International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
(Figure 1). These gadgets increase the precision of image 
acquisition conducted by UAV duri i i 
         
Figure 1. An example of fixed-wing UAV 
The photogrammetric products such as digital elevation 
model and digital orthophoto can be produced after a certain 
orientations through photogrammetric processes (Tahar and 
Ahmad, 2011; Tahar and Ahmad, 2012). The protogrammetric 
processes involve interior orientation, exterior orientation, aerial 
triangulation and bundle adjustment. Interior orientation requires 
information of camera calibration parameters such as focal length, 
principal distance (X,, Y,), radial lens distortion (K,, K,, Kj), 
tangential lens distortion (P,, P,) and affinity (B,) and scale factor 
(By). Exterior orientation requires coordinates on the ground to 
define the image position was same during flight mission. 
Exterior orientation can be processed by using ground control 
points which are established by total station or global positioning 
system. In addition, inertial measurement unit is used to improve 
onboard GPS coordinates during flight mission. Inertial 
measurement unit (Mikropilot) was link with navigation control 
board and records all UAV position, altitude and rotates 
coordinates during flight mission. These parameters were saved 
automatically in GPS log file and were used during post 
processing during exterior orientation. This study introduce a 
new method for image registration in the image processing phase. 
1.2 Study Area 
This study was conducted in Gelang Patah in Johor, 
Malaysia, which is located within latitudes 1° 26’N - 1° 27°N and 
longitudes 103° 34’E — 103° 35'E. The map of the study area is 
shown in Figure 2. The landuse at the study area mainly includes 
urban area, forest, plantation oil palm and bare land. 
    
Figure 2. Study area 
2. DATA ACQUISITION 
2.1 Flight Preparations 
Data acquisition is solely obtained from unmanned aerial 
vehicle, with a specific fixed wing unit which autopilot system 
has been adopt from Mikropilot product. This UAV is equipped 
494 
with the current and advanced technologies such as onboard GPS, 
fiber optics gyro, autopilot chipset, electronic speed controller, 
wireless antenna, camera mount, high resolution digital camera, 
high end transmitter and inertial navigation system (Mikropilot). 
Figure 3 shows the digital camera that was installed at the bottom 
of UAV. The images were taken autonomously by UAV based on 
flight path which was programmed in a flight mission control 
software. Pre-flight planning is a must in photogrammetric work 
because it will reflect the quality of the end products. The 
coordinates were obtained from Google Earth Pro to identify the 
area of interest. 
  
Figure 3. Digital camera 
Generally, Google Earth inherited 20-50 meter accuracy 
(Potere, 2008) but it is still the fastest and the easiest way to get 
an idea of the study area, other alternative is to visit the study area 
and conduct survey observation. Next, the images of study area 
were cropped and saved in jpeg file. Raster image (jpeg file) 
needs to be registered by using ground control points to perform 
georeference processing. These processes can be done with well 
known geographical information system (GIS) software such as 
ArcGIS, ArcView or MapInfo software. There are at least three 
control points needed to perform georeference processed which 
can be obtained from google earth or GPS observation. Then, 
georeferenced images will be opened in lentsika flight planning 
software. Lentsika software is very effective for UAV flight 
planning because it includes coverage area, required resolution, 
number of images, attitudes, altitudes and flight path. After the 
user is satisfied with the flight planning of the study area, then it 
is saved in *.fly file. In the software, user needs to specify the 
area of interest and to determine each corner of the study. This 
software can generate flight path automatically based on user's 
input. Finally, flight planning file from lentsika will be opened in 
ground control software known as Horizon software. Horizon 
software will finalize the flight pattern and altitude control. 
Normally, user is requested to enter ground resolution required 
for the mission. The software will automatically calculate the 
number of images taken, the number of waypoint, flight path and 
it will also calculate the exposure time. Flight planning file will 
be uploaded into autopilot chip or autonomous flight system in 
UAV via cable or wirelessly. In this study, we used 7 centimeter 
ground resolution at an altitude of 320 meter or 1200 feet. 
The operator will monitor on the availability of GPS onboard 
and will ensure that the wireless connection is working. The 
operator will also monitor on the speed of propeller, UAV wings, 
camera setting, and other function such as yaw and pitch sensor. 
In many cases, fixed wing UAV needs a runway to launch at the 
starting site. However, we use to throw the UAV to add some 
energy for the launch. The UAV will be radio controlled by 
operator until it reaches the first point of the planned flight route. 
After the UAV reaches the first point, it is operated autonomously 
by the flight mission control software. This kind of UAV also 
does not need a runway to land but it needs a net to hold the UAV 
during the landing steps.