Regional validation of retracked sea levels from SARAL/Altika over the South China sea and adjacent seas

This paper focuses on assessing the quality of sea level anomaly (SLA) data from the new generation of Ka-band SARAL/AltiKa satellite altimetry over the continental shelf of the South China Sea. The region consists of peninsulas, shallow seas, and small islands that produce complicated altimetric waveform patterns. The improved-accuracy of SLAs data from the MLE4, Ice1 and Ice2 retrackers which are provided in the AVISO-Sensor Geophysical Data Records (SGDR) were optimized in this study. The quality of retracked SLAs is assessed by making comparison with tide gauge data from six stations. In general, the percentage of data availability of Ice-1 retracker is superior ( > 68%) to those of MLE- 4 and Ice-2 retrackers. The improvement of percentage (IMP) also shows that Ice-1 retracker improves the standard deviation > 12% better than those of Ice-2 retracker. Over complex areas of Lubang and Ko Taphao Noi, the temporal correlation of Ice-1 retracker is superior (r > 0.80) to those of MLE4 and Ice-2 retrackers (r 5.8) and lower RMS error ( < 34 cm) than those of Ice-1 retracker. It can be concluded that the Ice-1 and Ice-2 retrackers were superior for the coastal region of Maritime Continent

Comparison of sea-ice freeboard distributions from aircraft data and cryosat-2

The only remote sensing technique capable of obtain- ing sea-ice thickness on basin-scale are satellite altime- ter missions, such as the 2010 launched CryoSat-2. It is equipped with a Ku-Band radar altimeter, which mea- sures the height of the ice surface above the sea level. This method requires highly accurate range measure- ments. During the CryoSat Validation Experiment (Cry- oVEx) 2011 in the Lincoln Sea, Cryosat-2 underpasses were accomplished with two aircraft, which carried an airborne laser-scanner, a radar altimeter and an electro- magnetic induction device for direct sea-ice thickness re- trieval. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a study about the comparison of the sea-ice freeboard and thickness dis- tribution of airborne validation and CryoSat-2 measure- ments within the multi-year sea-ice region of the Lincoln Sea in spring, with respect to the penetration of the Ku- Band signal into the snow

Regional Validation Coastal Sea Level Anomaly Estimation from Altimetry Satellite and Tide Gauges Data using Fuzzy Inference System: A Case Study Around Natuna Seas

The validation of waveform retracking analyses with Fuzzy Inferences system, which was previously developed to optimize the estimation of sea surface height (SSHs), particularly in coastal locations, is presented in this study. The fuzzy inference system has been tested and validated in the Natuna Sea, Indonesia, where altimetry waveforms varied based on water conditions. Validation was performed by comparing the waveform retracking result of Jason-3 data with in-situ tide gauge data and geoid. The validation of waveform retracking data for sea level anomaly (SLA) estimate against tidal data demonstrates that the waveform retracking with a fuzzy inference system is more accurate than previous approaches. Waveform retracking with fuzzy inference system is able to produce an average temporal correlation of 0.75-0.89 and RMSE between 0.15-0.17 m. The waveform retracking combined with a fuzzy inference system can improve SLA estimation accuracy in nearshore up to 4 km from the coastline. The results indicate that retracking with fuzzy inference system has the potential to be used in other complicated oceans

CAWRES: A waveform retracking fuzzy expert system for optimizing coastal sea levels from Jason-1 and Jason-2 satellite altimetry data

This paper presents the Coastal Altimetry Waveform Retracking Expert System (CAWRES), a novel method to optimise the Jason satellite altimetric sea levels from multiple retracking solutions. CAWRES' aim is to achieve the highest possible accuracy of coastal sea levels, thus bringing measurement of radar altimetry data closer to the coast. The principles of CAWRES are twofold. The first is to reprocess altimeter waveforms using the optimal retracker, which is sought based on the analysis from a fuzzy expert system. The second is to minimise the relative offset in the retrieved sea levels caused by switching from one retracker to another using a neural network. The innovative system is validated against geoid height and tide gauges in the Great Barrier Reef, Australia for Jason-1 and Jason-2 satellite missions. The regional investigations have demonstrated that the CAWRES can effectively enhance the quality of 20 Hz sea level data and recover up to 16% more data than the standard MLE4 retracker over the tested region. Comparison against tide gauge indicates that the CAWRES sea levels are more reliable than those of Sensor Geophysical Data Records (SGDR) products, because the former has a higher (≥0.77) temporal correlation and smaller (≤19 cm) root mean square errors. The results demonstrate that the CAWRES can be applied to coastal regions elsewhere as well as other satellite altimeter missions

