  The prediction of the arrival time and transit speed of CMEs near the Earth
is one of the key problems in understanding the solar terrestrial relationship.
Although, STEREO observations now provide a multiple view of CMEs in the
heliosphere, the true speeds derived from stereoscopic reconstruction of SECCHI
coronagraph data are not quite sufficient in accurate forecasting of arrival
time of a majority of CMEs at the Earth. This is due to many factors which
change the CME kinematics, like interaction of two or more CMEs or the
interaction of CMEs with the pervading solar wind. In order to understand the
propagation of CMEs, we have used the 3D triangulation method on SECCHI
coronagraph (COR2) images, and geometric triangulation on the J-maps
constructed from Heliospheric Imagers HI1 and HI2 images for eight
Earth-directed CMEs observed during 2008-2010. Based on the reconstruction, and
implementing the Drag Based Model for the distance where the CMEs could not be
tracked unambiguously in the interplanetary medium, the arrival time of these
CMEs have been estimated. These arrival times have also been compared with the
actual arrival time as observed by \textit{in-situ} instruments. The analysis
reveals the importance of heliospheric imaging for improved forecasting of the
arrival time and direction of propagation of CMEs in the interplanetary medium.
