[R-sig-Geo] Projection of a large spherical surface on to a plane [SEC=UNCLASSIFIED]

[Martin Renner]

While it should be straightforward to calculate great circle  
distances, designing a rectangular grid on a sphere is not. There's a  
solution for a global grid using hexagons (Teanby, 2006), but I  
haven't seen it implemented in R (yet). My gut feeling is that for  
Australia there's a standard projection used by geographers that's  
reasonably distortion-free and should be plenty accurate given that  
you're working on such a large scale. Checking the fine print of that  
big map on your wall might be a good start.

HTH,
Martin


Martin Renner					
current address:
Alaska Maritime NWR             		907-226-4672 (work)
Homer, AK 99603, USA				907-235-7783 (fax)





@article{Teanby:2006aa,
	Author = {Teanby, N. A.},
	Journal = {Computers and Geosciences},
	Number = {9},
	Pages = {1442--1450},
	Title = {An icosahedron-based method for even binning of globally  
distributed remote sensing data},
	Volume = {32},
	Year = {2006}}





On 28 Apr 2009, at 01:37 , Paul Hiemstra wrote:

> Hi Jin Li,
>
> I seem to remember that gstat can deal with Great circle distances,  
> but I could be wrong as I have never used them before. You say that  
> a certain projection does not produce satisfactory results, how have  
> you defined satisfactory?
>
> cheers,
> Paul
>
> Jin.Li at ga.gov.au wrote:
>> Dear all,
>>
>> We are going to interpolate biophysical variables into continuous  
>> surface data using point samples in Australian EEZ that covers an  
>> area of 10 utm zones and ca. 44 degrees in terms of latitude. Our  
>> data is in lat and long (i.e., WGS84). We intend to apply kriging  
>> methods to such a big area. Of course, we can divide the whole EEZ  
>> into some subregions and actually we are going to divide it into  
>> some subregions based on a number of factors, but these sub-regions  
>> are still quite large and can cover 2 to 3 utms and 7-15 degrees in  
>> terms of latitude. Obviously it is not quite appropriate to treat a  
>> spherical surface as a plane. Given that kriging can not handle a  
>> spherical surface (hope this assumption is still valid), perhaps an  
>> alternative is project such spherical surface on to a plane. We  
>> have tried some equal distance projections to convert our data for  
>> Australian EEZ, but it seems that none of them can produce  
>> satisfactory projections, although sinusoidal gave slightly bet!
> te!
>> r results in comparison with utm projection. Any suggestions?  
>> Thanks in advance.
>>
>> Cheers,
>>
>> Jin
>> _______________________________________
>> Jin Li, PhD
>> Spatial Modeller/Computational Statistician
>> Marine & Coastal Environment
>> Geoscience Australia
>> GPO Box 378, Canberra, ACT 2601, Australia
>>
>> Ph: 61 (02) 6249 9899; email: jin.li at ga.gov.au<mailto:jin.li at ga.gov.au 
>> >
>> _______________________________________
>>
>>
>>
>> 	[[alternative HTML version deleted]]
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at stat.math.ethz.ch
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>
>
> -- 
> Drs. Paul Hiemstra
> Department of Physical Geography
> Faculty of Geosciences
> University of Utrecht
> Heidelberglaan 2
> P.O. Box 80.115
> 3508 TC Utrecht
> Phone:  +3130 274 3113 Mon-Tue
> Phone:  +3130 253 5773 Wed-Fri
> http://intamap.geo.uu.nl/~paul
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo