<div dir="ltr"><div>Hi Karin,</div><div>Thanks for your comment. Yes, I had posted this problem also in the CDO forum.</div><div>Hope you can find some solution using CDO.</div><div><br></div><div>Thanks.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 26, 2021 at 8:42 AM Karin Meier-Fleischer via ncl-talk <<a href="mailto:ncl-talk@mailman.ucar.edu">ncl-talk@mailman.ucar.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
here, I weigh in to make some comments about CDO and the Python Iris <br>
projections. Your question about the OSGB data in the CDO forum had me <br>
running into the same problems days ago.<br>
<br>
CDO usually can handle pre-projected grids using a gridfile with the <br>
grid_mapping informaion, but in your case there is something missing to <br>
create a correct gridfile. Transverse Mercator projection is quite special.<br>
<br>
The python package Iris provides an extra class for the projection type <br>
OSGB.<br>
<br>
   class iris.coord_systems.OSGBA<br>
      Specific transverse mercator projection on a specific ellipsoid<br>
<br>
I'll see how Iris has solved the problem and get back to you, but maybe <br>
not today;).<br>
<br>
Ciao,<br>
Karin<br>
<br>
Am 25.02.21 um 22:07 schrieb Dennis Shea via ncl-talk:<br>
> I don't understand:<br>
> <br>
> "This data *can't also read* correctly with Climate Data Operator (CDO)"<br>
> <br>
> To me something is not correct with the file if the CDO and NCL are <br>
> having issues.<br>
> Python is rendering a correct plot?    Somebody has programmed around <br>
> the issue.<br>
> ===<br>
> <br>
> You can go back and forth between the lat/lon gridded coordinates and <br>
> x/y as indicated by the equations at:<br>
> <br>
> *<a href="https://idlecoding.com/transverse-mercator-with-python/comment-page-1/#:~:text=%20Transverse%20Mercator%20With%20Python%20%201%20The,any%20code%20to%20transform%20an%20actual...%20More%20*" rel="noreferrer" target="_blank">https://idlecoding.com/transverse-mercator-with-python/comment-page-1/#:~:text=%20Transverse%20Mercator%20With%20Python%20%201%20The,any%20code%20to%20transform%20an%20actual...%20More%20*</a> <br>
> <<a href="https://idlecoding.com/transverse-mercator-with-python/comment-page-1/#:~:text=%20Transverse%20Mercator%20With%20Python%20%201%20The,any%20code%20to%20transform%20an%20actual...%20More%20" rel="noreferrer" target="_blank">https://idlecoding.com/transverse-mercator-with-python/comment-page-1/#:~:text=%20Transverse%20Mercator%20With%20Python%20%201%20The,any%20code%20to%20transform%20an%20actual...%20More%20</a>><br>
> <br>
> But to me, these are both on the file.<br>
> <br>
>          double grid_longitude(projection_y_coordinate, <br>
> projection_x_coordinate) ;<br>
>          double grid_latitude(projection_y_coordinate, <br>
> projection_x_coordinate) ;<br>
> <br>
>          double projection_x_coordinate(projection_x_coordinate) ;<br>
>          double projection_y_coordinate(projection_y_coordinate) ;<br>
> <br>
> The information at:<br>
> <br>
>         int transverse_mercator ;<br>
>                  transverse_mercator:grid_mapping_name = <br>
> "transverse_mercator" ;<br>
>                  transverse_mercator:longitude_of_prime_meridian = 0. ;<br>
>                  transverse_mercator:semi_major_axis = 6377563.396 ;<br>
>                  transverse_mercator:semi_minor_axis = 6356256.909 ;<br>
>                  transverse_mercator:longitude_of_central_meridian = -2. ;<br>
>                  transverse_mercator:latitude_of_projection_origin = 49. ;<br>
>                  transverse_mercator:false_easting = 400000. ;<br>
>                  transverse_mercator:false_northing = -100000. ;<br>
>                  transverse_mercator:scale_factor_at_central_meridian = <br>
> 0.9996012717 ;<br>
> <br>
> is possibly useful, I have tried to use two of the attributes but it did <br>
> not work.<br>
> <br>
> <br>
> <br>
> <br>
> On Thu, Feb 25, 2021 at 1:08 PM S Br <<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a> <br>
> <mailto:<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a>>> wrote:<br>
> <br>
>     Hi Dennis,<br>
>     The plot is perfect with Python. Please see the attached image.<br>
>     The data I am talking about is generated using Python.<br>
> <br>
>     This data can't also read correctly with Climate Data Operator (CDO)<br>
> <br>
>     Thanks.<br>
> <br>
> <br>
>     On Thu, Feb 25, 2021 at 7:26 PM Dennis Shea <<a href="mailto:shea@ucar.edu" target="_blank">shea@ucar.edu</a><br>
>     <mailto:<a href="mailto:shea@ucar.edu" target="_blank">shea@ucar.edu</a>>> wrote:<br>
> <br>
>         Obviously, not over the UK but ......<br>
> <br>
>         I think more information from you might be necessary.<br>
>         "transverse_mercator" is not supported by NCL options.<br>
> <br>
>         You state: "The data is correctly displayed in Python but not in<br>
>         NCL."<br>
> <br>
>         Well, what does the plot look like via Python?<br>
> <br>
>         On Thu, Feb 25, 2021 at 12:19 PM Dennis Shea <<a href="mailto:shea@ucar.edu" target="_blank">shea@ucar.edu</a><br>
>         <mailto:<a href="mailto:shea@ucar.edu" target="_blank">shea@ucar.edu</a>>> wrote:<br>
> <br>
>             I **speculate** that the attributes associated with the<br>
>             "transverse_mercator" variable must be used.<br>
>             ====================================================<br>
>             ;---Get the source lat/lon grid<br>
>             tas   = f->tasmax(0,0,:,:)<br>
