Lab 7 - US Census

This Choropleth map shows the concentration of Blacks by county in the United States in 2000. (Source: Census 2000) The map shows that the population of Blacks are mostly concentrated in the South-East sector of Continental United States; notably in Georgia, Alabama, Mississippi, and Louisiana, where Blacks accounts for more than half of the population in some counties. This demographic trend is most likely the direct result of slavery in the past. It seems most of African Americans in United States still resides at where their ancestors settled.

 

This Choropleth map shows the concentration of Asians by county in the United States in 2000. (Source: Census 2000) The map shows that the population of Asians are mostly concentrated in the West Coast of Continental United States and Hawaii in the Pacific. This is most notable in California and Hawaii, where Asians accounts for more than 20 percent of the population in some counties. This demographic trend is most likely the proximity of this territories to the Pacific Ocean and therefore, Asia. However, Asians are more evenly spread out throughout United States as compared to Blacks and Some Other Races. This might be due to the nature of Asians who likes to move around in search of better opportunities.

This Choropleth map shows the concentration of Some Other Races (95 percent being Hispanic or Latino) by county in the United States in 2000. (Source: Census 2000) The map shows that the population of Some Other Races are most concentrated in the West Coast and South West; notably in California, Arizona, New Mexico, and Texas where Some Other Race accounts for more than 9 percent of the population in most counties and exceeding 22 percent of the population in some counties. This demographic trend is most likely the result of the proximity of this area to Central and South America.

My experience with creating Choropleth maps based on US census data is really a rewarding one as it requires me to use all my previous lab experiences to create a useful map that clearly shows the demographics of different races in United States. As I’m a international student and unaware of the demographics of United States, and it came as a surprise to me that United States is not as homogeneous as I previously envisioned. In all three maps, the Midwest have the smallest concentration of minority races. The coastal regions seems to have more diverse populations compared to inland areas. The distribution also tells me that the descendants of early immigrants whom are minorities tend to stay near the location where their ascendants settled. 

My experience with GIS was highly informative and hands on. GIS is a vital tool for policymakers (most whom have a humanistic rather than scientific background) to rely on to analyse raw data. They can make better and more informed decisions with such spatial analysis tools. I’m very certain that this knowledge acquired will come in handy in my career when I return to Singapore to work in the government. It is definitely an rewarding experience to be able to gain such exposure.

Lab 6 - DEMs

Shown below are the 3D model, aspect map, slope map and shaded relief model of the San Francisco Bay Area. In the 3D model, the white and blue denotes elevation above the water body and the brown area denotes the water body. I chose SF Bay Area because it consists of both land terrains and water bodies and I’m curious of what the area would look like in a 3D model. The combined information from the maps and model provided a wealth of information about the terrain in SF Bay Area. For example, it provides a clear picture on how the land terrain would look like on the ground. It also shows slope gradient and elevation, making it is perfect for terrain analysis. 

Extent information (in decimal degrees):

Top edge: 38.126944443792 Degree

Bottom edge: 37.6891666659854 Degree

Left edge: -122.648888888802 Degree

Right edge: -122.138888888768 Degree

Geographic coordinate system: GCS North American 1983

Map Projections

 

Map projection is a process of mathematical conversion whereby a 3 dimensional world is transformed into a 2 dimensional world. Map projection is extremely useful as it allows us to stored data of our 3 dimensional world in a flat plane map. However, this transformation inherently causes distortions. The extend of this distortions depends on the way the map is projected. As shown in the above diagrams, the distances for Washington, D.C. to Kabul varies depending on the map projection.


No perfect map projections exist. Rather, there are thousands of different projections and each serves certain specific purpose only. Many of these map projections preserves certain properties of a 3 dimensional map. Some of these properties are shape, direction, area and distance. We need to be extremely careful in choosing the right type of projection for the job. For example, the World Azimuthal Equidistant projection, which preserves distance and direction from the center point, is used by radio operators to find out where to point their antennas to and what wavelength to use depending on the distance. The Mercator projection is used by navigators to plot their course as it preserves direction.

Note that the 2 equidistant projections presents vastly different distances. This is because the World Two Point Equidistant projection have two control points in which distances from any point on the map to the two control points are preserved. However in a World Azimuthal Equidistant projection, only distances and direction from the center of the map is preserved. Since neither Kabul nor Washington is at the center of the World Azimuthal Equidistant projection, the distances between the two cities is not preserved and hence inaccurate.

The preservation of specific map properties are not always important in map projections. Some commonly used projections do not preserve any properties of 3 dimensional maps. One example would be the Robinson Map projection. It is commonly used in textbooks in Singapore. The projection intentionally abandoned preserving any property for a compromise that results in a better world view. Maps may even be even be deliberately distorted for illustration or propaganda purposes. The preservation of metric properties may also not be as important in small area maps (ie. street maps etc.) as distortions are negligible.