Object-Based Greenhouse Mapping Using Very High Resolution Satellite Data and Landsat 8 Time Series

Greenhouse mapping through remote sensing has received extensive attention over the last decades. In this article, the innovative goal relies on mapping greenhouses through the combined use of very high resolution satellite data (WorldView-2) and Landsat 8 Operational Land Imager (OLI) time series within a context of an object-based image analysis (OBIA) and decision tree classification. Thus, WorldView-2 was mainly used to segment the study area focusing on individual greenhouses. Basic spectral information, spectral and vegetation indices, textural features, seasonal statistics and a spectral metric (Moment Distance Index, MDI) derived from Landsat 8 time series and/or WorldView-2 imagery were computed on previously segmented image objects. In order to test its temporal stability, the same approach was applied for two different years, 2014 and 2015. In both years, MDI was pointed out as the most important feature to detect greenhouses. Moreover, the threshold value of this spectral metric turned to be extremely stable for both Landsat 8 and WorldView-2 imagery. A simple decision tree always using the same threshold values for features from Landsat 8 time series and WorldView-2 was finally proposed. Overall accuracies of 93.0% and 93.3% and kappa coefficients of 0.856 and 0.861 were attained for 2014 and 2015 datasets, respectively

Performance evaluation of object based greenhouse detection from Sentinel-2 MSI and Landsat 8 OLI data: A case study from Almería (Spain)

tThis paper shows the first comparison between data from Sentinel-2 (S2) Multi Spectral Instrument (MSI)and Landsat 8 (L8) Operational Land Imager (OLI) headed up to greenhouse detection. Two closely relatedin time scenes, one for each sensor, were classified by using Object Based Image Analysis and RandomForest (RF). The RF input consisted of several object-based features computed from spectral bands andincluding mean values, spectral indices and textural features. S2 and L8 data comparisons were alsoextended using a common segmentation dataset extracted form VHR World-View 2 (WV2) imagery totest differences only due to their specific spectral contribution. The best band combinations to performsegmentation were found through a modified version of the Euclidian Distance 2 index. Four differentRF classifications schemes were considered achieving 89.1%, 91.3%, 90.9% and 93.4% as the best overallaccuracies respectively, evaluated over the whole study area

Greenhouse Crop Identification from Multi-Temporal Multi-Sensor Satellite Imagery Using Object-Based Approach: A Case Study from Almería (Spain)

A workflow headed up to identify crops growing under plastic-covered greenhouses (PCG) and based on multi-temporal and multi-sensor satellite data is developed in this article. This workflow is made up of four steps: (i) data pre-processing, (ii) PCG segmentation, (iii) binary preclassification between greenhouses and non-greenhouses, and (iv) classification of horticultural crops under greenhouses regarding two agronomic seasons (autumn and spring). The segmentation stage was carried out by applying a multi-resolution segmentation algorithm on the pre-processed WorldView-2 data. The free access AssesSeg command line tool was used to determine the more suitable multi-resolution algorithm parameters. Two decision tree models mainly based on the Plastic Greenhouse Index were developed to perform greenhouse/non-greenhouse binary classification from Landsat 8 and Sentinel-2A time series, attaining overall accuracies of 92.65% and 93.97%, respectively. With regards to the classification of crops under PCG, pepper in autumn, and melon and watermelon in spring provided the best results (Fβ around 84% and 95%, respectively). Data from the Sentinel-2A time series showed slightly better accuracies than those from Landsat 8

Remote Sensing of Agricultural Greenhouses and Plastic-Mulched Farmland: An Analysis of Worldwide Research

The total area of plastic-covered crops of 3019 million hectares has been increasing steadily around the world, particularly in the form of crops maintained under plastic-covered greenhouses to control their environmental conditions and their growth, thereby increasing production. This work analyzes the worldwide research dynamics on remote sensing-based mapping of agricultural greenhouses and plastic-mulched crops throughout the 21st century. In this way, a bibliometric analysis was carried out on a total of 107 publications based on the Scopus database. Different aspects of these publications were studied, such as type of publication, characteristics, categories and journal/conference name, countries, authors, and keywords. The results showed that “articles” were the type of document mostly found, while the number of published documents has exponentially increased over the last four years, growing from only one document published in 2001 to 22 in 2019. The main Scopus categories relating to the topic analyzed were Earth and Planetary Sciences (53%), Computer Science (30%), and Agricultural and Biological Sciences (28%). The most productive journal in this field was “Remote Sensing”, with 22 documents published, while China, Italy, Spain, USA, and Turkey were the five countries with the most publications. Among the main research institutions belonging to these five most productive countries, there were eight institutions from China, four from Italy, one from Spain, two from Turkey, and one from the USA. In conclusion, the evolution of the number of publications on Remote Sensing of Agricultural Greenhouses and Plastic-Mulched Farmland found throughout the period 2000–2019 allows us to classify the subject studied as an emerging research topic that is attracting an increasing level of interest worldwide, although its relative significance is still very limited within the remote sensing discipline. However, the growing demand for information on the arrangement and spatio-temporal dynamics of this increasingly important model of intensive agriculture is likely to drive this line of research in the coming years

