4.1. General evaluation method
In AHP, with a system as the research object, the influence of each
factor in each level on the results is quantified. The evaluation method
is characterized by clear logic, simplicity, and practicality and can be
used for the systematic evaluation of unstructured characteristics and
multi-objective, multi-criteria, and multi-period systematic evaluation.
However, the evaluation method requires a large quantity of statistical
data and faces the difficulty in determining the weight. In addition,
the exact calculation methods of eigenvalues and eigenvectors required
in AHP are complicated.
In PCA, original complex variables are transformed into several
comprehensive variables for analysis. Factor analysis requires sample
size and does not fully consider the relative importance of the indices
themselves.
As traditional evaluation methods, both AHP and PCA have the advantages
of clear logic, simplicity, and practicality, and are suitable for
evaluating the systems with simple structures and clear hierarchical
relationships. As a composite ecosystem composed of water and green
spaces, the complex blue-green space may lead to its higher ecological
carrying capacity and stronger vitality. Therefore, a hierarchical
structure model can be established with AHP and the ecological carrying
capacity of blue-green space can be comprehensively evaluated from two
aspects of ecological support and environmental pressure (Zhao et
al. , 2020). The main factors affecting the vitality of blue-green
spaces can be analyzed with PCA. Although general evaluation methods
have a clear hierarchy, the weight determination process is subjective
and requires excessive calculation, thus affecting the accuracy of
evaluation results. Therefore, in the future, the basic evaluation
methods can be combined to improve evaluation results.