Presentation on theme: "The Use of Remote Sensing for Soil Mapping: A Review Ronald Vargas Rojas and Christian Omuto Nairobi, 12 th June, 2007."— Presentation transcript:
The Use of Remote Sensing for Soil Mapping: A Review Ronald Vargas Rojas and Christian Omuto Nairobi, 12 th June, 2007
WHAT’S SOIL? “Soil is the material composed of mineral particles and organic remains that overlies the bedrock and supports the growth of rooted plants” Soil varies along the different landscapes A-B B A
HOW SOIL IS FORMED? Soil Forming Factors, Jenny’s equation: S = f (cl, o, r, p, t) S = soil cl = climate o = organisms (plant, animal and humans) r = relief p = parent material t = time
WHAT IS SOIL? “Soil is considered an heterogeneous fourth dimensional body that is continuous along the landscape”. X Y Z 4 th dimension is time
SOIL VARIABILITY: horizontal Soil is spatially variable in terms of x, y, z………. Is it really soil what we are looking at? Geographic space or spatial variability
SOIL VARIABILITY: vertical Soil development through horizonation. A Btss BgBg
WHAT DO WE MAP? Soil individual vs. Soil continuum Soil as soil body (pedon). A soil unit (mappable) polipedon. Discrete Model of Spatial Variation (polygon based). Soil is a continuous resource in the geographic space. Continuous Model of Spatial Variation (grid)
WHAT IS A SOIL MAP? A soil map should show the location, distribution and pattern of soils in the landscape. Needs of soil spatial data has increased for different applications.
SOIL MAPPING METHODS Digital soil mapping (pedometrics) - CMSV, grid mapping (pixels). - Implementation of Jenny equation in quantitative terms. Spatial approach. - Different tools (geostatistics, digital terrain analysis, remote sensing, fuzzy logic, decision trees, etc). - Mapping mainly soil attributes. Range of organic carbon (%) for the topsoil. Minasmy, 2006.
PRINCIPLES OF REMOTE SENSING The principle of remote sensing RS – Collection of information about an object without physical contact with it. - Digital measurements of electromagnetic energy reflected/radiated by an object. Components of RS Object Target Transmission Sensor Energy source EM radiations are used Gamma X-Ray UV VIS Microwave IR Radio Energy increases EM Spectrum -Constant speed -Carry energy Obstruction
RS Characteristics & potentials in soil mapping Polarized Reflected Diffracted Attenuated Absorbed % R Wavelength Sensing windows.. and they influence spatial resolution spectral resolution TAXONOMY OF RS SYSTEMS Non-imaging Imaging Sounding SolarThermal Passive systemsActive systems IRMicrowave Radiometry A. Photo VIS/IR imaging IR UV sounding Microwave Radiometry Microwave SoundingIR Laser & M/NIR Spectrometry Radar Microwave Radar/SAR Lidar VIS/IR Microwave RS radiations can be: Sky Earth Sun Sensor Gamma X-ray X-ray/Gamma
Potentials and limitations of RS for soil mapping What RS can see Top of the clouds Land cover Land surface Soil particles/properties Potential uses from the above detectable features Land cover, biomass, global circulation, soil surface Sea/ocean surface, soil moisture, etc. Sky Earth Sun Sensor Limitations Below-clouds atmospheric dynamics Atmospheric attenuation, resolution, Penetration (vegetation and soil depth) Important opportunities Integration with pedometrics Integration with ground sampling Integration of products from different types of RS Estimation of the Jenny’s factors
Main applications of RS in soil mapping Optical Systems Land cover (biomass estimation) Soil cover or surface Soil erosion features from high resolution images Radar systems Digital terrain data Assessment of soil moisture Thermal systems Geophysical systems Little investigated, but mainly for soil pore structure Lithology and mineralization
How have researchers used RS in mapping soils? Infrared spectroscopy Janik et al. (1998); Aust. J. Exp. Agr. 38: Shepherd and Walsh (2002): SSSAJ: 66: Eshel et al. (2004): SSSAJ: 68: Thermal remote sensing VIS/NIR/MIR/NMR (laboratory, field??) for prediction of soil properties Sullivan et al. (2004): RS & Mod. Ecos. & Sus. 5544: Petersen et al. (1987): RSE: 23: Microwave RS Optical remote sensing Gamma radiometry Engman et al. (1996). Geos. & RS. 2(27): Bindlish et al. (2006). RSE. 103: Chabrillat et al. (2002). RSE. 82: (Hyperspec) Palacios-Orueta & Ustin (1998): RSE 65: (AVIRIS) Fusion techniques Wilford et al. (2001). AGSO J. geol & Geosp. 17: Taylor et al. (2002). Expl. Geophys. 33: Ricchetti (2001): IJRS, 22, RadarSRTM (DEM), GPS (position) Mapping soil moisture, temperature, and texture Mapping soil moisture Mapping soil cover, land cover….. Mapping land surface profile, DEM Combining solar bands and microwave/RADAR
CONCLUSIONS: is RS a useful tool for soil mapping? RS tools are very useful for soil mapping in both approaches (conventional and DSM). The idea of using optical RS for mapping soils directly is not possible since soil development is in depth and we could see that satellite images just reflect the soil surface or land cover. RS and Pedometrics are directly linked in generating ancillary data layers for mapping soils. Thus, they have huge potential in soil mapping. Conventional mapping can greatly benefit from RS, especially nowadays where many different satellite images and aerial photographs are available with different spatial, spectral, and temporal resolutions. Different unexplored fields of RS are under research and definitely promising tools for mapping soils in the near future. The conventional soil mapping activities are critiqued for being slow and expensive. Modern soil scientists are therefore trying to develop methodologies and tools to expedite the process. However, we can conclude that RS is a good tool but direct contact with the object cannot be replaced, specially when dealing with a complex system such as soils.