So, what happens if you use multiple bases or multiple rovers ? Here is a (non-exhaustive) overview of some of possibilities. What do you use and why ?
1 base +1 rover, single occupation per point:
Rover baselines per point: 1
Total Reach units in concurrent usage: 2
Triangles per point occupation: None
Possibilities/Benefits:
- RTK/PPK in classic form
- Quick setup time
- Instant results
Downsides:
- No way to check results without reversing rover/base for at least 1 point
- Rover relies upon the one base
- No redundancy in case of base failure
- Mechanical/systemic failures can’t easily be found/corrected/meaned out
1 base +1 rover, multiple occupations per point:
Rover baselines per point: 1
Total Reach units in concurrent usage: 2
Triangles per point occupation: 0
Possibilities/Benefits: Same as above, but in addition:
- Possible to mean or use Least Squares Adjustments on multiple occupations on a point, minimizing the risk of one-time bad fix, etc.
Downsides: same as above, but in addition:
- Much more walking around
- much more time-consuming as all points need to be observed multiples times.
2 receivers traversing in triangles:
Rover baselines per point: 1
Total Reach units in concurrent usage: 2
Triangles per point occupation: 1/4 (4 occupations on 3 points to generate 1 loop)
Benefits:
- Possible to generate loops for misclosure checks
- Possible to perform Least Squares Adjustment on the loop
- Points are related to each other from overlapping rover-obs
Downsides:
- Timeconsuming
- Complicated, easy to mess up the sequence.
- Requires strict overlapping 30 min obs time to ensure static processing method (15 min backsight point, 15 min foresight point).
- No stationary unit on site for more 30 min -1 hour making it hard to obtain trustworthy absolute coordinate when far from CORS.
2 bases + 1 Rover
Rover baselines per point: 2
Total Reach units in concurrent usage: 3
Triangles per point occupation: 0 (of collection in Survey mode with 30 sec obs time)
Benefits:
- Creates a triangle for each rover observation
- When setup, as easy as normal RTK survey
- Possible to perform Least Squares Adjustments on the loops
Downsides:
- 2 bases to setup
- More gear to haul
- Requires expensive commercial PP-software (like EzSurv) to make all the calculations and processing, as that could otherwise takes days in RTKlib+Excel
2 bases + 2 overlapping Rovers
Rover baselines per point: 3
Total Reach units in concurrent usage: 4
Triangles per point occupation: 4
Benefits:
- Creates a whopping 4 triangle for each rover observation, if 2 rovers overlaps data wise (traversing, but not in triangles)
- Requires strict overlapping 30 min obs time to ensure static processing method (15 min backsight point, 15 min foresight point).
- Possible to perform Least Squares Adjustments on the loops
- Points are related to each other from overlapping rover-obs
Downsides:
- 2 bases to setup
- More gear to haul
- Traversing rover requires more concentration on site
- Requires expensive commercial PP-software (like EzSurv) to make all the calculations and processing, as that could otherwise takes days in RTKlib+Excel
Here a table based excel sheet for an easy overview, including estimated working time on site for 30 points with the various methods:
| Type | #Bases | #Rovers | Req Rover Obs-time (mins) | #Occupations pr point | PP required pr occupation (min) | Total worktime for 30 points (mins) | Rover redunduncy in PP | Base redundancy in PP | Loop generation pr observation | #Baselines pr occupation | QA Possible from data | Network adjustable |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Classic RTK | 1 | 1 | 0.5 | 1 | 0 | 100 | No | No | 0 | 1 | No | No |
| RTK with mulitple occ. | 1 | 1 | 0.5 | 3 | 1 | 340 | Yes | No | 0 | 1 | Yes | Yes |
| 2 Traversing Triangles | 1 | 1 | 30 | 1.2 | 1 | 1213 | No | No | 0.25 | 2 | Yes | Yes (interlinked) |
| 2 Bases + rover (kine obs) | 2 | 1 | 0.5 | 1 | 1 | 150 | No | Yes | 0 | 2 | Yes | Yes |
| 2 Bases + rover (static obs) | 2 | 1 | 15 | 1 | 1 | 585 | No | Yes | 1 | 2 | Yes | Yes |
| 2 Bases + rover (static obs) | 2 | 1 | 15 | 3 | 1 | 1665 | Yes | Yes | 1 | 2 | Yes | Yes |
| 2 Bases + 2 rover | 2 | 2 | 30 | 1 | 1 | 590 | No | Yes | 4 | 3 | Yes | Yes (interlinked) |
| 1 Base + 3 rover | 1 | 3 | 45 | 1 | 1 | 575 | No | No | 4 | 3 | Yes | Yes (interlinked) |
| 3 Bases + 1 rover | 3 | 1 | 15 | 1 | 1 | 605 | No | Yes | 4 | 3 | Yes | Yes |
If I have forgotten something, feel free to add it in a comment!