International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
INSAR ATMOSPHERIC DELAY MIGITIGATION BY GPS; CASE STUDY IZMIT 
EARTQUAKE INTERFEROGRAMS 
M.U. Altin* *, E, Tari*, L. Ge° 
* ITU, Civil Engineering Faculty, 80626 Maslak Istanbul, Turkey — (altinm, tari)@itu.edu.tr 
^ UNSW, School of Surveying and Spatial Inf. Sys., Kensington, NSW 2052, Australia ge@unsw.edu.au 
KEY WORDS: GPS, SAR, InSAR, Troposphere, Turkey 
ABSTRACT: 
The Propagation delay when radar signals travel from the troposphere has been one of the major limitations for the applications of 
high accuracy Interferometric Synthetic Aparture Radar (InSAR). In this GPS data used for defining meteorological effects on radio 
signals. 1999 Izmit earthquake is chosen for the case study of tropospheric effects on InSAR images according to previous studies. 
Due to process of GPS data with BERNESE tropospheric delay model gained and compared with ROI PAC processed 
interferograms and it can easy figured out that the delay amounts are really reliable. As a result of this study, importance of 
atmospheric change in Turkey climate will be pointed out using SAR and GPS data integration with meteorological aspects. 
1. INTRODUCTION 
Earth sciences are developed in last decades with the 
development of space technologies especially in space 
geodesy and remote sensing. Global Navigation Satellite 
Systems (GPS) and remote sensing sensors are highly 
affected from these fast developments. As known space 
geodesy is based on electromagnetic waves and their 
reflection from earth surface. Variation in the refractive index 
of the atmosphere causes changes in the electromagnetic 
waves propagating through it. Therefore corrections of these 
atmospheric effects should be determined and applied with 
the assessed measurements. Atmospheric effects grouped in 
two types; ionospheric and tropospheric effects. Ionospheric 
effects can be removed by signal combinations during data 
processing. Tropospheric effects are directly related to 
troposphere and cannot be removed but can be modeled. The 
aim this of study is the correction of troposphere effects over 
Synthetic Aperture Radar (SAR) images and interferograms 
by using acquired GPS measurements in Izmit, Turkey. 
Turkey is divided into seven regions due to socio-economical, 
administrative, climate and natural (soil, vegetation) 
similarities of related land. Izmit Province (40° 45°N 30° 
01’E) which is in Marmara Region. Marmara has the largest 
share in production and industry of Turkey. The area is just 
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on the North Anatolian Fault (NAF), which extends from 
Karliova in Eastern Turkey to the Gulf of Saros in the 
Northern Aegean Sea, is one of the longest active strike-slip 
faults in the world with about 1500km length and hit region 2 
times with large earthquakes in 17 August and 12 November 
1999 with 7.4 and 7.2 Mw. After these earthquakes Ziyadin 
Cakir and Rob Reilinger worked with the SAR data and 
publish papers by the help of these papers using InSAR 
technique for deformation monitoring to get more current 
insight in Turkey.(Cakir et al., 2003)(Reilinger et al., 2000) 
2. GPS AND SAR DATA 
The data for this study are GPS and ERSI/2 tandem SAR 
images before and after earthquake (12-13 August 1999 and 
16-17 September 1999). GPS data is gathered form Marmara 
GPS Network (MAGNET) continuous operated GPS network 
which is designed and managed by TUBITAK Marmara 
Research Center and SAR images are taken from Dr. Ziyadin 
Cakir (Istanbul Technical University). (Figure 1) 
Open source software is chosen for image and GPS data 
analysis. BERNESE software used for troposphere modeling 
due to capabilities of modeling time interval to get the more