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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 1 of 25
Advanced Least Squares Adjustments for Post Processed GPS
Instructor:Alan R. Dragoo
Maser Consulting PA2018 Fall ConferenceOctober 18, 2018
College park, Maryland
Independent Baselines
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The observations for GPS receivers collecting raw satellite data for stations at the same time are the ranges to the satellites for each receiver.
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 2 of 25
Independent Baselines
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When the ranges for each satellite at each station are differenced relative to one station, relative positions for the other points are derived that have survey quality positions relative to the station that they are compared to.
Independent Baselines
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When the position of stations are determined, errors can be introduced into station positions by positional errors. It is important to use high quality positions for data processing.
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 3 of 25
Independent Baselines
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These positions are reduced to the corresponding vector data (GPS Azimuth, Slope Distance and change in height) between the stations for the adjustment process.
Independent Baselines
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Since one GPS session is a no check solution and there is no redundancy or over determination. It is not valid to compute more vectors than one less than the number of stations in the session.
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 4 of 25
Independent Baselines
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4 Receivers3 Independent Baselines3 Trivial Baselines
2 Receivers1 Independent Baseline
5 Receivers4 Independent Baselines6 Trivial Baselines
3 Receivers2 Independent Baselines1 Trivial Baseline
Dependent Vs. Independent (B/L’s) Base Lines
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• Independent B/L’s, data & setups divulge location of blunders.
• Processing independent B/L’s makes it easier to detect blunders.
• Network design using independent B/L’s makes it easier to assure sufficient redundancy.
• Even if you process all B/L’s design your network to satisfy redundancy with independent B/L’s
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 5 of 25
3 Receiver Session All Baselines Processed
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3 Receivers: Only Independent Baselines Processed
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 6 of 25
4 Receiver Session All Baselines Processed
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4 Receivers: Only Independent Baselines Processed
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 7 of 25
Real Life ‐ 4 Rec’sIndependent B/L Example
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NORFOLK EAST
126
VETERAN
45
27
MONOLA
KORBACH
138
COWAN
73
103
NGS 150M
92
114
50
1
118
63
CRAB
FERREL
3
44
106
NORFOLK WEST
(2)(2)
City of Norfolk VA
Real Life ‐ 4 Rec’sAll Base Lines Processed
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City of Norfolk VA
(2)
(2)
Norfolk East
(2)
Norfolk West
(2)
106
3
44
(2)(2)
Ferrel
50
114
63
(2)
(2)
(2)
(2)
92
(2)
1
(2)
Crab
NGS 150M
118
Cowan
(2)
Korbach
(2)
103(2)
(2)
Monola
Veteran
(2)
138
27
126
45 73
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 8 of 25
Real Life Example Saw Mill GPS Project
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3 Receiver SessionsAll Baselines Processed
Real Life Example Saw Mill GPS Project
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3 Receiver SessionsIndependent Baselines Processed21 Trivial Baselines Removed
Stations GLOS-1 and M-105 had problems with them and when a traverse was run between them it did not check
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 9 of 25
The Key to Post Processed GPS
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• IF YOU DO IT RIGHT IT CAN’T BE WRONG
• Good networks with sufficient redundancy give high confidence in results
• Weak networks makes you question what you have done.
If You Wonder If Your GPS Work Is Right, Your Work Probably Looks Like This
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Radial Surveys Have No Checks
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 10 of 25
Poor Network Geometry
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Bad Network Geometry
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 11 of 25
When you stakeout a house would these be the only measurements you make?
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Or would you include these?
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Does your GPS control deserve less?
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 12 of 25
Keep It Simple Network Planning
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123
107
101
105
120
109
114112
111
115
119
118
106
102121
113
110
122
104
116
108
103
117
3 Receivers: Independent Baseline Network Design
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1
2
3
4
5
6
7
8
9
10
11
121314
1516
3 Sta Horz
5 Sta Vert
23 Sta Total
123
107
101
105
120
109
114112
111
115
119
118
106
102121113
110
122
104
116
108
103
117
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 13 of 25
GPS Schedule Sheet Example:
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Station Receiver S/N Operator Remarks
Session #1
Start
Stop
Session #2
Start
Stop
Session #3
Start
Start
Session #4
Start
Stop
Session #5
Start
Stop
123103107
TomJerrySam
103101107
JerryTomSam
107108
SamTom
105 Jerry 103
123
107105
120
109
114112
115
122
116
119
118
106
121
113
110
108
117
101
102104
111
1
2
3
4
5
6
7
8
9
1011
1213 14
1516
11
13
120105109
120114112
SamJerryTom
SamJerryTom
123456789
456123789789123456789456123
789456123
Copy the session information from the sketch to the schedule sheet.
