About This vignette is its based in a similar vignette, developed for `RFmerge` version 0.1-6 or earlier, which worked only with the superseded `raster` package. This vignette, based on the `terra` package, describes a basic application of the `RFmerge` function to create an improved precipitation dataset by combining two different satellite-based precipitation products with ground-based observations and user-selected covariates (i.e., digital elevation model and Euclidean distances to rain gauge stations). We use as case study Valparaiso (Chile), as an example of how to generate this product at daily temporal scale and at 0.05° spatial resolution, from January to August 1983. This example requires the following data from the user: i) time series of rainfall observations, ii) metadata describing the spatial coordinates of the rain gauges, iii) the Climate Hazards Group InfraRed Precipitation with Station data version 2.0 (CHIRPSv2), iv) the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Climate Data Record (PERSIANN-CDR), and v) the Shuttle Radar Topography Mission (SRTM-v4) digital elevation model (DEM). In addition, Euclidean distances are also used as covariates. They are automatically computed within `RFmerge` as the Euclidean distances from each rain gauge station to every grid-cell within the study area. Citation If you find this tutorial useful, please cite it as Zambrano-Bigiarini et al. (2026): Zambrano-Bigiarini, M.; Baez-Villanueva, O.M.; Giraldo-Osorio, J.D. (2026). Tutorial for merging satellite-based precipitation datasets with ground observations using RFmerge (>=0.3-0). doi:10.5281/zenodo.20061104. The theoretical description of the merging algorithm is described in the following RSE article: Baez-Villanueva, O. M.; Zambrano-Bigiarini, M.; Beck, H.; McNamara, I.; Ribbe, L.; Nauditt, A.; Birkel, C.; Verbist, K.; Giraldo-Osorio, J.D.; Thinh, N.X. (2020). RF-MEP: a novel Random Forest method for merging gridded precipitation products and ground-based measurements, Remote Sensing of Environment, 239, 111610. doi:10.1016/j.rse.2019.111606. Last, but not least, you should cite the `RFmerge` R package as follows: Zambrano-Bigiarini, M.; Baez-Villanueva, O.M., Giraldo-Osorio, J. (2026). RFmerge: Merging of Satellite Datasets with Ground Observations using Random Forests. R package version 0.3-0. URL: https://hzambran.github.io/RFmerge/. doi:10.32614/CRAN.package.RFmerge. Required `RFmerge` version This tutorial was developed for `RFmerge >= 0.3-0`, which is the minimum version where `RFmerge` is based on the terra package. All the previous `RFmerge` versions until 0.1-6 were based on the superseded raster package. `RFmerge` 0.1-6 was removed from CRAN in 2023-02-25, because issues related to old spatial packages (e.g., rgdal) were not solved in time.
Zambrano‐Bigiarini et al. (Thu,) studied this question.