[ncl-talk] Regridding from OSGB spatial coordinate to Latitude-longitude in rotated pole coordinates
S Br
sbr.climate at gmail.com
Fri Feb 26 02:34:01 MST 2021
Hi,
The min and max of f->grid_latitude and f->grid_longitude prints wrong
information. You can see that the bounding box is not surrounding the UK.
(0) min=-0.8710618968191547 max=12.94984143216418
(0) min=-18.24145632530888 max=-6.580251255557555
Thanks.
On Thu, Feb 25, 2021 at 9:24 PM Dave Allured - NOAA Affiliate <
dave.allured at noaa.gov> wrote:
> Okay. We need to evaluate whether the lat and lon coordinates in your
> file are correct. I see Dennis's other reply, but I am suggesting a
> different approach using only attached coordinates, and nothing else. If
> the Iris package generated your file correctly, then nothing else should be
> needed.
>
> Please show the min and max of f->grid_latitude and f->grid_longitude.
> Don't show the whole array. The command *printMinMax (var, 0)* is useful
> for this. If these coordinate sets are correct, then the min and max
> should be a bounding box surrounding the UK.
>
> NCL works best with supplied coordinate arrays, which is the method I am
> recommending here. Python is doing something different, perhaps
> recalculating based on the projection information. I don't really care
> about that, I just want to help you get the normal NCL method working.
>
>
> On Thu, Feb 25, 2021 at 1:20 PM S Br <sbr.climate at gmail.com> wrote:
>
>> Hi Dave,
>> Please see the attached plot, this is how it looks like if we use the
>> above statements.
>> It obviously doesn't plot over the UK.
>>
>>
>> On Thu, Feb 25, 2021 at 6:59 PM Dave Allured - NOAA Affiliate <
>> dave.allured at noaa.gov> wrote:
>>
>>> I see what's going on. From your other e-mail, the data file contains
>>> two different sets of coordinates. There are the projection coordinates in
>>> meters. Those are not latitudes and longitudes, therefore not sufficient
>>> for NCL. But the geographic coordinates are also provided. Double
>>> coordinates are frequently encountered in GIS related applications. Try
>>> this:
>>>
>>> tas at lat2d=f->grid_latitude
>>> tas at lon2d=f->grid_longitude
>>>
>>>
>>> On Thu, Feb 25, 2021 at 11:42 AM S Br <sbr.climate at gmail.com> wrote:
>>>
>>>> If I print tas at lat2d and tas at lon2d, they give the following
>>>> information.
>>>>
>>>> Variable: taslat
>>>> Type: double
>>>> Total Size: 896 bytes
>>>> 112 values
>>>> Number of Dimensions: 1
>>>> Dimensions and sizes: [112]
>>>> Coordinates:
>>>> (0) -102000
>>>> (1) -90000
>>>> (2) -78000
>>>> (3) -66000
>>>> (4) -54000
>>>> (5) -42000
>>>> (6) -30000
>>>> (7) -18000
>>>> (8) -6000
>>>> (9) 6000
>>>> (10) 18000
>>>> (11) 30000
>>>> (12) 42000
>>>> (13) 54000
>>>> (14) 66000
>>>> (15) 78000
>>>> (16) 90000
>>>> (17) 102000
>>>> (18) 114000
>>>> (19) 126000
>>>> (20) 138000
>>>> (21) 150000
>>>> (22) 162000
>>>> (23) 174000
>>>> (24) 186000
>>>> (25) 198000
>>>> (26) 210000
>>>> (27) 222000
>>>> (28) 234000
>>>> (29) 246000
>>>> (30) 258000
>>>> (31) 270000
>>>> (32) 282000
>>>> (33) 294000
>>>> (34) 306000
>>>> (35) 318000
>>>> (36) 330000
