Digital orthophotos combine the geometric qualities of a map with the image qualities of a photograph. The orthophotos in this series are a mosaic of digital orthophoto quarter quads (DOQs) produced through the National Digital Ortho Photo Program (NDOP). The image characteristics of the orthophotos in this series follow that of the source DOQs. The ground sample distance is 1 meter in the x direction and 1 meter in the y direction. The images are resampled to 2 meters when an order is placed. The images are rectified to the UTM Coordinate System, NAD83.
The images are in JPEG format and each image covers a 7.5-minute quadrangle. The USGS DOQs are replaced by enhanced DOQs from APFO where available. The enhanced DOQs are mosaicked to remove visible seam lines due to characteristics of the source aerial photography. Mosaic cutlines are interactively defined within the DOQ image overedge by examining each DOQ pairwise with adjoining DOQs and placing the seam line where image tone differences and geometric misalignments are minimized. Due to the overedge between ortho quads, and depending on the placement of seam lines, each ortho quad can contain portions of as many as 16 DOQs. During the mosaicking process, the image tone of all input DOQs is adjusted towards a common value.
