[gdal-dev] NetCDF driver in gdal_translate ignores xllcorner and
yllcorner?
Michael Sumner
mdsumner at gmail.com
Fri May 21 01:56:07 EDT 2010
What is the result of running gdalinfo on the NetCDF file (or on the
desired subdataset)?
The y values are not regular, as you can see in this subset of the
sequence: 9165629, 9166645, 9167660, 9168676
That might be part of the issue.
Cheers, Mike.
On Fri, May 21, 2010 at 2:28 PM, Kyle Shannon <ksshannon at gmail.com> wrote:
> I have also had an issue with the geotransform being of by a factor of 1000,
> but it was a units issue. GDAL kind of assumes CF=1.x convention, as netcdf
> is very broad in its specification. Could you attach a small sample dataset
> to a ticket so I can take a look? Thanks.
>
> kss
>
> # ============================
> Kyle Shannon
> Physical Science Technician
> RMRS Fire Sciences Lab
> Fire, Fuels & Smoke - RWU 4405
> 5775 Highway 10 W.
> Missoula, MT 59808
> (406)829-6954
> kshannon at fs.fed.us
> # ============================
>
>
> On Thu, May 20, 2010 at 8:37 PM, Ole Nielsen <ole.nielsen at aifdr.org> wrote:
>>
>> Dear GDAL developers
>>
>> I have been using GDAL for a while with great success and really
>> appreciate
>> the toolkit.
>> As of recently, I now have the need to read NetCDF files and convert them
>> into AAIGRIDs. However, the cellsize is wrong and I don't think xllcorner
>> and yllcorner are correct either.
>>
>> I have searched this forum and I think this may be related to the thread
>> named "[gdal-dev] netcdf to geotiff and aaigrid" from 2008. However, I
>> didn't find a resolution in that thread - hence this posting.
>>
>> The content of the NetCDF file is obtained by running ncdump
>> merapi.res.nc:
>>
>> netcdf merapi.res {
>> dimensions:
>> x = 59 ;
>> y = 64 ;
>> alt = 6 ;
>> time = UNLIMITED ; // (4 currently)
>> variables:
>> float x(x) ;
>> x:units = "m" ;
>> x:description = "UTM. West-East distance" ;
>> float y(y) ;
>> y:units = "m" ;
>> y:description = "UTM. South-North distance" ;
>> .... (many lines removed here)
>> data:
>>
>> x = 412432.3, 413449.5, 414466.8, 415484, 416501.2, 417518.5, 418535.7,
>> 419553, 420570.2, 421587.4, 422604.7, 423621.9, 424639.1, 425656.4,
>> 426673.6, 427690.8, 428708.1, 429725.3, 430742.6, 431759.8, 432777,
>> 433794.2, 434811.5, 435828.7, 436846, 437863.2, 438880.4, 439897.7,
>> 440914.9, 441932.2, 442949.4, 443966.6, 444983.8, 446001.1, 447018.3,
>> 448035.6, 449052.8, 450070, 451087.3, 452104.5, 453121.8, 454139,
>> 455156.2, 456173.5, 457190.7, 458207.9, 459225.2, 460242.4, 461259.6,
>> 462276.9, 463294.1, 464311.3, 465328.6, 466345.8, 467363.1, 468380.3,
>> 469397.5, 470414.8, 471432 ;
>>
>> y = 9106709, 9107724, 9108740, 9109756, 9110772, 9111788, 9112804,
>> 9113820,
>> 9114836, 9115851, 9116867, 9117883, 9118899, 9119915, 9120931, 9121947,
>> 9122962, 9123978, 9124994, 9126010, 9127026, 9128042, 9129058, 9130073,
>> 9131089, 9132105, 9133121, 9134137, 9135153, 9136169, 9137185, 9138200,
>> 9139216, 9140232, 9141248, 9142264, 9143280, 9144296, 9145311, 9146327,
>> 9147343, 9148359, 9149375, 9150391, 9151407, 9152422, 9153438, 9154454,
>> 9155470, 9156486, 9157502, 9158518, 9159534, 9160549, 9161565, 9162581,
>> 9163597, 9164613, 9165629, 9166645, 9167660, 9168676, 9169692, 9170708
>> ;
>>
>> ...... (lines removed)
>>
>> TOPOGRAPHY =
>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 51.99445,
>> 124.9918, 103.0026, 170.9917, 191.9973, 183.0012, 214.9956, 215,
>> 204.0016, 246.9934, 231.0025, 221.0016, 226.999, 224.0005, 249.9954,
>> 211.0071, 232.9959, 242.9981, 224.0038, 231.9984, 222.0021, 240.9959,
>> 271.9932, 265.0016, 284.9954, 286.9995, 289.9993, 293.999, 311.9955,
>> 274.0097, 294.9946, 282.0034, 302.9944, 317.9959, 311.002, 314.9989,
>> 330.9954, 338.9977,
>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 105.9893, 183.9907,
>> 183.9983, 189.9981, 199.9982, 200.999, 215.9977, 224.9986, 217.0007,
>> 264.993, 260.0003, 273.9973, 246.0043, 249.9992, 291.9925, 299.998,
>> 300.9991, 277.004, 256.0034, 272.9964, 252.004, 246.001, 243.0005,
>> 256.9968, 242.0032, 268.9941, 253.0037, 249.0013, 272.9945, 271.0006,
>> 277.9984, 263.0042, 266.9991, 277.9973, 312.9904, 322.9971, 295.0079,
>> 295.0002, 273.0067, 336.9814, 334.0009,
>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 96.98979, 189.9899,
>> 180.001, 205.9969, 205.9997, 213.9988, 236.9966, 240.999, 255.9975,
>> ...... etc etc
>>
>> ========================
>>
>> The command I use to extract this topography variable is
>> gdal_translate -of AAIGrid NETCDF:"merapi.res.nc":TOPOGRAPHY
>> merapi.topography.asc
>>
>> and the header of the resulting file is
>> ncols 59
>> nrows 64
>> xllcorner 0.000000000000
>> yllcorner -64.000000000000
>> cellsize 1.000000000000
>> NODATA_value 9.9692099683868690468e+36
>> 0 0 0 0 0 0 0 0 0 0
>> 0 0 0 0 0 0 0 0 0 0 0
>> 51.99444
>> 9615478515625 124.9918365478515625 103.00257110595703125 170.99169921875
>> 191.9973297119140625 183.001190185546875 214.99560546875 215
>> 204.001617431640625
>> 246.993438720703125 231.0025177001953125 ........
>>
>> ---------------------------------------------------------
>>
>> I do not understand why the cellsize is 1.000000 when it should be in the
>> order of 1000.
>> Also, I do not understand why xllcorner and yllcorner aren't obtained as
>> e.g. the minimum values of the x and y vectors.
>>
>> The version of gdal-bin is 1.5.2-3ubuntu1 and my platform is Ubuntu 9.04
>> (64
>> bit).
>>
>> By the way, trying to contour directly from the NetCDF puts all the
>> contours at the south pole. I suspect this is another manifestation of the
>> origins being ignored.
>>
>> Can anyone help please?
>>
>> Cheers and thanks
>> Ole Nielsen
>>
>>
>> --
>> View this message in context:
>> http://osgeo-org.1803224.n2.nabble.com/gdal-translate-netcdf-to-aaigrid-wrong-cellsize-xllcorner-and-yllcorner-tp5073995p5073995.html
>> Sent from the GDAL - Dev mailing list archive at Nabble.com.
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