We discuss how to extract building map images to be used in a learning-based method for predicting radio wave propagation. Learning-based prediction methods for radio wave propagation use building map images as spatial data, and we have already proposed a prediction method that uses images around Tx, Rx, and their midpoint. The method works well but has missing regions between Tx and Rx when the distance between them increases. In this paper, we further modify the method to include the whole area between Tx and Rx and also their surrounding regions in a single image. We present the method of using the dataset generated from measured data and an evaluation of how much the proposed method improves the prediction accuracy of radio wave propagation.