Relief shown by spot heights. Map on sheet 18 shows portion of California and maps on sheets 18-20 show portions of Baja California. Photoimagery rectified by optical scanning from color infrared aerial photographs taken December 12-15, 1979 and July 11, 22, 1982 by the Dirección General de Geografía del Territorio Nacional (DGGTN), Mexico D.F., Mexico. Each sheet includes quadrangle location map and diagr. of adjoining color image maps.