Introduction:
Contouring is a technique used in surveying and mapping to represent the shape and elevation of the land on a two-dimensional map. It is particularly important in hilly terrains where there is significant variation in elevation. Different methods of contouring can be used depending on the specific terrain and requirements of the survey. In the case of hilly terrain, the tacheometric method is the most suitable option.

Tacheometric Method:
The tacheometric method is a surveying technique that uses a tacheometer, which is an instrument that combines a theodolite and a stadia rod. This method is commonly used in hilly terrains due to its ability to measure vertical distances accurately and efficiently.

Advantages of the Tacheometric Method:
- Accuracy: The tacheometric method provides accurate measurements of both horizontal and vertical distances. This is particularly important in hilly terrains where the elevation changes significantly.
- Efficiency: The tacheometric method allows for rapid data collection, reducing the time required for contouring in hilly terrains.
- Versatility: The tacheometer can be used for both direct and indirect methods of contouring, making it suitable for a variety of surveying tasks in hilly terrains.
- Flexibility: The tacheometric method can be used for both small-scale and large-scale surveys, making it suitable for different types of projects in hilly terrains.

Other Methods:
While the tacheometric method is the most suitable for hilly terrains, it is important to note that other methods of contouring can also be used depending on the specific requirements of the survey. These methods include:

- Direct Method: This involves taking measurements at regular intervals along the contour lines. It is suitable for relatively flat terrains but may not be as accurate or efficient in hilly terrains.
- Square Method: This method involves dividing the survey area into squares and taking measurements at the corners of each square. It is suitable for areas with a regular grid pattern but may not be practical in hilly terrains where the terrain is irregular.
- Cross-sections Method: This method involves taking measurements along cross-section lines at regular intervals. It is suitable for hilly terrains but may require more time and effort compared to the tacheometric method.

Conclusion:
In conclusion, the tacheometric method is the most suitable method of contouring for hilly terrains. It provides accurate measurements of both horizontal and vertical distances and allows for rapid data collection. While other methods can also be used depending on the specific requirements of the survey, the tacheometric method offers the most advantages in hilly terrains.