User:Kings GIS/sandbox

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Recognizing MAUP in Research 

By Efrain Reyes Jr

There are some issues that surround the Modifiable Areal Unit Problem (MAUP)[]and this is should be taken into account very seriously. Misinformation can be a potential source of error that can affect the analysis of spatial data. In a geographic analysis data are often added to present the results of a study the spatial analysis. The boundaries are clear examples of the type of addition of areas used to show the results of some spatial phenomena. These areas are often arbitrary in nature and different units that may only be significant in showing the same data. There are an infinite number of different options for the aggregation of data. Openshaw 1984[] presents, for example that if one attempts to add 1000 objects in groups of 20, we would be faced with 101260 different combinations for this simple solution.

The MAUP consists of a scale and zoning effects. The scale effect occurs when there are different from the same data results.[] This arises due to the aggregation of data into larger units. Different results can also produce when the scale remains constant.

One of the main problems related to the analysis of spatial data is related to the definition of the units of analysis. Many of these variables we work within a GIS cannot be measured in a grouped manner and must therefore separate the study for a given area. The areas which are defined to work with variables are essentially arbitrary. However, the use of one or another unit could be a problem; since it alters the results of the studied variables may have erroneous results. The effects of the MAUP can be divided into two components: one relating to the scale and the other related to the aggregation. The effect of scale describes the variation of the results obtained in relation to the number of areas in which the total of the study area is divided into the size of the units. In this part, the effect of zoning refers to the differences that occur when information is added to a different scale. To realize the importance of this fact, it should be noted that a large part of the geographic information that we use in a GIS originally has been created on a different scale and has occasionally suffered a grouping into bigger units. Both effects, zoning and scale, are not independent, and are closely linked with each other and the intensity with which these two effects affect analysis is highly variable.

In General, the use of small units implies that the number of elements contained in it is smaller and therefore less statistically reliable. At the opposite end, the use of large units gives values it is statistically more reliable but hides the variation that occurs within the own units. Despite having a meaning of geographic analysis solutions to the problem of the definition that a unitary area entails much analysis are not clear. Traditionally, considered that it is an intractable problem. However, some studies indicate that there is certain regularity in the aggregated statistical values; it depends on the automatic correlation of space and the result of the variable. Usual is that the definition of the objects of study must precede any attempt to measure their characteristics in a scientific experiment. However, this is not the case with data of area where spatial data exist only when data collected for a set of entities are subject to an arbitrary aggregation to produce a set of spatial units.

You can be said that the MAUP is still subject of extensive study and it is the objective of this analysis, for example; it is not nothing more than a complex analysis will be necessary to calculate the values of data for the original spatial resolution. A particular problem with the MAUP is called ecological fallacy, which is assume that the values calculated for a surface unit can be applied to persons of the population of the existing area.

Other aspects that we can use the MAUP is to analyses the patterns of migration and segregation geographically and from growth in places where we can in turn analyses what is happening there relating to social changes in different urban spaces. We can also analyze the effects of the growth in different areas and cities, linked to the socio-spatial segregation of its inhabitants by selecting a set of spatial variables. The factors of spatial growth of the different areas are analyzed using models multiple re-regression step by step, showing the population density and the distance to the center to explain shaped direct and reverse, in greater measure, the presence of the constructed surfaces. This we see it very clearly in the book "The Big Sort"[] of Bishop and Cushing where they presents to the effects of migration affects people communities and politic in different localities. We see it as "these people" describe by Bishop and Cushing has mobilized economically and politically without precedent to the American nation by creating groups or "tribes". These groups by reflecting the analysis typically migrate according to their political, religious, social and economic ideologies. "People want to be around people living like them, to think how they think and that have the same style of life". []

Even though the MAUP was raised for several decades, your solution does not seem today closer than then []. The best solution to the problem is use disaggregated data and to avoid the use of data grouped in units of area, and should work with areas more small in the way as possible doing fieldwork to verify the validity of the procedure.

Reference:

Interactive Spatial Data Analysis, 1995, Bailey, T. and Gatrell, Longman, Malaysia.

Quantitative Geography: Perspectives on spatial data analysis, 2000, ''Fotheringham, S., Brundson, C. and Charlton, M., Sage, Great Britain.

Hotbeds of crime and the search for spatial accuracy, 1999, Ratcliffe, J. H. and McCullagh, M. J.