>>>> (37) 342000
>>>> (38) 354000
>>>> (39) 366000
>>>> (40) 378000
>>>> (41) 390000
>>>> (42) 402000
>>>> (43) 414000
>>>> (44) 426000
>>>> (45) 438000
>>>> (46) 450000
>>>> (47) 462000
>>>> (48) 474000
>>>> (49) 486000
>>>> (50) 498000
>>>> (51) 510000
>>>> (52) 522000
>>>> (53) 534000
>>>> (54) 546000
>>>> (55) 558000
>>>> (56) 570000
>>>> (57) 582000
>>>> (58) 594000
>>>> (59) 606000
>>>> (60) 618000
>>>> (61) 630000
>>>> (62) 642000
>>>> (63) 654000
>>>> (64) 666000
>>>> (65) 678000
>>>> (66) 690000
>>>> (67) 702000
>>>> (68) 714000
>>>> (69) 726000
>>>> (70) 738000
>>>> (71) 750000
>>>> (72) 762000
>>>> (73) 774000
>>>> (74) 786000
>>>> (75) 798000
>>>> (76) 810000
>>>> (77) 822000
>>>> (78) 834000
>>>> (79) 846000
>>>> (80) 858000
>>>> (81) 870000
>>>> (82) 882000
>>>> (83) 894000
>>>> (84) 906000
>>>> (85) 918000
>>>> (86) 930000
>>>> (87) 942000
>>>> (88) 954000
>>>> (89) 966000
>>>> (90) 978000
>>>> (91) 990000
>>>> (92) 1002000
>>>> (93) 1014000
>>>> (94) 1026000
>>>> (95) 1038000
>>>> (96) 1050000
>>>> (97) 1062000
>>>> (98) 1074000
>>>> (99) 1086000
>>>> (100) 1098000
>>>> (101) 1110000
>>>> (102) 1122000
>>>> (103) 1134000
>>>> (104) 1146000
>>>> (105) 1158000
>>>> (106) 1170000
>>>> (107) 1182000
>>>> (108) 1194000
>>>> (109) 1206000
>>>> (110) 1218000
>>>> (111) 1230000
>>>>
>>>>
>>>> Variable: taslon
>>>> Type: double
>>>> Total Size: 656 bytes
>>>> 82 values
>>>> Number of Dimensions: 1
>>>> Dimensions and sizes: [82]
>>>> Coordinates:
>>>> (0) -210000
>>>> (1) -198000
>>>> (2) -186000
>>>> (3) -174000
>>>> (4) -162000
>>>> (5) -150000
>>>> (6) -138000
>>>> (7) -126000
>>>> (8) -114000
>>>> (9) -102000
>>>> (10) -90000
>>>> (11) -78000
>>>> (12) -66000
>>>> (13) -54000
>>>> (14) -42000
>>>> (15) -30000
>>>> (16) -18000
>>>> (17) -6000
>>>> (18) 6000
>>>> (19) 18000
>>>> (20) 30000
>>>> (21) 42000
>>>> (22) 54000
>>>> (23) 66000
>>>> (24) 78000
>>>> (25) 90000
>>>> (26) 102000
>>>> (27) 114000
>>>> (28) 126000
>>>> (29) 138000
>>>> (30) 150000
>>>> (31) 162000
>>>> (32) 174000
>>>> (33) 186000
>>>> (34) 198000
>>>> (35) 210000
>>>> (36) 222000
>>>> (37) 234000
>>>> (38) 246000
>>>> (39) 258000
>>>> (40) 270000
>>>> (41) 282000
>>>> (42) 294000
>>>> (43) 306000
>>>> (44) 318000
>>>> (45) 330000
>>>> (46) 342000
>>>> (47) 354000
>>>> (48) 366000
>>>> (49) 378000
>>>> (50) 390000
>>>> (51) 402000
>>>> (52) 414000
>>>> (53) 426000
>>>> (54) 438000
>>>> (55) 450000
>>>> (56) 462000
>>>> (57) 474000
>>>> (58) 486000
>>>> (59) 498000
>>>> (60) 510000
>>>> (61) 522000
>>>> (62) 534000
>>>> (63) 546000
>>>> (64) 558000
>>>> (65) 570000
>>>> (66) 582000
>>>> (67) 594000
>>>> (68) 606000
>>>> (69) 618000
>>>> (70) 630000
>>>> (71) 642000
>>>> (72) 654000
>>>> (73) 666000
>>>> (74) 678000
>>>> (75) 690000
>>>> (76) 702000
>>>> (77) 714000
>>>> (78) 726000
>>>> (79) 738000
>>>> (80) 750000
>>>> (81) 762000
>>>>
>>>> On Thu, Feb 25, 2021 at 6:26 PM Dave Allured - NOAA Affiliate <
>>>> dave.allured at noaa.gov> wrote:
>>>>
>>>>> It is starting to look like there is an error in the attached
>>>>> coordinates. What are the min and max values of tas at lat2d and
>>>>> tas at lon2d?
