Assessment of soil moisture

Preparation of the method for determining biomass and soil moisture changes on the basis of data delivered by recent satellite missions

Grant No 4 T12E 026 30 (IGiK G-92)
Project leader: prof. dr hab. Katarzyna Dabrowska - Zielinska
12.04.2006 - 11.04.2009


     ENVISAT ASAR IS6 HH image registered in 20.05.2007                ENVISAT ASAR IS6 VV image registered in 20.05.2007

So-called „Water Cloud Model” (WCM), which describes vegetation canopy as a cloud, prepared by Atema and Ulaby (1978), modified by Prevot (1993) and Champion (2000) is used within the project. The model is fed with various plant parameters (biomass, LAI) and soil moisture, which are derived from ground measurements. It allows to calculate total backscattering coefficient as a sum of signal coming from soil and plants. This coefficient will be calculated for each microwave wavelength (C, L, X) recorded by ENVISAT, ALOS, TERRA-SAR satellite sensors, as well as for various incidence angles and polarizations. Inversion of WCM model will enable to derive from satellite data plant parameters: biomass and LAI and soil moisture under plant canopies. Comparison of the obtained values with real measurements will permit to estimate accuracy of model application. Next WCM model based on satellite-derived parameters can be applied for different areas and time periods in order to obtain biomass and soil moisture information.

Simultaneously, on the basis of optical satellite data (ASTER, MODIS, CHRIS-PROBE, MERIS, AATSR) new indices characterizing biomass and soil moisture will be derived. These parameters will be next entered to WCM model, in order to use them for calibration instead of ground measurements. They will be also compared with parameters obtained as a result of inversion of WCM model, in order to assess precision of its prediction. The prepared method will allow to monitor with high temporal frequency soil moisture conditions and biomass, analysing their changes and spatial extent on large agricultural areas.


Elaboration of models for assessment of cereal growth and development using remote sensing

Grant Nr 5 T12E 026 23
Project leader: prof. dr hab. Katarzyna Dabrowska - Zielinska
22.11.2002 - 21.11. 2005

The scientific goal of the project was elaboration of the crop growth models for cereals yield forecasting using NOAA satellite data which are registered every day and covers the whole Poland area. The first attempt was to apply model PROBE which calculates LAI and then crop production on the basis of meteorological data. The second method calculates LAI from the statistical correlation between LAI and soil-vegetation indices developed from satellite data. The third attempt was to feed the PROBE model using calculated LAI for improving accuracy of outputs. Then PROBE model has been modified to use as inputs only satellite and meteorological data.

The new model PLONSAT describes processes at the large agricultural areas. The study has been concentrated at the area localized in Wielkopolska region for which many remote sensing campaign have been performed. During field works the ground truth measurements of soil-vegetation as well as spectral and radiometric and meteorological parameters have been done. Also, crop structure, crop development phase and vegetation condition have been noticed.

NOAA images registered in IGiK were atmospherically corrected using 6S program. ENVISAT MERIS images have been bought from ESA for CAT-1 1427 project and used for crop classification. These allowed the proper choice of "cereals" pixels on NOAA images. From NOAA data the vegetation index NDVI and soil moisture index H/LE have been developed. These indices were used for modeling APAR and LAI values. The algorithm for calculation of cereals yield from maximum LAI values has been elaborated using ground truth measurements. Then the PLONSAT model was fed with LAI and evapotranspiration values calculated from each of the cloud free NOAA data. As the results of running model the following outputs have been obtained: APAR, LAI, and evapotranspiration from which crop yield has been calculated for the chosen districts.

The new method of cereals yield assessment on the basis of crop growth models will deliver information apriori harvest. The forecast will allow governmental and other authorities to make an appriopriate economical decisions. According to EU policy these information can be used for proper management of the large agricultural areas in Poland.


The analysis of conditions for recognition of crops on microwave satellite images

