China’s Chang’e-3（ CE-3） probe

which includes a lander and a rover

successfully landed on the lunar surface on D ecember 14

2013. High precision and automatic mapping of the lunar surface surrounding the rover is of fundamental importance both for safe rover navigation and for achievement of scientific and engineering goals. During CE-3 mission

we routinely produced topographic maps

and rover traverse maps to support surface operations of the rover.In this research

we focused on mapping capability analysis and fast terrain reconstruction using Navcam（ navigation camera）stereo images acquired by Yutu rover. First

we performed topographic mapping capability analysis of Navcam stereo pairs using basic photogrammetric principles and error propagation law

and empirical formula. The expected measurement error of Navcam stereo images is less than 2 m within 44 m from the rover

and less than 1 m within a range of 31 m. To give a theoretical estimation of the mapping errors at different locations

a covariance matrix is used to depict the position error. The position errors are mainly in the radial directions. Given that the elevation differs in different distances

grid error in DEM is analyzed based on linear interpolation model

the elevation accuracy is higher than the horizontal accuracy.In order to complete terrain mapping

we presented a multi-threaded image processing method for fast generation of topographic products using rover images. The whole mapping process include automatic feature points extraction based on epipolar images

multi-threaded dense matching

three-dimensional compution

DEM interpolation by a parallel processing combined with multithread technique. First

epipolar images were generated using exterior orientation parameters

then bundle adjustment was used to refine the exterior orientation parameters of the rover images. Moreover

a triangulated irregular network-controlled dense image matching method was adopted for dense grid matching. After image dense matching

three-dimensional positions of the matched points were calculated using space intersection with co-linearity equations. The final DEM was generated using Kriging interpolation.To verify the accuracy of our method

experiments were conducted using simulated data. Seven pairs of stereo images were s imulated using resampled 0. 01 m CE-2 DEM and DOM. A new DEM with 0. 02 m resolution is generated from the simulated i mages; and 12 check points are used to verify the accuracy. The RMSEs（ Root Mean Square Errors） of these GCPs are 0. 036 m

0. 051 m and 0. 014 m in three directions. Experimental results using stereo images at waypoint D acquired by Yutu rover also d emonstrated the effectiveness and accuracy of the method.Until January 17

2014

Yutu rover has traveled 114. 8 m on lunar surface and performed a series of scientific investigations.The developed terrain mapping techniques and software have been routinely used in Chang’e-3 mission operations. Topographic products（ DEM and DOM） were generated quickly and at 17 waypoints using Navcam images based on multi-threaded image p rocessing to support mission operations.