International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
LAS.
Figure 4. Overlapped track of GPS and RFID
t
3.3.1 Accuracy verification at known reference point
Accuracy verification experiment will be conducted to measure
position at known reference point. VRS-GPS receiver and LEX
signal receiver set up on control point are measured by static
positioning for 3 minutes. This experiment is conducted on two
patterns that QZS located at the zenith and out of zenith in the
morning and afternoon respectively. We verify gaps of control
point by measuring using each receiver.
3.3.2 Accuracy verification at temporal control point
Accuracy verification experiment will be conducted to measure
position of temporal control point by VRS-GPS, LEX signal
and Total Station. Temporal control point is set up in separate
position of open sky 10m from known reference point. On the
other hand, it set up around the building and the tree. Accuracy
verification is conducted by affecting multipath and cycle slip.
3.3.3 Accuracy verification by moving speed
Accuracy verification by moving speed is conducted by
attaching LEX signal receiver on motor vehicle.
Moving speed will be within a range of 4 to 60km/h and
positioning device is fitted LEX signal receiver, VRS-GPS and
D-GPS. An experiment is verified by each moving speed that
can receive LEX signal and difference of Time To First Fix by
each GNSS.
4. VERIFICATION EXPERIMENT FOR SEAMLESS
POSITIONING BY ACTIVE RFID
4.1 Limited receiving range of reader
It exists the limit range where tag can be received normally the
signal though active RFID has the advantage with long
communication distance. As shown in Figure $5, the
experimenter with the tag walked toward a reader from a
distance position. We investigated whether the reader could be
read a tag at any position. However the shielding material was
not set between a reader and a tag in the experiment condition.
Figure 5. Experimenter with the tag walked toward a reader
from distance position
4.2 Equipment
Equipment was made by KYUSYU TEN Co., Ltd.
[Hardware ]
e Product name: TagStation
Wi-Fi model faint wireless reader
Faint wireless writer
Faint wireless tag
e Wireless Router
(Made by I-O DATA DEVICE .INC.)
[Software ]
e Product name: TagStation
Location management system
* Setting reader program
Setting tag program
Microsoft SQL Server 2005 Express Edition
4.3 Results and considerations
Table 1 shows distance that the reader read position of the
farthest tag. This experiment was repeated 7 times and the
distance average is 12m .As a results, maximum reader range is
12m. Thus, setting intervals of reader is advisable to set radius
12m intervals in using many readers at wide area.
Times 1 2 3 4 5 6 7
Walking
speed 120 | 125 | 120 | 120 | 120 | 1.25 | 1.15
[m/s]
Distatce. rose 14 a hot hate jubleo julérn/ aides} 16
[m]
44
Table 1. Distance that the reader read position of the farthest
tag
4.4 Relationship between RSSI, ATT and distance
Active RFID can confirm value of RSSI and ATT by recording
data of viewer. RSSI means a sensitivity of tag receiver, and
it changes from interval of receiver distance. ATT is
attenuator and signal of it is classified into 3 types which are
high, medium and naught. An experiment was conducted to
verify whether RSSI indicates concrete interval. ATT values of
RSSI were investigated when the examinee moves away from
reader every 50 cm (Figure 6).
Figure 6. Experimental outline of RSSI and ATT
4.5 Results and considerations
Table 2 shows the relationship between RSSI and ATT as
maximum range with high, medium and naught of ATT. RSSI
by each level of ATT were almost no change regardless of
received range. Maximum received range 12.5m and farther
range could not receive information of tag. The change of range
by ATT and specific range by RSSI could not confirm in the
experiment. However, receiving range of RSSI will be able to
roughly estimate position of tag.