Evaluation of Object-Based Greenhouse Mapping Using WorldView-3 VNIR and SWIR Data: A Case Study from Almería (Spain)

Plastic covered greenhouse (PCG) mapping via remote sensing has received a great deal of attention over the past decades. The WorldView-3 (WV3) satellite is a very high resolution (VHR) sensor with eight multispectral bands in the visible and near-infrared (VNIR) spectral range, and eight additional bands in the short-wave infrared (SWIR) region. A few studies have already established the importance of indices based on some of these SWIR bands to detect urban plastic materials and hydrocarbons which are also related to plastics. This paper aims to investigate the capability of WV3 (VNIR and SWIR) for direct PCG detection following an object-based image analysis (OBIA) approach. Three strategies were carried out: (i) using object features only derived from VNIR bands (VNIR); (ii) object features only derived from SWIR bands (SWIR), and (iii) object features derived from both VNIR and SWIR bands (All Features). The results showed that the majority of predictive power was attributed to SWIR indices, especially to the Normalized Difference Plastic Index (NDPI). Overall, accuracy values of 90.85%, 96.79% and 97.38% were attained for VNIR, SWIR and All Features strategies, respectively. The main PCG misclassification problem was related to the agricultural practice of greenhouse whitewash (greenhouse shading) that temporally masked the spectral signature of the plastic film

Classifiers in Image processing

Image classification is a necessary step in pattern recognition, the efficiency and accuracy mainly depends on the classification .To do the successful classification pre-processing, segmentation, at last feature extraction have to do. Recognition rate depends on all the steps but classification has its own importance in pattern recognition. Some important classifier such assupport vector machine (SVM),artificial neural network(ANN), decision tree, KNN etc. All has their importance in one or the other way. In this paper there is a discussion about many classifiers

Identifying and Determining the Length of The Greenhouses Cultivation Period Using Aerial Photos and Sentinel-2 Images

IntroductionOver the past 60 years, the use of plastic covers as a tool to increase the harvest and increase the yield of horticultural crops has steadily increased worldwide. Plastic greenhouses have turned desert areas into areas with modern agricultural development, the province of Almera in the south of Spain is a good example. It now has many greenhouses, making it a global model of agricultural development; but greenhouses contain large quantities of phthalates and cause harm to people, like hormonal disturbances, heart problems, cancer, etc. However, plastic greenhouses are widely built to produce vegetables and fruits near cities. As a result, several remote sensing methods have been developed to identify and monitor the distribution of plastic covered greenhouses in order to manage water resources, identify sites and quantities of plastic greenhouses. Remote detection is the only practical method to monitor plastic greenhouses in a vast geographic area. In the past few years, there have been few studies using high spatial resolution images. In one study, three main absorption ranges were identified that are unaffected by dust, washing and surface factors. In Spain, an artificial intelligence neural network has been proposed to identify greenhouse using Quick Bird images with a resolution of 1.5m. Studies based on medium spatial resolution imagery were also conducted, resulting in different results. In search on land cover classification using Landsat TM images, no favorable results were found. Research has proposed a new method for mapping greenhouses using Sentinel-2 dual-time images and 1D-CNN deep learning. The aim of the current research is to identify the length of the cultivation period of greenhouse crops using Sentinel-2 satellite images. Researchers used a variety of satellite imagery to identify and classify greenhouses. The innovative objective of the current research is to evaluate the Sentinel-2 satellite images in determining the length of the cultivation period of greenhouse crops; which was done for the first time within the country. Material and MethodsIn the first step, the cultivated area of greenhouses was identified using an aerial photograph. Then, useful bands were extracted in greenhouse studies using Sentinel-2 time series images. Next, vegetation and plastic cover indices were calculated for the greenhouse growing period. 1) Identify and determine the area under cultivation in greenhouses: By comparing the pixel-based classification algorithms and the object-oriented classification algorithms, the cultivated area of greenhouses was identified. ENVI and eCognition software were used for pixel-based classification and object-oriented classification, respectively. It should be noted that only one aerial photograph with three bands, blue, green and red, has been used in object-oriented classification. In order to classify the base pixel, learning samples were selected using expert knowledge from the study area. In some instances, Google Earth was used as well. Learning samples were selected scattered across the image to improve accuracy. For validation of the maps obtained from these algorithms, ground control points were used. To reduce human error, these points were also entered into Google Earth. 2) Identifying functional bands in the greenhouse study: The spectral behavior curve of different earth surface covers in Blue, Green, Red, SWIR, NIR bands was drawn in an image of the Sentinel-2 satellite. These spectral signatures were compared on May 20, 2020 i.e., when outdoor vegetation and greenhouse cultivation were at their peak. 3) Determining the duration of the greenhouse growing season: Vegetation indices of the NDVI, SAVI, OSAVI, MSAVI, GNDVI, RVI, DVI, RGVI, IPVI and plastic cover indices PGI, RPGI, PI, PMLI were compared using Sentinel-2 satellite time series images. Results and DiscussionGreenhouse cultivation is used to improve quality and increase food production. However, their development has many negative effects on the environment. Therefore, obtaining accurate and timely information on the distribution of greenhouses and the time of planting and harvesting crops under plastic covers can make a significant contribution to agricultural management, water management and soil protection. The present study is the first study to identify the length of the greenhouse cultivation period using Sentinel-2 satellite time series images. The results showed that among the object-oriented classification algorithms, two classification algorithms, Bayes and KNN, were more precise for the identification and determination of the cultivated area of greenhouses. The reflection of the plant below the plastic cover of the greenhouse in the NIR, Narrow NIR, Red Edge and SWIR bands increases by an equal amount in comparison with the reflection from the vegetation in the open space. Comparing vegetation cover and greenhouse cover indices showed that the indices designed based on SWIR and Red bands showed greater reflection during the hot season of the year. Indices based on NIR, Narrow NIR, and Red Edge bands were more reflective from October to late February. Based on the results obtained from the ground truth data, greenhouses are plastered during the warm season. This caused an increase in the reflectance in indices designed based on SWIR and Red bands and a decrease in reflectance in indices designed based on NIR, Narrow NIR, Red Edge bands, during the hot season. Therefore, combining all indices, two crop periods were observed: the first started in early March, peak cover was reached in April, and harvest continued. Until the middle of August. The second harvest started at the end of August and peaked in December, until the end of harvest in mid-February

