2

I am trying to convert geographic coordinates (in degrees east/north lon lat) to projected coordinates in meters for geostationary full disc data (GVAR Goes East data from CLASS). To do this, I tried using PyProj/ Proj4 and am running into errors due to the off earth pixels in the corners of the image.

This is the proj4 string given:

projection_coords = Proj("+proj=geos +h=35774290 +a= 6378137 +b= 6378137
+lon_0=-75 +units=meters +no_defs")

ll_x, ll_y = projection_coords_geos( LL_y_deg, LL_x_deg, inverse = False, errcheck=True)
'x=%9.3f y=%11.3f' % (ll_x,ll_y)

ur_x,ur_y = projection_coords_geos( UR_y_deg, UR_x_deg, inverse = False, errcheck=True)
'x=%9.3f y=%11.3f' % (ur_x,ur_y)

And the input 'LL_y_deg', 'LL_X_deg' etc are the values of the corner point extents lower left y pixel, lower left x pixel, upper right y and upper right x.

For full disc geos data I am receiving incorrect (1e30) values for the extents and was wondering if anyone has ever run into the same error or have a suggestion to correct this.

Here is an image to describe the problem further: Bounding Box Issue

We did try drawing a limiting box inside the earth extents to get all valid data points within, and this works but cuts out data in the edges of the earth (the data in between the blue dotted box and the earth). The geographic coordinate values in the red shaded off earth areas are very large (2.14 E9) and these are the values that throw the error.

Also, for remapping GOES data, should the 'sweep axis' always be included in the Proj string and set to 'y'?

Any suggestions or comments would be greatly appreciated!

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.