When draping images on the STM, OpenRoads Designer creates a single tiled image over the draped area. The pixel size of this image is defined as the smallest pixel size of all the draped rasters. However WMS and Bing Maps do not have a defined pixel size. In these cases the value of STM_DEFAULT_MINIMUM_PIXEL_SIZE_FOR_DRAPING is used to determine a suitable pixel size. It is set to 0.5 meter by default.