**2.7. Landsat image**

**2.5. Techniques in monitoring soil salinity**

70 Multi-purposeful Application of Geospatial Data

tion of EMI as it offers unique benefit over traditional methods.

**2.6. Soil mapping**

The classification of salt affected soils, assessment of the percentage of severity particularly in its early stage is important in terms of sustainable agricultural management [30]. Various approaches have been employed by researchers to analyze and monitor soil salinity. The three major techniques commonly used in soil salinity determination include traditional method, Electromagnetic Induction method and Remote Sensing and GIS method. The traditional or conventional methods used for detecting soil properties include ground-based geophysics and laboratory analysis methods [31]. Adeniran et al. [5] used this method to determine electrical conductivity of soil in Omi irrigation scheme by carrying out chemical analysis of the soil samples. The disadvantages of traditional method includes; time consuming, costly since dense sampling is required to adequately characterize the spatial variability of an area and demanding when considering large areas [32, 33]. Remote sensing methods are suitable for detecting, monitoring and controlling soil salinity. Researchers have used GIS and RS techniques to model, assessed, and investigate land use and land cover pattern, detect, map, monitor and forecast soil salinity on an irrigation scheme [34]. Ojo et al. [15] stated the advantages of remote sensing and GIS method includes; time saving, wide range of coverage, facilitation of faster and long term monitoring. Electromagnetic Induction (EMI) was first employed in agriculture to detect saline soils by measuring its electrical conductivity [35]. Electromagnetic approaches are reliable means used for rapid determination of soil salinity [36]. Spatially varying soil types and properties are identified easily and map out quickly with the applica-

There are varieties of methods to identify and map surface features using remotely sensed imagery. Techniques for mapping soil surface conditions, such as salinity and waterlogging are based on the presence or absence of spectral absorption features. Soil mapping include locating and identifying the various soils that occur, nature and properties, collecting information about soil location and recording this information on maps and in supporting documents to show their spatial distribution. Seghal et al. [37] applied Landsat MSS data for mapping salt affected soils in the frame of the reconnaissance soil map of Indian. Dwivedi [38] used Landsat MSS and TM data for more detailed mapping and monitoring of salt affected soils in the Indo-Gangetic alluvial plain. Landsat TM data have proved useful for mapping depositional environments on playas Tunisia [39]. Crowley [40] reported that gypsum and halite were likely to be the only evaporate phases detected and mapped on the Chott el Dyerid using TM data. Mehrjardi et al. [41] used Landsat TM+ taken in 2002 to map soil salinity in Ardakane Yazd by using an exponential model. They used band 3 of the images and soil salinity parameter in a regression analysis (R2 = 0.58) and reported a map accuracy of 0.87% and K coefficient equal to 0.47%. Various remote sensing data such as aerial photos, video, images, infrared thermography, visible and infrared multispectral, microwave and airborne geophysical data, is available for monitoring, classification and mapping out of saline soil [42]. According to [43] several authors have dealt with the study of soil salinization using satellite data, among them [12, 44–51]. In China, Peng [52] integrate Landsat image consists of three separate instrument subsystem, each operating in a different spectral region, using a separate optical system [54]. These subsystems are the Visible and Near Infrared (VNIR), the Short Wave Infrared (SWIR), and the Thermal Infrared (TIR), respectively. Landsat data has 14 bands allocated in three spectral regions as VNIR (band 1, 2, 3) with 15 m resolution, SWIR (bands 4–9) with 30 m resolution and TIR (bands 10–14) with 90 m resolution [55].
