International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
3.1 Hand-held device 
The hand-held device is the main component of the 
telephotogrammetry system. It plays the role of the MI, a thin 
client that incorporates the following functions: 
1) Image capture 
2) Coordinate measurement 
3) Temporary data storage 
4) Network connection 
5) Screen display 
6) On-screen digitizing 
On the market, no single device provides all of these functions. 
Considering the coordinate measurement function, two 
technologies exist: Global Positioning System (GPS) and mobile 
network positioning system. They greatly vary in terms of 
precision, cost and portability. Positioning information is not yet 
commonly available in mobile device. It needs further 
development and a public acceptance. 
Considering the other functions, two types of device were 
identified: Smartphones and Personal Digital Assistant (PDA). 
Both of them provide computational power associated with a 
color screen, image capture and data storage. Networking 
possibilities and on-screen digitizing depends on models. 
Three models were chosen for benchmarking: 
1) IPAQ H2210 with a camera module Flycam 1.3M (PDA) 
2) Sony Ericsson P900 (Smartphone) with built-in camera 
3) SPV 100 (Smartphone) with built-in camera 
A comparison of the two model specifications is given in table 1. 
For the moment, the best solution is the IPAQ combined with a 
camera module. It is a real pocket computer, but only lacking of 
wireless connection. This is solved by using an additional mobile 
phone connected on the Bluetooth port. 
Concerning image quality, provided capture software has 
systematic error in resampling and band alignment, so that pre- 
processing of image is required prior to compression. We also 
observed that image sharpness is not uniform and decreases 
towards on the edges of the image. Applying a edge filter on an 
image of a textured ground shows evidence of this fact (Figure 
2). 
3.2 Positioning technique 
Nowadays, positioning technology is still under development. 
Specialized tools and services with high precision are readily 
available for professionals and emergence of non-specialized 
tools of lower accuracy is increasing. External low accuracy GPS 
modules, with Bluetooth or Compact Flash connectivity, are 
readily found on the market. For higher accuracy professional 
GPS antenna along with differential GPS (DGPS) or Real-Time 
Kinematic (RTK) functionalities is required. 
    
25m 4m 
Figure 2 : Sharpness assessment : Edge image of a textured 
ground. Dark areas are sharper than bright ones. 
Post-processing of GPS signal is planned to be carried out at the 
PC (see Figure 1). Higher accuracy is reached using the RTK 
service provided by the Swiss Topographic Office, who is 
maintaining an automatic GPS network (AGNES). Precision 
range will reach between 0.01 to 0.5 meters. 
GSM positioning is not yet widely available, but might provides 
close synergy with GPS when signal is of poor quality, like often 
in densely urbanized areas. Such Assisted Global Positioning 
System (A-GPS) opens wide perspective for an accurate, outdoor 
positioning system. 
3.3 Data compression 
Another weak link in the telephotogrammetry system is wireless 
network performance. Various technologies were developed to 
transfer data. Table 2 shows the data rate for each (see acronym 
paragraph) and the time required to transfer 1 Mbytes of data. 
  
  
  
  
| Mode | GSM | HSCSD | GPRS EDGE | UMTS _ 
Data 9.6 kb/s | 14kb/s | <114kb | 384kb/s | 2Mb/s | 
rate — | /s | 
1 MB | 13min | 9.5min | 12min | 21 sec [4sec 4 
  
  
Table 2: Wireless Network performance 
Transfer of images requires a high data rate which is not yet 
available in mobile communication systems. So it is needed to 
reduce as much as possible the size of data transmitted by using 
compression techniques. JPEG 2000 file format is a newly 
widely used compression standard that preserves visual aspect of 
  
  
  
  
  
  
  
  
  
  
  
  
  
| IPAQ-Flycam pod — 777 7 T SPV i00 
| CPU | Intel XScale 400mhz ARM 9 156mhz 120mhz TI OMAP ARM | 
ROM L32MB : 
| RAM 64MB 48 MB 16 MB 
LOS 3. l Pocket PC Symbian OS 7.0 Smartphone 2002 
| Storage _ | SD card, Compact Flash | Memory Stick Duo SD card 
| Image | 1024x1280 640x480 640x480 
| resolution | 
| Network | Bluetooth, infrared, USB | Bluetooth, infrared, Infrared, GPRS, GSM, 
D 6 mie ! GPRS, GSM, USB USB 
| Screensize — | 240x320 208x320 176x220 
| java support | yes yes yes 
| Touch-screen | yes yes | no 
Table 1: Comparison of specifications f 
788 
  
or benchmarked hand-held devices 
     
   
  
     
  
   
   
  
   
  
   
    
  
  
   
   
   
  
  
   
   
   
   
  
   
  
    
   
    
   
   
   
  
  
  
  
   
    
  
    
   
  
   
  
   
   
   
     
  
   
   
  
   
  
  
   
  
  
    
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