İstanbul Büyükçekmece ve Küçükçekmece lagün gölleri arasındaki bölgenin yüzey deformasyonlarının PS-Insar tekniği ile izlenmesi
Monitoring surface deformations of the region between istanbul Büyükçekmece and Küçükçekmece lagoon lakes using PS-Insar technique
Yazar: SELMA ACAR
Danışman: PROF. DR. SERDAR EROL
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Geomatik Mühendisliği Ana Bilim Dalı / Geomatik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Jeodezi ve Fotogrametri = Geodesy and Photogrammetry

Özet:
Aktif fay hatları üzerinde bulunan ve 15 milyondan fazla nüfusa sahip dinamik bir 
şehir olan İstanbul'un yerleşim yerlerinin önemli bir kısmı bu diri fay hatlarının 
yakınında yer almaktadır. Deprem riski altında bulunan bu şehir önemli ekonomik ve 
kültürel merkezlere, aynı zamanda önemli ulaşım yollarına ve mühendislik yapılarına 
da sahiptir. O nedenle bu bölgenin sürekli olarak jeodezik teknikler ile izlenmesi 
gerekmektedir.
Açık topoğrafyada veya kentleşmiş alanlarda yüzey hareketlerini izlemek için jeodezik 
yersel ve uydu teknikleri birlikte veya ayrı ayrı kullanılabilir. Yersel izleme teknikleri 
daha fazla zaman ve maliyet gerektirirken, radar uydularından elde edilen ücretsiz 
görüntüler ile deformasyonların izlenmesi daha kısa sürede ve daha geniş alanda daha 
az maliyetle yapılabilmektedir.
Bu çalışmada Sentinel-1A ve 1B uydularından alınan yapay açıklıklı radar (SAR) 
görüntüleri kullanılarak uydu bakış açısı doğrultusunda meydana gelen değişimler ve 
bu değişimin zamana göre eğilimi (trendi) belirlenmiş ve analiz edilmiştir. 
Interferometrik yapay açıklı radar (InSAR) tekniği; tektonik hareketlerin, volkanların, 
buzul hareketlerinin, altyapı ve üstyapılardaki değişimlerin izlenmesine ve sayısal 
yükseklik modeli oluşturmaya olanak sağlamaktadır.
Persistent Scatterer InSAR (PS-InSAR) yöntemi ise 1999 yılında Politecnico Di 
Milano Üniversitesinde geliştirilen piksel tabanlı radar deformasyon izleme tekniğidir. 
Bu yöntem ile, farklı iki uydu görüntüsünde benzer elektromanyetik geri saçılım yayan 
sabit yansıtıcılar tespit edilip deformasyon ve deformasyonun zaman içindeki 
değişiminin izlenmesi mümkün hale gelmiştir. Bu tekniğin, mera, orman, inşaat alanı 
gibi sürekli değişkenlik gösteren bölgelerde, sabit yansıtıcıların bulunamaması 
nedeniyle, performansı düşüktür. Bu tekniğin en önemli avantajı, yüzey hareketlerinin
zamanla değişiminin (hızının) izlenmesini sağlamasıdır.
Tekniğin uygulama aşamasında görüntülerin işlenmesi ve interferogramların 
oluşturulması için Sentinel Application Platform (SNAP) yazılımı, PS noktalarının 
üretimi için ise Stanford Method for Persistent Scatterers (StaMPS) yazılımı 
kullanılmıştır. SNAP yazılımından çıkan sonuç ürünlerin standart bir dosya formatında 
hazırlanıp StaMPS yazılımına aktarılması için "snap2stamps" kodları kullanılmıştır. 
Tez kapsamında çalışma alanı, İstanbul'un depreme karşı hassas bölgelerinden olan 
Büyükçekmece ve Küçükçekmece lagün gölleri arasında kalan alan olarak seçilmiştir.
