Quote of the Day
Present to inform, not to impress; if you inform, you will impress.
— Fred Brooks
I have a boring task that requires that I be able to access a geographic database to gather a large amount of information.
Quote of the Day
Present to inform, not to impress; if you inform, you will impress.
— Fred Brooks
I have a boring task that requires that I be able to access a geographic database to gather a large amount of information. There are numerous databases out there, but the Wikipedia Geonames database is the one I would really like to learn how to use – it is large and free. I am not particularly skilled at web scraping and I have been procrastinating on my task for a while. I need a interesting problem to drive my interest.
Yesterday, I was reading about Mt. Everest on the Wikipedia when I saw the following statement that aroused my curiosity about the shape of the Earth.
The summit of Chimborazo in Ecuador is 2,168 m (7,113 ft) farther from Earth's centre (6,384.4 km (3,967.1 mi)) than that of Everest (6,382.3 km (3,965.8 mi)), because Earth bulges at the Equator. This is despite Chimborazo having a peak 6,268 m (20,564.3 ft) above sea level versus Mount Everest's 8,848 m (29,028.9 ft).
Mount Chimborazo is shown in Figure 1. While I have never heard of this mountain before, it apparently has the distinction of having a summit that is as far from the center of the Earth as a point on land gets.
I can see a little math here and now I start to stir. What if I constructed a list of the mountain peaks furthest from the center of the Earth? That would give me a problem that I am interested in that would also allow me to learn how to use the Geonames database.
Let's dig in...
My goal is generate a table of mountain heights sorted from by distance from the center of the Earth. While accomplishing my goal, I will also:
- learn how to grab data from the Geonames database.
- learn a bit about geodesy – the study of the shape and gravitational field of the Earth.
All of my work today will be done in Excel and I will provide a link to my spreadsheet at the end of this post. There will be a small Visual Basic for Applications (VBA) program used with Excel to access the data.
A big part of this effort is getting all the terms defined. Here are the definitions that I used.
- Reference Ellipsoid
- In geodesy, a reference ellipsoid is a mathematically defined surface that approximates the geoid, the truer figure of the Earth, or other planetary body. Because of their relative simplicity, reference ellipsoids are used as a preferred surface on which geodetic network computations are performed and point coordinates such as latitude, longitude, and elevation are defined (source).
- Ellipsoid Height
- The height of an object above the reference ellipsoid in use. This term is generally used to qualify an elevation as being measured from the ellipsoid as opposed to the geoid. GPS systems calculate ellipsoidal height (source).
- Earth's geoid is a calculated surface of equal gravitational potential energy and represents the shape the sea surface would be if the ocean were not in motion (source).
- Mean Sea Level
- Sea level is generally used to refer to Mean Sea Level (MSL), an average level for the surface of one or more of Earth's oceans from which heights such as elevations may be measured. MSL is a type of vertical datum – a standardize