CCD Data Research Articles

A three-band semi-analytical model for deriving total suspended sediment concentration from HJ-1A/CCD data in turbid coastal waters

The accurate assessment of total suspended sediment (TSM) concentration in coastal waters by means of remote sensing is quite challenging, due to the optical complexity and significant variability of these waters. In this study, three-band semi-analytical TSM retrieval (TSTM) model with HJ-1A/CCD spectral bands was developed for the retrieval of TSM concentration from turbid coastal waters. This model was calibrated and validated by means of one calibration dataset and three independent validation datasets obtained from three different turbid waters. It was found that the TSTM model may be used to retrieve accurate TSM concentration data from highly turbid waters without the spectral slope of the model requiring further optimization. Finally, the TSM concentration data were quantified from the HJ-1A/CCD images after atmospheric correction using the dark-object subtraction technique. Upon comparing the model-derived and field-measured TSM concentration data, it was observed that the TSTM model produced <29% uncertainty in deriving TSM concentration from the HJ-1A/CCD data. These findings imply that the TSTM model may be used for the quantitative monitoring of TSM concentration in coastal waters, provided that the atmospheric correction scheme for the HJ-1A/CCD imagery is available.

County-level rice area estimation in southern China using remote sensing data

Rice acreage estimation is a key aspect of assessing rice production. A method of estimating rice acreage at the county level is explored, using data from the HJ-1A/B Chinese Environmental Satellite for Hunan Province, which has complex rice cropping patterns. The method combines supervised and unsupervised classification using a mixed-pixel decomposition model. The rice acreage estimation results were validated by interpretation of RapidEye images for early-season rice and ground survey data for medium-season and late-season rice. The results showed a good correlation between the estimates derived from RapidEye and from HJ CCD data for pure rice pixels (R 2 =0.99 , 0.99, and 0.97 for early-, medium-, and late-season rice). The discrepancy was <10% at the plot level (6.5×6.5 km ) for early-season rice, while it was 12.20 and 12.36% at the plot level (1×1 km ) for medium-season and late-season rice. These results suggested that the method proposed in this study is capable of rice acreage estimation at the county level. The method can also be used in mountainous regions and areas of fragmented planting.

One method for HJ-1-A HSI and CCD data fusion

HJ-1-A satellite, developed by China independently, was equipped with two sensors of Hyper Spectral Imager (HSI) and multispectral sensor (CCD). In this paper, we examine the benefits of combining data from CCD data (high-spatial-resolution, low-spectral-resolution image) with HSI data (low -spatial-resolution, high -spectral-resolution image). Due to the same imaging time and similar spectral regime, the CCD and HSI data can be registered with each other well, and the difference between CCD and HSI data mainly is systematic bias. The approach we have been investigating compares the spectral information present in the multispectral image to the spectral content in the hyperspectral image, and derives a set of equations to approximately acquire the systematic bias between the two sensors. The systematic bias is then applied to the interpolated high-spectral CCD image to produce a fused product. This fused image has the spectral resolution of the hyperspectral image (HSI) and the spatial resolution of the multispectral image (CCD). It is capable of full exploitation as a hyperspectral image. We evaluate this technique using the data of Honghe wetland and show both good spectral and visual fidelity. An analysis of SAM classification test case shows good result when compared to original image. All in all, the approach we developed here provides a means for fusing data from HJ-1-A satellite to produce a spatial-resolution-enhanced hyperspectral data cube that can be further analyzed by spectral classification and detection algorithms.

