Topics in Radar Signal Processing Online Course https://giladjames.com Section: A 94-GHz Frequency Modulation Continuous Wave Radar Imaging and Motion Compensation Lesson: Azimuth compression Topics in Radar Signal Processing. This course is brought to you by Gilad James Mystery School. Learn more at Gilad James.com. Introduction Airborne and space-borne synthetic aperture radar (SAR) images are used in various fields of remote sensing. There are various applications in using high-resolution radar images. Several imaging algorithms were developed in the laboratory, which depend on the given geometry. SAR technology can be used to acquire images of disaster areas or other dangerous sites where direct human access is difficult. Traditional optical images have limitations, such as being weather- and environment-dependent, being too bright, or having no range information. As an alternative imager, the SAR can be loaded onto an unmanned aerial vehicle. SAR equipment was once too heavy and bulky for such an application. However, owing to recent technological improvements, radar has become smaller and more lightweight. In particular, frequency modulation continuous wave (FMCW) radar was developed as a chip and is lightweight, has a small size, and offers low power consumption, which has advantageous qualities for being mounted on a drone. FMCW radar can also be used at a close range. Attempts are being made to replace conventional radars with FMCW types for small and close-range systems. The higher the frequency is, the smaller is the antenna size. Thus, a high frequency is favorable for miniaturization and weight reduction. In this lecture, FMCW radar with a center frequency of 94 GHz is used. FMCW radar is commonly employed for relatively short distances. Also, a high-range resolution can be obtained, even though it has a low sampling rate. The developed FMCW radar only measures real components; nevertheless, it can obtain complex data by using the Hilbert transform . The higher frequency used in the proposed W-band SAR causes a narrower antenna beam width. Because the range is short and the width is narrow, range migration in SAR data can be ignored. In a short range, the matched filter phase for azimuth compression should change with the range. In this study, based on the range-variant azimuth chirp rate of the range Doppler algorithm (RDA), a SAR algorithm at a close range was developed and a resolution analysis of an impulse target was performed. In the airborne SAR, the movement of the aircraft greatly affects SAR focusing. Motion compensation is important because small and slow-flying objects have less inertia and are thus more notably affected by disturbances. Therefore, to obtain decent SAR images, the motion must be compensated. Motion information is acquired by navigation sensors and used for focusing SAR images by compensating them. The quality of the reconstructed image is very sensitive to the geometry determination accuracy. This factor has led to the development of autofocusing techniques. Several methods for autofocusing exist, such as entropy minimization , an FMCW analytic method , contrast optimization in ISAR, phase gradient autofocusing (PGA) , and prominent point processing (PPP) in SAR. These methods consist of range alignment and phase compensation. Moreover, they are applicable to circular synthetic aperture radar (CSAR) with wideband SAR. A SAR or ISAR autofocusing method using a prominent target was proposed. However, this method requires a prominent target, and it is difficult to find an ideal point target. Nonetheless, this method is faster than contrast maximization or entropy minimization. The algorithm based on contrast maximization is slow because of a high computing cost. It is difficult to apply these autofocusing methods because focusing cannot be performed when the motion is large. Therefore, navigation sensors that can provide position and velocity information, such as GPS and IMU, are needed to compensate for motion. The purpose of the proposed algorithm is to implement a video SAR with a high frame rate through fast signal processing. It is possible to obtain SAR images, such a #topics #in #radar #signal #processing ... https://www.youtube.com/watch?v=-X_YCPNu69U

Applied Geophysics with Case Studies on Environmental, Exploration and Engineering Geophysics Online Course https://giladjames.com Section: Advance Wave Modeling and Diffractions for High-Resolution Subsurface Seismic Imaging Lesson: Application of method in field data: Sigsbee (Gulf of Mexico) Applied Geophysics with Case Studies on Environmental, Exploration and Engineering Geophysics. This course is brought to you by Gilad James Mystery School. Learn more at Gilad James.com. Introduction Malaysian basins are structurally complicated because their assessment through different phases of continental accretion, rifting and mountain building. The geology of the Malay Basin is very old and different that the other part of Sarawak and Sabah basin. Geophysical and geological challenges include, fine sand imagery, often beyond seismic resolution; imaging under gas chimney and under carbonates; diffraction imaging; imaging of the internal architecture of the basement; understand the propagation of waves in efficient media and the associated anisotropy; speed analysis and anisotropy; Gas cloud