> <br>
>             lat2d = f->grid_latitude<br>
>             lon2d = f->grid_longitude<br>
>             printMinMax(lat2d,0)<br>
>             printMinMax(lon2d,0)<br>
> <br>
>             itm   = f->transverse_mercator<br>
> <br>
>             print(itm)<br>
>             print("itm@latitude_of_projection_origin="+itm@latitude_of_projection_origin)<br>
>             print("itm@longitude_of_central_meridian="+itm@longitude_of_central_meridian)<br>
> <br>
>             ; clarity<br>
> <br>
>             lat_shift = itm@latitude_of_projection_origin<br>
>             lon_shift = itm@longitude_of_central_meridian<br>
> <br>
>             ; apply 'shift'<br>
> <br>
>             lat2d = lat2d + lat_shift<br>
>             lon2d = lon2d + lon_shift<br>
>             printMinMax(lat2d,0)<br>
>             printMinMax(lon2d,0)<br>
> <br>
>             tas@lat2d = lat2d             ; use 'shifted' coordinates<br>
>             tas@lon2d = lon2d<br>
>             ================<br>
> <br>
>             See attached<br>
> <br>
> <br>
>             On Thu, Feb 25, 2021 at 12:00 PM Dave Allured - NOAA<br>
>             Affiliate via ncl-talk <<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a><br>
>             <mailto:<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a>>> wrote:<br>
> <br>
>                 I see what's going on.  From your other e-mail, the data<br>
>                 file contains two different sets of coordinates.  There<br>
>                 are the projection coordinates in meters.  Those are not<br>
>                 latitudes and longitudes, therefore not sufficient for<br>
>                 NCL.  But the geographic coordinates are also provided. <br>
>                 Double coordinates are frequently encountered in GIS<br>
>                 related applications.  Try this:<br>
> <br>
>                      tas@lat2d=f->grid_latitude<br>
>                      tas@lon2d=f->grid_longitude<br>
> <br>
> <br>
>                 On Thu, Feb 25, 2021 at 11:42 AM S Br<br>
>                 <<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a> <mailto:<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a>>><br>
>                 wrote:<br>
> <br>
>                     If I print tas@lat2d and tas@lon2d, they give the<br>
>                     following information.<br>
> <br>
>                     Variable: taslat<br>
>                     Type: double<br>
>                     Total Size: 896 bytes<br>
>                                  112 values<br>
>                     Number of Dimensions: 1<br>
>                     Dimensions and sizes: [112]<br>
>                     Coordinates:<br>
>                     (0) -102000<br>
>                     (1) -90000<br>
>                     (2) -78000<br>
>                     (3) -66000<br>
>                     (4) -54000<br>
>                     (5) -42000<br>
>                     (6) -30000<br>
>                     (7) -18000<br>
>                     (8) -6000<br>
>                     (9) 6000<br>
>                     (10) 18000<br>
>                     (11) 30000<br>
>                     (12) 42000<br>
>                     (13) 54000<br>
>                     (14) 66000<br>
>                     (15) 78000<br>
>                     (16) 90000<br>
>                     (17) 102000<br>
>                     (18) 114000<br>
>                     (19) 126000<br>
>                     (20) 138000<br>
>                     (21) 150000<br>
>                     (22) 162000<br>
>                     (23) 174000<br>
>                     (24) 186000<br>
>                     (25) 198000<br>
>                     (26) 210000<br>
>                     (27) 222000<br>
>                     (28) 234000<br>
>                     (29) 246000<br>
>                     (30) 258000<br>
>                     (31) 270000<br>
>                     (32) 282000<br>
>                     (33) 294000<br>
>                     (34) 306000<br>
>                     (35) 318000<br>
>                     (36) 330000<br>
>                     (37) 342000<br>
>                     (38) 354000<br>
>                     (39) 366000<br>
>                     (40) 378000<br>
>                     (41) 390000<br>
>                     (42) 402000<br>
>                     (43) 414000<br>
>                     (44) 426000<br>
>                     (45) 438000<br>
>                     (46) 450000<br>
>                     (47) 462000<br>
>                     (48) 474000<br>
>                     (49) 486000<br>
>                     (50) 498000<br>
>                     (51) 510000<br>
>                     (52) 522000<br>
>                     (53) 534000<br>
>                     (54) 546000<br>
>                     (55) 558000<br>
>                     (56) 570000<br>
>                     (57) 582000<br>
>                     (58) 594000<br>
>                     (59) 606000<br>
>                     (60) 618000<br>
>                     (61) 630000<br>
>                     (62) 642000<br>
>                     (63) 654000<br>
>                     (64) 666000<br>
>                     (65) 678000<br>
>                     (66) 690000<br>
>                     (67) 702000<br>
>                     (68) 714000<br>
>                     (69) 726000<br>
>                     (70) 738000<br>
>                     (71) 750000<br>
>                     (72) 762000<br>
>                     (73) 774000<br>
>                     (74) 786000<br>
