ALTA/ACSM Land Title Surveys ~An Introduction to the 2011 Standards~

Transcription

1 ~An Introduction to the 2011 Standards~ Massachusetts Association ~of~ Land Surveyors and Civil Engineers Westborough, Massachusetts April 29, 2011

2 A Brief History of the ALTA/ACSM Standards st version 1986 Min. Angle & Dist. Req Table A 1992 Misc. revisions 1997 Positional Tolerance 1999 Table A changes, etc Effective 1/1/ Effective February 23, 2011

3 2011 Minimum Standard Detail Requirements for ALTA/ACSM Land Title Surveys Section 1 Purpose Section 2 Request for Survey Section 3 Surveying Standards & Standards of Care Section 4 Records Research Section 5 Field work Section 6 Plat or Map Section 7 Certification Section 8 Deliverables Table A - Optional/NegotiableItems

4 Section 1 -Purpose The Standard Survey Exception Rights or claims of parties in possession, boundary line disputes, overlaps, encroachments, and any matters not shown by the public records which would be disclosed by an accurate survey and inspection of the land described in Schedule A.

5 Section 1 -Purpose What comprises a complete ALTA/ACSM Land Title Survey? Field work Section 5 Plat or Map Section 6 Relationship to Record Docs Any selected Table A items Certification Section 7

6 Section 2 Request for Survey Written authorization Title Company not responsible for payment Request shall include desired Table A items Discuss scope of work with client on atypical properties Client to secure access where necessary

7 Section 3 Surveying Standards and Standards of Care 3.A.- Effective Date 2/23/2011. Previous versions superseded 3.B.- Other standards and requirements 3.C.- Recognizing the Normal Standard of Care

8 Section 3.D. Boundary Resolution The boundary lines and corners of any property being surveyed as part of an ALTA/ACSM Land Title Survey shall be established and/or retraced in accordance with appropriate boundary law principles governed by the set of facts and evidence found in the course of performing the research and survey.

9 3.E.i.- Relative Positional Precision the length of the semi-major axis, expressed in feet or meters, of the error ellipse representing the uncertainty due to random errors in measurements in the location of the monument, or witness, marking any corner of the surveyed property relative to the monument, or witness, marking any other corner of the surveyed property at the 95 percent confidence level (two standard deviations).

10 3.E.ii.- Uncertainties in boundary corners and lines occur as a result of (1) the availability, condition, history and integrity of reference or controlling monuments

11 3.E.ii.- Uncertainties in boundary corners and lines occur as a result of (2) ambiguities in the record descriptions or plats of the surveyed property or its adjoiners

12 3.E.ii.- Uncertainties in boundary corners and lines occur as a result of (3) occupation or possession lines as they may differ from the written title lines

13 3.E.ii.- Uncertainties in boundary corners and lines occur as a result of (4) Uncertainties in measurement (Relative Positional Precision) Angles Distances GPS

14 3.E.iii.- 4 Types of Uncertainty The first 3 relate to evidence How do we interpret the evidence and where do we want to place the lines and corners?

15 3.E.iii.- 4 Types of Uncertainty Measurement Uncertainty (Relative Positional Precision) has to do with how precisely surveyors can mark and describe those locations Precise measurements do not necessarily equate to an accurate survey

16 1962 ATA/ACSM Standards Positional Tolerance measurement standard: 0.02 feet in urban areas where buildings can be erected along the property line 0.04 feet in urban or suburban areas 1 foot per 5000 feet of perimeter in rural areas The surveyor shall note on the plat or map of survey the following: Maximum positional tolerance of corners is.

17 1962 ATA/ACSM Standards When the surveyor has doubt as to the location on the ground of street or lot lines for such reasons as street and lot lines being undefinable or indefinite because of insufficient monuments or where errors are found to exist in the descriptions, the surveyor shall clearly indicate the nature of the difficulty or discrepancy and give his professional opinion as to [the] range and scope of differences possibly involved and the effect, under the circumstances, of same on surveyed positions.

18 1962 ATA/ACSM Standards It is expected that the exercise of professional judgment by the surveyor will minimize differences of opinions with other professional surveyors exercising equally prudent judgment in such situation.

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20 Section 4 Records Research Order to include record description Complete copies of record documents to be provided: Most recent title commitment Adjoiner descriptions Easements (benefitting and burdening) Cross-referenced documents Documents to ascertain Jr/Sr relationships where necessary (See 6.B.vii.)

21 Section 5 Field Work On the Ground (except per Table A item 15)

22 Section 5.A. Monuments 5.A.i.- Location and descriptions of controlling monuments 5.A.ii.- Location, size, and type of monuments found or set

23 Section 5.B. Rights of Way & Access 5.B.i.- Distance to nearest right of way line if no abutting right of way 5.B.ii.- Name, width and location of traveled way for abutting streets

24 Section 5.B. Rights of Way & Access 5.B.iii.- Visible evidence of physical access to abutting streets 5.B.iv.- Location & character of all forms of access by other than the apparent occupants

25 Section 5.B. Rights of Way & Access (continued) 5.B.v.- Encroaching ways of access onto the surveyed property 5.B.vi.- Parcel corners that might indicate the width or location of right of way lines 5.B.vii.-Access to/from waters

26 Section 5.C. Lines of Possession & Improvements along Boundaries 5.C.i.- Possession or occupation 5.C.ii.- Improvements within 5 feet of boundary lines 5.C.iii.- Encroaching structural appurtenances and projections

27 Section 5.D. Buildings Location of all buildings expressed to the appropriate degree of precision

28 Section 5.E. Easements and Servitudes 5.E.i.- Evidence of easements disclosed in Record Documents 5.E.ii.- Evidence of easements not disclosed in Record Documents, but observed

29 Utilities vs. Evidence of Easements

30 Section 5.E. Easements and Servitudes 5.E.iii.- Surface indications of underground easements 5.E.iv.- Evidence of use by other than apparent occupants

31 Section 5.F. Cemeteries Location of cemeteries, gravesites, and burial grounds (i) disclosed in the Record Documents provided to the surveyor, or (ii) observed in the process of conducting the survey.