imaging using complete waveform inversion; and multiple elimination. The focus of research in this part of the world is to enhance the image quality of the faults, fracture and karst using diffraction imaging. a shows the geographical location of the area which is near to the Borneo main land and a part of Sarawak Basin. b is the cross section taken from Malay Basin subsurface geometry which is an extensional regime and because of the tectonic activity the normal faulting can be seen. (a) Location map of the Sarawak Basin and (b) a cross section of Malay Basin subsurface structure. Fractured basement located at a depth of 2.0–5.0 km, varying with lateral extension . Diffraction imaging analyzes were carried out in the Sarawak Basin, located north-west of Borneo, forming the southern boundary of the Oligocene-Recent Basin of the South China Sea; its tectonic evolution has been almost matched by seabed rifting and spread in the marginal basin of the South China Sea. The majority of the Sarawak Basin, including this part of Malaysia, is composed of carbonates, making seismic imagery difficult. The pre-carbonated Oligocene deposit in the lower Miocene and later the terrestrial deposit filled the shelter zone in Cycle I and Cycle II. The cycles are described as follows: Cycles I and II (Upper Eocene to Lower Miocene) have been interpreted as channel sands, lowered clays, and deposited coal. Cycle III (lower-middle Miocene) contains fine limestone shale and sandstone, cycle IV (middle Miocene) is composed of limestone with few mixed clastics, cycle V (middle to upper Miocene) is recognized as limestone, cycle VI to cycle VIII (upper Miocene to Pleistocene) is composed of open marine and coastal clays and sand, respectively. The progradante sediments from cycle V1 to cycle VIII have gradually stifled the large accumulations of carbonates to the present day. In the center of Luconia, carbonate deposits began at the beginning of the Miocene (cycle III) and increased significantly in the middle and late Miocene cycles IV and V. The structure is dominated by a simple extension phase NS trend faults. These faults affected the deposits during cycles I and II and served as foci for the development of carbonate reefs of cycle IV and V and their accumulation. The dominance of intensive pre-carbonation structuring has therefore resulted in poor seismic image quality. Diffraction hyperbolic patterns occur frequently in recorded seismic data, particularly in carbonate reservoirs due to abrupt lateral changes in impedance contrast and discontinuity of subterranean layers. However, a very serious doubt to the application of classical theory has claimed that stacked seismic data is not true zero separation data because it is not clear that the results of the stacking of data recorded on a wide range of source-receiver separations is practically close to the results of real zero separation recording, since diffraction amplitudes are concerned. Berryhill also explained the concept and compared the theory of zero separation with source-geophone distance without zero separation, concluding that the diffraction amplitudes at a source-receiver separation d #applied #geophysics #with #case #studies #on #environmental, #exploration #and #engineering #geophysics ... https://www.youtube.com/watch?v=5KXHYi2KxfQ

Cartography Online Course https://giladjames.com Section: Web Map Tile Services for Spatial Data Infrastructures: Management and Optimization Lesson: Tiling schemes Cartography. This course is brought to you by Gilad James Mystery School. Learn more at Gilad James.com. Introduction Web mapping has become a popular way of distributing online mapping through the Internet. Multiple services, like the popular Google Maps or Microsoft Bing Maps, allow users to visualize cartography by using a simple Web browser and an Internet connection. However, geographic information is an expensive resource, and for this reason standardization is needed to promote its availability and reuse. In order to standardize this kind of map services, the Open Geospatial Consortium (OGC) developed the Web Map Service (WMS) recommendation . This standard provides a simple HTTP interface for requesting geo-referenced map images from one or more distributed geospatial databases. It was designed for custom maps rendering, enabling clients to request exactly the desired map image. This way, clients can request arbitrary sized map images to the server, superposing multiple layers, covering an arbitrary geographic bounding box, in any supported coordinate reference system or even applying specific styles and background colors. However, this flexibility reduces the potential to cache map images, because the probability of receiving two exact map requests is very low. Therefore, it forces images to be dynamically generated on the fly each time a request is received. This involves a very time-consuming and computationally-expensive process that negatively affects service scalability and users' Quality of Service (QoS). A common approach to improve the cachability of requests is to divide the map into a discrete set of images, called tiles, and restrict user requests to that set. Several specifications have been developed to address how cacheable image tiles are advertised from server-side and how a client requests cached image tiles. The Open