This study tries to examine horizontal positional accuracy of orthophotoof Addis Ababa cityrnusing in-situ Global Positioning System (GPS) data. GPS data is processed using differentrnprocessing systems like spectrum survey, Leica GeoOfice(LGO) and also online processingrnsystems AUSPOS and OPUS in a least square sense with a tie to local and regional GPSrnreference stations to predict horizontal coordinates at twenty checkpoints to assess the accuracyrnof orthophoto. The accuracy of horizontal coordinates of the checkpoints derived fromrnorthophoto was evaluated by comparing it with the corresponding coordinates measured directlyrnfrom in-situ GPS data. When we compared the orthophoto with that of online processing AUSPSrnit is in a good agreement with GPS data observed at twenty checkpoints with a root mean squarernerror of 9.3 cm in x- and 9.9 cm in y-coordinates. On the other hand, the horizontal accuracy ofrnorthophoto is determined at 3.19 cm as it compared with twenty check points with 95%rnconfidence level. Whereas, when the GPS data are processed using sokkia spectrum with a tie tornlocal GPS reference station the horizontal coordinates of the orthophoto are in agreement withrnin-situ GPS coordinates at an accuracy of 7.2 cm and 21.39 cm in x and y-directionsrnrespectively, The finding of the result illustrates that the horizontal accuracy of orthophoto isrndetermined at 8.81 cm with 95% confidence level, while the GPS data is processed with a tie tornlocal GPS network. Therefore, it can be concluded that, the accuracy of the orthophoto is withinrnthe national standard of error budget (~ 25cm).