Geostatistical mapping can be defined as analytical production of maps by using field observations, auxiliary information and a computer program that generates predictions. The purpose of this guide is to assist you in producing quality maps by using fully-operational open source software packages: R+gstat/geoR and SAGA GIS. Unlike other books from the "use R" series, or purely GIS user manuals, this book specifically aims at bridging the gaps between statistical and geographical computing. Materials presented in this book have been used for the five-day advanced training course "GEOSTAT: spatio-temporal data analysis with R+SAGA+Google Earth" that is periodically organized by the author and collaborators. This is an open access publication with a print-on-demand possibility. Printed copies can be ordered via www.lulu.com.