Lab 6

I obtained the data of this location from the UCLA Geography 7 class website, under Week 7 with the file name "dem." The extent information of this location is:

Top: 38.8291666661

Left: -105.788888889

Right: -104.969444445

Bottom: 39.3838888883

Shaded Relief Model

Slope Map

 

Aspect Map

3D Image

Lab 5

Conformal Projection

Mercator

Distance between Washington, D.C. and Kabul, Afghanistan –

Geodesic: 6930.974697 Miles

Loxodrome: 8097.020337 Miles

Great Elliptic: 6905.413763 Miles

Stereographic

Distance between Washington, D.C. and Kabul, Afghanistan –

Geodesic: 6965.062964 Miles

Loxodrome: 8082.927656 Miles

Great Elliptic: 6918.667463 Miles

Equal Area Projection

Bonne

Distance between Washington, D.C. and Kabul, Afghanistan –

Geodesic: 6,952.617257 Miles

Loxodrome: 8103.369102 Miles

Great Elliptic: 6934.483772 Miles

Behrmann

Distance between Washington, D.C. and Kabul, Afghanistan –

Geodesic: 6849.348747 Miles

Loxodrome: 8166.374623 Miles

Great Elliptic: 6909.309873 Miles

Equidistant Projection

Equidistant Conic

Distance between Washington, D.C. and Kabul, Afghanistan –

Geodesic: 6905.408254 Miles

Loxodrome: 8166.374623 Miles

Great Elliptic: 6849.353962 Miles

Azimuthal 

 

Distance between Washington, D.C. and Kabul, Afghanistan –

Geodesic: 6934.478105 Miles

Loxodrome: 8068.550472 Miles

Great Elliptic: 6930.680444 Miles

Map projections are mathematical transformation which transform the earth’s three-dimensional surface to create a flat map sheet. There are different kinds of map projections, and different projections cause different types of distortions. In conformal projections, local shapes are preserved by drawing the perpendicular graticule lines. However, the drawback of conformal projection is that the shapes are greatly distorted for larger areas. For example, in the Mercator Projection, Antarctica looks almost three times of the size of North America. And in the Stereographic Projection, North America looks a lot larger than South America.

To distinguish equal area projection and conformal projection are difficult unless documented or measured. In equal area projections, the area of displayed features are preserved. However, other properties, such as shape, angle, and scale might be distorted. For instance, in the Bonne Projection, Australia looks almost the same size of North America. And in the Behrmann Projection, the top of North America looks very squished and Greenland only contains a very small area. While in equidistant projections, the distance between certain points are preserved, but scale is not maintained correctly throughout the entire map. For example, both the Equidistant Conic Projection and the Azimuthal Projection portray Australia much larger, in the Azimuthal Projection, Australia is even larger than Africa.

Map projections are significant for us to understand the shape, area, and distance of the world we are living in, and different map projections allow people to use them in different purposes. For instance, in this lab, equidistant map projection would be useful for measuring more accurate distance between Washington, D.C. and Kabul, Afghanistan. But the perils of map projections would be that when people are not aware of the distortions of the map projections, they might be confused by the inaccurate information, such as that Australia is larger than Africa!

Although there are many drawbacks of map projections, in general, map projections are still very useful in human’s lives. And since map projections are transformations of three-dimension to two-dimension, it becomes easier for people to measure distance between two points, calculate area, and understand the shape of the lands. Without map projections, it would be inconvenient to do all these things, just imagine that a geographer holding a spherical earth trying to measure the distance between Washington, D.C. and Kabul, Afghanistan! However, the technology of making the map projections can be improved and perhaps someday there can be a map projection that contains least distortions.

Lab 4

In this lab, we learn to use some basic ArcMap™ skills by following the instructions on the ArcMap Tutorial. This tutorial guides us to create a set of maps for a county that is planning to expand its airport, and there are five exercises which each contains different skills of ArcMap. In each exercise, we learn to explore the existing data and working with these information into geographic features or tables. To finish all the exercises, it takes about five to six hours.

While following the instructions on the tutorial, I face some difficulties in Exercise 3 with the population density table. I have tried it several times using the Field Calculator to calculate the population values for each tract in people per square mile. However, I could not get the right values and the information does not even show in the table.  So I start over again from the “Adding data from ArcCatalog,” and later I find out that the reason I cannot get the right value is that I did not close the tract_pop table and TRACT_ID table before proceeding with the join, and the information on the table becomes incorrect from that point. Also, because the tutorial is written for ArcMap version 9.3, and we are using the latest 10.1 version in the computer lab, some of the features are different than explained in the tutorial. Especially the steps with the Editor Toolbar, I am not too sure whether simply skip these steps will affect the outcome of the map or not. But the rest of the tutorial is clear and relatively easy to follow.

As learning to use the AarMap, I find that this is a very useful software of GIS because it can combine many information and data onto one map, and make it easy to read and understand for the readers. In this specific tutorial, by using the ArcMap, we can easily identify whether there is any school that is within the noise contour, or categorize different land use based on different styles portray on the map, and even show population density on a single map. Also, we can use the ArcMap to create graph that shows the number of parcels of each land type. Base on different propose, we can use the ArcMap to reveal these information in different ways to make it easier for the readers to understand.

Although the ArcMap is relatively easy to use and operate and it has great potential to GIS, it sill has some pitfall to GIS. I believe there is much to improve for the software itself. Such as that while I was doing Exercise 3, I did not close both the tract_pop table and TRACT_ID table, so I did not get the right result. However, on the layout it did not show any other window that is left unclosed, and it became hard for me to find which step I did wrong. This is probably an error, and there might be more errors that can lead to significant wrong outcomes. Moreover, after I store my data and map into my flash drive, I cannot successfully reopen it on different computers. The software cannot find the files and data itself; instead, I have to manually search the data.