CVM Projection Issue Discussion
Contents
CCA and CVM-S4.26 Projection Correction Information:
During UCVM development, it was determined that several SCEC velocity models developed using full 3D tomography (CCA01 thru CCA06 and CVM-S4.1 thru CVM-S4.26) used an incorrect projection formula when converting from Lat/Lon to UTM. The required changes were integrated into CCA06, and an updated version of that model was produced and released as part of UCVM 17.3 This wiki entry details information we used confirm that these projection changes are included in both CCA06 and CVM-S4.26.
Discussion of Projection Issue
Looking through the closed git UCVM tickets, the project issue is mention in ticket numbers:
Correct Projection Issues For CVM-S4.26 #13 This ticket has a discussion of the issues, resolutions, and tests used to confirm the fix.
Impact of Projection Fix - Dated Dec 2016
In Dec 2016, David posted plots showing differences between CCA projections. He posted horizontal slices to the wiki showing the percentage differences between the CCA06 model as delivered (with the bad projection) vs. the CCA06 model with the projection fixed.
Most of the differences are small it looks like, but there are some clear differences as a result of expanding the grid spacing: https://scec.usc.edu/scecpedia/CCA_Model_Projection_Fix.
CVM-S4.46 (previously called CVM-S5)
In Feb 2017, David posted a tar.gz of the fixed CVM-S5 (also known as CVM-S4.26) for UCVMC to http://hypocenter.usc.edu/research/ucvm/cvms5_fixed.tar.gz. This has the correct configuration file and the nx and ny division fixes that were done for CCA for Scott but not retroactively applied to CVM-S5.
We want to confirm that this is the version of the model distributed as part of UCVMC.
CCA Git repos
There is a SCEC CCA git repo. The last commit was Sept 2016. This suggests that the projection changes are not included in this repo. This repo, however, does contains scripts that pull files from enjuilee/work directories and processes those into CCA model files.
UCVM Git repo
The python version 17.3 of UCVM is in the ucvm git repo. It contains scripts also mentioned in the CCA repo that seem to convert data files into CCA06 model files, including the projection change.
Correct Projection Issues For CVM-S4.26 #13 This ticket has a discussion of the issues, resolutions, and tests used to confirm the fix.
Correct Projection Issues with CCA #23 Discusses the acceptance tests changed to test for the projection fix.
