A. R. Expert Systems Research Trends. New York: Nova Science, 2007. Print.
Longley, Paul. Geographical Information Systems: Principles, Techniques, Management, and Applications. New York: Wiley, 2010. Print.
Shekhar, Shashi. "Data Types for Uncertain, Indeterminate, or Imprecise Spatial Objects." Encyclopedia of GIS (2011): 20-32. Web
Maling, D.h. "Surveying and Map Projections." Coordinate Systems and Map Projections for GIS (2012): 135-146. Web.