AssesSeg—A Command Line Tool to Quantify Image Segmentation Quality: A Test Carried Out in Southern Spain from Satellite Imagery

This letter presents the capabilities of a command line tool created to assess the quality of segmented digital images. The executable source code, called AssesSeg, was written in Python 2.7 using open source libraries. AssesSeg (University of Almeria, Almeria, Spain; Politecnico di Bari, Bari, Italy) implements a modified version of the supervised discrepancy measure named Euclidean Distance 2 (ED2) and was tested on different satellite images (Sentinel-2, Landsat 8, and WorldView-2). The segmentation was applied to plastic covered greenhouse detection in the south of Spain (Almería). AssesSeg outputs were utilized to find the best band combinations for the performed segmentations of the images and showed a clear positive correlation between segmentation accuracy and the quantity of available reference data. This demonstrates the importance of a high number of reference data in supervised segmentation accuracy assessment problems

Regional mapping of crops under agricultural nets using Sentinel-2

Geography and Environmental Studie

Evaluation of the Consistency of Simultaneously Acquired Sentinel-2 and Landsat 8 Imagery on Plastic Covered Greenhouses

Remote sensing techniques based on medium resolution satellite imagery are being widely applied for mapping plastic covered greenhouses (PCG). This article aims at testing the spectral consistency of surface reflectance values of Sentinel-2 MSI (S2 L2A) and Landsat 8 OLI (L8 L2 and the pansharpened and atmospherically corrected product from L1T product; L8 PANSH) data in PCG areas located in Spain, Morocco, Italy and Turkey. The six corresponding bands of S2 and L8, together with the normalized difference vegetation index (NDVI), were generated through an OBIA approach for each PCG study site. The coefficient of determination (r2) and the root mean square error (RMSE) were computed in sixteen cloud-free simultaneously acquired image pairs from the four study sites to evaluate the coherence between the two sensors. It was found that the S2 and L8 correlation (r2 > 0.840, RMSE < 9.917%) was quite good in most bands and NDVI. However, the correlation of the two sensors fluctuated between study sites, showing occasional sun glint effects on PCG roofs related to the sensor orbit and sun position. Moreover, higher surface reflectance discrepancies between L8 L2 and L8 PANSH data, mainly in the visible bands, were always observed in areas with high-level aerosol values derived from the aerosol quality band included in the L8 L2 product (SR aerosol). In this way, the consistency between L8 PANSH and S2 L2A was improved mainly in high-level aerosol areas according to the SR aerosol band