# What's the maskdata's format?

**URL:** <https://forum.cmascenter.org/t/whats-the-maskdatas-format/2919>\
**Category:** Run Time Errors and Issues\
**Tags:** cmaq\
**Created:** [December 19, 2021, 4:56am UTC](https://forum.cmascenter.org/t/whats-the-maskdatas-format/2919 "2021-12-19T04:56:38Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![pbwang](https://avatars.discourse-cdn.com/v4/letter/p/5daacb/32.png) [@pbwang](https://forum.cmascenter.org/u/pbwang)\
**Post date:** [December 23, 2021, 4:54pm UTC](https://forum.cmascenter.org/t/whats-the-maskdatas-format/2919/4 "2021-12-23T16:54:10Z")

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Thank you for your reply.  
I have download the the example GRIDMASK file with US states, and knew the header portions of that example file. My problem is I don’t know how the MASK\_REGION have something to do with the and the emission grid. Because I make maskfile with m3mask and m3merge for 11 regions,with the suggestion from this forum, such as [ISAM SA\_ACONC output error - CMAQ-ISAM - CMAS CENTER FORUM](https://forum.cmascenter.org/t/isam-sa-aconc-output-error/1622). And thank you again for your explanation. But the tracking result for each region is zero. I think the MASK\_REGION must be not connected to the emission file’s grid. So I conclude that my MASK\_REGION is not correct, and the problem should be the fomat of my maskdata file. Can you tell me what variable should be in the maskdata? I have tried with only COL and ROW, and also don’t work. Look forward to your reply, thank you.

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