muchas gracias

I dont know, sometimes selecting bursts is not work for some SNAP installation, thats why I go with safer workflow

Glad it was helpful!

You must install snaphu first from plugins menu

You are so welcome!

ah yeah, my fault, I should use the 1sec one, thank you for correcting

Precisely, I don't know for sure. This is actually a research question that only can be answered by experiment. however Based on my current understanding, it will improve the accuracy until the output spatial resolution of the SAR data limiting the vertical accuracy to its maximum allowed possible accuracy (you can't expect 0.5 meter vertical accuracy on 15 meters resolution in hilly terrain)

@@GEO2004 When using external DEM, I notice in the create interfergoram, the parameters will default to SRTM3sec. In order to use external DEM I need to activate the Substract topographic phase option. Is this the right thing to do? And theres option to check for earth gravity model as well. which is confusing too.

No, external dem can be used without activate the substract topographic phase option,

You should learn first about sar interferometry theories, keep in mind that if you learn about remote sensing, just dont forget about the concepts and theories.

There is a theoretical explanation why 2 images are needed instead of one

@@GEO2004 thank you for the replies. Really appreciate it

Sorry, I can't provide that because arcgis is esri's intellectual property, I think you can find it from google search,

There is none as far I know, but for more specific interferometry application like insar deformation, or land subsidence there are some, Thematic Exploitation platform from Terradue is one of them. However most of them are not free

@@GEO2004 thanks

Large scale building retrieval needs super fine SAR Imagery in 0.5 meters resolution or finer, that kind of data currently only can be obtained from commercial SAR imagery vendors such as UMBRA or some others, I also would like to get access to that kind of data for free if it is possible. I am not a millionaire ya know.

can you confirm that the noises correspondence with vegetated area?, if it is yes, then nothing you can do, because that is the limitation of sentinel-1 interferometric DEM processing, you can refers to SAR interferometry theories for further explanation,

@@GEO2004 thanks for the reply. Most of the part corresponds to vegetation but urban and water regions are also there.

Water is also can't be solved, urban area commonly have a good interferometric coherence due to its static appearance in the imagery. Good coherence will guarantee a good DEM result, but urban area just like its name suggest, usually have a lot of small size settlements and building with various height characteristics, so in the DEM result this characteristics will cause height noises. This would be different if you are using high resolution SAR like terrasar-x or cosmo skymed, the DEM result in urban area would be better.

@@GEO2004 Thankyou so much for the clarification. Actually I was stuck in determining the flood depth using Sentinel-1 data and DEM was required in that. If you know about how to determine flood depth with Sentinel-1 SLC data, please tell or please share any tutorial or video if you have.

You must do field survey for this matter, dem from sentinel-1 won't helps at all because sentinel-1 actually is not designed to provide good DEM data, sentinel-1 is only quite good to map the flood extent, but not flood depth

SLC (single Look Complex) commonly refer to SAR data in single look resolution (slant range). SLC data still have the original geometry when the data is recorded. SLC format is also store SAR backscatter in its original form (imaginary and real number), it is still maintain the radio wave phase information (not only the intensity and amplitude information). GRD (Multi Look Ground) commonly refer to SLC SAR data that has been resampled to ground range/multi look, it have same pixel size in X and Y direction (like commonly found in Optical Imagery). GRD data usually have lost its radio wave phase information so it cannot be used in Interferometry (however it is still can be used for Radargrammetry).

here is a guideline kzfaq.info/get/bejne/aLqodLuKuKrdiYU.html

Yes to some degree, as long as no vegetation jn the image coverage, and the baseline length between image pair is more than 150 meters, there is possibility a dem can be generated

glad it was helpful

check this thread from ESA SNAP forum forum.step.esa.int/t/error-nodeid-apply-orbit-file-xml-document-structures-must-start-and-end-within-the-same-entity/22502/6