Grant IGIK G-83
Project leader: dr Krystyna Stankiewicz
25-08-2004 - 24-02-2007

The aim of the project was to analyze the conditions under which the crop recognition on microwave satellite images is the most accurate. Microwave satellite images are the valuable source of data for Earth monitoring because they can be acquired almost in all-weather conditions. Due to this fact such images can be effectively used for vegetation monitoring during the whole life cycle of plants. However, microwave backscattering depends on a canopy architecture as well as on some other randomly changing factors. The most important factors influencing the microwave image of land surface are the following: biomass distribution, vegetation water content, soil fractional coverage and surface soil moisture. Water content in plants as well as in the uppermost soil layer that control the scattering of microwave beam from land surface vary significantly in space and time. Crop recognition on microwave images is the most accurate over areas with high moisture stability during the period of investigation. It was also confirmed during some earlier investigations performed by IGIK in Wielkopolska. Our target was to answer the question whether it is possible to identify crops on microwave images with sufficient accuracy despite the variations of soil moisture and vegetation status. The influence of image registration parameters on crop discrimination accuracy was also considered. The project was based on ENVISAT ASAR images acquired during the growth periods starting from the year 2003 till 2006. Test site area is located in the western part of Poland in Wielkopolska. Field campaigns were correlated in time with the satellite overpasses. Type of crops was observed on several hundreds of fields and the measurements of wet biomass and soil moisture were taken selectively.

These data were considered during the analysis of crop recognition on various sets of ASAR images. Numerous recommendations aiming on the most effective crop recognition on ASAR images were specified as a result of the analysis. These recommendations concern the following:

  • selection of image registration parameters
  • time schedule of image registration
  • selection of ancillary data on the investigated area
  • image preprocessing methods
  • algorithms of automatic classification 

Identification of plant communities and recognition of crops on microwave satellite images as a basis of preparation of land use maps

Project leader: dr Krystyna Stankiewicz
1.10.2001 – 31.12.2003

The aim of the project was to investigate the applicability of satellite microwave images in recognition of plant communities. The natural plant communities as well as agricultural crops were taken into consideration.

Activities concerning recognition of natural plant communities concentrated on peat bogs and marshes in the middle basin of Biebrza river. The classification of satellite images from Biebrza marhland had two targets: one was aimed at the identification of grasslands on various types of sites and the other - at the identification of bushes and shrubs. In the project a set of 12 ERS-2 images was used. The applied methods of preliminary image processing and automatic classification enabled proper identification of low vegetation. High moisture of sites constituted an additional guidance in the classification of microwave images.

Crop identification task was carried out on the test area in Wielkopolska during the growth season of 2003. using the images acquired by ERS-2 and ENVISAT satellites. Crop recognition depends strongly on the date of image acquisition and also on the weather conditions which accompany the acquisition

The following conclusions concerning identification of crops on satellite microwave images were drawn:

  • it was possible to differentiate the following types of crops: rape, sugar beets, maize, alfalfa and cereals;
  • rape was distinguished from the other crops as early as at the end of April by investigating two ENVISAT images with differing polarization;
  • differentiation of cereals on microwave images was possible but signatures of cereals revealed close similarity.

Vegetation season in 2003 was unusual because of extremely low rainfall in the test site area. Hence, conclusions concerning crop identification were not the generic ones.


Remote sensing based system for crop monitoring

Project leader: prof. dr hab. Andrzej Ciolkosz
01.07.1998 - 30.06.2001

The aim of the research project was to prepare a system, which enables to use information derived from satellite images for operational monitoring of crop conditions within agricultural land in Poland. As a result of the works INFOSAT database was created, in which data concerning spectral reflectance and temperature registered by NOAA AVHRR scanner were stored. At this database albedo values and radiation temperature values were gathered for each 10-day period between 1992 and 2000. On the basis of these data the following indices were calculated for each period and for each administrative unit: Normalized Difference Vegetation Index - NDVI, Vegetation Condition Index - VCI, Temperature Condition Index - TCI and Plant Development Index - WWR.

These indices characterizing crop conditions were compared with agrometeorological information. Detailed analysis of drought conditions in Poland in 1992 was carried out on the basis of agromet data and simulation model prepared by IMUZ. Next results of this analysis were compared with spatial distribution of TCI index; the results revealed, that using satellite remote sensing areas affected with drought can be detected and monitored.


Application of microwave ERS satellite images for estimating soil moisture under cereal crops

Project leader: prof. dr hab. Katarzyna Dabrowska - Zielinska
01.01.2000-21.10.2000

As a result of this project the method of estimating soil moisture under cereal crops was prepared. It was based on crop roughness determined with the use of LAI and on water content induced from plant development. On the basis of level of water content in cereals three classes were determined; they were related to corresponding stages of plant development. Within each class of moisture three classes of roughness represented by different LAI values were assumed. At the second stage of the works database of satellite and ground data was prepared and statistical analyses were performed, in order to determine relations between soil moisture under cereals and backscattering coefficient derived from microwave satellite images. High correlation coefficients were obtained; they confirm assumption, that soil moisture under cereals can be calculated on the basis of backscattering coefficient, obtained from microwave ERS satellite images collected in C band and with VV polarization.