>                     (75) 798000<br>
>                     (76) 810000<br>
>                     (77) 822000<br>
>                     (78) 834000<br>
>                     (79) 846000<br>
>                     (80) 858000<br>
>                     (81) 870000<br>
>                     (82) 882000<br>
>                     (83) 894000<br>
>                     (84) 906000<br>
>                     (85) 918000<br>
>                     (86) 930000<br>
>                     (87) 942000<br>
>                     (88) 954000<br>
>                     (89) 966000<br>
>                     (90) 978000<br>
>                     (91) 990000<br>
>                     (92) 1002000<br>
>                     (93) 1014000<br>
>                     (94) 1026000<br>
>                     (95) 1038000<br>
>                     (96) 1050000<br>
>                     (97) 1062000<br>
>                     (98) 1074000<br>
>                     (99) 1086000<br>
>                     (100) 1098000<br>
>                     (101) 1110000<br>
>                     (102) 1122000<br>
>                     (103) 1134000<br>
>                     (104) 1146000<br>
>                     (105) 1158000<br>
>                     (106) 1170000<br>
>                     (107) 1182000<br>
>                     (108) 1194000<br>
>                     (109) 1206000<br>
>                     (110) 1218000<br>
>                     (111) 1230000<br>
> <br>
> <br>
>                     Variable: taslon<br>
>                     Type: double<br>
>                     Total Size: 656 bytes<br>
>                                  82 values<br>
>                     Number of Dimensions: 1<br>
>                     Dimensions and sizes: [82]<br>
>                     Coordinates:<br>
>                     (0) -210000<br>
>                     (1) -198000<br>
>                     (2) -186000<br>
>                     (3) -174000<br>
>                     (4) -162000<br>
>                     (5) -150000<br>
>                     (6) -138000<br>
>                     (7) -126000<br>
>                     (8) -114000<br>
>                     (9) -102000<br>
>                     (10) -90000<br>
>                     (11) -78000<br>
>                     (12) -66000<br>
>                     (13) -54000<br>
>                     (14) -42000<br>
>                     (15) -30000<br>
>                     (16) -18000<br>
>                     (17) -6000<br>
>                     (18) 6000<br>
>                     (19) 18000<br>
>                     (20) 30000<br>
>                     (21) 42000<br>
>                     (22) 54000<br>
>                     (23) 66000<br>
>                     (24) 78000<br>
>                     (25) 90000<br>
>                     (26) 102000<br>
>                     (27) 114000<br>
>                     (28) 126000<br>
>                     (29) 138000<br>
>                     (30) 150000<br>
>                     (31) 162000<br>
>                     (32) 174000<br>
>                     (33) 186000<br>
>                     (34) 198000<br>
>                     (35) 210000<br>
>                     (36) 222000<br>
>                     (37) 234000<br>
>                     (38) 246000<br>
>                     (39) 258000<br>
>                     (40) 270000<br>
>                     (41) 282000<br>
>                     (42) 294000<br>
>                     (43) 306000<br>
>                     (44) 318000<br>
>                     (45) 330000<br>
>                     (46) 342000<br>
>                     (47) 354000<br>
>                     (48) 366000<br>
>                     (49) 378000<br>
>                     (50) 390000<br>
>                     (51) 402000<br>
>                     (52) 414000<br>
>                     (53) 426000<br>
>                     (54) 438000<br>
>                     (55) 450000<br>
>                     (56) 462000<br>
>                     (57) 474000<br>
>                     (58) 486000<br>
>                     (59) 498000<br>
>                     (60) 510000<br>
>                     (61) 522000<br>
>                     (62) 534000<br>
>                     (63) 546000<br>
>                     (64) 558000<br>
>                     (65) 570000<br>
>                     (66) 582000<br>
>                     (67) 594000<br>
>                     (68) 606000<br>
>                     (69) 618000<br>
>                     (70) 630000<br>
>                     (71) 642000<br>
>                     (72) 654000<br>
>                     (73) 666000<br>
>                     (74) 678000<br>
>                     (75) 690000<br>
>                     (76) 702000<br>
>                     (77) 714000<br>
>                     (78) 726000<br>
>                     (79) 738000<br>
>                     (80) 750000<br>
>                     (81) 762000<br>
> <br>
>                     On Thu, Feb 25, 2021 at 6:26 PM Dave Allured - NOAA<br>
>                     Affiliate <<a href="mailto:dave.allured@noaa.gov" target="_blank">dave.allured@noaa.gov</a><br>
>                     <mailto:<a href="mailto:dave.allured@noaa.gov" target="_blank">dave.allured@noaa.gov</a>>> wrote:<br>
> <br>
>                         It is starting to look like there is an error in<br>
>                         the attached coordinates.  What are the min and<br>
>                         max values of tas@lat2d and tas@lon2d?<br>
> <br>
> <br>
>                         On Thu, Feb 25, 2021 at 10:45 AM S Br<br>