Sentinel-1 uydusunun 2018-2022 yılları arasındaki yükselen ve alçalan yörüngedeki
görüntüleri, kendi aralarında ayrı ayrı değerlendirilmiştir. İki farklı değerlendirmeden 
elde edilen sonuçlar benzerlik göstermiştir. Bu iki benzer sonuca göre Avcılar sanayi 
bölgesi ve Büyükçekmece Türkoba konut alanında, Gürpınar iskele ve Beylikdüzü
iskele yapılarında ve Çatalca ilçesinin bazı kısımlarında uydu bakış doğrultusunda
çökme görülürken, Gürpınar bölgesinde ve Başakşehir ilçesi meskûn alanında uydu 
bakış doğrultusunda yükselme trendi tespit edilmiştir. Çalışma bölgesinde elde edilen
PS noktaları incelendiğinde yaz aylarında çökme, kış aylarında yükselme trendinin 
olduğu görülmüştür. Bu bölgede gerçekleştirilen daha önceki çalışmalarda, bölgenin 
killi toprak yapısından dolayı yaz aylarında kuraklığın etkisiyle çökme, kış aylarında 
ise yağışların artışıyla yükselme eğilimde olduğu belirtilmiştir. Bu çalışma sonucunda
da daha önceki çalışmalarla tutarlı sonuçlar elde edilmiştir.

Abstract:
Istanbul, a dynamic city with a population of over 15 million, is located on active fault 
lines and a significant part of the residential areas are located near these fault lines. 
This city, which is at risk of earthquakes, has important economic and cultural centers, 
as well as important transportation routes and engineering structures. Therefore, this 
city needs to be constantly monitored with geodetic techniques.
Classical terrestrial and satellite-based geodetic techniques can be used together or 
stand-alone to monitor surface movements in open topography or urbanized areas. 
While terrestrial monitoring techniques require more time and cost, monitoring 
deformations with free images obtained from radar satellites can be done in a shorter 
time and at less cost over a larger area.
Using the GNSS technique, positioning can be handled at any location outdoors and 
in any detail, however, this technique is weak in determining the vertical component 
due to the satellite geometry. This technique needs to have more than one receiver on 
the topography for high-accuracy positioning. It is not preferable to make 
measurements in large areas using this technique because of its high cost compared to 
radar satellite techniques. Also, it is difficult to repeat frequently and they are prone to 
make errors caused by the operator. Radar satellite techniques are suitable for 
monitoring volcanoes, glaciers, oceans, and large surfaces, but the spatial resolution 
problem is a significant disadvantage of this technique. Therefore, the appropriate 
monitoring technique should be selected considering the size of the structure/region 
planned to be observed, environmental factors, the estimated magnitude of the 
deformation, and the economic conditions of the project.
In this study, 48 synthetic aperture radar (SAR) images taken from Sentinel-1A and 
1B satellites separately, which have been made available free of charge by the 
European Space Agency (ESA) since 2014, were used. Using these images, surface 
deformations in the satellite line-of-sight (LOS) were determined and analyzed, and 
then the trend of this change over time was investigated.
In this study, Sentinel-1 synthetic aperture radar (SAR) images covering our study 
region with a six-day temporal resolution were used. Although Sentinel-1 satellite has
a six-day temporal resolution, a total of 96 SAR images were used in this study, 
including 48 ascending and 48 descending orbit, one image per month over 4 years 
between 2018-2022. Sentinel-1 SAR satellite moves in a certain orbit and takes images 
in different frames in ascending and descending orbits. In this thesis project, the 
Interferometric Synthetic Aperture Radar (InSAR) technique was used to determine 
surface deformations and movements in engineering structures. InSAR technique is a 
suitable technique for monitoring the region between Büyükçekmece and 
Küçükçekmece Lagoon Lakes, which are our area of interest.
