# Icon nesting error

**URL:** <https://forum.cmascenter.org/t/icon-nesting-error/5586>\
**Category:** CMAQ-PREP\
**Tags:** cmaq\
**Created:** [February 13, 2025, 4:25am UTC](https://forum.cmascenter.org/t/icon-nesting-error/5586 "2025-02-13T04:25:51Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\
**Post date:** [February 14, 2025, 4:31pm UTC](https://forum.cmascenter.org/t/icon-nesting-error/5586/2 "2025-02-14T16:31:13Z")

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Hello @TJDOFLEARN ,

there are several approaches you could take in your specific case.

- Given that you’re certain that your grids match and you’re just dealing with a precision issue, you could comment out the relevant grid consistency checks on lines 176 - 237 of subroutine [m3\_ck\_ctmmet.F](https://github.com/USEPA/CMAQ/blob/main/PREP/icon/src/m3conc/m3_ck_ctmmet.F) and then recompile ICON

- you could presumably also edit line 277 in the same file linked above to change `94000 FORMAT( E15.5 )` to `94000 FORMAT( E15.4 )` or `94000 FORMAT( E15.3 )` to require a lower level of precision matching but leave the actual consistency checks in place and then recompile ICON

- for a more robust and general solution, the code in lines 176 - 237 could be updated along the lines described by @cjcoats in this [related post](https://forum.cmascenter.org/t/cmaq-v5-2-ddm-error-for-init-casc-1/3122/9).

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