Geographic Information Systems

Q . 1-What is the difference between accuracy and precision ? Give examples of both in a GIS context

Ans . Accuracy and Precision are two important factors related with GIS Their meaning and difference between these two is explained below

1 . Accuracy : The statistical meaning of accuracy is the degree with which an estimated mean differs from the true mean . In the GIS context the term accuracy refers to the degree to which the information presented on a map or in a digital database matches with true or accepted values . The accuracy is directly

related with quality of data and number of errors that exist in a dataset or map . In discussing a GIS database , accuracy could be of various types , such as horizontal and vertical with respect to geographic position , as well as attribute conceptual , and logical accuracy . The level of accuracy required for specific applications varies greatly . Highly accurate data can be very difficult and costly to produce and compile . Sometimes the true value cannot be determined so an accepted value is used as the reference

For Example , if the elevation of a point on a topographic map is determined to be 100 meters , then , accuracy can be calculated by determining how close is that to the real value ? In some situation , it is not possible to determine the true value . In such cases , an accepted value is used for the reference . Suppose , the coordinates of a location read from a map are (10 , 20 , but , those calculated from accurate...