ESECT and EMAP are subroutines which provide a computer algorithm for mapping arbitrary meshes onto rectangular meshes in cylindrical (r,z) geometry. Input consists of the lines defining the rectangular mesh and the coordinates of the arbitrary mesh, which are assumed to be joined by straight lines. Output consists of the intersection volumes with designation of common mesh zones. The ESECT and EMAP routines do not comprise a ''free-standing'' code but, instead, are intended for inclusion in existing codes for which one mesh structure (typically Lagrangian) needs to be mapped onto an Eulerian mesh. Such mappings are of interest in coupled hydrodynamic and neutronic calculations. Exact expressions for the volumes of rotation (about z-axis) generated by the planar mesh intersection areas are used. Intersection points of the two meshes are computed and mapped onto corresponding regions on the rectangular mesh. Intersection points with the same regional indices are recorded into multilaterals, and the multilaterals are triangulated to facilitate computation of the intersection volumes. Dimension statements within ESECT/EMAP presently allow for rectangular and arbitrary meshes of 10k and 3.6k grid points. Scaling of all arrays to suit individual applications is easily effected. Computations of intersection volumes generated by overlapping 10k rectangular andmore » 2.2k radial meshes require an average of 18 s computer time, while computation times for the same meshes scaled by a factor of /sup 1///sub 4/ in number of grid points average 3 s on the CDC 7600. Generally, cases of small cell rectangular meshes overlaid on large cell arbitrary meshes require the longer running times. 10 figures, 2 tables.« less