Geological Remote Sensing Research Articles

How Weather Affects over Time the Repeatability of Spectral Indices Used for Geological Remote Sensing

Geologic remote sensing studies often targets surface cover that is supposed to be invariant or only changing on a geological timescale. In terms of surface material characteristics, this holds for rocks and minerals, but only to a lesser degree for soils (including alluvium, colluvium, regolith or weathered outcrop) and not for vegetation cover, for example. A view unobstructed by clouds, vegetation or fire scars is essential for a persistent observation of surface mineralogy. Sensors with a continuous multi-temporal operation (e.g., Landsat 8 OLI and Sentinel-2 MSI) can provide the data volume needed to come to an optimal seasonal acquisition and the application of data fusion approaches to create an unobstructed view. However, the acquisition environment always changes over time, driven by seasonal changes, illumination changes and the weather. Consequently, the creation of an unobstructed view does not necessarily lead to a repeatable measurement. In this paper, we evaluate the influence of weather and resulting soil moisture conditions over a 3-year period, with alternating dry and wet periods, on the variance of several “geological” spectral indices in a semi-arid area. Sentinel-2 MSI data are chosen to calculate band ratios for green vegetation, ferric and ferrous iron oxide mineralogy and hydroxyl bearing alteration (clay) mineralogy. The data were used “as provided”, meaning that the performance of the atmospheric correction and geometric accuracy is not changed. The results are shown as time-series for selected areas that include solid rock, beach sand, bare soil and natural vegetation surfaces. Results show that spectral index values vary not only between dry and wet periods, but also within dry periods longer than 45 days, as a result of changing soil moisture conditions long after a last rain event has passed. In terms of repeatability of measurements, an overall low soil-moisture level is more important for long-term stability of spectral index values than the occurrence of minor rain events. In terms of creating an unobstructed view, we found that thresholds for NDVI should not be higher than 0.1 when masking vegetation in geological remote sensing, which is lower than what usually is indicated in literature. In conclusion, multi-temporal data are not only important to study dynamic Earth processes, but also to improve mapping of surfaces that are seemingly invariant. As this work is based on a few selected pixels, the obtained results should be considered only indicative and not as a numerical truth. We conclude that multi-temporal data can be used to create an unobstructed view, but also to select the data that give the most repeatability of measurements. Images selection should not be based on a certain number of days without rain in the days preceding data acquisition but aim for the lowest soil moisture conditions. Consequently, weather data should be incorporated to come to an optimal selection of remote sensing imagery, and also when analyzing multi-temporal data.

Spectral Absorption Feature Analysis for Finding Ore: A Tutorial on Using the Method in Geological Remote Sensing

Geologists have been instrumental in shaping Earth observation satellite missions; likewise, geology has been the subject of many remote sensing studies [1]. Applications of optical remote sensing in geology date back to some early studies using the Earth Resources Technology Satellite-1 , the predecessor of the Landsat satellite program [2]. In the 1980s, the seventh channel in the short-wave infrared (SWIR) of the Landsat thematic mapper program was added, as a result of spectroscopic mineral studies by geologists [58]. A subsequent satellite-borne instrument, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), launched in 1999, had specific bands in the SWIR and thermal infrared dedicated to mapping mineral groups [3].

A Study of the Regularity of Quaternary Geological History Evolution in Songliao Plain Based on Geological Remote Sensing Survey

On the basis of geological remote sensing survey and from the point of view of Quaternary geological evolution,this paper deals systematically with the neotectonic fractures and the evolution of Quaternary geological history and paleo-environment in Songliao Plain.Eight evolution stages of Quaternary geological history and their controlling action on the eco-geological environment in Songliao Plain are proposed in this paper.

From Geological Remote Sensing to Land Resources Investigation

From Geological Remote Sensing to Land Resources Investigation

The Planetary Data System Geosciences Node

The purpose of the Planetary Data System Geosciences Node is to archive and distribute planetary geosciences datasets relevant to the surfaces and interiors of the terrestrial planets and moons. This objective is accomplished through the following efforts. The Node works with planetary missions to help ensure that data of relevance to the geosciences discipline are properly documented and archived. The Node restores and publishes selected geoscience datasets from past missions on CD-ROM for distribution to the planetary science community. Data archived at the Node are distributed on CD-ROM, magnetic tape, CD-WO, or by electronic transfer over the Internet. The Geo-sciences Node provides information and expert assistance on its data holdings. Derived image, geophysics, microwave, spaceborne thermal, and radio science data are archived at the lead node or at one of the subnodes. Currently, the amount of data archived at the Node is on the order of 500 Gbytes stored on a combination of nearly 800 CD-ROMs and CD-WOs. Current archives within the Node include data from the Magellan and Viking missions, the Geological Remote Sensing Field Experiment, and a collection of radar, altimetry, and gravity datasets for Venus, Mercury, Mars, Earth, and the Moon, together with software to analyze the data. The Node maintains on-line catalogs that enable the science community to search through the Geosciences Node archives and to order selected datasets. Access to the Node's catalogs and on-line datasets is available via the Internet using a remote login or via the World Wide Web (WWW).

Directional variations in thermal emission from geologic surfaces

We investigated the directional emission properties of geologic surfaces using a ground‐based, hand‐held infrared radiometer and thermistor probe. Field sites involved surfaces ranging from smooth playa and sand surfaces to a very rough aa lava flow in the Lunar Crater Volcanic Field, NV, as part of the Geological Remote Sensing Field Experiment. Large directional variations in thermal emission were found; they result from the presence of surface roughness–at large scales producing spatial variations in kinetic temperature and at small scales producing emissivity variations. These variations are important in remotely determining surface structure and understanding surface energy balance and emission spectra.

A review of: “Frontiers for Geological Remote Sensing from Space.” Edited by F. B. HENDERSON III and B. N. ROCK. (Falls Church: American Society of Photogrammetry, 1984.) (Report of the Fourth GEOSAT Workshop, Flagstaff, Arizona U.S.A., 12-17 June, 1983.) [Pp. 80.] Price U.S. $15·00 (members); $25·00 (non-members)

A review of: “<i>Frontiers for Geological Remote Sensing from Space.</i>” Edited by F. B. HENDERSON III and B. N. ROCK. (Falls Church: American Society of Photogrammetry, 1984.) (Report of the Fourth GEOSAT Workshop, Flagstaff, Arizona U.S.A., 12-17 June, 1983.) [Pp. 80.] Price U.S. $15·00 (members); $25·00 (non-members)