Non-satellite observations support a wide range of applications in monitoring and forecasting of the atmosphere, of the oceans, and land surfaces, across a broad range of time scales (including near-real-time and delayed mode applications). These activities support an increasing range of services with high socio-economic benefits. User requirements have become more stringent and emergent requirements have increasingly appeared with respect to these applications (and undoubtedly will continue to do so). These observing systems provide their products in one or more of real-time, near-real-time and non-real-time (those that provide a mix may apply different processing to different timescale releases with, in general, greater quality assurance for delayed mode products). In order to allow EO providers and users to maximize the value of existing observations and implement a user-friendly mapping facility, a comprehensive review of the current observing capabilities at both the European and global scales is needed for all ECVs. This will also facilitate an identification of the existing geographical gaps in the global observing system. The mapping of current non-satellite observing capabilities is insufficient compared to the comprehensive review of space-based missions. For satellite missions, the review must be reported and routinely updated within official documents of the international community (e.g. for satellite observations, the CEOS Handbook and the “Satellite Supplement” to the GCOS Implementation Plan). For the in-situ segment in contrast, it is based on the information provided voluntarily by each network or station to some international data portals in an uncoordinated way, often on an ECV by ECV and network by network basis. WMO, GEOSS, GCOS have provided extensive metadataset and station inventories, but their sets of information are limited to their own specific mission and to those networks and ECVs upon which they have a coordination role. This inevitably increases the level of heterogeneity among the different assessments, which may often disagree with one another over both perceived adequacy of the current capabilities and posited remedies / innovations. This leads to reduced uptake of the outcomes of such assessments.