Lab 6: DEMs in ArcGIS

 

The following is the DEM Data of Grand Canyon. As one of the seven natural wonders of the world, Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. Because it has such drastic change in elevations due to the fissure, it was a good choice to do analysis on the elevation data. The Range of elevation changes are conspicuous in the 3D model of the area. The Shaded Relief Model shows the layout of the region, we can easily spot where the Colorado River flows through. The Slope map shows where the most drastic changes of slope are located. Finally, the Aspect map makes it clear to spot the vastness of the Grand Canyon visible in all directions. The four images gives us a vivid picture regarding the region about the geographical features of Grand Canyon.

----Extent----
Top: 36.4361111103
Left: -112.407222223
Right: -111.689444445
Bottom: 35.8655555548

---Geographic Coordinate System---
GCS_North_American_1983
Angular Unit: Degree (0.017453292519943295)
Datum: D_North_American_1983

3D Image

Lab5: Projections in ArcGIS

This lab exercise greatly demonstrated the importance of map projections. First thing I noticed was the distortions present on each map. Because the world is in three dimensions, and maps are in two dimensions, distortions exist when projecting the world onto a map. There exist three major categories of projection (based on the geometric properties they keep): Conformal, Equal Area, Equidistant. Conformal map projections preserve angles locally; examples are Mercator and Eckert I. Equal Area map projections preserve area; examples are Goodes Homolosine and Bonne. Equidistant map projections preserve distance from some standard point or line; examples include Azimuthal equidistant and Two-point equidistant.

The most important thing when looking at a map is to find out which of those properties the map keeps; this helps the understanding of the purpose behind the map and can be utilized accordingly. For example Mercator and Eckert I, conformal maps which keeps the angles are suited for navigations rather than settling area disputes (Antartica looks bigger than the other continents combined on the Mercator projection). For a dispute regarding area, Equal Area projections are much more suited than other projections. Goodes Homolosine shows the continent of Africa is bigger than Antarctica unlike on the Mercator projection. The Equidistant map keeps equal distance properties based off of its set standard, so it is not suited for measuring distance from one random point to another on the map, but rather is used for more specific measurements related to that standard.

While trying to find the distance between the two cities, Washington D.C. and Kabul, I found out that these distortions caused a great deal of errors. For example, a straight line distance on a Mercator projection (Conformal) was about 10,112 miles, when the correct distance is 6,934 miles. None of the six maps gave a close enough measurement in straight line. The lack of this knowledge can potentially cause great disaster. With the increasing prevalence of amateur uses of maps, the danger for spread of wrong information through the web without any authoritative verification increases.

I think the equidistant maps best demonstrate the purpose of this lab. To use the maps based on the purpose and the properties they are meant to be used for. Equidistant projections, for example have such a specific usage that it did not seem logical to me what the name “equidistant” meant at first. They exemplify why certain types of map projections are better than others for different purposes. Yet just by the name “equidistant” it gave me the wrong idea that the distances between random points would somehow be conserved; the idea which soon became clear to me that it was not feasible. This exercise clearly demonstrated the dangers that one might face if one is not careful with the use of the maps.

Lab4: Introducing ArcMap

ArcMap Experience + Potential and Pitfalls of GIS:

As this was my first experience using the ArcMap software, I must say it was an interesting experience. When I first started the program and following the guide, I was intimidated by the amount of things that the program allows the user to do. But as I stepped through the tutorial, I realized that the program was actually very well organized. I guess that is expected of a program that has been through 10 major versions. The tutorial was very easy to follow, and I was able to create an awesome looking map in just 2 hours. The way that the program manages information just left me in awe of it after I looked at the map I exported.

There is a lot of potential in ArcMap software that is very beneficial for a user to take advantage of. First is that manipulation of data was very easy. It allows the user to access the database and display it in a meaningful way without the need to understand how the data is stored. The hundreds of options for each task really simplify the tasks to be done by the user, creating a very user-friendly access to the world of GIS. Examples of these include drawing tools, as well as calculation tools that really made me say, ‘wow’.

The one pitfall of the ArcMap software I noticed is the sheer size of the program. In trying to load the database and manage it, the program took a long time to load in the beginning. The machines at the lab, as well as remote accessing to the lab, made me feel uncomfortable whenever the program stalled. Although I did not experience any data loss though frequent saving, absent the habit, I would have had to start over. Another pitfall of the ArcMap software is that there still is a high learning curve. After going through the 56 page tutorial, I feel that I only know the very small portion of the software mentioned in the tutorial. The portion of options I have used/understand versus the options I do not understand is just amazingly high. I think a user will need to use this program for months before fully understanding what each part does.

Overall, I think ArcMap is a very powerful yet flexible GIS tool. It is user-friendly while being very robust and full of options. The program seems flawless on first try (provided that it is run on a powerful machine). I think I understand why ArcGIS dominates the market after only using it once.