Cross-Comparison Between China HJ1A-CCD and Landsat TM Data Guoqing Li, Xiaobing Li*, Hong Wang, Lihong Chen, Wanyu Wen State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing, China,

1. Introduction 2. Selection of Image Test Zone 3. Methodology 4. Results and Discussion

1. Introduction With the increasing service life of Landsat 5, the stability of over-life operation of sensor is facing important challenges. In addition, many currently used data outcomes directly or indirectly come from TM or ETM+ data. It is especially necessary to choose a remote sensing data source similar to Landsat TM data which can replace TM in a certain degree.

The HJ-1 satellite was launched successfully in 2008, and carried two satellites: HJ-1A and HJ-1B. HJ-1A carries two CCD sensors with 30 m spatial resolution and a hyper- spectral sensor with 100 m spatial resolution. HJ-1B carries two identical CCD sensors and an infrared sensor with two kinds of spatial resolution (150 m at near, short- wave and middle-infrared band scope and 300 m at far- infrared band). The return period of the HJ-1 satellite is two days, with synergistic operation of HJ-1A and HJ-1B. The scan width exceeds 700 km with the two satellite CCD sensors working together. This enables HJ-1 CCD remote sensing images covering all lands of China to be captured every two to three days.

SatelliteAltitude(km)Inclination （ ° ） Repetition cycle(d)Cycles/d HJ1A 、 1B /31 Landsat Tab1. Orbital characteristics of Landsat5 and HJ satellites Tab2 Contrasting between HJ-CCD and Landsat TM imaging parameters ParticularHJ1A 、 1B-CCD/ Landsat TM Spatial resolution /m30/30 Swath width(km)360/185 Bands no.4/7 HJ CCD band(1-4)/μm LandsatTM band (1-7)/μm （ Omission ）

Figure1. Spectral response profiles of Landsat TM and HJ1A-CCD1 in corresponding 1 st to 4 th wavelength region

Satellite SensorScene_Center_Scan_Time (GMT) Sun Elevation （ ° ） Sun Azimuth （ ° ） Earth-Sun distance in astronomical units HJ1-CCD : Landsat-TM : Selection of Image Test Zone

HJ1A-CCD1 4(R) 3(G)2(B) Landsat-TM 4(R) 3(G)2(B)

3.1 Radiation Precision Analysis Radiation precision is the index which reflects the information richness of the image. Many scholars have adopted grayscale mean-value and grayscale variance to evaluate radiation precision, and they believe that for different images of the area, the bigger is the distribution range of grayscale, the bigger the variance, and the richer the image information ( Franke2006 ， LI Shi-hua 2009 ). 3. Methodology

3.1 Radiation Precision Analysis (m, n are the height and width of the image; f(i, j) is the radiances of the image; v is the mean value of radiance.)

3.2 Calculation of Texture and Definition Information entropy is a measurement of the information amount that the image possesses. The higher complexity the texture has, the bigger the image information amount is, and the bigger its information entropy is.

is the probability of pixel gray value of “ i ”, MAX is the max valve of grayscale. ( m, n are the height and width of the image; df is the amplitude of the image grayscale; dx is the distance increments between pixels; “a” is the number of pixels around pixel “i”.)

4. Results and Discussion TM/HJ1A- CCD1 MinMaxMeanVariance Band1(B)40.99/ / / / Band2(G)33.92/ / / / Band3(R)14.99/ / / / Band4(N-I)21.01/ / / / Table3.Landsat TM and HJ1A-CCD1 mean value and variance of radiance

TM \ HJ1A-CCD1Band1Band2Band3Band4 Band Band Band Band Table4.The correlation matrix of Landsat TM and HJ1A-CCD1 spectrum statistics

Satellite sensor DefinitionInformation Entropy HJ-1A-CCD1Landsat-TMHJ-1A- CCD1 Landsat-TM Band Band Band Band Table5.The Definition and texture statistic

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