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(3a) Map Projection and Data Structure 
Chairman: Jan-Peter Muller 
University College London 
Ideal Requirement 
Distortionless (for areal & distance measurements) 
Seamless 
"Error-free" relationships to original data 
"Error-free" spatial operations 
Global "perspective" 
Presentation to be different to integration & correlation 
Indexation 
Flexibility 
3D, time, multiple attributes 
Map Projection 
EOS - "ISCCP" grid (nested sinusoidal) 
DMA - ARC (area raster grid) - regional sinusoidal 
ZOT - spherical tessellation (octahedral) 
Plate Carree 
Polar Stereographic 
Question: What map projection should be used for a global database? 
Answer: No clear "winner" but all agreed 
- need for common reference datum & geoid 
- presentation needs different to integration & correlation 
- "Jand" needs different to ocean & atmospheres 
- need to address different uses and users will produce different requirements 
- need to minimize error for spatial operations 
- need to include 3D, time, multiple attributes 
- need to include rapid indexation 
- need to use appropriate pixel/point/vector data structure 
N.B. Alternative approach is to leave data in original format/satellite projection but provide 
SW and necessary ancillary data to resample into any other map projection. 
Question: What data structure is suitable for global database? 
Answer: Triangles, Cartesian, Spherical angles 
Spherical tessellation 
Spectral decomposition