Thursday, September 21, 2006
Lab 2: Representations of the Earth.
First I drew the sphere, the sphere was the first round representation of the earth. Newton proved that the earth was an ellipsoid flattened at the poles.
This representation is still a pretty good way to visualize the earth. The flattening at the poles is only 1\298 which is pretty small. I tried to make my ellipsoid geometrically correct; my width was 432 points or six inches. Dividing 432 by 298 results in approximately 1.45 points. This difference is not enough to be seen when superimposed onto the sphere. So I exaggerated the ellipsoid so that the flattening would be apparent.
The geoid presented a different problem all together. It is supposed to represent how gravity acts on the earth if the entire earth's surface was mean sea level. This is useful for geodetic surveys when accuracy really counts. But I had no idea what it would look like. Below is the picture I found at Google Images which gave me an idea of what to draw. I was surprised at its shape, it looks like a child's ball of play-doh, but once I thought about it it made sense. The earth is not an homongeneous rock, it is a sludge in the center and so it should deform when strong forces act on it and it does, locally. So when we look at the earth it is still looks like a sphere, but when we do extremely accurate geodetic surveys for things like bridges we have to take into account the changes that occur because of gravity at the local level. When I drew the geoid I was not sure about what size it should be so I made it about the size of the ellipsoid.
The natural surface I stylized to represent rocky and smooth surfaces laid on top of the ellipsoid.
First I drew the sphere, the sphere was the first round representation of the earth. Newton proved that the earth was an ellipsoid flattened at the poles.
This representation is still a pretty good way to visualize the earth. The flattening at the poles is only 1\298 which is pretty small. I tried to make my ellipsoid geometrically correct; my width was 432 points or six inches. Dividing 432 by 298 results in approximately 1.45 points. This difference is not enough to be seen when superimposed onto the sphere. So I exaggerated the ellipsoid so that the flattening would be apparent.
The geoid presented a different problem all together. It is supposed to represent how gravity acts on the earth if the entire earth's surface was mean sea level. This is useful for geodetic surveys when accuracy really counts. But I had no idea what it would look like. Below is the picture I found at Google Images which gave me an idea of what to draw. I was surprised at its shape, it looks like a child's ball of play-doh, but once I thought about it it made sense. The earth is not an homongeneous rock, it is a sludge in the center and so it should deform when strong forces act on it and it does, locally. So when we look at the earth it is still looks like a sphere, but when we do extremely accurate geodetic surveys for things like bridges we have to take into account the changes that occur because of gravity at the local level. When I drew the geoid I was not sure about what size it should be so I made it about the size of the ellipsoid.
The natural surface I stylized to represent rocky and smooth surfaces laid on top of the ellipsoid.
// posted by Elizabeth Hull @ 6:36 AM 
