IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
  
latitude for each of the span of observation time (Table-5 and 
6). The maximum error in position (latitude) is about 22 for the 
observation period between 1200-1800 hrs. The error in 
position was about 10 m for the observation period between eem 
  
  
  
EP 
0000-0600, and 0600-1200. The error in height is found to be 60: ore polt 27/09/08; 
more as compared to the errors in lat/long and the maximum | — 38i — point1;28/09/01 | 
was about 56 m for the observation period between 1200-1800. 50 - hc - # - -point1:29/09/01 | A 
The error in height is about 20-30 m when the observation was > m angi 
taken in between 0600-1200 and 1800-2400 hrs. The error in E 40- 
height is less than 10 m for the observation period between © 
0000-0600 hrs. E-99; 
‘ $2: 
© 
TQ 
0 
  
  
06, | —9— oint1:27/09/01 | 
| | 7 38— point1;28/09/01 | Time in hours 
057 | a point1;20/09/01 | 
  
  
    
0.4 - 
Figure 3. Effect of observation time on height 
difference of latitude in sec 
© 
C3 
  
  
  
  
  
  
  
  
  
  
0.1 4 
Table 5. Maximum and minimum errors in position and height 
0 : for point A 
0 6 s 12 18 24 
timo in hours Observation Error in Error in Error in 
Time Latitude (m) Longitude height (m) 
(m) 
Figure 1. Effect of observation time on latitude Max Min Max Min 
Max Min 
0000-0600 8.80 3.90 4.42 0.86 . 10.54 7.70 
0600-1200 7.48 4.88 2.27 0.76 28.86 25.11 
1200-1800 15.16 5.84 3.03 1.46 49.09 42.12 
1800-2400 15.14 12.16 10.92 874 -- 30.76 * 22.26 
| —2-— point: | 
| pointt;2//00/04 | Table 6. Maximum and minimum errors in position and height 
|  —4-— point1;28/09/01 — | for point B 
$04. | - - 4 - -point1;29/09/01 — | A 
£ es : Observation Error in Error in Error in 
$ Time Latitude (m) Longitude height (m) 
E (m) 
Max Min Max Min 
Max Min 
0000-0600* 3.79 1.47 4.72 
0600-1200 = - - 
> 1200-1800 21.92 13.76 ; 4.66 2.28 56.68 52.88 
S. 1800-2400 23.90 6.91 30.95 
  
  
Time in hours * only one observation was available for time period 1800- 2400 hrs 
5. CONCLUSIONS 
Figure 2. Effect of observation time on longitude 
From the present study it can be concluded that the accuracy of 
the coordinates of points established by dual frequency GPS 
observations in stand alone mode depends on the time and 
duration of measurements. In all spans of observation the error 
in latitude is more compared to error in longitude. It can be 
observed that the error in height is more than that in the 
position. 
The large positional and height errors for the observation period 
1200-1800 may be attributed to time delay of the signal due to 
648