Lab 6: DEMs in ArcGIS

3D Image:

In this lab exercise, I choose a regional area of the west Grand Canyon where I just visited in the winter break. I choose this area because I think the dramatic elevation change of the canyon is really suitable to build a beautiful 3D model. What's more, the color ramp I choose is perfect for the shaded relief model and the 3D image: white for the snow cover, brown fro the bare stones and green for the vegetation, which make the images look quite real. The original DEM was retrieved from the USGS Seamless Data server using the 1983 North American GCS datum.


Extent:  
Top: 36.301 
Bottom: 35.994
Left: -114.15
Right: -113.561

Lab 5: Projections in ArcGIS

Map projections:

Conformal:

Equidistant:

Equal Area:

As we know, our earth is a slightly irregular ellipsoid. Since it is not convenient to map in a three-dimensional space, it is important to put the surface of the earth onto a two-dimensional plane. Also, because the earth surface is a curved surface that cannot be flattened, we introduce many different map projections to preserve some of the features of the earth surface for diverse uses. In ArcMap, there are a lot of map projections for us to choose. By making these map projections, I had a further understanding about conformal, equal-distant and equal-area map projections, and I also perceived the strengths and pitfalls of different map projections.

First of all, it is quite interesting to see the same map in different map projections. Although I cannot imagine what the Bonne map projection with a shape of heart can be used for (but I believe it is useful for some purposes), it's just quite fun to look at it. However, in spite of the beautiful shapes, the distortions of the maps are also easy to be observed. In Mercator map projection, the area of Antarctica is much bigger than its actual size. Also, in Lambert Conformal Conic map projection, Australia is almost as large as Eurasia which is impossible, and I could not even see where Antarctica is in that map. 

In this lab assignment, we also compared the distance from Washington D.C. to Kabul. We could see that the distortions in different map projections do influences the accuracy of the maps. On the internet, I found the actual distance between Washington D.C. and Kabul is about 7000 miles, which has a very big deviation to the data I measured on some of the map projections. I think the distortions may be neglected in a small area, but it should be definitely taken into consideration when we are making measurements or projections in a large area of the earth.

It is true that each kind of map projections has its strengths and pitfalls, and it seems that there is no "perfect" map projection. However, when we are making a map, we can simply choose the most suitable map projection to use. For example, when we are making maps reflecting features like population density or administrative division which requires the accuracy of areas, Equal Area map projections should be the most suitable. Also, if we want to have a direct perception of the world, a conformal map projection which shows the longitudes and latitudes intersect at right tangle should be a good choice. 

To sum up, when we are making maps, we just need to make best use of the advantages of different map projections for different purposes. Since we have so many different map projections to choose from, we will always be able to find a most suitable projection to use. What's more, since maps are playing a more and more important part in our daily life, and we need different maps for different purposes, I think there will be other map projections invented to adapt to the demand. 

Lab 4: Introducing ArcMap

Using the ArcMap to make maps was overall an interesting experience to me. Although it was the first time that I used a GIS software, the detailed tutorial was quite helpful to me. Although I had to spend many extra hours in the lab to do my work since I was not skillful in using the ArcMap, it was all worth it when I finally accomplished my maps. I almost followed every step in the tutorial this time, but I think the next time when I have the chance to make a map using ArcMap, I will probably add more personal characteristics in it, like the color of the background or the shape. 

As a modern tool of mapping, GIS has many advantages. The map can show architectures, roads, regions and other features on different layers, making it easier to see and analyze the information on the map (we can choose not to show certain layers when they are disturbing). We can put the data directly in the digital maps and the powerful function of making charts enables us to export the data to have a more intuitive grasp. Unlike traditional maps that cannot be updated after they are printed, digital maps can be easily updated. The change of roads, the newly built architectures can be showed on the digital map, and can even be showed to more people through the Internet. The timeliness of GIS makes it more useful in modern society since the change of geography is exceedingly frequent because of human activities. 

It is true that GIS has many benefits that traditional mapping tools do not have. However, GIS still has some pitfalls that can be improved. I'm not going to complain about the complexity of the software because I think people can get used to the software through practicing.In addition, one thing I noticed is the problem of format conversion. Since different GIS softwares were developed in independent and restricted platforms, they use different spacial data models and different organizations of geological data, which make it difficult to exchange data between different softwares. For example, the ArcGIS we use have the format of mxd that various other softwares may not be able to open and edit. What's more, since I found the ArcGIS quite interesting, I checked its price online to see if I could download one so I could make maps on my own computer. Although there is a 60-day free trial for users to use, it costs at least 1500 dollars to buy the software which is definitely too expensive for amateurs who have interests in GIS.

As a significant part of the geographic study, GIS can help us to analyze geographical information more effectively as well as show the out put in a more precise way. It is true that using GIS needs a lot of geography knowledge, but I found that using GIS can also help us review and consolidate our geographic knowledge. In contemporary society, GIS is playing a more and more important part in our life. GIS, as well as the techniques of remote sensing and GPS, is forming a more and more complete technology system of geography that can be used for us to better understand our environment and better construct our earth. The improvement of the intelligence of GIS will also make it more easy to manage and more accessible to the public. GIS is becoming more and more associated with us.