## 3 Fiducial Reference Measurements (FRMs)
### Achieving and Evidencing FRM Status
Whilst aspects of what is entailed within meeting FRM compliance could benefit from and indeed may be most easily achieved through use of services adhering to ISO standards, e.g. ISO 17025 for calibration of instruments, it is not anticipated that the formality and inherent cost associated with such an endorsement process will be necessary or even practical at this time. However, the increased investment required to meet the full criteria of CEOS-FRM needs to be recognised and an appropriate scientific value attributed to it, by funding agencies and in particular those running satellite programs. The CEOS WGCV framework takes a more pragmatic approach; relying on self-assessment and transparency/accessibility of evidence against a set of criteria where the evidence is then subject to peer review through a board of experts led by CEOS WGCV. In order to be flexible, to maximise inclusivity and to encourage the development and evolution of CEOS-FRM from new or existing teams, compliance with criteria will be based on a gradation scaling rather than a simple pass/fail. The degree of compliance and associated gradation can then be presented in a Maturity Matrix (MM) model, similar to that of EDAP (Earthnet Data Assessment Project) [7], to allow intended users of the FRM to assess suitability for their particular application and indeed funds to decide on where and what aspects to focus any investment. The matrix model provides a visual'simple' assessment of the state of any FRM for all given criteria, making visible where it is mature and where evolution and effort need to be expended. The CEOS-FRM Maturity Matrix provides a high-level colour-coded summary of the characteristics of the FRM under analysis against specific criteria. Although the criteria are intended to be generic, how they are interpreted and assessed in detail may vary with the nature of the FRM and sensor class. It is intended that this same concept can be used for an individual measurement/method at a geo-located site, e.g., a test site, as well as at a network of such similar sites. The matrix contains a column for each 'high level' category/criterion, i.e., the row: Nature of FRM, FRM Instrumentation etc., and cells for each aspect (subsection of category) in a column below each of these categories. Grades are indicated by the colour of the respective grid cell, which are defined in the key (the grade criteria). The CEOS-FRM Maturity Matrix can be further subdivided into two parts as follows:  
* Self assessment CEOS-FRM MM
* Verification CEOS-FRM MM  
An example of such a maturity matrix is provided in Tables 2 and 3 for a fictitious FRM provider; note that the exact labels for each category in the MM is subject to change at the time of publication due to ongoing review and should be considered indicative. In addition to this broad-based summary, an overall classification of the degree of compliance will be provided based on meeting specific gradations for particular criteria. At present there are four classifications (note the number and definitions for these classifications is subject to change as CEOS finalizes the framework:  
* Class A--Where the FRM fully meets all the criteria necessary to be considered a CEOS-FRM for a particular class of instrument and measurand. It should achieve a grade of 'Ideal' in the 'guidelines adherence' in the verification section of the MM and green (at least 'excellent') for all other verification categories where these have been carried out. * Class B--Where the FRM meets many of the key criteria and has a path towards meeting the Class A status in the near term. It should achieve at least 'Excellent' in guideline adherence in the verification section of the MM and green (at least 'excellent') for all other verification aspects where these have been carried out. Ideally, it should have a roadmap/timeline of activities being undertaken to reach the higher class.