Inversion of CDOM and COD in water using HJ-1/CCD data

With the in-situ measurement data including the absorption coefficient of the CDOM, apparent optical properties and the COD, a regression model was established for retrieving ag(440) based on the remote sensing reflectance of the first and the third band of the environment satellite HJ-1/CCD. The measurement data were obtained at the regions of Panjin, Liaoning province in May 2008 and August 2009. Secondly, the remote sensing regression model was created based on the correlation of the CDOM optical properties and the COD. Finally, using the HJ-1/CCD data from 2009 to 2011 in Liaodong bay, the thematic snapshots of water environmental parameters in coastal waters, such as the CDOM and the COD, were calculated and analyzed. The results showed that: (1) the distribution of the CDOM tends to decrease from offshore areas to distant sea with some zonated character; (2) Most of the retrieved CDOM values vary between 0.2–1.7m-1, which is consistent with the measured value in 2009 and 2010 years; (3) the spatial distribution of the COD has good consistency with the CDOM, also shows a certain zonated distribution in coastal-offshore areas; (4) in September 2009 and September 2011, the values of the COD was basically below 40 mg/L while the values of the COD in September 2010 are relatively higher, mostly above 55 mg/L; (5) in June 2011 and May 2010, the COD values are nearly all larger than 55 mg/L.

Monitoring crop leaf area index time variation from higher resolution remotely sensed data

The leaf area index (LAI) is significant for research on global climate change and ecological environment. China HJ-1 satellite has a revisit cycle of four days, providing CCD data (HJ-1 CCD) with a resolution of 30 m. However, the HJ-1 CCD is incapable of obtaining observations at multiple angles. This is problematic because single angle observations provide insufficient data for determining the LAI. This article proposes a new method for determining LAI using HJ-1 CCD data. The proposed method uses background knowledge of dynamic land surface processes that are extracted from MODerate resolution Imaging Spectroradiometer (MODIS) LAI 1-km resolution data. To process the uncertainties that arise from using two data sources with different spatial resolutions, the proposed method is implemented in a dynamitic Bayesian network scheme by integrating a LAI dynamic process model and a canopy reflectance model with remotely sensed data. Validation results showed that the determination coefficient between estimated and measured LAI was 0.791, and the RMSE was 0.61. This method can enhance the accuracy of the retrieval results while retaining the time series variation characteristics of the vegetation LAI. The results suggest that this algorithm can be widely applied to determining high-resolution leaf area indices using data from China HJ-1 satellite even if information from single angle observations are insufficient for quantitative application.

Remote sensing of atmospheric PM2.5 from high spatial resolution image of Chinese environmental satellite HJ-1/ CCD data

Due to lack of the middle infrared wavelength, it is difficult to employ the classic dark target method to retrieve aerosol optical depth (AOD) from Chinese Environmental satellite HJ1-CCD data. Therefore, focusing on extracting weak information from mixed satellite signals of atmosphere and land surface, we developed the Multi-wavelength, Multi-sensor, Multi-day (3M) approach in order to utilize maximally the observation information, and with the consideration of a prior knowledge, e.g. the surface property changes quickly with location but slowly with time. We present the AOD retrieval algorithm based on HJ1-CCD blue and green bands, based on the look-up table approach constructed using 6S radiative transfer model to provide the simultaneous determination of AOD and the ground reflectance. The aerosol and particle size information obtained from ground-based sun-sky radiometer are then used to estimate PM2.5 on the surface level, while air humidity and height of planetary boundary layer from reanalysis data are employed to improve the correlation between AOD and PM2.5. Validation of the retrieval results with different spatial resolutions (300, 500 and 1000 m), are also performed by comparison with ground-based measurements at three sites of North China regions.

Exploring effect of segmentation scale on orient-based crop identification using HJ CCD data in Northeast China

Crop identification and acreage estimation with remote sensing were the main issues for crop production estimation. Object-oriented classification has been involved in crop extraction from high spatial resolution images. However, different imagery segmentation scales for object-oriented classification always yield quite different crop identification accuracy. In this paper, multi-scale image segmentation was conducted to carry out crop identification using HJ CCD imagery in Red Star Farm in Heilongjiang province. Corn, soybean and wheat were identified as the final crop classes. Crop identification features at different segmentation scale were generated. Crop separability based on different feature-combinations was evaluated using class separation distance. Nearest Neighbour classifier (NN) was then used for crop identification. The results showed that the best segmentation scale was 8, and the overall crop identification accuracy was about 0.969 at that scale.

