The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products
Leaf area index (LAI) is a critical vegetation structural parameter in biogeochemical and biophysical ecosystems. High-resolution LAI products play an essential role in regional studies. Empirical methods, which normally use field measurements as their training samples and have been identified as th...
Main Authors: | , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
MDPI AG
2018-07-01
|
Series: | Remote Sensing |
Subjects: | |
Online Access: | http://www.mdpi.com/2072-4292/10/8/1187 |
id |
doaj-29457b3fee6242fd89a4d206ad26c3c0 |
---|---|
record_format |
Article |
spelling |
doaj-29457b3fee6242fd89a4d206ad26c3c02020-11-24T22:22:57ZengMDPI AGRemote Sensing2072-42922018-07-01108118710.3390/rs10081187rs10081187The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS ProductsJianmin Zhou0Shan Zhang1Hua Yang2Zhiqiang Xiao3Feng Gao4State Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Remote Sensing Science, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaUSDA (United States Department of Agriculture), Agricultural Research Service, Hydrology and Remote Sensing Laboratory, 10300 Baltimore Avenue, Beltsville, MD 20705, USALeaf area index (LAI) is a critical vegetation structural parameter in biogeochemical and biophysical ecosystems. High-resolution LAI products play an essential role in regional studies. Empirical methods, which normally use field measurements as their training samples and have been identified as the most commonly used approaches to retrieve structural parameters of vegetation from high-resolution remote-sensing data, are limited by the quality of training samples. Few efforts have been made to generate training samples from existing global LAI products. In this study, two methods (a homogeneous and pure pixel filter method (method A) and a pixel unmixing method (method B)) were developed to extract training samples from moderate-resolution imaging spectroradiometer (MODIS) surface reflectance and LAI products, and a support vector regression (SVR) algorithm trained by the samples was used to retrieve the high-resolution LAI from Landsat data at Baoding, situated in the Hebei Province in China, and Des Moines, situated in Iowa, United States. For the homogeneous and pure pixel filter method, two different sets of training samples were designed. One was composed of upscaled Landsat reflectance at the 500-m resolution and MODIS LAI products (dataset A1); the other was composed of MODIS reflectance and LAI products (dataset A2). With them, two inversion models were developed using SVR. For the pixel unmixing method, the training samples (dataset B) were extracted from unmixed MODIS surface reflectance and LAI products at 30-m resolution, and the third inversion model was obtained with them. LAI inversion results showed that good agreement with field measurements was achieved using these three inversion models. The R2 (coefficient of determination) value and the root mean square error (RMSE) value were computed to assess the results. For all tests, the R2 values are higher than 0.74 and RMSE values are less than 0.73. These tests showed that three models for the two methods combined with MODIS products can retrieve 30-m resolution LAI from Landsat data. The results of the pixel unmixing method was slightly better than that of the homogeneous and pure pixel filter method.http://www.mdpi.com/2072-4292/10/8/1187leaf area indexMODIS productsLandsathigh resolutionhomogeneous and pure pixel filterpixel unmixing |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Jianmin Zhou Shan Zhang Hua Yang Zhiqiang Xiao Feng Gao |
spellingShingle |
Jianmin Zhou Shan Zhang Hua Yang Zhiqiang Xiao Feng Gao The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products Remote Sensing leaf area index MODIS products Landsat high resolution homogeneous and pure pixel filter pixel unmixing |
author_facet |
Jianmin Zhou Shan Zhang Hua Yang Zhiqiang Xiao Feng Gao |
author_sort |
Jianmin Zhou |
title |
The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products |
title_short |
The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products |
title_full |
The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products |
title_fullStr |
The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products |
title_full_unstemmed |
The Retrieval of 30-m Resolution LAI from Landsat Data by Combining MODIS Products |
title_sort |
retrieval of 30-m resolution lai from landsat data by combining modis products |
publisher |
MDPI AG |
series |
Remote Sensing |
issn |
2072-4292 |
publishDate |
2018-07-01 |
description |
Leaf area index (LAI) is a critical vegetation structural parameter in biogeochemical and biophysical ecosystems. High-resolution LAI products play an essential role in regional studies. Empirical methods, which normally use field measurements as their training samples and have been identified as the most commonly used approaches to retrieve structural parameters of vegetation from high-resolution remote-sensing data, are limited by the quality of training samples. Few efforts have been made to generate training samples from existing global LAI products. In this study, two methods (a homogeneous and pure pixel filter method (method A) and a pixel unmixing method (method B)) were developed to extract training samples from moderate-resolution imaging spectroradiometer (MODIS) surface reflectance and LAI products, and a support vector regression (SVR) algorithm trained by the samples was used to retrieve the high-resolution LAI from Landsat data at Baoding, situated in the Hebei Province in China, and Des Moines, situated in Iowa, United States. For the homogeneous and pure pixel filter method, two different sets of training samples were designed. One was composed of upscaled Landsat reflectance at the 500-m resolution and MODIS LAI products (dataset A1); the other was composed of MODIS reflectance and LAI products (dataset A2). With them, two inversion models were developed using SVR. For the pixel unmixing method, the training samples (dataset B) were extracted from unmixed MODIS surface reflectance and LAI products at 30-m resolution, and the third inversion model was obtained with them. LAI inversion results showed that good agreement with field measurements was achieved using these three inversion models. The R2 (coefficient of determination) value and the root mean square error (RMSE) value were computed to assess the results. For all tests, the R2 values are higher than 0.74 and RMSE values are less than 0.73. These tests showed that three models for the two methods combined with MODIS products can retrieve 30-m resolution LAI from Landsat data. The results of the pixel unmixing method was slightly better than that of the homogeneous and pure pixel filter method. |
topic |
leaf area index MODIS products Landsat high resolution homogeneous and pure pixel filter pixel unmixing |
url |
http://www.mdpi.com/2072-4292/10/8/1187 |
work_keys_str_mv |
AT jianminzhou theretrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT shanzhang theretrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT huayang theretrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT zhiqiangxiao theretrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT fenggao theretrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT jianminzhou retrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT shanzhang retrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT huayang retrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT zhiqiangxiao retrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts AT fenggao retrievalof30mresolutionlaifromlandsatdatabycombiningmodisproducts |
_version_ |
1725766628701896704 |