c-squares - a new method for representing, querying, displaying and exchanging dataset spatial extents. System concept and development by: Tony Rees Divisional Data Centre CSIRO Marine Research, Australia. some example Metadatabases (Data Directories). + many others -- 100 < 1000?.
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c-squares - a new method for representing, querying, displaying and exchanging dataset spatial extents
System concept and development by:
Divisional Data Centre
CSIRO Marine Research, Australia
some example Metadatabases (Data Directories)
+ many others -- 100 < 1000? ...
----- data bounding rectangle (MBR)
--------- search rectangle
current “base level” representation of spatial data coverage in metadata is by bounding box (minimum bounding rectangle, MBR)
SRTM 8-449 catch data
Catch records - Hoplostethus atlanticus
How well do MBR’s represent spatial data?
(examples from our own metadata system)
MBR actual data locations
Franklin 02/1999 hydrology data
alternatives to MBR’s for representation of data spatial extents ...
global grid systems already available ...
WMO 10-degree squares notation (part)
(Available via the web in NODC, 1998:World Ocean Database 1998 Documentation)
Concise Spatial Query and Representation System
same using 0.5 x 0.5 degree c-squares
data “footprint” using 1 x 1 degree c-squares
data “footprint” using bounding rectangle
actual ship’s track - “Franklin” voyage 10/87
“c-squares” numbering system
0.5- and 0.1- degree squares
Codes have straightforward relationship with lats/longs, mapsheets, etc. ...
1400:458(1-degree square with origin at
45 ºN, 008 ºE)
additional degrees E [00+8] =8
additional degrees N [40+5] = 45
5-degree quadrant, i.e. 3 4
tens of degrees E (i.e., 00)
tens of degrees N (i.e., 40)
global sector (1=NE, 3=SE, 5=SW, 7=NW)
“quad tree” -type approach used where numerous adjacent squares are occupied
squares can be “bulked” - example: 3212:*** instead of specifying every 1-degree square within 10 degree square 3212.
This leads to corresponding data reduction, e.g. Australia (at 1-degree resolution) can be described in 343 squares rather than 800:
Example database-level implementation of c-squares for metadata records(e.g. at 1 degree resolution)
Spatial queries using c-squares
example search result ...
Viewing the full metadata record produces ...
with clickable link to show dataset extent using c-squares:
Base maps for displayed data can be changed at will by the user, e.g.:
(numerous other maps available, sample only shown)
Process invoked for web mapping
c-squares strings can be sent directly to the CMR c-squares mapper (accessible via the web), e.g. from OBIS (Ocean Biogeographic Information System, USA):
<form action = "http://www.marine.csiro.au/cgi-bin/cs_map.pl" method="post">
<INPUT TYPE="hidden" NAME="csq" VALUE="3215:459:4|3215:459:3|3215:459:4|(etc.)">
<INPUT TYPE="hidden" NAME="title" VALUE="Global Distribution of <i>Raja</i>">
<INPUT TYPE="submit" NAME="submit" VALUE="make map ...">
c-squares strings are suitable for inclusion as a new metadata element alongside “bounding box”, for example ...
<title>Franklin Voyage FR 10/87 CTD Data</title>
<custodianOrg>CSIRO Marine Research</custodianOrg>
… would permit interoperability with both enabled and non-enabled systems
Summary - strengths and weaknesses of c-squares
other comments ...
c-squares current and future status...
(NB: handout available at this meeting)
My email: Tony.Rees@csiro.au