NETWORK DESIGN |
This generally includes such factors as the minimum and maximum station
spacing, minimum number of connections to existing horizontal and vertical
control, minimum spacing between azimuth and station marks, length of observation
sessions, type of GPS technique used, direct connection requirements, etc.
No guidelines on network shape are usually
given, as the location and distribution of points in a GPS survey are more
likely to be influenced by the intent of the survey rather than
by prescribed network "figures" that must be observed. On the
other hand, more importance is placed on direct connections, multiple station
occupancies, repeat observations, etc., for the purpose of aiding quality
control.
The Table below summarises the Australian network design specifications for various classes of GPS survey. Note that no recommendations are made as far as connection requirements to existing geodetic control (these would influence the ORDER of the GPS survey).
Australian network design specifications - internal GPS (ICSM, 1994).
| CLASS | 3A | 2A | A | B | C | D |
|---|---|---|---|---|---|---|
c-values for the CLASS(Part A,2.2.1) |
1 |
3 |
7.5 |
15 |
30 |
50 |
Technique |
||||||
Classic Static |
 |
|
|
|
|
|
Quick Static |
|
|
|
| ||
Pseudo Kinematic |
|
|
| |||
Stop and Go |
|
|
| |||
Guide to minimum station spacing in km (a) |
5 | 1.5 | 0.5 | 0.1 | NA | NA |
Typical station spacing km (b) |
100-500 | 10-100 | 0.5-10 | 0.1-5 | >0.05 | NA |
Independent occupations per station (c) |
50% 100% |
40% 100% |
20% 100% |
10% 100% |
-- -- |
-- -- |
Minimum common satelites |
Four satelites, five or more an advantage |
|---|---|
Minimum PDOP required (e) |
Less than ten (10) |
Minimum satelite elevation |
Fifteen (15) degrees |
Data rate |
Optional |
Minimum observation period(static method) (f) |
180 min | 120 min | 60 min | 30 min | 30 min | 30 min |
|---|---|---|---|---|---|---|
Minimum independent baselines at each station |
3 | 3 | 2 | 2 | 2 | 2 |
Notes:
(a) Minimum station spacing is illustrated using a 5 mm noise level after
adjustment. Below these minimum distances, special efforts are required
to reduce the error budget. For a noise level of 10 mm these values are
to be approximately doubled.
(b) These values relate to the using of conventional equipment and proprietary software.
(c) Independent occupations per station may be back to back, but the antenna should be re-setup for each occupation. Antenna heights are to be changed by at least 0.1 to 0.2 m unless set up on a pillar. The full specified minimum observation period should be observed with each occupation.
(d) For example for a CLASS A network aim for: 20% of stations are to be occupied at least three times; 100% od stations are to be occupied at least twice.
(e) Less than 10 after resolution of ambiguities.
(f) As a guide 30 minutes as a definitive minimum + about 2 minutes per kilometre.
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© Chris Rizos, SNAP-UNSW, 1999