Remote sensing in geology

[1] This spectral fingerprint is governed by the physio-chemical properties of the surface of the target object and therefore helps mineral identification and hence geological mapping, for example by hyperspectral imaging.

[1] Second, the two-way travel time of radiation from and back to the sensor can calculate the distance in active remote sensing systems, for example, Interferometric synthetic-aperture radar.

[3] These geological studies commonly employ a multitude of tools classified according to short to long wavelengths of the electromagnetic radiation which various instruments are sensitive to.

[3][4] Such tools permit a range of quantitative analyses, such as using different wavelengths of collected data sets in various Red-Green-Blue configurations to produce false color imagery to reveal key features.

[6] A suitable sensor sensitive to the particular wavelength region, according to the designated use, is selected and employed to collect the electromagnetic wave reflected or emitted from the target object.

[3] As a point to note, the data collected is a blend of both reflection of solar radiation and emission (according to Planck's law) from the object for visible and near infrared (VNIR) region.

[8] The main advantage of employing remote sensing to deal with geological problem is that it provides direct information on the surface cover using a synoptic coverage or sometimes stereoscopic view.

In addition to high signal-to-noise ratio (>40:1), a fine spatial resolution, which limits the number of elements inside one single pixel, also promotes decision accuracy.

For short wavelength VNIR region, in the same theory, clayey surface with smaller grain size promoting more backscattering should give higher spectral response.

[5] The higher the amount of organic content in the soil, incident energy would be greatly absorbed and as a result lower reflectance is expected in general.

[10] 3-dimensional geomorphological features arising from regional tectonics and formation mechanisms could also be understood from a perspective of small scale images showing a large area acquired in elevation.

[4] Although field mapping is the most primary and preferable way to acquire ground truth, the method does not work when areas become inaccessible, for example the conditions are too dangerous or extreme.

[21] Similarly, automated approach using band math and DEM calculations using high resolution data is requisite to look into the glacial variations due to dynamic environmental conditions.

For instance some soil type, which is prone to liquefaction (e.g. saturated loose alluvial material), do more damage under vibration and therefore earthquake hazard zoning may help in reducing property loss.

[3] Another one is to locate historical earthquakes in neotectonism (past 11000 years) and analysis its spatial distribution, and hence fault zones with structural ruptures are mapped for further investigations.

[3] From a geodetic perspective, the radar technique (SAR Interferometry, also called InSAR) provides land displacement measurement up to cm scale.

[4][31] Split-based approach to divide large images into subimages for further analysis by redefining change detection threshold have reduced computation time and have shown to be consistent with manual mapping of affected areas.

[3] To advance the understanding in volcanological science and active volcano monitoring, the main data streams aided by remote sensing include surface deformation and thermal measurement plus the gas flux and composition.

[32] While remote sensing is able to collect data of ground, 3-D modeling using finite element analysis added with geophysical subsurface survey is highly encouraged.

Feasible resources explorations should be backed up by accurate geological models to locate prospect ore and petroleum deposits from a preliminary regional overview.

While much of the information is indeed provided from hydrogeology, geophysical methods and drilling, the remote sensing technique, using the same principle to integrate data collected for the surface, can infer possible confined/ unconfined aquifers.

As an example of planetary applications using remote sensing could be illustrated by the volcanism observation on Io, which features the highest number of active volcanoes per square kilometer in the Solar System.

Modeling has shown that a suitable distance between the surveyed ground and the sensor has to be maintained to ensure a meaningful pixel size to resolve the Io surface.

Digital supervised or unsupervised landform classification employing crisp or fuzzy clustering logic have opened new possibility to the viable solutions.

There are a variety of applications of GIS and remote sensing data in water management, ranging from exploration, modeling of subsurface flow and natural recharge, pollution control and hydrogeologic process monitoring.

[43] A case study in Burdur, Turkey presenting the use of remote sensing data and spatial analysis performed by GIS is one of the pioneer projects.

[34][49] Besides the examples in Europe, landslides in Hong Kong brought casualties and property damage to the territory before the establishment of relevant government organization to carry out systematic studies to reduce risk of slope failure.

[4] For instance, Interferometric synthetic-aperture radar[27] and aerial photo interpretation[35] is the tool used in history for detecting surface deformation and updating landslide inventory respectively.

GIS is also used to overlay layers of terrain (elevation and slope angle), lithology with rainfall data to generate landslide hazard maps.

To name a few, the land use planning (for instance nuclear power plant location & dumping sites), monitoring of soil erosion and atmospheric pollution, vegetation etc.