Source Geospatial Foundation (OSGeo) developed the WMS Tile Caching (usually known as WMS-C) proposal. Later, the OGC released the Web Map Tile Service Standard (WMTS) inspired by the former and other similar initiatives. Most popular commercial services, like Google Maps, Yahoo Maps or Microsoft Virtual Earth, have already shown that significant performance improvements can be achieved by adopting this methodology, using their custom tiling schemes. The potential of tiled map services is that map image tiles can be cached at any intermediate location between the client and the server, reducing the latency associated to the image generation process. Tile caches are usually deployed server-side, serving map image tiles concurrently to multiple users. Moreover, many mapping clients, like Google Earth or Nasa World Wind, have embedded caches, which can also reduce network congestion and network delay. This lecture deals with the algorithms that allow the optimization and management of these tile caches: population strategies (seeding), tile pre-fetching and cache replacement policies. #cartography ... https://www.youtube.com/watch?v=l_9rNIc50Jo

Soil Moisture Online Course https://giladjames.com Section: Thermal Inertia-Based Method for Estimating Soil Moisture Lesson: Thermal inertia retrieval from energy balance models Introduction: thermal inertia of unsaturated soil Thermal inertia P is one of the parameters used to characterize the thermal properties of soil and is defined as the square root of the product of the volumetric heat capacity C and thermal conductivity λ , which is given as Thermal inertia appears in the formulation of the ground heat flux when it is formulated with a unique variable known as the land surface temperature (LST), and one does not have to consider the vertical profile of the soil temperature. In terms of the relation between soil thermal properties and soil moisture, both the volumetric heat capacity C , which is the product of specific heat c and the bulk density ρ of the soil, and the thermal conductivity λ increase as the soil moisture increases. Accordingly, thermal inertia P also increases as soil moisture increases. Therefore, soil moisture can be estimated inversely if the thermal inertia value is known ( ). The volumetric heat capacity is a moderate linear function of soil moisture. By contrast, thermal conductivity has a strong nonlinearity with soil moisture, making it difficult to parameterize thermal conductivity and hence thermal inertia. Schematic of the relationship between volumetric heat capacity, thermal conductivity, and thermal inertia in terms of soil moisture. Thermal inertia is effective when the time series of the surface temperature is available, but the vertical profile of the soil temperature is not available. The differential equation for heat diffusion is given as where Tzt is the soil temperature at depth z and time t , which is the difference from a constant value at an infinite depth. This equation is solved to reproduce the daily and yearly periodic cycles of soil temperature, under the boundary conditions that the temperature change is sinusoidal at the surface and constant at an infinite depth. The basic solution is as follows using the complex number expression: (3) is rewritten as follows using the real number expression: The conductive heat flux in soil at depth z and time t , Gzt , is defined as where the vertical profile of soil temperature is obviously required to calculate the soil heat flux. However, when the soil temperature solution (3) or (5) is applied to the soil heat flux (6) and then z is set to zero, it only uses the time series of surface temperature as follows: In deriving (7), the following relation derived from (3), The above derivation describes thermal inertia being effective for quantifying soil thermal properties when only the LST is known, which leads to the analysis of the land surface processes using satellite LSTs. The above procedure leads to the studies proposed by Matsushima and co-researchers, which are described in Section 2. Considerable effort has been made to estimate the thermal inertia of the Earth’s surface mainly using LST data from satellites. Most of this effort has been concentrated on retrieving daily values of thermal inertia due to the availability of daily maximum and minimum LSTs observed from polar orbiting or geostationary satellites. Models using these types of satellite LSTs are based on the Earth’s surface energy balance principle, which includes not only the radiation budget but also turbulent heat flux. A Fourier series expansion was introduced to solve (1) under the above Earth’s surface boundary conditions using the solution of the real number expression, (5). Models have been improved from those using only the two daily extreme LSTs to those using LSTs that are irrespective of time in a diurnal change and other significant studies that follow a series of important proposals by Xue and Cracknell , which are also described in Section 2 when compared with studies by Matsushima and co-researchers. This lecture reviews former and state-of-the-art methods for estimating soil moisture by exploring the relationship between thermal inertia and soil moisture. Section 2 reviews past developments of methods for the #soil #moisture ... https://www.youtube.com/watch?v=Poo4_zHwxZs