Real Life ‐ 4 Rec’s Independent B/L Network Design Example
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NORFOLK EAST
126
VETERAN
45
27
MONOLA
KORBACH
138
COWAN73
103
NGS 150M
92
114
50
1
63
CRAB
FERREL
3
44
106
NORFOLK WEST
City of Norfolk VA
118
(2)
1
2
34
5
6
7
8
9
10
11
12
13
1415
16
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 14 of 25
GPS Log Sheet Data
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• Station Name
• Calendar Date
• Julian Date
• Session Number
• Start Time
• End Time
• Receiver Serial Number
• Antenna Serial Number
• Antenna Model
• HI Meters
• HI Feet
• Measurement Method
– (Slope or Bottom Antenna Mount)
• Observer
• Comments
Use One Sheet of Paper For Each Station Occupation
Example of Simple GPS Observation Log
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GPS OBSERVATION LOG
Station Name:
Calander Date: Julian Date: Session Number:
Start Time: End Time:
Observer:
Receiver Serial Number:
HI Meters: If Reg Trpod Feet:
Comments:
Antenna Serial Number:
Antenna Model Type:
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 15 of 25
POST PROCESSING YOUR DATA IN TRIMBLE BUSINESS CENTER
l29
Prepare TBC For Network Adjustment
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• Load known horizontal and vertical control points and set to control quality
• Download GPS data files
• Check in GPS data files
• Make sure station names are correct and use the same name for each data set at that station.
• Make sure HI information is correct
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Alan R. Dragoo [email protected] ©2018 Page 16 of 25
When Bluebooking Project
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• Use 4 Characher ID for TBC “Point ID”
• Use SPSN for TBC “Feature Code”
• Use Descriptor 1 and 2 as you wish
Click on View Menu and Choose “New Time‐Based View”
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 17 of 25
“Time‐Based View” is Shown
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Right Click In This Area and Choose “Zoom Session”
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 18 of 25
Hold the Shift Key Down and Choose All Baselines In Session
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Choose Plan View and Hold Down the Control Key and Left Click to Deselect the Dependent Baselines
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 19 of 25
Continue Deselecting The Dependent Baselines
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Continue Deselecting the Dependent Baselines
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 20 of 25
When Only The Independent Baselines are Highlighted Click on the Survey Menu and Choose Process Baselines
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Pick “Time‐Based View” and Right Click on a Baseline in the next Session
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 21 of 25
Hold Down the Shift Key and Choose All Baselines In Session
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Hold Down The Control Key and Left Click to Deselect the Dependent Baselines Then Process Baselines
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October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 22 of 25
Click on View and Choose “View Filter Manager” and Under GNSS Data Type Choose Processed Baselines Only
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TBC Tips And Tricks
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• Be careful of spaces in station names. Computers think E26 and E 26 are different stations.
• Have data sets start and end at close to the same time.
• Do not allow data sets in one session to overlap data sets in another session. This is done by controlling the start and stop times for the field operations.
• Use the shift key to select more than one baseline for processing in one session.
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 23 of 25
TBC Adjustment Roadmap
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• Process Independent Baselines
• Check RMS values
• Check Horizontal and Vertical precisions
• Check loop closures
• Hold 1 point fixed horizontal and vertical
• Assign H & V Setup Errors
• Perform minimally constrained adjustment
• Check for outlines
• Set station weighting until Chi Square Test passes
• Add one point at a time fixed horizontal
• Check for outlines
• Add one point at a time fixed vertical
• Check for outlines
Class ProjectDesign Fast Static Network
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4
3
2
1
00
October 18, 2018
Alan R. Dragoo [email protected] ©2018 Page 24 of 25
GPS Schedule Sheet
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Station Receiver S/N Operator Remarks Session #0 Start Stop Session #1 Start Stop Session #2 Start Stop Session #3 Start Stop Session #4 Start Stop
1001JAGUARS1000
1001WADE1002
1001STATE COLLEGE1000
WADEPULLENSTATE COLLEGE
JAGUARSPULLENSTATE COLLEGE
BILLALANKEN
BILLALANKEN
BILLALANKEN
BILLALANKEN
BILLALANKEN
Start all sessions on arrival.
End all sessions on completion of last receiver.
001600714893
001600714893
001600714893
001600714893001600714893
Completed GPS Observation Logs Samples 3 of 15
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