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Sean et al. First of all, I'm coming from outside the GML-JP2 group, so I'm not sure about what's actually going on with that activity. However, within the OGC Sensor web Enablement (SWE) activity, there is an effort going on that may be relevant to both your question and the JP2 work. As you may know, in earlier SWE efforts, an Observation&Measurement schema was developed, mostly by Simon Cox, to support sensor observations. He built this upon GML, added some extensions to support basic scalar types, and developed application schemas for observation and for measurements. From what I understand from Ron Lake, about 70% of this has been incorporated into core GML. The challenge that we have had in getting acceptance of O&M outside of simple in-situ sensors, has been a lack of decent support for high-volume data sets (e.g. 5000x5000 resolution images, video, 500x500x100 resolution grids, 40,000 particles, etc.) that are common in the remote sensing and modeling communities. In SWE, we are interested in supporting those data sets, as well as real-time streaming data. I believe GML is certainly starting to address these issues, but is perhaps not fully mature yet in this regard. Within SensorML development and particularly in response to harmonization with TransducerML (streaming data), we have played around with some encodings that are flexible and efficient for large ascii or binary data sets or streaming data. The key has been to describe the data's reference system (and I don't just mean spatial or temporal reference system) and structure within one XML element (class) and then to provide the data encoding and data values separately within a _DataProvider class. This ends up being very similar to a somewhat more limited data block structure defined in GML, but one that I haven't seenexercised much.
For example, I might describe within the data reference system that the data coming from an aircraft sensor will output data clusters composed of time, latitude, longitude, altitude, sensor mode, CO2, NOx, SO2, etc. ... this essentially defines a tuple of data that might be updated at a rate of say 5 times per second. The reference description would in essence define the order of these components, the type of measurement (Quantity, Category, Boolean, etc), and their units of measure. This is similar to defining a CRS, but is not confined to to only spatial and temporal coordinates. We are also describing arrays of values using this scheme in order to support images, grids, volumes, etc. The actual values of the observations can then be provided as an XML-based tuple data block, binary images, video segments, flat-file binary data, or a TML data stream. The values could be inline or linked by URI to an online resource or perhaps a mime attachment with a SOAP message. It would seem that this would also work within the JPEG2000 structure. As of 2 weeks ago at the OWS3 Kickoff meeting, we have initiated an accelerated effort to define a Common Observation model that combines lessons-learned from GML, O&M, SensorML, and TML and provides a single schema capable of efficiently supportiing simple observations, as well as images, grids, streams, etc. In addition, the Observation model would point to sensor descriptions (in SensorML) as well as procedures or process chains describing the lineage of the data. More than likely, the Observation model and encoding will be based somewhat on the current Observation model used in O&M, possibly built upon GML as is the current O&M. We are also looking at possible enveloping mechanisms for combining the Observation "header" description with binary attachements, using protocols such as SOAP messaging with attachments, etc. Those involved in this effort have scheduled another face-to-face meeting in Huntsville, AL in 2 weeks. We should have the Common Observation model pretty well defined at that time and could make that available for review by the GML and GML-JP2 groups. Seems like there is some possible synergy here between the GML-JP2 and the SWE Common Observation activity. I understand that even after this long email, I didn't address all of your questions. Thanks, Mike Botts ----------------------------------------------------------------------- Mike Botts, Ph.D. mike.botts@xxxxxxxxxxxxx Principal Research Scientist http://vast.uah.edu Earth System Science Center (256) 961-7760 GHCC - NSSTC (256) 652-0165 (cell) University of Alabama in Huntsville (256) 961-7755 (fax)Huntsville, AL 35899 USA -----------------------------------------------------------------------
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