Mathematics is employed in cultural activities in traditional and nontraditional societies. Ethnomathematics refers to mathematical ideas integrated into a culture. The culture can be used as a transformation effort to explore mathematical concepts in order to bring the mathematics closer to the reality and understanding of its people. Moreover, culture can be used as a groundwork for school mathematics. This study investigated ethnomathematics as geometry context illustrations of the patterns of Tapis Lampung in Indonesia. With an ethnographic approach and Rasch measurement that is to measure of persons and items on the same scale, this research is a quantitative study. Data were collected through test and documentation with tapis pattern results. It was discovered that the designs of the Tapis Lampung include geometric concepts that can be expressed as translations, rotations, reflections, and dilations. Moreover, students have different results of the creative thinking in mathematics. Each Tapis pattern also includes local values (i.e. sacred values, social stratification, history and understanding, creativity, inclusiveness, and economic value). Tapis Lampung can be used to disseminate and inform the world about Indonesian local wisdom and potentially as a source of contextual mathematics in rural schools and urban areas.