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Modern Geomatics Technologies and Applications

waveform using a rectangle around the COG. This algorithm is mostly used to determine the primarily parameters for other re-
tracking methods [9]. Davis et al presented threshold algorithm in 1997 for better estimations. This algorithm is based on
empirical method which simplify the OCOG method to estimate more precise re-tracked gate from the rectangular dimensions
[10]. In recent years researchers offered variety of different methods for waveform re-tracking in different study areas.
Improved threshold re-tracking (ITR) algorithm was used in Taiwan coast to estimate water level using GeoSat altimeter’s
waveform based on meaningful sub-waveforms. The results showed two times better than that of the 5β- parameter function-
fitting method and threshold method, and three times better than that of GDRs improvements [11]. ITR method optimized using
Envisat data over coastal area of Mediterranean Sea and the results showed that the presented methods could improve other re-
tracking estimates (except the OCOG re-tracking) and the optimized threshold re-tracking algorithm is the most robust re-
tracking method and more suitable for the Envisat waveform re-tracking over the study area [12]. Jason-2 (JA2) data was
analysed over California Ocean coastal areas in 2–5 km offshore and beyond 10 km of the coast to compare the improved re-
trackers with Ocean and Ice re-trackers in SGDR data also comparing threshold re-tracker with ITR in shallow and deep waters.
The results showed that in shallow waters in 2-5 km away the coast and in deep ocean the ITR and Ice re-trackers provide the
most precise Sea Surface Height (SSH) estimates respectively [13]. Jason-1 (JA1) waveforms re-tracked by the developed
OceanCS algorithm to estimate the SSH and the significant wave height (SWH) over China’s costal zones and offshore. This
algorithm is based on waveform classification and sub-waveform using Ocean re-tracking. The developed re-tracker also
compared with the empirical re-tracking algorithms and the comparisons showed that the OceanCS re-tracking strategy was more
suitable than the other five algorithms tested (Ocean, OCOG, Ice-2, Beta5 and Threshold) and has uniform performance both in
the open ocean and coastal regions [14]. Envisat and JA2 waveforms re-tracked using modified waveform base on definition of
a reference waveform and with threshold re-tracking algorithm in four study regions in North America. In the study the applied
algorithm validated using 4 other re-trackers including Ice (JA2), Ice-1 (Envisat), Ocean, Threshold and ITR on standard
waveforms, to compare retrieved coastal SSHs. The retrieved SSHs comparing to the TG data records showed improvements
rather than other algorithms [15]. A new re-tracking method called Brown-Peaky (BP) using JA1 waveforms in two Australian
coastal areas and offshore developed for peaky waveforms. The main feature of the BP is that it fits peaky waveforms using the
Brown model without introducing a peak function. The comparison results showed that three compared re-trackers (MLE4,
ALES and BP) have similar performance over open oceans but significant improvements of BP re-tracker occur for distance ≤7
km to the coastline, where validation results indicate that data re-tracked by BP are more accurate [16]. Optimized performance
of primary meaningful sub-waveform peak re-tracker using CryoSat-2 (CS2) waveforms proved in the Arctic. This has been
done using threshold and OCOG algorithms comparing to the traditional OCOG, threshold and five parameter beta (5β-parameter)
re-trackers as well as the ESA Re-tracker in level-2 data [17]. Multi lakes with different shapes, size and water levels have been
evaluated using CS2 data by presenting mean multi-peak sub-waveforms in a waveform re-tracking. By multiple empirical and
analytical re-trackers comparisons, the first and the mean-all sub-waveforms (mean correction from all sub-waveforms) re-
tracking with the threshold and SAMOSA3 algorithm retrieved robust water levels in small lakes. However over large lakes and
icy-lake objects, sub-waveform re-tracking scenarios (the first and mean-all sub-waveforms) are more precise than the other
scenarios [18].
The present study provides original waveform, first meaningful sub-waveform, mean waveform per each cycle and a
newly developed re-tracking approach calling maximum correlated waveform to the mean waveform per each cycle using
threshold re-tracking algorithm have been evaluated. The results show notable precision to retrieve SST time series (compared
to TG records) using the presented method in comparison with level-2 data and other methods.

2. Study Area and Datasets

 Study Area

Strait of Hormuz is one the world's most strategically important choke points which is the only sea passage from the
Persian Gulf to the open ocean located between the Persian Gulf and the Gulf of Oman. About 35% of the world’s oil traded at
this are which makes making it a highly important strategic strait. At its narrowest, the strait is 21 nautical miles (39 km) wide
with almost 90m depth[19]. Atmospheric conditions over the region are derived by north-west winds, with seasonal variations
and the main water circulation is due to large annual evaporation over the Persian Gulf, which drives a shallow inflow of water
and a deep outflow of dense, hyper-saline water[20]. In this study an area 10km offshore located in the north part of the strait at
Iranian coastal zones has been selected to study, figure 1.

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