Fallow land mapping for better crop monitoring in Huang-Huai-Hai Plain using HJ-1 CCD data

The prediction of grain production is essential for socio-economic development planning, guidance and control of macro cropping structure adjustment. Fallow areas should be identified each growing season which is critical for grain production prediction. This paper focuses on fallow arable land monitoring during summer grain season in the Huang-Huai-Hai Plain using China Environment Satellite HJ-1 CCD data. With the two satellites HJ-1A and HJ-1B, high temporal Normalized Difference Vegetation Index (NDVI) can be obtained. HJ-1 CCD data were acquired from early March to early June in 2010 over the Huang-Huai-Hai Plain. Multi-temporal HJ-1 CCD data were pre-processed and time series of NDVI were derived. An algorithm for separating cropped and fallow areas was developed based on three key periods of NDVI in early-March, mid-April and mid-May, 2010. The influence of fallow arable lands to yield estimation and crop condition monitoring over the Huang-Huai-Hai Plain were also investigated and analyzed. Preliminary results in this paper showed that HJ-1 CCD data are capable for fallow land monitoring. Information of fallow arable lands is an essential part of crop monitoring and it should be incorporated into crop monitoring systems. In the future, the fallow lands over autumn grain season should also be identified and information of fallow arable lands should be generated yearly in order to get more reliable production prediction.

Case study of atmospheric correction on CCD data of HJ-1 satellite based on 6S model

In this study, atmospheric radiative transfer model 6S was used to simulate the radioactive transfer process in the surface-atmosphere-sensor. An algorithm based on the look-up table (LUT) founded by 6S model was used to correct (HJ-1) CCD image pixel by pixel. Then, the effect of atmospheric correction on CCD data of HJ-1 satellite was analyzed in terms of the spectral curves and evaluated against the measured reflectance acquired during HJ-1B satellite overpass, finally, the normalized difference vegetation index (NDVI) before and after atmospheric correction were compared. The results showed: (1) Atmospheric correction on CCD data of HJ-1 satellite can reduce the "increase" effect of the atmosphere. (2) Apparent reflectance are higher than those of surface reflectance corrected by 6S model in band1~band3, but they are lower in the near-infrared band; the surface reflectance values corrected agree with the measured reflectance values well. (3)The NDVI increases significantly after atmospheric correction, which indicates the atmospheric correction can highlight the vegetation information.

The iron K line profile of IRAS 18325–5926

IRAS 18325-5926 is an X-ray bright, Compton-thin, type-2 Seyfert galaxy and it was the first Seyfert 2 in which the presence of a broad Fe K-alpha emission line was claimed. However, although the structure of the Fe line appears broad, there is tentative evidence that it may comprise multiple lines. Nevertheless, previous analyses have only consisted of fitting standalone broad components to the Fe K band. Here, we have analyzed all available X-ray CCD data from Suzaku, XMM-Newton and ASCA to fully investigate the nature of the emission complex by testing broad-band physical models and alternative hypotheses. We find that both a model consisting of broad, blurred reflection from an ionized accretion disc and a model consisting of cold, neutral reflection plus narrow emission lines from highly-ionized photoionized gas (log \xi = 3.5) offer statistically comparable fits to the data although the true reality of the Fe line cannot currently be determined with existing data. However, it is hoped that better quality data and improved photon statistics in the Fe K band will allow a more robust distinction between models to be made.

基于环境星与MODIS时序数据的面向对象森林植被分类

基于环境星与MODIS时序数据的面向对象森林植被分类

Signals of solar cosmic ray flux variations inferred from the noise in raw CCD solar images taken by SOHO/EIT

