GE 
is of both 
whole sky 
with map 
jection. In 
id levelled 
ere) image 
| the image 
on (3). 
(3) 
; on whole 
dinates (u, 
1e ground- 
whole sky 
given the 
| type, and 
>d to map 
of fisheye 
ft out of 
emisphere 
5). 
(4) 
G) 
v (pixels) 
| has 1650 
(R) is 825 
24, 824) in 
image, the 
ed to map 
coordinates using zenith (0) and azimuth (4) angles by given 
any cloud heights approximately. Generally, lower clouds such 
stratocumulus appears from near the ground to 2km and in case 
of cumulus, it appears from 0.6 to 6km. 
The conversion from the each pixel (uj vj) of cloud area on 
whole sky image to map coordinates (x; y;) can be shown in 
equation (6) and (7). 
HD; = tan 0i x CHapr (6) 
x; = sine; x HD; + Ke 
(7) 
yi = cos p; X HDit yo 
where — HD; ; the horizontal distance from ground-based 
cloud observation point (m) 
CH,,, ; approximate cloud height (m) 
X;, y;; map coordinates of image coordinates u;, v; (m) 
Xo» Yo ; map coordinates of ground-based cloud 
observation point (m) 
4. RESULT AND DISCUSSSION 
As one of experiment, we examine to compare and overlay with 
several whole-sky images of different cloud types and those 
synchronous Terra & Aqua/ MODIS images observed in central 
Kyoto, Japan. The grand-based cloud observation point is 
located at (N35.018243°, E135.768278°). In this experiment, 
we use UTM (Zone53N, WGS84) as map projection. 
Figure 2 shows one of the results of cloud discrimination from 
whole sky images taken at 12:54 and 12:56 on Aug. 26^ 2005. 
  
Aug. 26, 2005 at 12:56 (JST) 
Figure 2. Results of sky classified image (right) from whole sky 
images (left) of 2-minutes different images. 
Cloud discrimination area is painted as light green on whole sky 
image. Red circle shows the area of zenith angle less than 65 
degrees. 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
Red circle corresponds to the area of zenith angle less than 65 
degrees. Cloud type is recognized as cumulus of small size 
visually. Also cloud type such cumulus and stratocumulus have 
low SI, very close to SI = 0, and high BI values digitally. 
Outside of this red circle seems to overestimate cloud coverage 
because of the long pass of atmospheric layer from the view at 
large zenith angle. Here, the target area is in less than 65 
degrees of zenith angle. 
Figure 3 shows Aqua/ MODIS observed at 12:55(JST) on Aug. 
26^ 2005 as one of the sample satellite images in this 
experiment. 
  
  
Figure 3. Aqua/ MODIS VIS (ch.1) and NIR (ch.2) composite 
image (RGB: ch.1,2,1) with 250m ground resolution observed at 
12:55(JST) on Aug. 26", 2005. 
Red x is the point of ground-based cloud observation. Red circle 
indicates the overlaying area with zenith angle less than 65 
degrees in case of HD calculation as CH, = 2000m. 
There are not seen so much cloud coverage around the 
observation point by comparing with northern part of this 
MODIS image. However, it is certainly confirmed the clouds 
existence in the red circle visually. 
For overlaying clouds area, the horizontal distribution of 
cumulus clouds area discriminated from whole sky image are 
calculated in four cases of CH, = 600, 1000, 1500, 2000m by 
considering general cloud height of cumulus firstly. After 
calculations, it is the best fit to both ground and satellite-based 
images in the case of CH, = 2000m. 
Figure 4 shows the results of overlaying the cumulus clouds 
area discriminated from whole sky images taken at 12:54 and 
12:56 (figure 2) to Aqua/ MODIS observed at 12:55 on Aug. 
26^ 2005 (figure 3). Legend colors show SI value calculated 
from whole sky image. SI in almost clouds area shows very low.