Prismatic compass surveying is the method of surveying in which the direction of surveying lines and angular measurements are determined with a magnetic compass and the length of surveying lines are measured with a tape or chain.
The following are disadvantages/demerits of using prismatic compass surveying
- can not be conducted in areas known to have magnetic materials
- demand knowledge especially about rocks to identify the presence of iron ore
- it is difficult to hold the compass absolutely steady when taking the bearing hence it is impossible to eliminate the errors completely
- prismatic compass surveying is not useful over long distances