>>>>>
>>>>>
>>>>> On Thu, Feb 25, 2021 at 10:45 AM S Br <sbr.climate at gmail.com> wrote:
>>>>>
>>>>>> Hi Dennis,
>>>>>> The data draws on a wrong location and the map boundary is not
>>>>>> aligning.
>>>>>> It should plot over the UK which is about 50-60N.
>>>>>>
>>>>>> Thanks.
>>>>>>
>>>>>> On Thu, Feb 25, 2021 at 5:41 PM Dennis Shea <shea at ucar.edu> wrote:
>>>>>>
>>>>>>> It helps to give NCL the correct lat/lon array information.
>>>>>>>
>>>>>>> See attached
>>>>>>>
>>>>>>> On Thu, Feb 25, 2021 at 10:23 AM Dave Allured - NOAA Affiliate via
>>>>>>> ncl-talk <ncl-talk at mailman.ucar.edu> wrote:
>>>>>>>
>>>>>>>> That script looks pretty good. You can see from the error messages
>>>>>>>> that NCL is trying to understand @lat2d and @lon2d, but something is not
>>>>>>>> quite right with them. We need to see printVarSummary for tas, tas at lat2d,
>>>>>>>> and tas at lon2d. It is possible that dimensions are mismatched
>>>>>>>> between data and coordinates, for some reason.
>>>>>>>>
>>>>>>>> There is also this note in that doc page: "If your data variable
>>>>>>>> is a two-dimensional (2D) array ordered lon x lat, you will need to reorder
>>>>>>>> it to be lat x lon." Please check and see if this is the problem.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, Feb 25, 2021 at 10:00 AM S Br <sbr.climate at gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hi Dave,
>>>>>>>>> Many thanks for your reply. Sorry I missed to provide the details.
>>>>>>>>> I have run the following NCL script and came across the errors
>>>>>>>>> given below.
>>>>>>>>> You can see the attached plot that it draws value throughout the
>>>>>>>>> globe. It is supposed to be drawn only over the UK.
>>>>>>>>> Am I doing something wrong?
>>>>>>>>>
>>>>>>>>> ;********
>>>>>>>>> srcFileName="tas_rcp85_land-rcm_uk_12km_01_mon_198012-208011.nc"
>>>>>>>>>
>>>>>>>>> ;---Read File
>>>>>>>>> f=addfile(srcFileName,"r")
>>>>>>>>> print(f)
>>>>>>>>>
>>>>>>>>> ;---Get the source lat/lon grid
>>>>>>>>> tas=f->tas(0,0,:,:)
>>>>>>>>> tas at lat2d=f->projection_y_coordinate
>>>>>>>>> tas at lon2d=f->projection_x_coordinate
>>>>>>>>>
>>>>>>>>> ;---Plot data
>>>>>>>>> wks = gsn_open_wks("x11","map")
>>>>>>>>>
>>>>>>>>> res = True
>>>>>>>>> res at gsnMaximize = True ; maximize plot in frame
>>>>>>>>> res at cnFillOn = True ; turn on contour fill
>>>>>>>>> res at cnLinesOn = False ; turn off contour fill
>>>>>>>>> res at gsnAddCyclic = False
>>>>>>>>> ; res at mpMinLatF = 48.0 ; only plot 30S to 30N
>>>>>>>>> ; res at mpMaxLatF = 60.0
>>>>>>>>> ; res at mpMinLonF = -15.0 ; only plot 30S to 30N
>>>>>>>>> ; res at mpMaxLonF = 6.0
>>>>>>>>> res at mpDataBaseVersion = "MediumRes"
>>>>>>>>> res at mpLandFillColor = "white"
>>>>>>>>>
>>>>>>>>> plot = gsn_csm_contour_map(wks,tas(:,:),res)
>>>>>>>>>
>>>>>>>>> ********************
>>>>>>>>> (0) is_valid_latlon2d_attr: Warning: The 'lat2d' attribute must
>>>>>>>>> either be
>>>>>>>>> (0) the same dimension sizes as the data, or one element larger in
>>>>>>>>> both directions.
