Hi Mike- > So I see itâs a software-specific issue. It is not as if the data is > distributed with lat/lon already calculated for the polygons, which just need > to be plotted on the 2-D map (no interpretation need by the software)? No, there is no lat/lon for each polygon in the file. Typically, the data is in range, azimuth and elevation for the radial products (e.g reflectivity, radial velocity). Some Level III products are gridded, and then they are in distance along a projection from a central point. The display software handles the conversion to lat/lon(/alt). Hope that helps. Don Murray > -----Original Message----- > From: Unidata IDV Support [mailto:address@hidden > Sent: Thursday, March 25, 2010 10:27 AM > To: Richards Michael > Cc: address@hidden > Subject: [IDV #OHK-595448]: question about WSR-88D Level-II data > > Hi Michael- > > It will depend on the software being used to display the data. The IDV does > take into account the curvature of the earth for the 2 and 3D displays. > Other software may not. > > Don Murray > > > I don't know if UNIDATA is the right place for this question...but > > perhaps if it can't be answered through you guys, maybe you could point > > me in the right direction. > > > > I am trying to get some info of the mapping (ground projection) of > > WSR-88D data using whatever software. I am going to assume that the > > same coordinate calculation process is done regardless of moment and > > scan angle...and this focuses on the universally distributed "NEXRAD" > > data that can be read by numerous pieces of "meteorological" software > > (i.e. through the NCDC)....although I admit I don't know too much > > about the nuts and bolts of the distributed data. I am neglecting the > > increasing bin size with distance for this discussion... > > > > I essentially want to verify that the coordinates (lat/lon) of every 2-D > > bin/polygon have been calculated with consideration of the curvature of > > the earth. Really not an issue unless a good distance from the radar > > site and at a high altitude. But I want to make sure that when looking > > at target data that has been retrieved at 300km from the radar site at a > > height of 11km (for example)...that the NEXRAD data is distributed in such > > a way that when it is mapped using my favorite software, the polygons > > correspond to the lat/lon underneath the target (which considers the > > earth surface)...and places it a bit further from the radar site than > > if the earth was flat (also stretching it out a bit). > > > > A really silly way I visualize this to help me is that if there was a > > 20km tall building normal to the earth surface at a distance of 300km > > from the rad ar site...as each scan angle of the radar increased, the > > radar-detected range (slant range) of the building would increase. > > However when all of buildin g retrievals (and their unique lat/lon > > boundaries) from different scans were plotted on a map (common weather > > radar projection) they would all be locate d at the same place on the > > map, which would exactly correspond to the base of the bulding.....and > > not represent the difference in slant range. > > > > I assume this to be the case since height estimations are done with > > regard to the earth curvature (and refraction coefficient) but I guess > > I need to make sure that this is the standard for NEXRAD data and no > > geographical correct ion needs to be made to the coordinates in the data. > > > > Thanks, > > Mike > > > > > > > > ***CONFIDENTIALITY NOTICE***: THIS E-MAIL TRANSMISSION MAY CONTAIN > > INFORMATION THAT IS PRIVILEGED, CONFIDENTIAL, PROPRIETARY, SUBJECT TO > > COPYRIGHT, AND/OR EXEMPT FROM DISCLOSURE UNDER APPLICABLE LAW. IT IS FOR > > THE USE OF INTENDED RECIPIENTS ONLY. If you are not an intended recipient > > of this message, please notify the original sender immediately by > > forwarding what you received and then delete all copies of the > > correspondence and attachments from your computer system. Any use, > > distribution, or disclosure of this message by unintended recipients is not > > authorized and may be unlawful. > > > > > > > Ticket Details > =================== > Ticket ID: OHK-595448 > Department: Support IDV > Priority: Normal > Status: Open > > > ***CONFIDENTIALITY NOTICE***: THIS E-MAIL TRANSMISSION MAY CONTAIN > INFORMATION THAT IS PRIVILEGED, CONFIDENTIAL, PROPRIETARY, SUBJECT TO > COPYRIGHT, AND/OR EXEMPT FROM DISCLOSURE UNDER APPLICABLE LAW. IT IS FOR THE > USE OF INTENDED RECIPIENTS ONLY. If you are not an intended recipient of > this message, please notify the original sender immediately by forwarding > what you received and then delete all copies of the correspondence and > attachments from your computer system. Any use, distribution, or disclosure > of this message by unintended recipients is not authorized and may be > unlawful. > Ticket Details =================== Ticket ID: OHK-595448 Department: Support IDV Priority: Normal Status: Open
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