Studi Waveform Retracking Jason-2 di Pesisir Barat Daya Sumatera

Monitoring sea level changes in coastal areas is critical to understand ocean dynamics and their impact on the environment and human activities. Satellite altimetry has been the main tool in these studies, but its use in coastal areas still faces obstacles, especially due to variations in waveforms reflected from the sea surface. This study evaluates the accuracy of several altimetry waveform retracking methods (OCOG, Threshold 10%, and Threshold 30% ) on the southwest coast of Sumatra. The analysis was conducted using Jason-2 data on two passes, namely pass 077 and pass 153, with validation against two tide gauge stations nearby. Results showed that the Threshold 30% method provided a more accurate estimation of the Leading Edge Point (LEP) position than the other methods, with an average difference of only 0.1 gates (0.32%) from the reference value. Meanwhile, the OCOG method has the worst performance with a difference of 6.27 gates (20.22%), indicating its inability to handle coastal waveform variations on the location. Validation of the tide gauge data shows that retracking with a 10% Threshold improves the precision of Sea Surface Height (SSH) data with the highest IMP improvement value of 65.2% and the smallest standard deviation on the Threshold 30%. This finding confirms that choosing the right retracking method plays a crucial role in improving the accuracy of satellite altimetry in coastal areas. Therefore, the Threshold method is recommended for further analysis to improve the quality of altimetry data in coastal Indonesia.   Pemantauan perubahan muka air laut di wilayah pesisir sangat penting untuk memahami dinamika laut dan dampaknya terhadap lingkungan serta aktivitas manusia. Satelit Altimetri telah menjadi alat utama dalam studi ini, tetapi penggunaannya di wilayah pesisir masih menghadapi tantangan, terutama akibat variasi bentuk waveform yang dipantulkan dari permukaan laut. Studi ini mengevaluasi keakuratan metode waveform retracking altimetri OCOG, Threshold 10%, dan Threshold 30% di pesisir barat daya Sumatra. Analisis dilakukan menggunakan data Jason-2 pada dua jalur lintasan, yaitu pass 077 dan pass 153, dengan validasi terhadap data pasang surut. Hasil penelitian menunjukkan bahwa metode Threshold 30% memberikan estimasi posisi Leading Edge Point (LEP) yang lebih akurat dibandingkan metode lainnya, dengan selisih rata-rata hanya 0,1 gate (0,32%) dari nilai referensi. Sementara itu, metode OCOG memiliki performa paling tidak akurat dengan selisih sebesar 6,27 gate (20,22%), yang mengindikasikan ketidakmampuannya dalam menangani variasi waveform di pesisir. Validasi terhadap data pasang surut menunjukkan bahwa retracking dengan Threshold 10% meningkatkan presisi data Sea Surface Height (SSH) dengan nilai peningkatan IMP tertinggi sebesar 65,2% dan standar deviasi terkecil pada metode Threshold 30%. Temuan ini menegaskan bahwa pemilihan metode retracking yang tepat berperan krusial dalam meningkatkan akurasi satelit altimetri di wilayah pesisir. Oleh karena itu, metode Threshold direkomendasikan untuk analisis lebih lanjut guna meningkatkan kualitas data altimetri di kawasan pesisir Indonesia

Vuforia v1.5 SDK: Analysis and evaluation of capabilities

This thesis goes into the augmented reality world and, being more specific in Vuforia uses, searching as an achievement the analysis of its characteristics. The first objective of this thesis is make a short explanation of what is understood by augmented reality and the actual different varieties of AR applications, and then the SDK’s features and its architecture and elements. In other hand, to understand the basis of the detection process realized by the Vuforia’s library is important to explain the approach to the considerations of image recognition, because it is the way in which Vuforia recognizes the different patterns. Another objective has been the exposition of the possible fields of applications using this library and a brief of the main steps to create an implementation always using Unity3D, due to Vuforia is only a SDK not an IDE. The reason to choose this way is due to the facilities that are provided by Unity3D when creating the application itself, because it already has implemented all necessary to access the hardware of the smartphone, as well as those that control the Vuforia’s elements. In other way, the Vuforia’s version used during the thesis has been the 1.5, but two months ago Qualcomm was launched the new 2.0 version, that it is not intended to form part of this study, although some of the most significant new capabilities are explained. Finally, the last and perhaps the most important objective have been the test and the results, where they have used three different smartphones to compare the values. Following this methodology has been possible to conclude which part of the results are due to the features and capabilities of the different smartphones and which part depends only of the Vuforia’s library.Català: Aquest projecte s’endinsa al món de la realitat augmentada, més concretament a l’anàlisi de les característiques y funcionalitats del SDK Vuforia. En primer objectiu serà posar en perspectiva el que s’entén per realitat augmentada i de les variants existents avui dia d’aplicacions que fan ús de la RA. A continuació es mencionen les característiques d’aquest SDK, la seva arquitectura i els seus elements. En aquesta part també s’han tingut en compte les consideracions de reconeixement d’imatge, ja que es la manera en la qual Vuforia realitza el reconeixement dels diferents patrons. El següent pas es tractar d’exposar els possibles camps d’aplicació d’aquesta llibreria, i una breu explicació dels principals passos per crear una aplicació sota Unity3D, tenint en compte sempre que Vuforia es només un SDK i no un IDE. La raó per escollir aquest entorn es degut a les ventatges que ofereix Unity3D a l’hora de crear l’aplicació, degut a que ja disposa de tot el necessari per accedir tant al hardware del propi dispositiu mòbil com a els propis elements que integren Vuforia. D’altra banda, la versió de Vuforia utilitzada durant el projecte ha sigut la 1.5, encara que fa poc més de dos mesos Qualcomm va alliberar la nova versió 2.0, la qual no forma part dels objectius d’aquest projecte, encara que una part de les noves funcionalitats més significatives s’exposen breument. Finalment, es conclourà amb els tests i resultats obtinguts. Per realitzar totes aquestes proves s’han utilitzat tres terminals diferents per poder comparar valors. A més, utilitzant aquest mètode, ha sigut possible concloure quina part dels resultats obtinguts es deuen a les característiques i capacitats dels diferents terminals i quina part depèn exclusivament de la pròpia llibreria Vuforia