Directional drilling relies on mapping system to accurately identify location of the wells. Therefore, it is very important to learn the basics of mapping and other relevant information. This topic is about Geodetic Datum.
The Earth is not a complete sphere shape but it is actually Oblate Spheroid (“Spheroid”). It means that the shape of the Earth is almost a sphere. It can be proven from the fact that the equatorial diameter (the longest diameter) is approximately 12,756 km and the diameter from the North Pole to the South Pole is approximately 12,714 km (Figure 1). Additionally, the Earth has a different attitude based on location. So, people developed a model to help describe the Earth, which is called “Geodetic Datums”.