Hi Knut-Frode, Il giorno Mon, 16 May 2011 09:39:30 +0200 Knut-Frode Dagestad <[email protected]> ha scritto:
> Hi RSyaoxin and Antonio, > > I share your interest in these metadata. In addition to the MPH and > SPH metadata in ASCII-format, Envisat files contain a lot of metadata > in binary form, e.g. for ASAR: > http://envisat.esa.int/handbooks/asar/CNTR6-6.htm#eph.asar.asardf.asarrec > > It would probably be too much to ask for the GDAL Envisat driver to > import all of this. However, there are some missing metadata which > are of special importance: > > - the calibration factors, which RSyaoxin mentions > - the incidence angles: > http://envisat.esa.int/handbooks/asar/CNTR6-6-9.htm#eph.asar.asardf.asarrec.ASAR_Geo_Grid_ADSR > > Both of this is necessary to be able to calibrate the data, and hence > to be able to make any geophysical calculations from them. > It would be really nice if the GDAL Envisat driver could be updated > to read this as well, and most users would not need to rely on (or > create) external software. > From a practical point of view it should be relatively easy to implement this feature using a lower level library like the libepr-api. I could manage to do it in a relatively short time. Unfortunately, apart from other considerations, the solution is not acceptable since libepr-api is GPL3. An alternative solution is to write from scratch the routines for decoding of ENVISAT records but this is would require a larger effort. Again I could try to do it but I would like to receive some sign of interest in this feature from GDAL developers before starting to code. > The incidence angles are stored in a small grid at the same size as > the GCP´s, (order of 100 elements), which does not fit very nicely > into the GDAL datamodel - it would probably have to be stored as a > list of metadata strings. > > Best regards from Knut-Frode > Yes, it is indeed a problem. My feeling is that the currant trend is keeping metadata as flat and simple as possible. > > On 15/05/2011 18:18, Antonio Valentino wrote: > > Hi RSyaoxin, > > > > Il 15/05/2011 14:46, RSyaoxin ha scritto: > >> Hi,I want to calibration the ENVISAT ASAR DATA(.N1 Format). I need > >> to get it's main processing parameters,such as > >> calibration_factors[0].ext_cal_fact[0],first_line_tie_point_angles[0-10],and > >> I wrote: CString > >> sDomain=m_pDataset->GetMetadataItem("MAIN_PROCESSING_PARAMS_ADS_CALIBRATION_FACTORS[0].EXT_CAL_FACT[0]");but > >> I can't get result. > >> However, "CString > >> sDomain=m_pDataset->GetMetadataItem("SPH_FIRST_MID_LAT")" is > >> right.That's Why?How should I go to get necessary information? I > >> turn to Anybody who once did this job for some advice. Thank you! > >> Kind regards. > >> > > > > It seems that the envisat driver do not extracts all metadata from > > all ENVISAT records. > > It just exposes MPH, SPH and GCPs > > > > http://www.gdal.org/frmt_various.html#Envisat > > > >> From my point of view it would be very useful to be able to have > >> access > > to a richer set of metadata from GDAL (at east for SAR products). > > > > If you are only interested in ENVISAT then you could give a try to > > > > https://github.com/bcdev/epr-api > > > > that give you full access to the ENVISAT products eve if, IMHO, it > > is not so handly as GDAL for imagery IO. > > > > Maybe you can use them both: EPR for metadata and GDAL for imagery. best regards -- Antonio Valentino _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
