The Structural Similarity Index Measure for Maps R package SSIMmap version 0.4.0 Extends the classical SSIM method proposed by 'Wang', 'Bovik', 'Sheikh', and 'Simoncelli'(2004) <doi:10.1109/TIP.2003.819861>. for irregular lattice-based maps and raster images. The geographical SSIM method incorporates well-developed 'geographically weighted summary statistics'('Brunsdon', 'Fotheringham' and 'Charlton' 2002) <doi:10.1016/S0198-9715(01)00009-6> with an adaptive bandwidth kernel function for irregular lattice-based maps. Software Depends: R (>= 3.5.0) Imports: stats, scales, terra, ggplot2, sf, knitr, FNN Suggests: RColorBrewer, testthat (>= 3.0.0), rmarkdown, patchwork, tidyterra Hui Jeong (Hailyee) Ha <hha24@uwo.ca> Comprehensive R Archive Network (CRAN) Hui Jeong (Hailyee) Ha [aut, cre] (ORCID: <https://orcid.org/0000-0002-5229-4528>), Jed Long [aut] (ORCID: <https://orcid.org/0000-0003-3961-3085>) MIT + file LICENSE (https://CRAN.R-project.org/package=SSIMmap/LICENSE) 2026-05-07 application/tgz https://CRAN.R-project.org/package=SSIMmap doi:10.32614/CRAN.package.SSIMmap