Persistent Scatterer InSAR (PS-InSAR) method is a pixel-based radar deformation 
monitoring technique developed at Politecnico Di Milano University in 1999. With 
this method, it has become possible to detect fixed reflectors emitting similar 
electromagnetic backscatter in two different satellite images and to monitor 
deformation and its change over time. Thus, constantly changing areas such as 
pastures, forests, and construction areas remain outside the working area of this 
technique, since sufficient PS points cannot be found. This technique allows 
monitoring of the change (velocity) of residential areas and surface movements over 
time. PS-InSAR technique was used in this study to monitor the large area between 
Büyükçekmece and Küçükçekmece Lake economically. Since the SAR technique, 
which provides continuous images weekly and economically, is also suitable for 
observing seasonal effects, this technique was used in this study.
In the application phase of the technique, Sentinel Application Platform (SNAP) 
software was used to process the images and create interferograms, and Stanford 
Method for Persistent Scatterers (StaMPS) software was used to produce PS points. 
"snap2stamps" codes were used to prepare the resulting products from the SNAP 
software in a standard file format and transfer them to the StaMPS software.
Within the scope of the thesis, the study area was chosen as the area between 
Büyükçekmece and Küçükçekmece lagoon lakes, which are among the earthquakesensitive regions of Istanbul. Images of the Sentinel-1 satellite in ascending and 
descending orbit between 2018 and 2022 were used for the study. In ascending images, 
the 58th path, 129th frame was used, and in descending images, the 36th path, 457th 
frame was used. Surface deformations were obtained in one dimension in the satellite 
line of sight (LOS) direction, and they were evaluated separately as ascending and 
descending orbit. 
The study was completed in two parts. In the first stage, "image splitting", "apply orbit 
file", "georeferencing", "enhancing spectral diversity", "interferogram formation", 
"TOPSAR deburst", "topographic phase removal" and "StaMPS export" operations
were applied using the SNAP program. In the second stage; "initial load of data", 
"estimate gamma (phase noise estimation)", "PS selection", "PS weeding", "phase 
correction of wrapped phase", "unwrapping", "calculation of spatially correlated look 
angle error", "filtering atmospheric noise" and "producing deformation velocities" 
operations are performed using StaMPS software.
The results obtained from ascending and descending orbit mode evaluations were 
similar. According to these two similar results, while there was a subsidence in Avcılar 
industrial zone, Büyükçekmece Türkoba residential area, Gürpınar pier and 
Beylikdüzü pier structures and some parts of Çatalca district, an uplift trend was 
detected in the Gürpınar region and Başakşehir district residential area. When the PS 
station time series obtained in the study area were investigated, it was seen that there 
was a trend of downward in the summer season and an upward trend in the winter 
season. Previous studies carried out in this region have stated that due to the clayey 
soil structure of the region, there is a tendency for it to subsidence due to drought in 
the summer months and to uplift with the increase in precipitation in the winter 
months. As a result of this study, results consistent with previous studies were obtained.
In this study, the movements of engineering structures were also investigated. The 
movements on the Karasu Viaduct, Hezarfen Airport, Ambarli Port and Gürpınar Pier 
in the area were investigated separately. While seasonal uplift and subsidence
movements are observed in all engineering structures, an average annual upward rate 
of 2-3 mm is observed in the Karasu Viaduct and movements at different rates 
depending on the material along with seasonal movements are observed in Hezarfen
Airport. A downward trend and sudden collapse were observed in Ambarlı Port and 
Gürpınar Pier due to the effect of the 5.7 magnitude earthquake centered in Silivri on 
September 26, 2019.
It has been observed that the PSI technique works well in residential areas, but is weak 
in natural environments. It has been concluded that both land surface deformations and 
structural deformations can be observed at high resolution by using the SBAS 
technique and the PSI technique together, which is effective in natural environments 
and used to observe large land surfaces.
Since the region between Büyükçekmece and Küçükçekmece Lake has active 
landslides, important residential areas and transportation connections, and new 
underground projects are planned in the region, it was concluded that it would be 
appropriate to continuously monitor this region with the SAR satellite technique.