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An Intelligent Mobile Locator hi-GPS 1000 and the Precision Assessment


(2) Continuous positioning in movement
We have carried out many actual positioning tests in movement with the HI-GPS1000 set up on a car. By running the car in urban area, in residential area, on highway and so on, a lot of actual measured data of single GPS continuous positioning have been obtained.

In order to presume the probability of location errors by single GPS in movement, we made a rough estimation based on the logged positioning data with following steps.

Firstly, determine the lanes with width of 5m, 10m and 15m from the center line of road by using the digital map with the scale of 1 to 2500. Then extract and total up the numbers of positioning within each lane.

Table 3 shows the results of estimation as mentioned above. According to this table, more than 50% of the mobile locating keeps the error within 5m, and, the probability of the location error with 10m is 80%.

As an example, Figure 2 plots the mobile track by single GPS positioning on running in Dennenntyoufu city, Tokyo.

As a mobile locator, HI-GPS1000 can satisfy the needs of management and observation of moving vehicles.

Table 3. The probability estimation of location error by single GPS positioning in movement
DATE  District  Milegae D   Number ofPositioning N   < 5 m   5 to 10 m    10 to 15 m   > 15 m
(D)  (N)  (D)  (N)  (D)  (N)  (D)   (N)
2004/04/02  (A)  100.379  5,387  3,427  63.6%  1,521  28.2%  289  5.4%  150   2.8%
2004/04/03  (B)  117.345  9,240  6,238  67.5%  1,693  18.3%  376  4.1%  933   10.1%
2004/04/07  (C)  129.528  12,857  6,545  50.9%  5,051  39.3%  1,056  8.2%  205   1.6%
2004/04/08  (D)  64.783  15,353  6,783  44.2%  2,985  19.4%  1,836  12.0%  3,749   24.4%
Total  412.035  42,837  22,993  53.7%  11,250  26.3%  3,557  8.3%  5,037   11.8%




Figure 2. The mobile track by single GPS positioning in Dennenntyoufu city, Tokyo

5. Conclusion
This paper introduced a new GPS terminal unit, HI-GPS1000, developed by PASCO Corporation, and used for location based services.

As an intelligent mobile locator with Linux OS loaded, HI-GPS1000 is filling the role of micro-server and suitable for secondary developments. Also, it can provide positional information per second with a precision of about 1 to 3m when it uses the differential correction and 5 to 7m if no correction information is used.

HI-GPS1000 has its unique added value and many advantages with its excellent customizing and programmable function that can change the terminal configurations and exchange information with the server by a remote controlling method.

With the communication functions, HI-GPS1000 can make use of wireless LAN, a data communications network such as the DoPa, Air H” and GSM. Moreover, HI-GPS can solve the problems as following:
  1. The precision of log in moving
  2. Terminal customizing and secondary developing
  3. Terminal extending
  4. Running cost for communication
  5. The security of system
  6. Communication in overseas
This suggests that HI-GPS1000 can be used for vehicle monitoring, fleet operating, logistical management, and the prediction for traffic congestion and so on.

We expect that the HI-GPS1000 will be effectively utilized as a practical mobile locator and a micro-server in various applications.

Acknowledgements
The authors wish to acknowledge to the Geographical Survey Institute for allowing to use the baselines for GPS calibration.

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