With the successful launch of the first scientific satellite of the Republi
c of China (ROCSAT-1) on 27 January 1999, Taiwan enters the era as a satell
ite data providing country. There are three scientific payloads on the sate
llite. One of them is the Ocean Color Imager (OCI). OCI is a push-broom ref
lective imager for monitoring ocean colors. OCI has taken images since Marc
h 1999. Because there is no on-board calibrator on OCI, a comparison with S
ea-viewing Wide Field-of-view Sensor (SeaWiFS) data was performed in order
to validate OCI data. Simultaneously in-situ observations of optical proper
ties and chlorophyll a concentration were also collected in waters adjacent
to Taiwan for vicarious calibration. We applied SeaWiFS atmospheric correc
tion and bio-optical algorithms on OCI data to derive normalized water-leav
ing radiance and chlorophyll a concentration. Results show that the chlorop
hyll a concentration derived from OCI is generally larger than that derived
from SeaWiFS. The correlation coefficient is about 0.60 with a root-mean-s
quared (RMS) of difference of chlorophyll a concentration of 0.10 mg/m(3).