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Mapping errors
Dr Beena Chintalapuri, V Raghu Venkataraman

Application of cognitive psychology for reduction of mapping errors

Human factors contributing to mapping errors made by operators working on digital mapping systems were studied from Cognitive Psychology perspective to evolve suitable strategies to reduce errors.

Mapping errors

Study area
Large scale topographic maps of better than 1:5000 scale with 1 to 2 m contours are currently prepared on digital photogrammetric workstations (DPWS) using block adjusted 3D models derived from aerial photographs. Errors made by operators during vector capture from 3-D models in a production environment require extensive rework. Obviously there is a lot to be gained in terms of cost and time if such errors can be eliminated or at least minimized.

Current perception
It is generally perceived that the cause for such errors is carelessness and the only mechanisms to deal with it are stringent quality control and increase in expertise of both the operators as well as quality control staff.

New approach
In this study an attempt was made to study the factors which contribute to the human errors made by operators from Cognitive Psychology perspective. The human side of man machine interaction comprising of perception, memory, cognitive styles, problem solving abilities, decision making, attitude towards work and stress play an important role in the quality of the final product and therefore the focus of the study was on the persons who carry out digital mapping.

Classification of mapping errors
Webster’s New Encyclopedia Dictionary defines six different meanings of an error:
a) A deviation from a code of behaviour
b) An act involving unintentional deviation from the truth or accuracy
c) An act through ignorance, deficiency or accident fails to achieve what should be done
d) A false belief or a set of false beliefs
e) Something produced by mistake
f) The difference between an observed or calculated value and the true value

Based on Generic Error Modeling System (GEMS) of Rasmussen (1986), mapping errors were classified into three types based on the performance level into Skill Based (SB), Rule Based (RB) and Knowledge Based (KB)

Skill based
Skill based performance takes place with automated and highly practiced patterns of behaviour. According to Rasmussen (1986) “ behaviour at SB level represents sensory motor performance during acts or activities that after a statement of an intention, takes place without conscious control as smooth, automated and highly integrated pattern of behavior.” Generally these are routine and non problematic activities in familiar situations. SB errors can also be called as slips and lapses and arise due to inattention or over attention to the task at hand or attention to the wrong points of the task.

Rule based
Rule based performance is related to problem solving. Performance is goal oriented and is structured by feed forward control through a stored rule. It is assumed that rules are arranged in an order of priority and it becomes imperative for an individual to predict and apply these rules to the task for a successful outcome (Reason, 1991). RB errors take place due to the misapplication of good rules or failure to recognize a situation in which the rule does not apply or application of inappropriate rules. RB errors involve inappropriate matching of environmental signs to the situational component of well tried trouble shooting rules.

Knowledge based
Knowledge based performance is involved in problem solving and formulations at a more abstract level of representation. According to Rasmussen (1986) knowledge based level comes into play in novel situations in which actions must be planned on the job or on the task or on line using conscious analytical processes and stored knowledge. KB errors arise during the subsequent attempts to find a solution. KB errors arise when an individual has run out of applicable problem solving routines. They arise from a complex interaction between “bounded rationality” and “incomplete or inaccurate mental models”. Knowledge based performance errors can take a wide variety of forms, none of which are necessarily predictable on the basis of individual’s acquired knowledge. (Backstorm, 1997). Yet another piece of information according to him is that knowledge based performance mistakes are the hardest of all to detect as expertise is required. At best, it is possible to forecast the general cognitive and situational factors that will conspire to create knowledge based performance mistakes (Reason, 1991).

It is also claimed that knowledge based errors are complex & diverse and tend to arise due to limited capacity of working memory and due to misuse or overuse of heuristics and biases in information processing (Tversky & Kahnueman, 1974).

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