>                         <<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a><br>
>                         <mailto:<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a>>> wrote:<br>
> <br>
>                             Hi Dennis,<br>
>                             The data draws on a wrong location and the<br>
>                             map boundary is not aligning.<br>
>                             It should plot over the UK which is about<br>
>                             50-60N.<br>
> <br>
>                             Thanks.<br>
> <br>
>                             On Thu, Feb 25, 2021 at 5:41 PM Dennis Shea<br>
>                             <<a href="mailto:shea@ucar.edu" target="_blank">shea@ucar.edu</a> <mailto:<a href="mailto:shea@ucar.edu" target="_blank">shea@ucar.edu</a>>> wrote:<br>
> <br>
>                                 It helps to give NCL the correct lat/lon<br>
>                                 array information.<br>
> <br>
>                                 See attached<br>
> <br>
>                                 On Thu, Feb 25, 2021 at 10:23 AM Dave<br>
>                                 Allured - NOAA Affiliate via ncl-talk<br>
>                                 <<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a><br>
>                                 <mailto:<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a>>> wrote:<br>
> <br>
>                                     That script looks pretty good.  You<br>
>                                     can see from the error messages that<br>
>                                     NCL is trying to understand @lat2d<br>
>                                     and @lon2d, but something is not<br>
>                                     quite right with them.  We need to<br>
>                                     see printVarSummary for tas,<br>
>                                     tas@lat2d, and tas@lon2d.  It is<br>
>                                     possible that dimensions are<br>
>                                     mismatched between data and<br>
>                                     coordinates, for some reason.<br>
> <br>
>                                     There is also this note in that doc<br>
>                                     page:  "If your data variable is a<br>
>                                     two-dimensional (2D) array ordered<br>
>                                     lon x lat, you will need to reorder<br>
>                                     it to be lat x lon."  Please check<br>
>                                     and see if this is the problem.<br>
> <br>
> <br>
>                                     On Thu, Feb 25, 2021 at 10:00 AM S<br>
>                                     Br <<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a><br>
>                                     <mailto:<a href="mailto:sbr.climate@gmail.com" target="_blank">sbr.climate@gmail.com</a>>> wrote:<br>
> <br>
> <br>
>                                         Hi Dave,<br>
>                                         Many thanks for your reply.<br>
>                                         Sorry I missed to provide the<br>
>                                         details.<br>
>                                         I have run the following NCL<br>
>                                         script  and came across the<br>
>                                         errors given below.<br>
>                                         You can see the attached plot<br>
>                                         that it draws value throughout<br>
>                                         the globe. It is supposed to be<br>
>                                         drawn only over the UK.<br>
>                                         Am I doing something wrong?<br>
> <br>
>                                         ;********<br>
>                                         srcFileName="<a href="http://tas_rcp85_land-rcm_uk_12km_01_mon_198012-208011.nc" rel="noreferrer" target="_blank">tas_rcp85_land-rcm_uk_12km_01_mon_198012-208011.nc</a><br>
>                                         <<a href="http://tas_rcp85_land-rcm_uk_12km_01_mon_198012-208011.nc" rel="noreferrer" target="_blank">http://tas_rcp85_land-rcm_uk_12km_01_mon_198012-208011.nc</a>>"<br>
> <br>
>                                         ;---Read File<br>
>                                         f=addfile(srcFileName,"r")<br>
>                                         print(f)<br>
> <br>
>                                         ;---Get the source lat/lon grid<br>
>                                         tas=f->tas(0,0,:,:)<br>
>                                         tas@lat2d=f->projection_y_coordinate<br>
>                                         tas@lon2d=f->projection_x_coordinate<br>
> <br>
>                                         ;---Plot data<br>
>                                            wks = gsn_open_wks("x11","map")<br>
> <br>
>                                            res              = True<br>
>                                            res@gsnMaximize  = True     ;<br>
>                                         maximize plot in frame<br>
>                                            res@cnFillOn     = True     ;<br>
>                                         turn on contour fill<br>
>                                            res@cnLinesOn    = False    ;<br>
>                                         turn off contour fill<br>
