Preparation soil colour map using Landsat satellite imagery

Determining and mapping the soil colour are important to identify the important chemical, biological, and physical properties of the soil, especially through the areas where their measurement is difficult or not precisely practical. Several researchers in different parts of the world have used remote sensing to study soil temperature and humidity and its relation with different uses in environmental sciences. However, using of satellite imagery and remote sensing technology to determine the soil colour have been not observed worldwide in the literature. Therefore, such research can be useful in the field of environmental sciences, especially soil science and geomorphology. Hence, in the present study to study of soil colour through four different classes of calcareous, salty, coarse, and sandy soil samples, with the most colour variation, were used based on two methods of field operation and remote sensing approaches in Harat Plain, Yazd province.

The study area of Harat Plain is located in the geographical coordination of northern latitude range from 29° 54' 27" to 30° 27' 12" and eastern longitude range from 54° 07' 11" to 54° 36' 16". It covers a surface area of 1220 square kilometers, including a large part of saline land and bare ground and marginal cities of Harat and Marvast. This arid region with typical geomorphology of Central Iranian playas has a mean annual rainfall of 110 mm and an average annual temperature of 20 degrees Celsius.

Firstly validation and verification of data revealed total accuracy and Kappa coefficient of 82% and 0.792, respectively indicating comprehensible levels. Then to obtain the soil colour in the field operation, Munsell’s colour system was used and to measure remote sensing data, Landsat 8 imagery was used. Also, with the aim of using remote sensing technology and satellite imagery data for soil science studies, evaluation of different bands in ENVI software and preparation of soil colour map have been done in ArcGIS software. The results revealed that in the calcareous, salty, coarse, and sandy soils, the best band showing the Hue parameter is 5, 10, 7, and 10, respectively. Therefore, in the calcareous, salty, coarse, and sandy soils, the best band showing the Chroma parameter is 7, 7, 1, and 11, respectively. Finally, in the calcareous, salty, coarse, and sandy soils, the best band showing the Value parameter is 6, 11, 11, and 10, respectively. According to the linear equations between soil colour parameters and various bands, the spectrum band, which have the most correlations, were selected for each soil component. Then by combining all produced multi band images, one image was generated that represents the soil colour in respecting regions.

In conclusion, for the study area, which is a desert plain in central Iran, Landsat 8 satellite imagery can be used to map the soil colour map for different types of soil units.