1. Yes, you are right 2. Yes you are also right about tiff output 3. That is inenvitable, basically sentinel-1 is not designed for insar DEM extraction (it is using C-band with quite a long temporal difference/six days in equator), after all insar also depends on line of sight constructed from baseline length (sensor distance between acquisitions), so those height differences are expected. Sentinel-1 radio phase also not free from ionosphere and troposphere effects, and those effects will tremendously affect the accuracy of phase extraction information. Snap 9 have some new features for interferometry like ionosfer correction and bandpassfilter, personally I am excited if those new features will improve the insar DEM extraction or not, I have a plan to make a video about it if those new features are really promising. In the mean time, what about you learn it first?. May be those new features could improve the DEM result. One more thing, if your application only needs height differences instead of absolute height, I guess you can ignore those absolute height differences between datasets and just focusing on using relative height obtained from the elevation_vv data.

@@GEO2004 Dear sir, thank you so much for your comprehensive explanation. Actually, I need absolute DEM value. If as what you mentioned above new features that could improve the DEM, I will look forward to your next tutorial on that and also check it myself if I have time. However, I have limited time and need to decide whether to use open source DEM 30 meter (like Alos) for my study. Will also appreciate it if you can recommend me any open source data for my study area that I want to study about urban flood. Again, really appreciate your kindness.

as far as open source data available for public, I think other than already available public DEM in 30 meters (copernicus dem, nasa dem, srtm, alos world 30 etc), higher quality and higher resolution data can only be provided from national data repository, and every country in the world (developed or developing countries) should have one, I guess maybe you can try to look the data for your country first.

@@GEO2004 Very well noted with many thanks, sir. I will check it out. Have a nice day, sir.

Have you check your internet connection is fine?

@@GEO2004 i finally found the problem. With same satelite image, time but different site for download it. When i download from alaska it got problem like that. But when i download from copernicus, finally it worked. Thnks

I am sorry, I never use PSI on SNAP processed data, usually I directly using stamps or other PSI software to do PSI/SBAS.

@@GEO2004 thanks

Absolutely

@@GEO2004 Please tell what kind of baseline criteria has to be followed for India. Which one should I choose aacending or descending?

Ascending or descending doesn' matter, the most important thing is not mixing up the descending and ascending images Baseline length is not specific for any country, good baseline length is between 150-500 meters

If there is no vegetation on the area, I am sure the accuracy is quite good. The one factor that remain need to be resolved is the atmospheric disturbance to the radar signal, that yeah you are right, one solution to overcome this atmospheric effect is only using n-pass interferometry

Bisa di merge pake TOPS-Merge

You can use ASF baseline tool,

this might be due to the interferogram quality is bad, so unwrapping found some unresolved calculation

@@GEO2004 Thanks

Yes you must use at least two imagery covering same area. Why? Because it is using interferometric principles. You can read and dig about it if you want to know more, Explaining here would be just too long and too complex if you are not understand even the most basic understanding

@@GEO2004 so I can't create DEM if I'm not using two imagery

Yes

@@GEO2004 can I use the same iagery product twice just by changing the name so SNAP can accept it

Read first about interferometry brother. Don't be such an ignorant person. This is not good for your learning progress

Sure, validation is necessary in research

@@GEO2004 Sir my doubt is the Dems which are generated using Sentinel -1 sar data , using SNAP SOFTWARE, can we validate them??

Sepertinya karena memory ram ga kuat. Bisa diinfokan ram nya berapa?

@@GEO2004 RAM nya 8 gb kok, apa masih kurang untuk app SNAP ini?

Oke, berikutnya, anda memproses satu subswath atau hanya beberapa bursts?

@@GEO2004 satu subswath

Coba dulu dua atau tiga burst dalam satu subswath, kalau sukses, berarti ram 8gb anda tidak cukup buat ngolah satu subswath,

Kemungkinan proses unwrapnya tidak benar atau inteferogramnya sangat jelek sehingga unwrapnya tidak berhasil. Interferogram jelek ditandai dengan tidak adanya pola pola fringe yg unik dan hasil inteferogram jelek lebih kayak random warna pixelnya seperti siaran tv yg tidak daapt sinyal, layarnya cuma kayak semut2 bertebaran hehe

Betul, interferogram yg saya hasilkan, tidak seperti warna pelangi di video, namun lebih seperti siaran tv rusak. Apakah ada solusinya untuk itu? 🥹🙏​@@GEO2004

@@GEO2004 iya memang betul interferogramnya tidak seperti pelangi seperti di video, namun seperti tv tidak ada sinyal, jika interferogram nya jelek apakah ada solusinya? Terimakasih..

