Phenology Detection of Forest Area Using Satellite Data
4.3 Satellite Data
For satellite data, we used NOAA/AVHRR data. NOAA/AVHRR data have 1km/pixel resolution and we used it of Yatsugatake Area for two months(Fig. 6).
| 2000/04/25 | 2000/05/05 | 2000/05/09 |
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Fig.6 Satellite(NOAA/AVHRR) data
4.4 Result of analysis
For image data (CCD camera image and camera image), to extract the amount of vegetation, we used irvep program(Ichikawa, 2000). And for spectrometer data and satellite data, we calculated the values of NDVI for two months. The result of vegetation amount by each of the image data(CCD camera and camera) show as follows(Fig.7.1), and the result of NDVI(spectrometer data and NOAA/AVHRR data) shows as follows(Fig.7.2) :
Fig.7.1 Changes of Vegetation amount of CCD camera, camera
and NDVI of spectrometer data
Fig7.2 NDVI of NOAA/AVHRR data
5. Conclution and Problems for the Future
Looking at the graph(Fig. 7.1), we can know the difference of recognition period by each of measurement system(camera, CCD camera, spectrometer). And the value of NDVI of NOAA/AVHRR is not so big compare with ground truth data(Fig.7.2). It is to say, NOAA/AVHRR data doesn't show accurately and it is clear that there is a gap between satellite data and ground truth data.
We can guess the reason why satellite data didn't show bigger value than ground truth data is because of the vapor and dust in the air over Japan. And these problems make it more difficult to specify phenology of forest area.
And, the data which we have used this time was only two months, so we have to check the past data and continue our research with a long period after this, and know the difference according to the year.
Acknowledgement
This work has been supported by CREST (Core Research for Evolutional Science and Technology) of Japan Science and Technology Corporation (JST).