>>>>>>>>> (0) Your data will most likely not be overlaid on the map
>>>>>>>>> correctly.
>>>>>>>>> (0) check_for_y_lat_coord: Warning: Data either does not contain
>>>>>>>>> (0) a valid latitude coordinate array or doesn't contain one at
>>>>>>>>> all.
>>>>>>>>> (0) A valid latitude coordinate array should have a 'units'
>>>>>>>>> (0) attribute equal to one of the following values:
>>>>>>>>> (0) 'degrees_north' 'degrees-north' 'degree_north' 'degrees
>>>>>>>>> north' 'degrees_N' 'Degrees_north' 'degree_N' 'degreeN' 'degreesN' 'deg
>>>>>>>>> north'
>>>>>>>>> (0) is_valid_latlon2d_attr: Warning: The 'lon2d' attribute must
>>>>>>>>> either be
>>>>>>>>> (0) the same dimension sizes as the data, or one element larger in
>>>>>>>>> both directions.
>>>>>>>>> (0) Your data will most likely not be overlaid on the map
>>>>>>>>> correctly.
>>>>>>>>> (0) check_for_lon_coord: Warning: Data either does not contain
>>>>>>>>> (0) a valid longitude coordinate array or doesn't contain one at
>>>>>>>>> all.
>>>>>>>>> (0) A valid longitude coordinate array should have a 'units'
>>>>>>>>> (0) attribute equal to one of the following values:
>>>>>>>>> (0) 'degrees_east' 'degrees-east' 'degree_east' 'degrees east'
>>>>>>>>> 'degrees_E' 'Degrees_east' 'degree_E' 'degreeE' 'degreesE' 'deg east'
>>>>>>>>>
>>>>>>>>> On Thu, Feb 25, 2021 at 4:17 PM Dave Allured - NOAA Affiliate <
>>>>>>>>> dave.allured at noaa.gov> wrote:
>>>>>>>>>
>>>>>>>>>> Does your file contain its own lat and lon coordinate arrays?
>>>>>>>>>> You will need to check this yourself with ncdump or NCL plus print commands.
>>>>>>>>>>
>>>>>>>>>> If the file has its own coordinate arrays, then do not regrid or
>>>>>>>>>> reproject. Doing that will lose detail and reduce the quality of the
>>>>>>>>>> plotted image. NCL is quite capable of directly displaying any data with
>>>>>>>>>> attached coordinate arrays, and it does not need to know anything about the
>>>>>>>>>> projection of the data. Please see documentation for "Plotting data on a
>>>>>>>>>> map" for much more information about aligning data on a map plot.
>>>>>>>>>>
>>>>>>>>>> https://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml
>>>>>>>>>>
>>>>>>>>>> If the coordinate arrays in the file are two dimensional, then
>>>>>>>>>> see example 3, "Curvilinear grid". When you have 2-D coordinates, they
>>>>>>>>>> must be passed to the NCL plot routine with special attributes
>>>>>>>>>> *lat2d* and *lon2d*, or alternatively *sfXArray* and *sfYArray* attached
>>>>>>>>>> to the plot resource variable. Note that 1-D coordinates do not need this
>>>>>>>>>> special treatment because they are normally attached directly to the data
>>>>>>>>>> variable to plot.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Thu, Feb 25, 2021 at 8:24 AM S Br via ncl-talk <
>>>>>>>>>> ncl-talk at mailman.ucar.edu> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hi All,
>>>>>>>>>>> I have a set of regional gridded data in the British National
>>>>>>>>>>> Grid (OSGB) spatial coordinate system. I am looking to use this data in NCL
>>>>>>>>>>> but the projection is not correctly displayed? Could it be possible to
>>>>>>>>>>> regrid this data to Latitude-longitude in rotated pole coordinates or to a
>>>>>>>>>>> regular lat/lon grid.
>>>>>>>>>>>
>>>>>>>>>>> I would like to mention that these data sets are generated using
>>>>>>>>>>> the Iris package in Python. The data is correctly displayed in Python but
>>>>>>>>>>> not in NCL.
>>>>>>>>>>>
>>>>>>>>>>> For your convenience I have attached here a sample NetCDF file.
>>>>>>>>>>>
>>>>>>>>>>> Thank you.
>>>>>>>>>>> SBR
>>>>>>>>>>>
>>>>>>>>>>
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