AbstractThe noise embedded in the raw data in one scientific discipline has sometimes been proven to be a valuable signal for another discipline, and there are examples throughout science history. The solar images taken by the solid state detectors (CCDs) of the Sun monitoring satellites are usually cleaned by removing the traces of cosmic rays on the raw CCD data files. Thus, while applying the method of removing the cosmic ray traces, we may be able to estimate the cosmic ray flux by counting the number of traces. The net cosmic ray flux is the sum of galactic cosmic rays and solar‐originating particles. The latter are seen as highly transient flux changes related to solar eruptions. We can identify this kind of “cosmic ray” event from the association with phenomena revealed in processed solar images, and we show this using the data of SOHO/extreme ultraviolet imaging telescope (EIT). On the other hand, the estimated cosmic ray flux in the steady state is anticorrelated with solar cycle sunspot number. The profiles of estimated solar cosmic ray flux showing significant increase are found to be strongly correlated with the ground neutron monitor ground level enhancements. Additionally, the profile of estimated cosmic ray flux is consistent with that of the GOES P6 channel. It indicates that the particles with energy higher than 80 MeV may mainly produce the tracks on CCD of EIT. In conclusion, the raw solar images are valuable data for estimating both long‐term cosmic ray variations and transient solar particles events.

Retrieval of 30-m-Resolution Leaf Area Index From China HJ-1 CCD Data and MODIS Products Through a Dynamic Bayesian Network

The leaf area index (LAI) is a characteristic parameter of vegetation canopies. This parameter is significant in research on global climate change and ecological environments. The China HJ-1 satellite has a revisit cycle of four days and provides CCD (HJ-1 CCD) data with a resolution of 30 m. However, the HJ-1 CCD is incapable of obtaining observations at multiple angles. This is problematic because single-angle observations provide insufficient data for determining the LAI. This article proposes a new method for determining the LAI using the HJ-1 CCD data. The proposed method uses background knowledge of the dynamic land surface processes that is extracted from MODerate resolution Imaging Spectroradiometer (MODIS) LAI data with a resolution of 1 km. The proposed method was implemented in a dynamitic Bayesian network scheme by integrating an LAI dynamic process model and a canopy reflectance model with the remotely sensed data. The validation was conducted using field LAI data collected in the Guantao County of the Hebei Province in China. The results showed that the determination coefficient between the estimated and the measured LAI was 0.791, and the RMSE was 0.61. The results suggest that this algorithm can be widely applied to determine high-resolution leaf area indexes using data from the China HJ-1 satellite even if the information from single-angle observations are insufficient for quantitative application.

Effect of Ecological Water Supplement on Land Use and Land Cover Changes in Diaokou River

Diaokou River is one of the old courses of the Yellow River access to the sea before 1976 and its estuarine delta is an important part of National Nature Reserve of Yellow River Delta. The Yellow River Conservancy Commission decided the ecological water supplement to the wetland during the water and sediment regulation period in 2010. In this study, we analyzed the land use and land cover changes before and after the ecological water supplement in Diaokou River by using HJ-1B CCD data. The impact of the ecological water supplement on land use and land cover changes in Diaokou River was remarkable. The expansion of shrub-grassland and water body at large scale is conspicuous, while decreasing areas of shallows was 15.03 km2 and unutilized land decreasing amplitude was 28%. The main area of land use change was in Yiqianer protected areas, where concentrated in the estuary of the Diaokou River.

Structure and mass function of three young open clusters

Using UBVRI CCD data taken from 104-cm Sampurnanand Telescope, ARIES, Nainital, we present the structure, initial mass function and mass segregation of three young age (∼10Myr) open star clusters: NGC 2129, NGC 1502 and King 12. Based on photometric as well as astrometric criteria, the cluster member stars as well as field stars have been identified. We construct luminosity function which is further used to estimate the mass functions by employing theoretical stellar evolutionary isochrones. The entire cluster region mass function (MF) slopes for NGC 2129, NGC 1502 and King 12 are obtained as −2.55±0.14, −2.73±0.36 and −1.94±0.12 respectively. It is found that changes in the MF slope of King 12 are significantly different compared to NGC 2129 and NGC 1502 from inner region to outer region. The MF slope for King 12 is steeper at larger radii. The dynamical relaxation times for all three clusters are found to be less than age of the clusters. This indicates that all these clusters are dynamically relaxed. We show that for NGC 1502 and King 12, passing off of low mass stars from the inner region of the clusters to the halo occurs during the course of evolution.