>                                            res@gsnAddCyclic     = False<br>
>                                         ;   res@mpMinLatF    =  48.0    <br>
>                                                  ; only plot 30S to 30N<br>
>                                         ;   res@mpMaxLatF    =  60.0<br>
>                                         ;  res@mpMinLonF    =  -15.0    <br>
>                                               ; only plot 30S to 30N<br>
>                                         ;   res@mpMaxLonF    = 6.0<br>
>                                           res@mpDataBaseVersion =<br>
>                                         "MediumRes"<br>
>                                             res@mpLandFillColor = "white"<br>
> <br>
>                                            plot =<br>
>                                         gsn_csm_contour_map(wks,tas(:,:),res)<br>
> <br>
>                                         ********************<br>
>                                         (0) is_valid_latlon2d_attr:<br>
>                                         Warning: The 'lat2d' attribute<br>
>                                         must either be<br>
>                                         (0) the same dimension sizes as<br>
>                                         the data, or one element larger<br>
>                                         in both directions.<br>
>                                         (0) Your data will most likely<br>
>                                         not be overlaid on the map<br>
>                                         correctly.<br>
>                                         (0) check_for_y_lat_coord:<br>
>                                         Warning: Data either does not<br>
>                                         contain<br>
>                                         (0) a valid latitude coordinate<br>
>                                         array or doesn't contain one at all.<br>
>                                         (0) A valid latitude coordinate<br>
>                                         array should have a 'units'<br>
>                                         (0) attribute equal to one of<br>
>                                         the following values:<br>
>                                         (0)    'degrees_north'<br>
>                                         'degrees-north' 'degree_north'<br>
>                                         'degrees north' 'degrees_N'<br>
>                                         'Degrees_north' 'degree_N'<br>
>                                         'degreeN' 'degreesN' 'deg north'<br>
>                                         (0) is_valid_latlon2d_attr:<br>
>                                         Warning: The 'lon2d' attribute<br>
>                                         must either be<br>
>                                         (0) the same dimension sizes as<br>
>                                         the data, or one element larger<br>
>                                         in both directions.<br>
>                                         (0) Your data will most likely<br>
>                                         not be overlaid on the map<br>
>                                         correctly.<br>
>                                         (0) check_for_lon_coord:<br>
>                                         Warning: Data either does not<br>
>                                         contain<br>
>                                         (0) a valid longitude coordinate<br>
>                                         array or doesn't contain one at all.<br>
>                                         (0) A valid longitude coordinate<br>
>                                         array should have a 'units'<br>
>                                         (0) attribute equal to one of<br>
>                                         the following values:<br>
>                                         (0)    'degrees_east'<br>
>                                         'degrees-east' 'degree_east'<br>
>                                         'degrees east' 'degrees_E'<br>
>                                         'Degrees_east' 'degree_E'<br>
>                                         'degreeE' 'degreesE' 'deg east'<br>
> <br>
>                                         On Thu, Feb 25, 2021 at 4:17 PM<br>
>                                         Dave Allured - NOAA Affiliate<br>
>                                         <<a href="mailto:dave.allured@noaa.gov" target="_blank">dave.allured@noaa.gov</a><br>
>                                         <mailto:<a href="mailto:dave.allured@noaa.gov" target="_blank">dave.allured@noaa.gov</a>>><br>
>                                         wrote:<br>
> <br>
>                                             Does your file contain its<br>
>                                             own lat and lon coordinate<br>
>                                             arrays?  You will need to<br>
>                                             check this yourself with<br>
>                                             ncdump or NCL plus print<br>
>                                             commands.<br>
> <br>
>                                             If the file has its own<br>
>                                             coordinate arrays, then do<br>
>                                             not regrid or reproject. <br>
>                                             Doing that will lose detail<br>
