Lab 6: DEMs in ArcGIS

The area that I looked at for this lab is a mountainous area just south of Palm Dessert and east of Temecula. While most of the terrain is mountainous, the northeast corner is flat because of where the dessert begins. There is also a very large peak directly in the middle of my map. This was a very good area to use for the lab because of the large variations in elevation and slopes. The extent of the area is N 33.6525 W 116.63389 on the northwest corner to N 33.3825 W 116.20111 on the southeast corner. The geographic coordinate system is the North American 1983.

Shaded Relief Model:

Slope Map:

Aspect Map:

3D Image:

Lab 5: Projections in ArcGIS

Map projection is the process of converting a three dimensional earth ellipsoid to a two dimensional surface through mathematical conversion. There are many different ways to make a map projection and each one has its own features. To start, the globe is projected onto either a plane, a cylinder, or a cone. All of these surfaces are able to then be unwrapped to take the form of a flat surface. The three main types of projections are conformal, equal area, and equidistant. Each of these map projections preserve a particular property: local shapes, areas, and distances.

While projections make it much easier to view the earth's surface on a flat plane, it does have its disadvantages as well. While some properties might be preserved, others will be greatly skewed. For example, in the mercator projection, while local angles and shapes remain the same, the areas change greatly. This is why when you look at the map, Alaska looks like it's the same size as Brazil.

For this exercise, we were asked to show 6 different projections of the world and map the locations for Washington DC and Kabul, Afghanistan. I made 2 of each type of map projection then used the measuring tool to find the distance in miles between the two locations. After finding all of the distance, I found the map projections can greatly skew long distances on a map. I ended up with a wide range of distances from as high as 10,082 miles to as low as 5,061 miles, a difference of 5,021 miles. The actual distance between the two cities is approximately 6,900 miles. We can see that using map projections can be dangerous when making measurements.

While map projections can seem to not be accurate when dealing with measurements and comparison of values like area and shape, they are still very important. The thing you have to remember about map projections is that it is meant for illustrative purposes. When using these maps, we are concerned with relative locations and not necessarily quantitative values.

Lab 4: Introducing ArcMap

I found the ArcMap tutorial to be very informative and helpful with understanding how to use GIS. The first four exercises were very straight forward and made it very easy for a first time user to follow along without any problems. Aside from a few hiccups, I worked through the these exercises very quickly and obtained the same results that were seen in the diagrams from the tutorial.

The last exercise I really enjoyed because they weren't as straight forward with the steps. They told you what you were supposed to do, and based on the previous exercises, you had to find out how to do that. This allowed me to realize how much I had learned so far and really test my skills with the program. Although the steps didn't really deal with data, I think that tinkering around with the formatting still allows a user to feel more comfortable using the program on future projects. I understand the importance of going through the tutorial multiple times in order to truly understand what each step means for the analysis of GIS.

Although the tutorial was very easy to use, it was also obvious that there were some pitfalls with using the program. First of all, it was not always clear how to take parts of information from one data set and use it with parts of another map. This means, although I was able to work through the tutorial easily, I do not know if I would be able to obtain similar results with my own data and analysis. Also, it is very easy to make mistakes using GIS and ArcMaps. The user has to be very careful to keep track of units, make sure proper figures are selected with doing any formatting or analysis, and verify that their analysis is valid and applicable.

Despite these pitfalls, ArcMaps and GIS has a lot of potential for creating very informative maps. GIS allows us to take data stored in different maps and overlap them onto each other in order to create many different maps with new information. Combining data is very fast and simple once a user has mastered using the program. It allows for simple formatting and has many features that makes the types of maps a person can make endless. GIS and ArcMaps is a very important tool that will continue to be used for creating informative and easy to read maps.