This commentary honours the seminal and foundational contributions of Professor Gregory G. (Greg) Brown to the fields of public participation geographic information systems (PPGIS), natural resource management and spatial planning. We synthesise his work into four theses that underpinned his three decades of research: 1) The mapping of place values provides place-specific information about sense of place which can aid in the assessment of the risks associated with landscape modification; 2) PPGIS analysis techniques can support socially acceptable and scientifically defensible land-use decisions in multiple planning contexts; 3) Issues of representation and data quality can be systematically investigated and managed; and 4) While PPGIS is increasingly being applied by cities and other organisations globally, there remains multiple challenges regarding the use of PPGIS findings in land-use decision making. We then briefly summarise his future visions for PPGIS research into: improving participation, and identifying and controlling threats to spatial data quality; turning PPGIS from a participation tool to a political force that can engage with the politics of place and, related to the previous vision; building capacity and champions for those who see the value in participatory mapping methods and are willing to articulate publicly how participatory contributions will be used. The co-authors and all signatories to this commentary are deeply grateful for the many ways that Greg has touched our lives over the years. He will be sadly missed.