DEM related topics K Thome NASA WGCV Plenary

DEM related topics K. Thome NASA WGCV Plenary # 45 CSIRO, Perth July 16 -19, 2019 Working Group on Calibration and Validation

DEM related topics WGCV-45 Reminder – Motivation for studying DEMs • • • DEM differences cause differences in product inter-comparisons (for example during QA 4 EO Snow. PEX) Optical sensors with IFOV≤ 1 km and any off-nadir directional viewing ≥ 30 m require terrain relief correction to co-align pixels Atmospheric correction requires calculation of path radiance which depends on altitude Land cover classification of VIS/ SWIR multispectral/hyperspectral imagery require hill-shading correction to minimize misclassification errors All land (To. A & Bo. A) VIS/SWIR products require geo-radiometric correction (e. g. Sentinel-2 requires 30 m DEM) Working Group on Calibration and Validation 2

DEM related topics WGCV-45 Open DEM-related actions # Action Item Lead Due Date Status WGCV 39 -18 Global DEM Task work plan including objectives; schedule; and deliverables Muller (UCL) WGCV-42 Recommend as closed based on WGCV-44 discussions WGCV 39 -19 Add cross-reference on the WGCV web page to GMTED 2010 for coarse resolution sensor geometric and radiometric calibration Muller (UCL) WGCV-42 Awaiting cal/val portal redesign • • Thome Burini/Bojkov (ESA) Result of the efforts from the Radebul meeting held early in 2015 Momentum lost in defining the task group Working Group on Calibration and Validation 3

DEM related topics WGCV-45 Open DEM-related actions # Action Item Lead Due Date WGCV- CEOS WGCV Chair will contact WGCV members Chair 15 October 41 -02 and subgroup Chairs by email to solicit 2016 information regarding on-going and proposed efforts related to DEM studies including definitions, requirements, and methods for DEMs, and points of contact. The deadline for responses will be two months after the email request and responses will be forwarded to the WGCV DEM Task Group # Action Item WGCV- Proposed approach to address 42 -11 DEM Task Group goals • • Lead Chair Due Date WGCV-43 Status Recommend as closed at end of WGCV 45 based on presentations for path forward Status Recommend as closed based on WGCV-44 and -45 Agreed on importance of DEMs to data product quality, interoperability, and CARD 4 L There was no clear path forward amongst WGCV agencies Working Group on Calibration and Validation 4

DEM related topics WGCV-45 WGCV-44 presentation What to do next • • Easy first step is to add cross-reference on the WGCV web page to GMTED 2010 for coarse resolution sensor geometric and radiometric calibration § Clears an action from WGCV-39 § Could help point out the current state of DEM knowledge and gaps in global validation Next steps more difficult § Limited availability of experts to assess the “best” DEM § Many have expressed willingness to help but not to lead Working Group on Calibration and Validation 5

DEM related topics WGCV-45 WGCV-44 presentation Listed three possible options – others exist as well • • • Let DEM Task Team fade away – technically only had a two-year lifetime so could be viewed as non-existent Volunteer to lead and organize the DEM experts to revive the task team DEMIX? § Concentrate on the impact of DEM choices rather than selecting the best DEM § Would still require significant modeling efforts § Follows from the points of the original effort to o Quantify geometric and radiometric requirements for current and future EO sensors for 10 -15 m, 30 m & 90 m DEMs o Assess whether spaceborne DEMs are “fit for purpose” and whether CEOS users need “bare earth” or can work with heights “somewhere in the canopy-top” § Sentinel-2 study could be a model for further work Working Group on Calibration and Validation 6

DEM related topics WGCV-45 WGCV-44 presentation Let us not forget Terrain Mapping Subgroup • • • Could be reorganized as Global DEM Subgroup § Proposed originally by J-P Mueller § Recommended inviting and supporting a small team of experts to define requirements, work on simulation, test different DEM fusion methods, assess impact of non “bare-earth” DEM retrieval Does it become absorbed within one of the other subgroups? § Truly cross-cutting since it relies on various sensors approaches § Would still suffer from no expert lead Survey WGCV agency leads for their DEM/geolocation experts as a means to determine if there is sufficient numbers to warrant a subgroup § If so, a non-expert could be selected as subgroup lead in an effort to revive the sub-group § DEMIX could be a way to organize this Working Group on Calibration and Validation 7

DEM related topics WGCV-45 WGCV-44 presentation Last thoughts • DEM discussion can become wrapped up in the interoperability, ARD, and data cube arenas • Impact of DEM is one of the proposed evaluations within ACIX • DEM could be rolled into further work related to CARD 4 L efforts • So as for the DEM Task Team concept • Should it stay or should it go? • Decided that it would stay Working Group on Calibration and Validation 8

DEM related topics WGCV-45 WGCV-44 outcomes New actions • • WGCV-44 -01 § Survey recent results from Surface Reflectance ARD efforts within LSI-VC to determine current DEMs being used and provide a list of DEMs and their resolutions and uncertainties. § Stensaas § WGCV-45 WGCV-44 -02 § Draft an approach that could quantify the geometric and radiometric uncertainties from DEMs of varying spatial postings and vertical resolutions. § Thome § WGCV-45 § Presentations on Friday should help close this action Working Group on Calibration and Validation 9