Friday, October 23, 2015

Integrating GIS and MCDM Methods

By: Piotr Jankowski

Summary:

In the early 1980s geographical information system (GIS) software emerged commercially as a new information processing technology offering unique capabilities of automating, managing, and analyzing a variety of spatial data. GIS has been depicted as a decision support technology with many applications of GIS developed over the last decade providing information necessary for decision-making in many diverse areas.  One perspective on developing better decision support capabilities of GIS can be identified based on integration of GIS and specialized analytical models.  This perspective improves the decision support capabilities on the expansion of GIS descriptive, prescriptive, and predictive capabilities by integrating GIS software with other general software packages and with specialized analytical models like environmental and socioeconomic models.

This article’s term MCDM is used in reference to multiple attribute decision making (MADM) which is concerned with choice from a moderate/small size set of discrete actions, involving choosing, based on the decision criteria and criteria priorities, from a moderate/small size set of alternatives.

MCDM techniques can be classified according to the level of cognitive processing demanded from the DM and the method of aggregating criterion scores and the DM's priorities.  Two classes of MCDM techniques can be distinguished:  compensatory and non-compensatory.  The compensatory approach is based on the assumption that the high performance of an alternative achieved on one or more criteria can compensate for the weak performance of the same alternative on other criteria.  The compensatory approach is cognitively demanding since it requires the DM to specify criterion priorities expressed as cardinal weights or priority functions.  Under the non-compensatory approach, a low criterion score for an alternative cannot be offset by another criterion's high score. The non-compensatory approach is cognitively  less demanding than  the  compensatory  approach  since  it requires, at the most,  the ordinal  ranking of  criteria  based on  the DM's priorities.  Both the classes of techniques can be further broken down as illustrated in the article. 
DMs can then use five different choice strategies that can be matched with characteristics of different MCDM techniques.  There are:

  1.  Screening of absolute rejects: elimination of clearly dominated alternatives as the first step before any further choice deliberation
  1. Satisficing principle: the DM will consider all the alternatives  that satisfy conjunctively or disjunctively the minimum  performance levels
  1. First-reject: the DM wants to use exclusively the conjunctive elimination rule to reject  all the alternatives that do not pass  minimum  threshold values
  1. Stepwise elimination: The DM narrows down the choice re-evaluating  the set of remaining alternatives every time one of  the alternatives is eliminated
  1. Generation of linear ordering: the DM wants to generate a ranking of alternatives from the most preferred to the least preferred one



The first four choice strategies can be implemented using exclusively the non-compensatory MCDM techniques with the last strategy requires the full processing approach so it can be implemented using the compensatory MCDM techniques. 

A few of the MCDM techniques can be implemented directly in GIS using the operators of the database query language. Others, however, can be implemented more efficiently using external programs and integrating these programs with GIS. Two strategies for integrating GIS and MCDM are proposed. The first strategy called the loose coupling strategy suggests linking GIS and MCDM techniques using a file exchange mechanism. The second strategy called the tight coupling strategy suggests linking GIS and MCDM techniques using a shared database.

Critique:

Overall, this article was very interesting in how it broken down the various aspects of MCDM into categories, techniques within these categories, choice strategies paired with the techniques, and finally the recommended strategies.  At points, the article was somewhat dense with in depth mathematical explanations for utilizing the various techniques, but was nonetheless very clear in how to perform the various listed techniques of MCDM.   The role of MCDM in GIS is to look for suitable alternatives while helping the DM assign priority weights to decision criteria, evaluate the suitable alternatives, and visualize the results of choice.  While often several results satisfy the minimum threshold values, MCDM techniques are often required to further reduce the alternatives and select the best choice.  Thus, introducing MCDM techniques into the GIS context will likely improve GIS decision support capabilities.  Additionally, the article notes that further research is needed on sensitivity analysis topics in an integrated GIS-MCDM system and facilitating group decision making in the GIS-MCDM context.

Source:

Piotr Jankowski (1995) Integrating geographical information systems and multiple criteria decision-making methods, International Journal of Geographical Information Systems, 9:3, 251-273, DOI: 10.1080/02693799508902036

8 comments:

  1. This is a great article. I agree that introducing MCDM techniques into the GIS context will likely improve GIS decision support capabilities. I did have one question. Do you believe sensitivity analysis would be more effective before or after conducting MCDM?

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    1. I believe in this context, sensitivity analysis would be most beneficial after conducting MCDM, but before the DM has to eliminate alternatives. It is important to understand the uncertainties in the inputs in order to judge the uncertainties of the outputs. Similar to analytic confidence, all of these uncertainties then need to be accounted for in the decision making process.

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  2. My only issue with this article is the emphasis on the DM doing the analysis and elimination of alternatives in the first four techniques. I think the fifth technique is the most likely scenario, in which the analyst presents the DM with a list of ranked options. Provided the analyst can support their ranking system, I think this is the best scenario to allow the DM to make the decision while the analyst does the work.

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    1. In my opinion, I agree that the fifth option was the best for providing the DM easily digestible results in addition to using the full processing approach of the compensatory MCDM techniques. As for the other four options, I think the analyst is still highly responsible for analyzing the material and disseminating it for the DM to use one of the other four elimination methods, but the use of non-compensatory techniques does not take compensation of high and low results into account so it processes the results somewhat less. The DM has results to look at and consider, but the fifth option, with the use of compensatory techniques, takes the process a step further by obtaining the results and adding another layer of analysis to them for a better overall picture.

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    2. Like Andrew said, I question having the DM doing the analysis. It would keep them involved but usually DMs don't want to do their own analysis.

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  3. I believe combining GIS analysis with MCDM techniques is a very helpful way for analyst. The author mentions two strategies for integrating GIS and MCDM. Does the author explain how to integrate them more in detail?

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    1. Yes, the article goes into much greater detail about how to integrate GIS and MCDM than I could fit in one summary. The short version is that a few of the MCDM techniques can be implemented directly in GIS using the operators of the database query language. Others, however, can be implemented more efficiently using external programs and integrating these programs with GIS. The article does note that it mainly focuses the guidelines for implementing the loose-coupling strategy, while the tight coupling strategy needs further work.

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  4. Nice post,it's very informative.i found the best information.I updated my knowledge with this blog.it can help me to crack GIS jobs in Hyderabad.

    ReplyDelete