Defining perceived urban density

This initial study aims to identify parameters that might be relevant for defining perceived urban density. The context of the study is rooted in the perception of western European cities, specifically Switzerland. Hundreds of participants world-wide have taken part in our online questionnaire in which the role of six factors on perceived urban density is tested. The research hypothesis is that perceived urban density is the inverse of visibility.

Six factors that influence perceived urban density are tested:
1. Visibility. The median visibility of each image was computed from a depth perception map created for the study.
2. Amount of building matter per image
3. Amount of visible road
4. Amount of visible sky
5. Amount of green space
6. Amount of vehicles
The photographs were analysed according to the six parameters, and for image properties of luminosity, contrast, and r/g/b values.

Method overview
The study was conducted as an online questionnaire using the Qualtrics online survey platform. The survey was an optional task at the end of the Massive Open Online Course (MOOC) “Future Cities” course run by the Chair of Information Architecture. Respondents of the questionnaire were students of that MOOC. During the questionnaire participants viewed two photographs of urban locations and had to choose which one was more dense.
The question participants responded to was: “Which location is more dense?”. We gathered a basic profile of the participants through a number of questions pre- (e.g.. where they currently lived, where they grew up, age, gender) and post- questionnaire (e.g.. what factors most influenced their judgement, how they ranked the importance of those factors etc.). Photographs used in the questionnaire were 12 stills taken from a 360 degree video of a route in central Zurich, Switzerland (fig. 4), that was created for another project (Hijazi et al., 2016). The large sample of possible images was reduced to 12 in order to be able to run a full pairwise comparison i.e. each participant viewed all possible comparisons of every photograph paired against every other photograph. The 12 images are the highest and lowest of each of the 6 parameters listed. The images are ranked according to how relevant they are for the perception of urban density.

Initial results
Close to 600 people have taken part to date (June 2018). An analysis of the first sample (190 participants) revealed that  visibility alone is
not enough to explain participants’ judgements. Participants reported four factors to be the most important when making their judgement: 1) number of visible buildings, 2) building height, 3) visibility, and 4) presence of green spaces. The number of visible buildings was reported as being the single most important factor when judging the perceived urban density of an image.

For further discussion of the initial results see the published article.