Lab #6 DEM

I chose to acquire a DEM from a region of the Yosemite National Park. I had a difficult time finding this region from just looking at the map on the website, however there was a tab which added the counties to the map and I was able to find the park. The process of downloading the map was very practical and easy to do.
The different overlays which I projected the map in were hillshade, slope, and aspect. The DEM layer was set above these other layers in the ArcMap table of contents in order to see the information portrayed on the DEM layer. I picked different color schemes to best suit the information displayed.
Finally there was a 3D map to be made. The DEM had to be in ArcScene in order for this 3D map to be made. When recently inputting the information into ArcScene, I could not find my 3D image, the screen was blank. The problem was solved by adjusting the value for the "Z unit conversion factor" to a .0001 value.
There were more toolbars to be used for this DEM lab which allowed the viewing of the DEM in multiple ways. It was necessary to keep track of which toolbars to use and when to use them. This lab was interesting, especially when working with a 3D visual in ArcScene.

Lab #5 Map Projections

Original Map


Conformal Projections
Mercator


Gall Stereographic


Equal Area Projections
Sinusoidal


Bonne


Equal Area Projections
Equidistant Conic


Aitoff (Equatorial Azimuthal)


The map projections which I chose belong to three different categories which are conformal, equal area, and equidistant. For the conformal map projections I chose Mercator and Gall Stereographic; for the equal area category, I chose Sinusoidal and Bonne; the equidistant map projections were Equidistant Conic and Aitoff. To understand and analyze how the different map projections change the perception of the world map, distance in miles was taken for all map projections between the cities of Kabul and Washington D.C. across the Atlantic ocean; the distances are as follows: Mercator-10,163 mi, Gall Stereographic-7,167 mi, Sinusoidal-8,094 mi, Bonne-6,779 mi, Equidistant Conic-6,992, and Aitoff-8,649 mi.

It is important to understand the characteristics of each type of map projection to have a better understanding of how the world is perceived on each map. Conformal map projections have parallels and meridians which intersect at right angles; this can be observed from the Gall stereographic map. However the most important characteristic of a conformal map projection is that map scale is preserved across the map; meaning that shape and angles are preserved. In equidistant map projections, the distance from the center of the map is equal in all directions; this is clearly observed in the equidistant conic map. Lastly, in equal area projections, areas on the map maintain the same proportional relationship.

Because variation in the distance measurements from Kabul to Washington D.C. are noticed in all six map projections, it is important to understand what each map will be used for. A clear understanding of the purpose the specific map in terms of what information it provides, makes it easier to choose a map and understand why a given measurement is what it is. Also, the person analyzing a specific map projection might benefit more from an equidistant map projection if his study needs a map with the qualities of this type of projection.

Questions answered about the general map were measurements of the span of the equator-360 degrees. From northern to southern-most graticule the measurement is 180 degrees.