# How to use m3tools to convert emission in lat-lon grid to CMAQ grid cell cols-row? **URL:** \ **Category:** I/O API\ **Created:** [June 10, 2020, 4:49am UTC](https://forum.cmascenter.org/t/how-to-use-m3tools-to-convert-emission-in-lat-lon-grid-to-cmaq-grid-cell-cols-row/1567 "2020-06-10T04:49:02Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![UCASY](https://avatars.discourse-cdn.com/v4/letter/u/49beb7/32.png) [@UCASY](https://forum.cmascenter.org/u/UCASY)\ **Post date:** [June 10, 2020, 4:49am UTC](https://forum.cmascenter.org/t/how-to-use-m3tools-to-convert-emission-in-lat-lon-grid-to-cmaq-grid-cell-cols-row/1567/1 "2020-06-10T04:49:02Z")
Hello all: I want to transform local emissions to CMAQ grid cell (COLS ROWS), for example, i input the lat and lon information and it can automatically calculate the lat lon information belongs to which model grid cell(COLS ROWS), and put emissions to this gird cell. for example i input the (38.993,117.319), it can calculate the model gridcell (13,39) ? Thank you! ---
**Author:** ![UCASY](https://avatars.discourse-cdn.com/v4/letter/u/49beb7/32.png) [@UCASY](https://forum.cmascenter.org/u/UCASY)\ **Post date:** [June 10, 2020, 5:34am UTC](https://forum.cmascenter.org/t/how-to-use-m3tools-to-convert-emission-in-lat-lon-grid-to-cmaq-grid-cell-cols-row/1567/2 "2020-06-10T05:34:46Z")
it may be like this in m3tools call latlon2colrow(lat,lon,projection,cols,rows),but i can’t find it, thank you! ---
**Author:** ![cjcoats](https://avatars.discourse-cdn.com/v4/letter/c/ac8455/32.png) [@cjcoats](https://forum.cmascenter.org/u/cjcoats)\ **Post date:** [June 10, 2020, 11:06am UTC](https://forum.cmascenter.org/t/how-to-use-m3tools-to-convert-emission-in-lat-lon-grid-to-cmaq-grid-cell-cols-row/1567/3 "2020-06-10T11:06:46Z")
Since presumably the lat-lon grid is coarser than the CMAQ grid, you want to use interpolation instead of area-weighted transformation matrices. so the appropriate program is m3cple – see [https://cjcoats.github.io/ioapi/M3CPLE.html](https://cjcoats.github.io/ioapi/M3CPLE.html). On the other hand, you’ll need to take care of the units-rescaling: CMAQ emissions traditionally are not in interpolatable MKS units, but rather in “mass per grid cell” units, and you will probably need some rescaling dependent upon the units of the input data and the grid-cell areas of the CMAQ output grid. _m3combo_ can be used for that re-scaling. ---
**Author:** ![UCASY](https://avatars.discourse-cdn.com/v4/letter/u/49beb7/32.png) [@UCASY](https://forum.cmascenter.org/u/UCASY)\ **Post date:** [June 11, 2020, 12:54am UTC](https://forum.cmascenter.org/t/how-to-use-m3tools-to-convert-emission-in-lat-lon-grid-to-cmaq-grid-cell-cols-row/1567/4 "2020-06-11T00:54:10Z")
Thank you. professors.