## 1 Introduction  
In the area of agriculture, surface water content is known as soil moisture and is an important variable to consider and study to improve crops and yield. Depending on the soil moisture percentages, plant growth will be optimized, increasing nutrient absorption and the presence of microorganisms, regulating soil temperature, and affecting the speed of matter degradation and weathering processes. From a chemical point of view, soil moisture is essential for plants to undergo photosynthesis [1]. The Andes mountain range is a contrasting region with microclimates associated with its relief, where soil moisture is an important hydrological parameter that plays a vital role in the complex and vulnerable ecohydroology [2]. In agriculture, soil moisture is a complex parameter that can support soil sustainability [3]. In tropical countries such as Colombia, understanding soil moisture behavior is important to control plant growth, particularly in drought periods. The existent inter-annual climate variability and consequent soil moisture changes can affect agricultural production and by extension planting dates, varieties, and other agricultural management practices [4]. The effect of land use on andosol water storage is poorly understood and implies a high variability of soil moisture surfaces. [PERSON] et al. [5] recently stated that high-resolution remote sensing images are a good alternative to study large areas of land in the tropical Andes, providing unique insights into the surface and subsurface hydrologic processes that move and store water within these heterogeneous mountain environments. One of the main challenges in agriculture and hydrology is estimating soil moisture content by means of remote sensing [6; 7; 8]. Remote sensing techniques can be categorized by the sensor--optical (visible and infrared), thermal, or microwave (active or passive)--and depending on the range of the electromagnetic spectrum monitor [9]. These sensors are placed in private and public satellites in space. For instance, SAR (synthetic aperture radar) sensors work by means of microwave pulses that are transmitted towards the Earth's surface by an antenna, measuring the microwave energy scattered back to the sensor, in addition to the time delay between the emission and the backscattered reception signal [10]. Remote optically sensed images are obtained by measuring the solar radiation reflected by targets on the ground. Radiation reflects, transmits, and absorbs differently at different wavelengths depending on the features of the materials on the Earth's surface. When the optical sensors have several channel detectors (3 to 15) sensitive to radiation within a narrow wavelength band, the result is a multispectral image based on multiple layers containing the brightness and spectral information of the observed Earth surface at each specific wavelength band. There are satellite initiatives that periodically capture multispectral images of the Earth's surface, including Landsat, Sentinel, Spot, and Ikonos [11]. While there have been several relevant initiatives to analyze soil moisture using satellite optical and radar sensors, which provide soil moisture products on several scales, the number of in situ soil moisture networks that are accessible and suited for satellite soil moisture evaluation is especially low for tropical regions [7]. Spatial soil moisture approximations are based on the indirect climate approach, with specific programs launched by ESA (European Space Agency) and NASA (National Aeronautics and Space Administration) in the USA. An important remote sensing project specific to the study of global soil moisture is the European Space Agency's Climate Change Initiative for Soil Moisture (ESA CCI SM), with a resolution of 25 km [12]. NASA launched its SMAP (Soil Moisture Active Passive) mission on January 2015, consisting of a radar and radiometer to monitor the amount of water in the top 5 cm of soils worldwide [6].