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/simile-widgets@googlegroups.com/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?