Lab 6

3D Model

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        This week's lab is focused on performing spatial analysis in ArcGIS based on a particular form of raster data called the digital elevation model. A particular area is divided into raster sectors, with elevation data assigned to each. The process of creating various representations based on the raster data was enjoyable and intriguing as we are allowed to choose a color ramp to our liking. I was particularly fascinated by ArcScene and its presentation of raster data using 3D graphics. Being able to actually rotate and view the area from all 360 degrees gave me more information about the area than any other 2D maps. The process of creating the other 2D maps was quite simple and painless. The spatial analysis tool from ArcToolbox was extremely helpful and did almost all the necessary work for me, including dividing data into subgroups and assigning color ramps based on it. It was, however, a bit inconvenient that I could not find the units used for the data in each raster layer easily. As a result, the legends may appear confusing to readers who don't know the units beforehand. Also, there seemed to be some glitch within ArcScene, such that a corner of the 3D landscape turned blank after I left the program idle for some time. I tried rotating and zooming but the problem persisted. Fortunately I exported the image before this glitch occurred. 

Lab 5

        
          In this week's lab we explore a variety of global map projections along with their strengths and weaknesses. Since the earth is a three-dimensional object, it's not possible to project its surface onto a continuous two-dimensional surface without distortions. As a result, no map is truly equidistant in such a way that all distances between any two points on the map are of the same scale. Given that there no perfect way to project the earth's surface, many different projection methods were invented to preserve certain geometric elements at the cost of distorting the others. 

          One element of such is the shapes earth's continents. In order to preserve shapes, angles must be locally preserved. Maps that preserve angles are called conformal. In a conformal map, longitudes and latitudes must intersect at right angles, and from any given point scale should be the same in all direction. This does not necessarily mean that conformal maps have one consistent scale throughout the entire map. Most conformal maps in fact have different scales in different zones. The most popular and widely used conformal projection is the Mercator projection, in which loxodromes on the globe (line that cross meridians at a constant angle) are simply straight lines on a Mercator map. This feature proved to be very useful for nautical navigation. However, conformal projections such as the Mercator have many limitations. For example, a straight line between two points on a Mercator map is often not the shortest route (geodesic line) between those points on earth's surface. Also, area distortion worsens when moving away from the equator. As a result, Mercator maps suffers area area distortion so severe in the polar regions that most Mercator maps are clipped between 85 degree North and South.

          Of all the geographic elements, area is perhaps the most important and useful one for the application of maps. Accurate presentation of area on maps are crucial for the analysis and comparison of data regarding geographical distribution. As a result, many equal-area projections were invented for this purpose. On an equal-area map, the ratio of any two areas is always the same as the actual ratio on the globe. The preservation of area, however, comes with distortion of shape as a cost. In the maps of cylindrical equal-area projection and sinusoidal projection, shapes of continents toward polar regions seem extremely compressed in order to maintain their corresponding small surface area. Besides area, distance between two points is another important geometric factor that is preserved by many map projections.  However, as mentioned earlier, no map is truly equidistant; instead, most equidistant maps only have a limited number of lines that have the same consistent scale throughout their lengths. For example, in the Azimuthal equidistant projection only distances of straight lines that pass through the center of the map are preserved. As for the cylindrical equidistant projection, only the meridians and equator are of consistent scale. Horizontal scales rapidly increases as one moves vertically away from the equator. 

          Choosing the right map projection is all about knowing which geographic element is important for the purpose of the map and compromising between them. For example, aesthetically, conformal maps are favored for their accurate portrayal of shapes, while equal-area maps are extremely important for GIS because of their ability to accurately present the distribution of a certain attribute per unit area. However, one would be mistaken to think that every map favors just one geographic element. In fact, there are plenty of projections that attempt to compromise between different map properties by not strictly preserving any single one of them. For example, the Robinson projection, though neither conformal nor equal-area, compensate by bending meridians slightly to reduce distortion toward the poles but not enough to get rid of it completely like the sinusoidal projection. 

Lab 4

 

                

               In lab 5 from week 4 we finally began the instruction and operation of a professional GIS system named ArcGIS. The assignment of lab 5 is to utilize ArcMap from ArcGIS to create maps which outlines an airport expansion along with data on lands that will be affected by the proposed expansion. Given this my first experience with a GIS system, I was both excited and a bit intimated by the seemingly complicated interface. Fortunately, thanks to the extremely detailed and step-by-step tutorial PDF I was able to progress smoothly through the assignment with little difficulty until I ran into that infamous bug.
                Like many others from the lab, I encountered a problem such that the population field from the tracts layer would lose all its data once I add an additional field for population density. The problem remains even after I attempted the steps aimed to resolve this issue suggested by the TA. Finally, in the following lab session I found that I am not supposed to delete the newly created population density field when I attempt rejoining even if it’s filled with null data.  After overcoming this troublesome bug I managed to proceed and finish the assignment without much difficulty. The only other problem that I encountered was toward the end when the instruction manual requires us to modify the elements of the legend for the schools and noise contour map without demonstrating how to do so. Fortunately it didn't long for me to find the right options in the legend properties window.
               Though my overall experience with ArcGIS was pleasant, there were definitely some inconveniences in the process. For example, many actions or events in ArcMap cannot be undone through the edit menu. This is especially frustrating for me because most programs that I've used trace every action such that mistakes can always be fixed with a simple ctrl+z. Moreover, the display area does not seem to be synchronized with the table of contents. For instance, ArcMap doesn't automatically reflect my selection in the display area unto the table of contents. It would be more convenient if a layer in the table of contents is automatically selected whenever I click on the corresponding layer in the display area. Another slight inconvenience is that browsing seems a bit unintuitive in ArcCatalog, especially when I try to navigate to an arbitrary folder that’s not under the root directory or existing database locations.
                GIS systems such as ArcGIS are an essential tool for professionals such as geographers or engineers. In ArcGIS, data are organized into layers so that different kinds of data can be easily edited without affecting others. Layers also enable maps to display different level of information on top of each other at the same time. ArcGIS also allows users to embed lots of useful elements, such as texts, legends, or scale bars to make their maps more informative. However, the sheer amount of functionalities within ArcGIS makes the program seems rather complicated. Without a user-friendly interface or extensive tutorials, ArcGIS may appear daunting to beginners or non-professionals.  Also, license for a professional GIS application like ArcGIS is rather expensive. Most people would be limited to neogeographic tools because of the extensive amount of money and time needed for professional GIS tools. 

Lab 3

      The map below is a short tour I created for Six Flags Magic Mountain. I've only been to Six Flags Magic Mountain once and was not able to visit all the rides. This tour highlights the ones that I want to visit if I ever get the chance to go again.



View Six Flags Magic Mountain in a larger map
     
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 In the age of neogeography, maps development is no longer a privilege limited to professionals. Anyone given internet access is able to create and share geographic information with others. Maps may contain not only empirical data such as elevation or geographic coordinates, but now also personal information such as tagged photos or reviews for tourist attractions. As a result, maps can be more informative and easier to understand as people may find certain information easier to relate to. For instance, two maps of the same location, while one has photos tagged by celebrities, would have very different meanings to people reading them.
        However, the freedom of neogeography also comes with a cost. Just like the internet itself, greater accessibility and publicity usually results in overall decrease in quality. As more and more people from the general public are able to publish maps, the average quality and reliability of all maps are expected to fall, as non-professionals are prone to provide inaccurate or biased data.