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It is not enough to collect the data and produce data products. In order to be useful the data has to be used. To facilitate data use eventually a search interface has to be developed, probably many. And those interfaces can only be as good as the metadata they have to work with. HDF is not so much a data format as a file format that packages the data with the metadata, so facilitating data access by providing adequate and appropriate metadata starts with data production. In many areas this is not much of a challenge. The temporal coverage of the granules is generally well known, channel and derived parameter names are generally just a matter of convention, etc. But spatial coverage can vary quite a bit, especially for remotely sensed data, and can often be problematic. This paper goes through the five most common spatial types (point, grid, tile, scene, and swath) discusses the problems associated with each, and makes some recommendations for the metadata that needs to be included with the data to facilitate fast, efficient, accurate search when the time comes.
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Fall, 2004 National Snow and Ice Data Center 1
Spatial Types
Fall, 2004 National Snow and Ice Data Center 2
Point Data
Fall, 2004 National Snow and Ice Data Center 3
Sparse Point Data
Fall, 2004 National Snow and Ice Data Center 4
Dense Point Data
Fall, 2004 National Snow and Ice Data Center 5
Gridded Data
Fall, 2004 National Snow and Ice Data Center 6
MODIS CMG - Coverage
Fall, 2004 National Snow and Ice Data Center 7
SSM/I Ease-grid
Fall, 2004 National Snow and Ice Data Center 8
SSM/I EASE Grid - Coverage
Fall, 2004 National Snow and Ice Data Center 9
Polar Stereo (Sea Ice)
Fall, 2004 National Snow and Ice Data Center 10
Polar Stereo (Sea Ice) - Coverage
Fall, 2004 National Snow and Ice Data Center 11
Polar Stereo (Sea Ice) - Coverage
Fall, 2004 National Snow and Ice Data Center 12
Polar Stereo (Sea Ice) - Coverage
Fall, 2004 National Snow and Ice Data Center 13
Polar Stereo (Sea Ice) - Coverage
Fall, 2004 National Snow and Ice Data Center 14
Polar Stereo (Sea Ice) - Coverage
Fall, 2004 National Snow and Ice Data Center 15
Polar Stereo (Sea Ice) - Coverage
Fall, 2004 National Snow and Ice Data Center 16
Tiles
Fall, 2004 National Snow and Ice Data Center 17
05v08h Coverage
Fall, 2004 National Snow and Ice Data Center 18
05v08h w/ lat/lon bounding box
Fall, 2004 National Snow and Ice Data Center 19
05v08h Spherical
Fall, 2004 National Snow and Ice Data Center 20
AVHRR L1b (Scene)
Fall, 2004 National Snow and Ice Data Center 21
AVHRR L1b (Scene) - Coverage
Fall, 2004 National Snow and Ice Data Center 22
AVHRR L1b (Scene) - Coverage
Fall, 2004 National Snow and Ice Data Center 23
AVHRR L1b (Scene) - Coverage
Fall, 2004 National Snow and Ice Data Center 24
AVHRR L1b (Scene) - Coverage
Fall, 2004 National Snow and Ice Data Center 25
AVHRR L1b (Scene) - Coverage
Fall, 2004 National Snow and Ice Data Center 26
Weird Shape
Fall, 2004 National Snow and Ice Data Center 27
Full Orbit - Coverage
Fall, 2004 National Snow and Ice Data Center 28
Full Orbit - LLBox
Fall, 2004 National Snow and Ice Data Center 29
Full Orbit – Lat/lon Blocks
Fall, 2004 National Snow and Ice Data Center 30
Full Orbit – Spherical Blocks
Fall, 2004 National Snow and Ice Data Center 31
Full Orbit - Coverage
Fall, 2004 National Snow and Ice Data Center 32
Full Orbit - Coverage
Fall, 2004 National Snow and Ice Data Center 33
Full Orbit – Using Backtrack
Fall, 2004 National Snow and Ice Data Center 34
Summary
Point Data: use points or multi-points.
Grids: Use a lat/lon bounding box if appropriate, otherwise use a spherical n-gon. Accuracy is more important than speed.
Tiled Data: A form of regional grid, use a lookup table.
Scenes: Use a spherical quadrilateral, maybe up to a spherical decagon for larger scenes. Speed is more important than accuracy.
Orbits: The best way to define the coverage of an orbit is to define the orbit. The best way to search for orbital data is to search orbits. Use Backtrack.