A methodology can be defined as a systematic and orderly logical arrangement of doing something that particularly helps to organise and direct a research in a specific field of study. Specially, in relation with visual material there are no so many methods to use for interpreting and analysing, and even fewer references about how to develop those methods.
Visual methodologies can be divided in qualitative and quantitative approaches, but not all these methods can be used for all analyses. The step of choosing the most appropriate method or group of methods is essential in an investigation.
As it is not probable for one method to be exhaustive in its own, for my research I have used a mix of qualitative approaches for analysing visual material (visual disaggregating, comparative analysis, and visual coding), and social science methods for collecting key information (analytic relational surveys), both approaches having as a starting point my case study (underground diagrammatic maps).
One main question about social science methods is whether they have scientific rigour or depend on philosophical discourses and subjectivity. I think that if a method is rigorously used and follows a step-by-step structure/process, the obtained results do have scientific credibility because, at the end, they are results of a scientific analysis.
At the beginning of any visual research project, before selecting a methodology, there are two questions to answer:
1) How visual material and information is going to be collected
2) How this material is going to be interpreted, analysed and examined