Tidak ada solusi, karena selisih waktu perekaman antar citra cukup lama, apalagi kalau penutup lahannya banyak vegetasi, kalau mau lebih baik hasilnya, cari lokasi yang tidak ada/minim vegetasi

Karna saya pribadi masih belum terlalu paham interferometri ini

Kalau uda acer download data sentinel dari portal ASF, disana ada alat untuk memilih citranya berdasarkan sudut dan jarak tangkapan, namanya ASF baseline tool, nanti kalau ada waktu coba saya buat kan video tutorialnya

@@GEO2004 Terimakasih sblmny mas Saya saat ini sedang melaksanakan penelitian untuk skripsi tentang perubahan topografi di salah satu gunung vulkanis, dan PKL di badan informasi geospasial di Bagian PPIT. Dari video d yt ad video d bogor, apakah mas juga bertugas di BIG? jika iya saya berencana juga hendak belajar langsung, khususny tntng interferometri ini Kira2 apakh bisa itu mas?

@@acerminang1522 bukan, saya enggak di BIG

@@GEO2004 izin bertanya kembali mas, mohon bantuannya 🙏 untk arah penerbangannya jika ascending brarti pasangan citra nya juga harus ascending kan? Tidak match jika ascending dan descending

Vary between 10 to 15 meters

@@GEO2004 what is the maximum definition achievable in a DEM?

About the resolution? 10 meters is maximum

@@GEO2004 how is it possible to obtain measurements to the millimeter to monitor, for example, bridges? see the research "Displacement monitoring and modeling of a high-speed railway bridge using C-band Sentinel-1 data"

It is possible because theoretically radar backscatter phase is so precise and accurate (gps technology is also using wave phase measurement to determine location), The problem is, SAR phase measurement is heavily depended on many factors. For example, SAR based displacement measurement is considered as LoS (line of sight) displacement. Different incidence angle of SAR measurement will resulting different displacement result. There are also components in SAR displacement measurement, vertical and horizontal component. They are adding the complexity. This is why single interferometric displacement measurement wont gave accurate displacement rate. To overcome this, SAR based displacement measurement employ Persistent scatterer interferometry technique. It is a technique to monitoring the height difference of certain object (such as bridge) over a very long time. So it is will cancel out or generalize the variance between measurement, and average displacement rate measurement result can be obtained with a higher degree of confidence.

I cant help if you are not describes your error

@@GEO2004 I want to show you to image but I cannot send my image to you by a comment in KZfaq. Could you send me your email?

You can upload the images yo googledrive or dropbox, and refer the link to this comment box

@@GEO2004 this is my link of my problem. mega.nz/file/UOIijZxK#QShGhVZsGk_DDuNY-j58DFiIQ-KVFtIpFM_HAhxMpLg

Your result cant be avoided and that is the common result if you are using sentinel-1 data for your dem interferometry, here are why: 1. Sentinel-1 is a C band SAR. Radar at C band, X band, even L band cant penetrate the landcover, so significant temporal differences will resulting in failure interferogram generation (due to low coherence), that is because the landcover of the master and the slave images has been changed. Then may be you asking why my result is quite good?, .my result is good because I am using imagery that covers desert/arid region which mostly didnt have vegetation cover, so the landcover condition is not changed between the dates, I can get a good coherence and upmy interferogram can be formed 2. The only way to get a good DEM from C-band or X-band SAR sensor is the master and slaves imagery temporal differences should be as short as possible (even few hours differences cant be accepted, it should be in seconds or minutes), that is also explain why SRTM which is also using C-band bring two SAR antennas, it is designed to make the temporal differences is super short, and Sentinel-1 isnt.