# (RESOLVED) how to set dx and dy based on input data grid spacing

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#### jokervtv

##### New member
Greetings,

I am trying to run metgrid.exe and after correctly establishing the WPS, but I get some errors.

a part of my namelist.wps:
----------------------------------
e_we = 248, 145,
e_sn = 120, 109,
dx = 27000,
dy = 27000,
map_proj = 'lambert',
ref_lat = 37.00,
ref_lon = 104.00,
truelat1 = 30.0,
truelat2 = 60.0,
stand_lon = 104.0,
----------------------------------

When I change dx and dy to 6 km，run it again， it be right.

I would like to ask, because I have seen that some scholar’s papers are all 1 degree data with 27km(dx,dy), 0.5 degree data is used 4km(dx,dy), all are in China. And my 0.25 degree data with 27km should have problems, so I am very confused now, the calculation of this spacing, I think of a grid point of 0.25 degrees, the spacing is about 1 longitude length / 4, so I use 27km.

Thank you!

Hi,

I'm not sure I understand your question. Your data has a resolution of 0.25 by 0.25 degrees. Is that correct?

Is your question whether your dx and dy need to correspond to the resolution of your input data?

Kim

hello,

My data do has a resolution of 0.25 by 0.25 degrees. And my dx and dy both are 27000, because I think 1 degree is 110 Km.

But it might be wrong, I saw other people's data has a resolution of 1 by 1 degrees and dx is 27000.

So I can't undersant why.