Title of Paper: Using COM Objects for Data Access and Visualization


Principal Author: Ganesh Gopalan


Abstract: An Earth Science product could be the end result of several software tasks that process the raw data. In this paper we describe how different processing tasks maybe mapped to various technologies to achieve the end result. The focus has been on building and using COM objects to accomplish specific tasks and also using COM as a means to leverage the functionality of existing applications such as MATLAB. Three applications are discussed; first the AVHRR Temperature Extractor  that extracts sea surface temperatures from AVHRR images for a given drifter track and compares them with the temperatures collected by the drifter. User parameters are first submitted to the web-server.COM objects extract temperature values from the pixels in the image that correspond to the drifter's location (track). Drifter and image temperatures and return them to the web-server. The output can be viewed as XML which is rendered using an XSL stylesheet. If the user now chooses to see a plot of the data, temperature values are extracted from the XML tree and passed to MATLAB using OLE automation. MATLAB can be launched both on the web-server and on the client and its methods invoked to generate a JPEG file as the final result. The technologies used in this application include DCOM, OLE automation and XML. The next application is the generation of volumetric slice plots from temperature and other data available at different depths. 3D slices can be applied along any of the latitude, longitude or depth axes. MATLAB is again accessed as an automation server to generate the plot. Finally we discuss the development of smart sensors. This project involves adding logic to an instrument such as a drifter to enable it to be controlled remotely or to provide near real-time access to data. A Windows CE device was selected to host the instrument. A DCOM client and server are used for accessing data on the device. Serial I/O is used to read parameters from the measuring instrument and supply it to the device.