The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
66 
The Tab. 1 lists the experiment results when we consider the 
nadir point is the principal point of photograph, The Tab.2 lists 
the experiment results for the nadir point. In the two tables, the 
“Horizontal” represents the height results calculated with the 
formula (4), the “Titled 1” represents the height results 
calculated with the formula (3), the “Titled 2” represents the 
height results calculated with the formula (2), the “Error 
1” ,”Error 2”, “Errir 3” separately represent the error between 
the calculated height with the the formula (4),(3),(2) and the 
true height value. The unit of the “Height”, “Horizontal”, 
“Titled 1”,“Titled 2”,“Error 1”,“Error 2”,“Error 3” is meter, and 
the unit of the projection error and the radiation distance is 
millimeter. 
The error analyzation of the two group data is drawn on the 
Figure 3, in the figure, the horizontal ordinate and the vertical 
ordinate separately represent the radiation distance and the 
“Error 1”. The continuous line represents the results when we 
consider the nadir point is the principal point of photograph, the 
imaginary line represents the results for the nadir point. 
Through the experiment results, we can conclude that: 
(1) The precision of the results for the nadir point of 
photograph is higher than the results for the principal point of 
photograph; 
(2) When the image is approximately horizontal, we can 
use the principal point of photograph to substitute the nadir 
point to calculate the buildings’ height. 
(3) When the radiation distance and the projection error 
are great, the precision of the height calculation is higher; 
(4) When the image is approximately horizontal, the 
calculation results with the formula (2), (3), (4) are 
approximately equal. 
5. CONCLUSIONS 
In the paper we developed the method to calculate the 
building height with the projection error formula with the help 
of DEM, the calculation process is simple, convenient and the 
precision is very high. The vertical line of the buildings on the 
image can be extracted with the line extraction operator to 
substitute the captured process manually, we will introduce the 
research achievements in other papers. 
REFERENCES 
Liu J Y(1995). The aerial photogrammetry. The PLA Press, 
Beijing, pp. 35-39. 
Zhang Z X, Zhang J Q,1996. The digital photogrammetry, The 
Press of the Surveying Sientific and Technical University, 
Wuhan, pp.98-117. 
Jiang Y Ch, 1991. The analytical photogrammetry, The Press of 
the Surveying and Mapping Institute, Zhengzhou, pp. 5-22