Thanks for the information, i had already found some things like that. As a matter of fact it appears i misunderstood what i need to do. I need to reproject data in that are on "some kind" of sinusoidal projection with a GEM6 ellispsoid to some regular lat/lon grid.
My initial raster in "GEM6" is georeferenced (gcps) so i think i will be able to use gdal to reproject this data. As i can't test this because i do not have any input data right now, can anyone confirm ? 2009/5/6 Peter J Halls <[email protected]> > For detailed information on DGG's see > http://cs.sou.edu/~sahrk/dgg/<http://cs.sou.edu/%7Esahrk/dgg/> > . > > There is a paper in the journal Cartography and Geographic Information > Science, 'Geodesic Discrete Global Grid Systems' by Kevin Sahr, Denis White > and A. Jon Kimerling, linked from the above web page, which surveys DDG in > detail. In summary, DDG is a data structure, based on 'regular, > multi-resolution partitions of polyhedra' where 'each region has a single > point associated with it'. It is analogous to Voronoi cells, but regular, > rather than irregular. 'Usually, this series consists of increasingly finer > resolution grids; i.e., the grids in the series have a monotonically > increasing number of cells.' - this seems similar to using a quad-tree > approach. > > 'Grids based on square partitions are by far the most familiar to users, > and they map efficiently to common data structures and display devices. But > such grids also have limitations. Discrete Global Grid Systems induced by > the latitude–longitude graticule do not have equal-area cell regions, which > complicates statistical analysis on these grids.' A wide variety of cell > forms have been proposed by various workers but, according to Sahr et al, > 'It is highly unlikely that any single Geodesic DGGS will ever prove optimal > for all applications. Many of the proposed systems include design > innovations in particular areas, though their construction may have involved > other, less desirable design choices.' > > I rather doubt GDAL has the functions for this approach, but I may be > wrong. > > Peter > > reg ister wrote: > >> Hello everyone, >> i ve ran into some odd projection and i would like to know if i can use >> gdal >> to reproject georeferenced data in this projection (gcp included in my >> raster) . I'm used to gdal and projections but here i can't seem to find >> enough information. >> The idea is to reproject to a DGG (discrete global grid) The projection is >> an adapted sinusoidal grid with an ellipsoid based on GEM 6 model (Goddard >> Earth Model) >> >> Any insight or experience is apreciated but if no one already encountered >> such a thing here are some precise questions that can help me >> >> I never encountered the name DGG before, does it implies some specific >> feature about projection or is it just a synonym of grid ? >> the grid considered seems to be composed of octaedrons, is it even >> relevant >> when projecting data considering i have the ellipsoid and type of >> projection >> ? >> I have the major and minor axises for GEM 6 ellipsoid, would it be correct >> ( >> and possible ) to specify these to gdal along with a sinusoidal projection >> to reproject my data? >> as you may have noticed, is said adapted sinusoidal grid... i don't what >> adapted implies. would it be possible in gdal to "adapt" the built in >> sinusoidal projection ( to what cost in dev )? >> >> >> any help apreciated. >> >> Thanks everyone, keep up the good work >> >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> gdal-dev mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/gdal-dev >> > > -- > > -------------------------------------------------------------------------------- > Peter J Halls, GIS Advisor, University of York > Telephone: 01904 433806 Fax: 01904 433740 > Snail mail: Computing Service, University of York, Heslington, York YO10 > 5DD > This message has the status of a private and personal communication > > -------------------------------------------------------------------------------- >
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