>                                             and reduce the quality of<br>
>                                             the plotted image.  NCL is<br>
>                                             quite capable of directly<br>
>                                             displaying any data with<br>
>                                             attached coordinate arrays,<br>
>                                             and it does not need to know<br>
>                                             anything about the<br>
>                                             projection of the data. <br>
>                                             Please see documentation for<br>
>                                             "Plotting data on a map" for<br>
>                                             much more information about<br>
>                                             aligning data on a map plot.<br>
> <br>
>                                             <a href="https://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml" rel="noreferrer" target="_blank">https://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml</a><br>
>                                             <<a href="https://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml" rel="noreferrer" target="_blank">https://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml</a>><br>
> <br>
>                                             If the coordinate arrays in<br>
>                                             the file are two<br>
>                                             dimensional, then see<br>
>                                             example 3, "Curvilinear<br>
>                                             grid".  When you have 2-D<br>
>                                             coordinates, they must be<br>
>                                             passed to the NCL plot<br>
>                                             routine with special<br>
>                                             attributes *lat2d* and<br>
>                                             *lon2d*, or alternatively<br>
>                                             *sfXArray* and<br>
>                                             *sfYArray* attached to the<br>
>                                             plot resource variable. <br>
>                                             Note that 1-D coordinates do<br>
>                                             not need this special<br>
>                                             treatment because they are<br>
>                                             normally attached directly<br>
>                                             to the data variable to plot.<br>
> <br>
> <br>
>                                             On Thu, Feb 25, 2021 at 8:24<br>
>                                             AM S Br via ncl-talk<br>
>                                             <<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a><br>
>                                             <mailto:<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a>>><br>
>                                             wrote:<br>
> <br>
>                                                 Hi All,<br>
>                                                 I have a set of regional<br>
>                                                 gridded data in the<br>
>                                                 British National Grid<br>
>                                                 (OSGB) spatial<br>
>                                                 coordinate system. I am<br>
>                                                 looking to use this data<br>
>                                                 in NCL but the<br>
>                                                 projection is not<br>
>                                                 correctly displayed?<br>
>                                                 Could it be possible to<br>
>                                                 regrid this data to<br>
>                                                 Latitude-longitude in<br>
>                                                 rotated pole coordinates<br>
>                                                 or to a regular lat/lon<br>
>                                                 grid.<br>
> <br>
>                                                 I would like to mention<br>
>                                                 that these data sets are<br>
>                                                 generated using the Iris<br>
>                                                 package in Python. The<br>
>                                                 data is correctly<br>
>                                                 displayed in Python but<br>
>                                                 not in NCL.<br>
> <br>
>                                                 For your convenience I<br>
>                                                 have attached here a<br>
>                                                 sample NetCDF file.<br>
> <br>
>                                                 Thank you.<br>
>                                                 SBR<br>
> <br>
>                 _______________________________________________<br>
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> <br>
> <br>
> _______________________________________________<br>
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