[gdal-dev] GEM 6 sinusoidal projection

reg ister clairlune.register at gmail.com
Thu May 7 07:46:45 EDT 2009

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 <P.Halls at york.ac.uk>

> 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
>> ------------------------------------------------------------------------
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> --
> --------------------------------------------------------------------------------
> 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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