Assessing the effect of weather on human outdoor perception using Twitter

Dissertation submitted in partial fulfilment of the requirements for the degree of Master of Science in Geospatial TechnologiesHuman Comfort in Outdoor Spaces (HCOS) is linked to physical, physiological and psychological responses of people to environmental variables. Previous studies have established comfort ranges for these variables through questionnaires, reaching only small populations. However, larger amounts of data could not only generate more robust results in local studies, but also allow the possibility of creating an approach that could be applied into a wider range of weather conditions and different climates. This thesis describes a new methodology to assess people’s perception of weather based on human responses to weather conditions extracted from tweets, with the purpose of establishing comfort ranges for environmental variables. Tweets containing weather-associated keywords were collected using the Twitter API and then linked to real-time meteorological data acquired from the Open Weather Map API, which provides weather variables measured nearby the locations in which the tweets were posted. Afterwards, people’s perception of weather was extracted from the tweets using a classifier trained specifically on weather data that identified irrelevant, neutral, positive and negative tweets. The obtained tweets and their related meteorological data were analyzed to establish comfort ranges. Comparing the resulting ranges to others obtained in previous studies, a generally good agreement was found with the indices Effective Temperature (ET) and Termohygrometric index (THI) derived from questionnaires, but the peak of comfort is shifted towards lower and higher temperatures, respectively. Regarding the single weather variables, the obtained comfort ranges are alike the ones found in previous research, in particular, the temperature comfort range matches perfectly at 20 °C – 22 °C. Therefore, it was concluded that tweets can be used for the assessment of HCOS; not only the results of this methodology are comparable to the ones obtained in previous studies, but also the procedure itself shows new features and opportunities for future applications