Remote sensing mapping for uni-temporal cross-region forest burned area based on fuzzy set theory

It is very difficult to tackle the problems of the selection of optimal parameters and the determination of thresholds for the forest burned area mapping by using remote sensing data. In this paper,HJ- 1B CCD and IRS data were combined to make a contribution to the spectral indices. An ordered weighting averaging( OWA) operator based fuzzy set theory was utilized to aggregate the positive evidence and negative evidence used to revise the positive information so as to reduce the commission error. Thermal infrared band was added to aggregate the negative evidence to test its validity. Then,the revised positive evidence was input for a regional growing algorithm to produce the result. The performance of the method was tested for two HJ- CCD / IRS images of Skovorodino in Russia and Xunke County in Heilongjiang Province in China. The results show that the overall accuracy is higher than 85% in both research areas,which indicates that the method proposed in this paper could meet the application need for burned area mapping.

Research on Fast Geometric Precision Correction of HJ-1 Remote Sensing Image

As the basis application of remote sensing image ,the satellite remote sensing image geometric precision correction is an important means that to weaken the image itself with the real terrain morphological differences. In this paper, we used HJ-1 satellite CCD data as the research object, using the SIFT algorithm in combination with GPU parallel computing fast extracting and matching feature points, based on polynomial correction model to build calibration system, independent of the HJ-1 satellite imagery geometric precision correction, and achieved a higher accuracy.

A scanning CCD detector for powder diffraction measurements

Several different approaches have traditionally been used for detection of X-ray powder diffraction patterns, including area detectors, point detectors and position-sensitive detectors. Each has advantages. This paper discusses use of a low-cost CCD detector attached to a diffractometer arm, where line-by-line readout of the CCD is coupled to continuous motion of the arm. When this type of detector is used and where X-ray optics are employed to focus the source image onto the detector plane both high-resolution and rapid measurements can be performed, with data collection over a complete 2θ range. This is particularly advantageous for synchrotron applications but valuable also for Guinier diffractometer laboratory instruments. Peak resolutions are shown to be moderately better than what can be obtained with a position-sensitive detector and significantly better than with an area detector. Many samples have intrinsically broadened peak shapes for which little improvement in data quality could be obtained with an analyzer-crystal detector. With comparable numbers of modules, these CCD data collection speeds can be close to those with position-sensitive detectors, but without the low-angle asymmetry seen in the latter.

PROPERTIES OF THE CLOSE-IN TERTIARY IN THE QUADRUPLE SYSTEM V401 CYG

V401 Cyg is a quadruple system in which the spectroscopic signature of a close-in tertiary and a distant visual companion star were reported. Orbital properties of the close-in companion should provide valuable information on the formation of close binaries and stellar dynamical interaction. By analyzing new times of minimum light together with those collected from the literature, we discovered that the observed-calculated (O - C) curve of V401 Cyg shows a cyclic change with a short period of 3.5 yr and a semi-amplitude of 0.00436 days while it undergoes an upward parabolic variation. Those photoelectric and CCD data covered more than two cycles and were analyzed for the light-travel time effect via the presence of the tertiary companion. The mass of the third body was determined to be M-3 sin i' = 0.65(+/- 0.08) M-circle dot, which is close to the value estimated from the spectroscopic data (M-3 similar to 0.64 M-circle dot). This reveals that the orbital inclination of the tertiary was about i' similar to 90 degrees, indicating that the contact components of V401 Cyg have the possibility of being eclipsed by the tertiary at an orbital distance of about 3.0 AU, and it may be a triply eclipsing hierarchical triple system. The upward parabolic change indicates a period increase at a rate of (P) over dot = 1.5 x 10(-7) revealing a mass transfer from the secondary to the primary ((M) over dot(2) = 5.9 x 10(-8) M-circle dot yr(-1)). This is consistent with the predictions of the theory of thermal relaxation oscillation (TRO) suggesting that V401 Cyg is undergoing an expanding-orbit stage in the TRO cycles.

Burned Area Mapping Using HJ-1A/B CCD Data based on Two-phase Algorithm

Burned Area Mapping Using HJ-1A/B CCD Data based on Two-phase Algorithm