[gradsusr] Negative Longitude of -360 in xdef of ctl file

[Raphael Ranieri]

Hello Clay,
Thank you for the answer.

Actually if I subtract 360 from the long I will get -360 longitude as well

Opening the file and asking to print the max and min longitude, I checked that it is from 0 to 360.0000000000111
See:
[cid:3f98e46c-b2ec-4f10-b591-db55e78b775f]

If I print point by point values with respective Lat and Long I also get longitude of 360 in the end:

[cid:e27cf20c-bda9-40f2-a9d0-c57f07f58938]

I thought it could be a custom projection or something like that, but in ctl it is not specifying anything.

I sent a message to the institute also, but didn't get an answer.

I'm very confused.

If anyone have any other hint I appreciate a lot.

Regards,

Raphael Ranieri
________________________________
De: gradsusr <gradsusr-bounces at gradsusr.org> em nome de Raphael Ranieri <raphaelcr93 at hotmail.com>
Enviado: terça-feira, 11 de agosto de 2020 18:07
Para: gradsusr at gradsusr.org <gradsusr at gradsusr.org>
Assunto: [gradsusr] Negative Longitude of -360 in xdef of ctl file

Hello All,

I'm trying to use some files of a Brazillian institute of meteorology and I'm facing a problem with the longitude values.

They used grads to create a ctl file that can be accessed in this FTP from the institution:
http://ftp.cptec.inpe.br/modelos/tempo/BAM/TQ0666L064/recortes/regioes/2020/07/29/00/BAM_CO_2020072900.ctl

[cid:78306f6d-96b0-45b9-b892-7fcc822a714b]

Here we can see that they are using a linear mapping for xdef with a 0.18 step starting from a longitude of -360 degrees according to GrADs docs:
http://cola.gmu.edu/grads/gadoc/descriptorfile.html#XDEF


Since in our case we need the actual longitude and latitude of a point, when we try to read this file we receive longitudes of 360 for example, which do not correspond to any existing longitude.

We are not using Grads to open the file, we are using pygrib ... to use it in a python program.

Since this ctl file is generated by grads we tought you guys could help.

Do you know why the longitude is starting at -360?

Thanks in advance!

Raphael Ranieri
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