Mission Planning and SP1

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Mission Planning and SP1
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Outline of Session

• Standards
• Errors
• Planning
• Network Design
• Adjustment

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ICSMStandards and Practices for Control
SurveysSP1
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Positional Uncertainty

• 95 circle of uncertainty (metres)
• Independent of the nearby network
• SP1 the uncertainty, in metres, at the 95
  confidence level, with respect to the defined
  reference frame (in our case GDA94)
• Order is relative PU is absolute
• From 2005, PU replaces Order

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Assigning Positional Uncertainty

• Formula in SP1 by Leenhouts, 1985
• C b/a
• K q0 q1C q2C2 q3C3
• Radius aK
• Where
• a semi-major axis of the standard error
  ellipse
• b semi-minor axis of the standard error
  ellipse.
• q0 1.960790
• q1 0.004071
• q2 0.114276
• q3 0.371625

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Local Uncertainty

• 95 confidence level
• Average relative uncertainty with respect to
  adjacent points
• Similar to Order which refers to 1s
• Same formula as PU but error ellipse refers to
  relative average between adjacent points

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Class and Order

• Quality Indicators
• Determined by
• The field and reduction procedures of the survey.
• The quality of the origin data
• Adjustments are an important element of verifying
  Class and Order

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Class
CLASS is a function of the precision of a survey
network, reflecting the precision of observations
as well as suitability of network design, survey
methods, instruments and reduction techniques
used in that survey. Preferably the CLASS is
verified by an analysis of the minimally
constrained least squares adjustment of the
network.
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Class is determined by

• The network design.
• Observing procedures and practices.
• Reduction of observations.
• The results of a minimally constrained adjustment.

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Testing Class

• The semi major axis of each relative error
  ellipse is tested against-
• r c(d 0.2)
• r Maximum allowable semi-major axis in mm
• c Factor to relate Distance to Error
• d Distance between stations in km

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C Values for Each Class
C Value
Typical Applications
Class
(for 1
sigma)
1
3A
Special high
precision projects
3
High precision
2A
National Geodetic
Surveys
7.5
National and State
A
geodetic surveys
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Densification of
B
geodetic surveys
100
Lower class surveys
E
r c (d 0.2) e.g. Class A 1km GPS Line r
9mm
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Relative Error Ellipse
lt r
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Order
ORDER is a function of the class of a survey,
the conformity of the new data set AND the
precision of any transformation process required
to convert the results from one datum to another
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Order

• Order is determined in the same way as class but
  AFTER a fully constrained adjustment
• The same formula for r is used

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Some Order and C values
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Significance of Class and Order
4th Order
4th Order
Class A
4th Order
4th Order
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GPS Surveying Observations in SP1

• Static Surveying
• Quick Static Surveying
• Pseudo-kinematic Surveying
• Kinematic Surveying
• Real Time Kinematic Surveying (RTK)

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General Requirements

• Use of Manufacturers Instructions
• Ancillary Equipment
• Geodetic Receivers and Software
• Satellite Geometry, Number and Elevation
• Need for closure in work and connection to
  existing geodetic network
• Connection to GDA and AHD as appropriate
• Warning on site Dependent Errors

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GPS Calibration

• SP1 now deals with GPS calibration before
  starting GPS campaigns!

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GPS Field Techniques Vs Class
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Independent Occupations

• Occupy the mark another time and gather another
  data set
• Ideally separated in time with observations to
  different set of satellites
• Ideally occupied from different base station in
  the case of RTK
• Back to back but with a new set up of the antenna
  is the minimum
• Enables detection of Errors

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Errors in GPS Surveying
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Avoiding Errors

• Specifications and Recommended Practices have
  been designed to minimize errors
• GPS Errors can be put in 2 groups...
• Factors which affect Phase data and thus the GPS
  Processing
• Factors external to Processing which can affect
  the final result

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Factors Affecting Processing

• Observation Time
• Number and Geometry of Satellites
• Quality of Starting Coordinates
• Broadcast vs Precise Ephemeris
• Ionospheric and Tropospheric delay
• Site Specific Errors such as Multipath
• All affect ability to correctly solve for
  ambiguities and / or resulting precision

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SP1 Covers Processing
S Single Frequency. D Dual Frequency. DD
Double difference. FX Fixed Ambiguity solution.
FT Fixed ambiguity with repaired cycle slips. T
Triple Difference. NCP Narrow correlation ie
DGPS.
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Factors External to Processing

• Centring Error
• Antenna Height Error
• Number of repeat occupations of sites
• Quality of existing control to which GPS survey
  is being fitted
• Datum Transformation
• For Heights - quality of Geoid Ellipsoid
  Separation

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GPS Survey Planning
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Survey Planning

• Station Marking
• Station Naming
• Manpower
• Funding
• GPS Equipment Available
• Other Resources
• key maps, access information, program sheets,
  booking forms, ancillary equipment

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Reconnaissance

• Office Preparation
• Site Selection
• Visibility
• Accessibility
• Multipath
• Permanency
• Future Use

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Reconnaissance

• Station Documentation
• Speedo Traverse
• Travel Times
• Special Requirements
• Field Records
• Logistics
• Travel time
• Setup
• Observation time
• Optimum Times

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Observationand NetworkDesign
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Networked Observation
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Networked Observation
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Observation Design
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Connections to ControlNetwork Mode
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Connections to ControlBase Station Mode
Used for RTK and covered in SP1
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Adjustment
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Minimally Constrained Adjustment

• Only sufficient constraints in order to achieve a
  solution.
• Confirms internal accuracy of data.
• Computed on ellipsoid of GPS computation.
• No N values are included.
• Used to assign CLASS to coordinates.

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Fully Constrained Adjustment

• All constraints are included.
• GPS baselines may have to be transformed (say to
  AGD) as part of the adjustment process.
• Include N Values in this adjustment.
• Used to assign ORDER to coordinates.

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Adjustment Analysis

• Essential to verify Class and Order
• Variance factor should pass Chi - Square test
• Standardized residuals inspected

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RTK
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Questions?