a web based solution for spatio-temporal visualization bo zhao university of florida july 15 th,...
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A Web based solution for spatio-temporal visualization
Bo ZhaoUniversity of Florida
July 15th, 2009
Issues
• the dimension of spatio-temporal visualization
• the cache of historical events
• the limits of value types
• the expression of different calendars
the dimension of spatio-temporal visualization
Big Bang and the spatio-temporal integrated model
umbrella
Big Bang Theory in Astronomy
Spatio-Temporal Cube
J. Ronald Eastman, Earth Trends Modeler, Clark University, 2008
Temporal model
Temporal model
Understandability
Spatio-temporal dimensions
N = ?
the cache of historical events
the cache of historical events
• What is cache?
the cache of historical events
• Synchrony: download all the events at once– Different data format support: KML, CVS,
GeoRSS, Json– Sort the events at the client side
• Asynchrony: download the events required– Limited data format support– Sort the events at the server side
Markercluster
• For vector data: Markercluster• cluster = new MarkerClusterer( map, markers, { gridSize: 1, maxZoom: 15});
http://cga-3.hmdc.harvard.edu/timeslider~/
raster data cache?
http://www.openlayers.org/dev/examples/wmst.html
http://mesonet.agron.iastate.edu/cgi-bin/wms/nexrad/n0r-t.cgi?LAYERS=nexrad-n0r-wmst&TRANSPARENT=true&FORMAT=image%2Fpng&TIME=2005-08-29T23%3A00%3A00&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=EPSG%3A4326&BBOX=0,22.5,22.5,45&WIDTH=256&HEIGHT=256
TIME=2005-08-29T23%3A00%3A00
WMS-T• wms_timeextent:
return the valid time values for the layer.
• wms_ timeitem: this is the name of the field in the DB that contains the time values.
• wms_timedefault: this value is used if it is defined and the TIME value is missing in the request.
http://mapserver.org/ogc/wms_time.html
the limits of value types
• the year range changes due to the programming language or libraries themselves.• Ruby: 3156527048337996BC to
3156527048337998AD• Python: 0 to 9999AD
• For ECMAScript 3.0 (the standard for javascript),– 53-bit double floating point – (-2^53, 2^53 - 1) – (-9,007,199,254,740,992, 9,007,199,254,740,991) – the year range will be from 271821BC to 275760AD.
[1] http://www.mail-archive.com/[email protected]/msg01472.html[2] ECMAScript Language Specification, Page 117, Dec, 1999,
Calendars (ISO8601)
• From Julian Calendar to Gregorian Calendar– 1582, Oct. 5 to Oct. 14 doesn’t exit.
• javascript still have this time period, in our program, we should remove this time period.
– Different countries adopted the Gregorian Calendar at different time, so we have to pay attention to the exact calendar the events are using.• George Washington’s Birthday:
– February 22, 1732 Gregorian Calendar– February 11, 1732 Julian Calendar
• The October Revolution– October 25, 1917 Julian Calendar – November 7, 1917 Gregorian Calendar
Future work
• When user moving the map or specify the time, the calendars would be changed due to the current countries within the map extent.
• Support Raster data
Demo
• http://code.google.com/p/cga-gmaps-tools/
Thanks, any questions?