Talk:Terminal Doppler Weather Radar
 | A fact from Terminal Doppler Weather Radar appeared on Wikipedia's Main Page in the Did you know column on 14 August 2009 (check views). The text of the entry was as follows:
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Angular resolution?
editHey all. I use TDWR data pretty regularly and have always wondered - why do all sources (including wikipedia) cite a 0.5 deg beamwidth? All data i have worked with, level II or level III, has all had a 1.0 deg beamwidth. Is there a reason for this discrepancy? Is it worth mentioning in the article? — Preceding unsigned comment added by Bryan C. W. (talk • contribs) 14:05, 6 September 2017 (UTC)
Bryan, keep in mind that angular resolution is not singularly defined by the beamwidth. If you are looking at specs that say that beamwidth is 1-deg, that's probably accurate. But radars can employ something called Monopulse processing (https://en.wikipedia.org/wiki/Monopulse_radar). You can easily get sub-beamwidth accuracy and resolution by comparing the Sum/DeltaEl/DeltaAz channels, resulting in resolution that can be less than the beamwidth. Resolution is just the ability to differentiate between two targets in that particular dimension. So without knowing all of the radar specs, I don't know what the real angular resolution capability is, I just know that it's not necessarily the same as the beamwidth. Willkeim (talk) 20:30, 21 March 2019 (UTC)
Introduction: Range Resolution
editThe introduction section says that the TDWR has a much finer range resolution because of it's small beam. There is a source cited pointing to MIT Lincoln Laboratories, but the link is no longer valid.
Typically, range resolution is not determined by your beam, it is inversely proportional to your signal bandwidth. A really small range resolution requires a large-bandwidth signal, whereas a very narrowband signal has a larger range resolution. See Skolnik, Introduction to Radar Systems, Section 6.3.
I would recommend that the first paragraph be re-written to say either:
- TDWR has finer range resolution because of its wideband operating channels
- TWDR has a finer overall resolution cell because of its wideband operation combined with a smaller beamwidth
You do get better elevation and azimuth resolution by having a smaller beam, but not range resolution.
We also might want to differentiate between "accuracy" and "resolution". You can have a very large bandwidth and a very small beam giving you a very tight measurement accuracy, but that doesn't necessarily mean that you can resolve two or more targets. The ability to resolve targets depends on having accuracy measurements but also on having appropriate signal processing mechanisms to differentiate targets which could both be reflected in the same sets of measurements. You could have very poor range and azimuth accuracy, for example, but still have good resolution if you employ a very high PRF and you can resolve in Doppler. Conversely, a very high accuracy radar could, in theory, have sub-optimal resolution if it achieved that accuracy averaging over many pulses but in fact had a large digitization cell preventing different target measurements from being separated out during A/D conversion. Willkeim (talk) 20:26, 21 March 2019 (UTC)
Weather Underground link goes to 404 now, removed
editI know the new URL, but decided to leave it out because I can't seem to get TDWR data from it for some reason. All the older NEXRAD data is still available, but that's a different wiki page. 184.221.150.124 (talk) 05:17, 7 July 2020 (UTC)