Our paper “Evaluating Predicates over Dynamic Fields” has been accepted to the 5th International SIGSPATIAL Workshop on Geostreaming

Technological advances have created an unprecedented availability of inexpensive sensors able to stream environmental data in real-time for which we still seek appropriate data management technology that can keep up with this onslaught of sampling in previously unavailable spatial and temporal density.

In previous work we have shown that DSEs can be extended to generate smooth representations of continuous spatio-temporal fields sampled by up to 250K sensors on-the-fly in near real-time, creating a new representation every second.

In this paper we have investigated a spatio-temporal stream operator framework that efficiently executes predicate operators over spatio-temporal fields. We introduced a definition of predicates over dynamic fields, analyzed requirements for stream query evaluation and presented several pipelined stream based query operators algorithms. The work is based on the assumption that it is more efficient to find ‘seeds’ of regions that are part of the predicate result and expand them into the complete predicate result regions instead of interpolating the entire continuous phenomenon first, and filtering all cells based on the predicate condition. We investigated different seed expansion algorithms (Breadth First and Scanline region growing, and tile expansion) as well as exploring the impact of using the knowledge of the previous window query result. Our analysis and performance results show that both region growing algorithms perform best for all data set sizes and characteristics; tile-based approaches are efficient for tiles sizes 4×4 and 8×8. History-aware tile expansion performs better if the phenomenon changes slowly (as expected). Future work will include investigating adaptive query evaluation using the different algorithms based on the changing phenomenon characteristics.


Hiking Camden Hills State Park

It was another exceptional Indian summer weekend here in Maine, and we got a small group together to go for another, this time much longer hike, in Camden Hills State Park. Up Maiden Cliff, over to Ridge Trail, over the shady Jack Williams trail towards the little steep hike up to Ocean Viewpoint, and back to Mount Battie and the toll road. 5h later everyone was ready for a chilled beer. (with Mark Plummer, Susan Plummer, Shirly Stevens, Chitra, Erica, Helen Chaggaris, Xueying Gu, Maohui Zheng, Liping Yang, Haifei Chen and Henghan Li)







Hiking Sauveur Mountain

Thanks to good weather, we went on a beautiful hike one week into the semester — with Reinhard Moratz, Reginal Bennett, Mark Plummer, Shirley Stevens, Pathum Mudannayake, and Darshika.








Real-time Heat Maps with an Arduino Sensor Network

This summer, ECE grad student Nikhil Patil programmed an Ardunio temperature sensor network that updates streams of values into MySQL.  Using RStudio/Shiny, he programmed an application that queried the latest data from the database, and spatial interpolated a set of sensor values using Inverse Distance Weighting to create a heat map. The program continuously pulls the latest data every 5 seconds and generated a new heat map.

Largest robot swarm to date

Pretty cool!

Largest robot swarm to date, consisting of 3-legged kilobots using decentralized coordination and collaboration to achieve global tasks. (Harvard Self-Organizing Systems Research Group).

kilobot swarm

More info here.

New heights

Someone made it up Kathadin this summer for the first time (actually, everyone in this photo — Torsten Hahman, Helen Hahman, Xueying, Shirly and Mark).

Kathadin, 2014

One step closer to crowd radiation sensing

Video about the CT007 sensor, which can work standalone or connect via bluetooth to a mobile phone.


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