Determination of areas characterized by excessive soil moisture at the region affected with flood in 1997 with the use of radar satellite data

Project leader: Stanislaw Mularz (AGH)
(Cooperation with AGH Cracow)
01.06.1998-31.05.2000

Analysis of usefulness of radar ERS-2 images for determining excessively wet areas in the region affected with flood in 1July 997 was carried out within this project. As a result of the works the method of analysis of backscattering coefficient was prepared, which enables to derive information on soil moisture. The obtained statistical relations between satellite data and ground measurements allowed for modeling of spatial extent of wetness in the form of maps presenting excessively wet areas.

In the course of the works integrated Landsat TM and ERS satellite images were analysed; this analysis enabled to produce land cover maps and to asses changes of soil moisture, especially in long-term period.


Determination of acreage and structure of crops with the use of aerial and satellite remote sensing

Project IGIK PC-1
Project leader: prof. dr hab. Andrzej Ciolkosz
01.07.1997-01.04.1999

As a result of this project the method of estimating acreage and structure of crops in Poland with the use of satellite and aerial images was prepared. Various approaches to stratification of agricultural land were tested in the course of the project, in order to choose the optimal method for selecting test areas. Distribution of agricultural land in Poland was determined on the basis of analysis of Landsat TM satellite data. Next stratification of agricultural land was done into 3 layers, different in intensity of production. Stratification map was a basis for selecting test areas distributed within particular voivodships according to the rule of mathematical statistics. At the next stage of the works field interpretation of structure of crops was done within test areas, using aerial photographs for this purpose. Information about crop structure was next processed, in order to determine acreage on the main crops within boundaries of particular voivodships.

In 1998 vegetation period the described method was applied for determining acreage of the main crops for 40 % of the country. The obtained results were finally compared with the results of agricultural census done by the Head Statistical Office, in order to asses accuracy and effectiveness of remote sensing based method prepared at the Institute of Geodesy and Cartography.


Integrated information system on agricultural land in Poland (cooperation with IUNG Pulawy)

Project leader: prof. dr hab. Katarzyna Dabrowska-Zielinska
1998 - 2000

Possibilities of yield forecast with the use of satellite remote sensing were studied with the project. In order to do the work, database of NOAA satellite images covering the whole Poland was established. In this database information derived from visible and infrared bands of NOAA AVHRR, aggregated to 4x4 km grid, was stored. At the same time, AGROMET database, comprising meteorological and agronomic data for the whole country was created. Using both databases AgroTelMod GVI model based on vegetation indices derived from satellite images was prepared. Possibilities of applying other forecast models, based on meteorological data - AgroMetTelMod GVI and TelSat/GVI, were also examined. Accuracy of estimating yields with the use of different models was determined.


Application of microwave multifrequency and multipolarization satellite images for characterizing soil-plant communities

Project leader: prof. dr hab. Katarzyna Dabrowska - Zielinska
01.07.1997 - 30.06.1999

Crop classification based on ERS-2, JERS-1 and RADARSAT-1 composite was carried out within the research project. Possibilities of determining soil moisture zones on microwave satellite images were studied, as well as impact of soil-plant surface on backscattering coefficient for various polarizations was assessed. It was found in the course of the works, that for estimating soil moisture JERS images collected in L-band (23.0 cm) are the most suitable, while images registered in C-band (5.7 cm), depending on polarization, inform about water content in plants and their roughness related to canopy structure. Integration of 3 types of radar images - ERS, JERS and RADARSAT was done within the project, in order to better characterize soil-plant surface.


Preparation of the method for crop condition assessment on the basis of NOAA satellite images

Project leader: dr Zbigniew Bochenek
01.07.1996 - 31.12.1998

Crop condition assessment system based on using NOAA AVHRR satellite images was prepared for the whole Poland within the project. The system was created in cooperation with the Canada Centre for Remote Sensing - CCRS and INTERMAP company. Technology of acquisition and processing of NOAA satellite data with the use of specialized software for geometric and radiometric correction was prepared. Archival database of NOAA AVHRR satellite images, indispensable for proper functioning of the system, was created. The method of comparative assessment of crop conditions on the basis of Normalized Difference Vegetation Index - NDVI in relation to previous and mean year has been prepared. In the final stage of the project the outputs from the system were created in the form of maps and comparative images characterizing crop growth development within particular administrative units.