Efficient Large-scale Object Counting in Satellite Images with Importance Sampling

The quantities of physical capital, or object counts, provide important insights into human activities and the socio-economic development of a region. For example, the number of buildings reflects the level of urbanization in a region; the number of brick kilns is related to the level of air pollution, and the number of cars correlates with the poverty level of a region. For example, the Demographic and Health Surveys (DHS) collects population-related statistics of about 90 countries at a cost of 1.9 million dollars over a five-year interval [1]. Recently, object detection in high-resolution satellite imagery has emerged as an alternative to ground-based survey data collection in socioeconomic monitoring tasks like counting brick kilns in Bangladesh [2] and counting solar panels in the U.S. [3]. A common detection-based pipeline [2, 4] to collect object count statistics over a large region exhaustively downloads all satellite images covering the target region, counts the objects in each image using a trained detection model, and takes the summation of counts in all the images to produce a total count.