f latitude, 
D of back 
3C, bahr, 
as rover 
computed 
he actual 
ordinates 
A 
fference 
eight 
m) 
-57.16 
-0.52 
-4.52 
5.24 
-6.88 
$.91 
ordinates 
B 
fference 
eight 
-36.66 
15.55 
33.96 
15.02 
13.23 
accuracy 
ne mode, 
rvations, 
ours i.e. 
. 1800 to 
was done 
3roadcast 
ne mode. 
here the 
lescribed 
vas given 
'Ocessing 
IAPRS & SIS, Vol.34, Part 7, "Resource and Environmental Monitoring", Hyderabad, India, 2002 
  
Table 3. Effect of Observation Time on Single Point accuracy 
for the point A 
  
  
Date Duration Difference of Observations 
of of (Observed coordinate. — actual coordinate) 
observa  Observat- 
t-ion ion difference difference difference 
of of of 
latitude longitude height 
(sec) (sec) (m) 
26-09- 12:00:40 0.4183 -0.0488 45.17 
01 to 
18:05:10 
26-09- 18:01:40 0.5048 0.1913 27.45 
01 to 
23:59:00 
27-09- 00:00:30 0.1800 0.0405 7.70 
01 to 
06:00:30 
27-09- 06:00:50 0.2494 -0.0756 25.24 
01 to 
12:01:30 ; 
27-09- 12:01:40 0.5053 -0.0499 42.12 
01 to 
18:02:20 
27-09- 18:00:00 0.4459 0.2884 30.76 
01 to 
23:59:50 
28-09- 00:00:30 0.2932 0.1473 9.64 
01 to 
06:01:30 
28-09- 06:00:10 0.2284 -0.0698 28.86 
01 to 
12:01:10 
28-09- 12:01:20 0.4325 -0.1009 43.84 
01 to 
17:57:50 
28-09- 18:17:00 0.5005 0.1943 25.35 
01 to 
23:59:20 
29-09- 00:01:40 0.1300 0.0288 8.61 
01 to 
06:05:30 
12:03:10 0.3927 -0.0132 48.92 
29-09- to 
01 18:00:40 
29-09- 18:00:50 0.4900 0.3634 26.35 
01 to 
23:59:50 
30-09- 00:01:40 0.1940 0.0547 9.14 
01 to 
06:00:40 
05-10- 12:00:40 0.1946 -0.0666 49.09 
01 to 
18:00:10 
05-10- 18:00:20 0.4055 0.2670 22.26 
01 to 
23:58:50 
06-10- 00:01:00 0.2740 0.0939 10.54 
01 to 
06:00:30 
  
647 
Table 4. Effect of Observation Time on Single Point accuracy 
for the point B 
  
  
Date Duration Difference of Observations 
of of (Observed coordinate. — actual coordinate) 
observa Observat- 
tion ion difference difference difference 
of of of 
latitude longitude height 
(sec) (sec) (m) 
05-10- 12:02:10 0.7292 -0.1550 55.60 
01 to 
18:00:30 
05-10- 18:00:50 0.7966 0.2303 30.95 
01 to 
00:00:00 
06-10- 00:01:10 0.1265 0.0489 4.72 
01 to 
06:01:10 
08-10- . 09:56:40 0.2426 -0.0687 28.93 
01 to 
12:00:40 
08-10- 12:00:20 0.5945 0.0761 56.68 
01 to 
18:00:50 
09-10- 12:00:20 0.4586 0.1553 52.88 
01 to 
18:00:20 ; 
10-10- 12:00:30 0.7307 -0.1553 53.55 
01 to 
18:00:00 
  
4. RESULTS AND DISCUSSIONS 
To establish a point, precisely in WGS-84 datum, observation 
needs to be taken for more than 24 hours and is to be corrected 
with IGS stations. The results given in Table 1 clearly indicate 
that the accuracy of point A is about 11 cm in position and 57 
cm in height. From Table 2, one can infer that the accuracy of 
point B is 16cm in position and 37 cm in height. 
A graph was drawn between observation time and difference in 
latitude with respect to actual coordinate for point A (Figure-1). 
From the Figure-1, it can be inferred that, error (observed 
latitude — actual latitude) is more for the observation period 
1200 — 1800 hrs. The observations of three days i.e., 26" 
September, 27" September, 28" September 2001 were chosen 
for point A, because for these three dates, the observation was 
available from 0000 — 2400 hrs. From Figure-2 it can be 
inferred that, the difference of longitude is positive for the 
observation taken between 0000-0600 and 1800-2400 hrs and 
the difference of longitude is negative for the observation taken 
between 0600-1200 and 1200-1800 hrs. It can also be inferred 
from that Table 3 and Table 4 that the difference of longitude is 
positive for the observation taken between 1800-2400 hrs. The 
difference in longitude is much less compared to difference in 
latitude. Figure-3 shows the error in height with observation 
time. The error in height is found to be maximum when the 
observation is taken between 1200 to 1800 hrs. Table- 5 and 
Table- 6 shows the maximum error and minimum error in 
position and height for different spans of observation time. For 
point B, the observation was not available for the period 0600- 
1200 (Table-6), it was available up to 0600-0900 and also for 
the observation time between 0000-0600 and 1800-2400 only 
one reading was available. From the Table-5 and Table-6 it can 
be referred that the errors in longitude are less compared to