Search found 9 matches

by NISAR - hfattahi
Tue Sep 08, 2026 3:46 pm America/New_York
Forum: Home
Question: NISAR geolocation error .. or plotting error?
Replies: 2

Re: NISAR geolocation error .. or plotting error?

Thanks for reporting your observation. Yes July 10 product for this specific frame has known issue and will be reprocessed in future. Due to an edge case in raw data processor, the raw data may be shifted when there is a discarded/missing pulse and that impacts the downstream products. The issue wil...
by NISAR - hfattahi
Thu Aug 27, 2026 11:11 am America/New_York
Forum: Home
Question: Region-scale integer-cycle inconsistency in a distributed P05023 GUNW, identified by a five-acquisition loop-closure net
Replies: 4

Re: Region-scale integer-cycle inconsistency in a distributed P05023 GUNW, identified by a five-acquisition loop-closure

Thanks for posting the plot of connected components. Yes I agree that the connected component in this case is affected by invalid region at the boundary of the swath and is not immediately useful for identifying/correcting unwrapping errors. It looks to me that the unwrapper has not respected the su...
by NISAR - hfattahi
Mon Aug 24, 2026 2:18 pm America/New_York
Forum: Home
Question: Region-scale integer-cycle inconsistency in a distributed P05023 GUNW, identified by a five-acquisition loop-closure net
Replies: 4

Re: Region-scale integer-cycle inconsistency in a distributed P05023 GUNW, identified by a five-acquisition loop-closure

Thank you for sharing your analysis. Yes users should be aware that there is no easy way to connect possible disconnected islands in an operational system. The provided connected components should help users to identify the separated components and adjust as they wish if they have auxiliary informat...
by NISAR - hfattahi
Mon Aug 24, 2026 2:01 pm America/New_York
Forum: Home
Question: Azimuth offset issues in P05023 processed GUNWs
Replies: 3

Re: Azimuth offset issues in P05023 processed GUNWs

P05023 provisional products, do not include masks and metrics to help users discard such data. We are indeed adding these metrics in the next delivery. We understand the importance of such metrics for users and will update as they become available.
by NISAR - hfattahi
Mon Aug 24, 2026 1:54 pm America/New_York
Forum: Home
Question: Ghost images in azimuth
Replies: 1

Re: Ghost images in azimuth

The cause of this issue is same as the post here : https://forum.earthdata.nasa.gov/viewtopic.php?t=8118 The root cause is an edge case in raw data processor which does not correctly time-tag the raw data in presence of discarded rangeline. I confirm that the ghost image disappears after using a new...
by NISAR - hfattahi
Mon Aug 24, 2026 1:00 pm America/New_York
Forum: Home
Question: Azimuth offset issues in P05023 processed GUNWs
Replies: 3

Re: Azimuth offset issues in P05023 processed GUNWs

Thanks for reporting this issue. The problem originates from corrupted input raw data. Looking at the reference RSLC shows that the image is fully defocused and therefore the interferometry fails to produce any useful product. For example see this RSLC product: NISAR_L1_PR_RSLC_010_077_A_024_4005_DH...
by NISAR - hfattahi
Thu Aug 20, 2026 12:37 am America/New_York
Forum: Home
Question: Coherence seams along whole-degree meridians in NISAR GSLC interferograms over Alaska
Replies: 2

Re: Coherence seams along whole-degree meridians in NISAR GSLC interferograms over Alaska

Thank you for reporting this edge case. We were able to reproduce the issue. The source of the issue is the DEM at higher latitudes which seems to have a small discontinuity between tiles. We are investigating a possible solution and will update when we have more information.
by NISAR - hfattahi
Wed Aug 19, 2026 1:50 pm America/New_York
Forum: Home
Question: Sharp azimuth offset transitions
Replies: 1

Re: Sharp azimuth offset transitions

Thank you for reporting this issue. This is a known issue due to missing rangelines or discarded rangelines in raw data and an edge case in raw data processor that does not properly update the time tag of remaining pulses after discarding some (in this case probably only one pulse out of 100s of tho...
by NISAR - hfattahi
Thu Mar 12, 2026 2:22 am America/New_York
Forum: Home
Question: NISAR satellite backscatter coefficient image generation
Replies: 9

Re: NISAR satellite backscatter coefficient image generation

Thanks for your post. Your approach to convert the GSLC backscatter to sigma-0 is not correct. The RSLC and subsequently GSLC are provided as Beta-0 with respect to an ellipsoid. If you want to convert to sigma-0 you must use the sigma-0 correction factor which is included in theGSLC products at the...