INTRODUCTION

A topographic map is a two-dimensional representation of a portion of the three-dimensional surface of the earth. A topographic profile of the earth surface is obtained from topographic profiling. Topographic Profile is a cross-sectional view along a line drawn through a portion of a topographic map. Topographic map alone provides details of underground features such as dip, strike, thickness of the rock formations etc, which will be useful for many practical analyses. Geologic graphics is the computation of dip, strike and other measurable structural parameters of rock masses by geometrical methods from the topographic map. Geologic graphics helps determination of the geology of an area comprising of the rock formations, their two dimensional configuration, thickness and sequence at or below the ground surface which are the most important geological data for planning and execution of earth works like cuttings, quarrying, underground works and improvement of site conditions, design, construction and maintenance of complex, costly and vital engineering structures.

Borehole is one such structure, which provides information about the composition of the ground. Typically, a borehole is used as:

• Down hole heat exchangers
• Groundwater wells
• Production wells for hydrocarbons, natural gas or petroleum
• Pumping of grout for example, concrete for drilled piles

The underground water

2. the cuttings
3. the drilling advance rate
4. measurements in the borehole

With downhole surveys, a sensor or a camera is passed down the hole to a appropriate depth. Some practical methods also make it possible to test the surrounding rock in the borehole. The underground property can also be analysed by using a topographic map of the area and by identifying the type of rock features, its thickness etc., the depth of the borehole can be estimated.