32 Section 5.G. Water Features 5.G.i.- Location of springs; location of water features bordering on or running through the property 5.G.ii.- Location of any water boundary Attribute located should be congruent with described water boundary

33 Section 6 Plat or Map 6.A.- Evidence and locations gathered in field work outlined in Section 5

34 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.i.- Record description and any new description prepared Avoid new descriptions unless necessary Avoid new descriptions of lots/blocks in platted subdivisions 6.B.ii.- Location & description of elements that control boundaries or that were relied upon

35 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.iii.- All distances and directions in record description and in any new description Where a measured/calc dimension differs from record show both

36 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.iv.- Dimensional data necessary to compute a mathematical closure of the surveyed boundary. A note if record description does not mathematically close Basis of bearings and difference from record

37 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.v.- Show remainder of surveyed tract where it is part of a larger existing parcel 6.B.vi.- A note regarding the nature of water boundaries. A note on any changes in water boundaries

38 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.vii.- Relationship of boundaries to adjoiners Gaps and overlaps between parcels where surveyed property is composed of multiple parcels Disclosure of gaps/overlaps to title company and client prior to completion of plat or map

39 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.viii.- Notes on face of plat or map When results differ significantly from the record When a fundamental decision cannot be clearly reflected graphically

40 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.ix.- Note on face of plat or map Explaining site conditions that resulted in R.P.P. exceeding 2 cm and 50 ppm

41 Section 6.B. Boundaries, Descriptions, Dimensions & Closure 6.B.x.- Note on face of plat or map Identifying title commitment number, date and company

42 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.i.- Information on plottable rights of way, easements and servitudes Width Recording information

43 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.ii.- Notes regarding rights of way, easements and servitudes Location cannot be determined No observed evidence Blanket easement Not on or touching the subject property Limits access Which parcels are affected, when multiple parcels

44 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.iii.- Note on face of plat or map When no physical access to a public way observed

45 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.iv.- Width of abutting rights of way and source of information Where available from jurisdiction Where disclosed in record documents provided

46 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.v.- Identifying information of documents which the survey represents. e.g.- Recorded plats Filed maps Right of way maps Etc.

47 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.vi.- Names and recording information for non-platted adjoiners Recording data of subdivision where adjoiner is platted

48 Section 6.C. Easements, Servitudes, Rights of Way, Access and Record Documents 6.C.vii.- Platted setback or building restriction lines Which appear on recorded subdivision plats Which were disclosed in Record Documents provided

49 Section 6.D. Presentation 6.D.i.- Drafting standards Not less than 8½ by 11 Legible, standard scale Scale in words and graphically Produced in recordable form when required Boundary distinguishable North arrow Legend Vicinity Map

50 Section 6.D. Presentation 6.D.ii.- Detail/supplemental diagrams when necessary 6.D.iii.- Note when no buildings

51 Section 6.D. Presentation 6.D.iv.- Surveyor s Information Project number Name Registration/License Number Signature and seal Address, telephone number address Dates of revisions

52 Section 6.D. Presentation 6.D.v.- Sheet numbers, if multiple sheets 6.D.vi.- Captioned ALTA/ACSM Land Title Survey

53 Section 7. Certification Only the unaltered certificate contained in Section 7 Except as may be required by, for example, state rules (See Section 3.B.) Date of Field work Date of Plat or Map

54 Lenders Certificates Do NOT invalidate your E & O coverage Make ONLY factual statements What did you observe? What do you know as fact? Negotiate or contract ahead of time to use specified certificate

55 Lenders Certificates

56 Lenders Certificates Successors and Assigns? Only for Lender Additional fee? C:\users\grk\Liability_Joe_Jones_ doc

57 Lenders Certificates

58 Lenders Certificates

59 Lenders Certificates

60 Sent: To: Subject: Wednesday, October 07, :51 AM Gary Kent RE: ALTA/ACSM Certifications Gary, Surveyors 1, Lenders 0. The bank has relented. The actual reply from the lender s attorney was The Lender will accept your short-form ALTA Survey certification as currently written. As to my reply, I sent them a copy of your article from the August 2006 ACSM Bulletin to help explain my opinion on the matter. Thanks for the support! Darrell

61 He called last night demanding Rick R. make all these changes he said no. So he called me this morning. His comments were: Add certain Table A items we only added what we did. New certified party we did that He thought Kyle might be a moron and not know how to plot flood zone that was funny. We were right. He wanted language changed on Item 5 in report I said no He wanted his own certificate. I threw your name out and told him NO. Let s just say he never looked at the survey and I think he opened it for the 1st time this morning.

62 Section 8. Deliverables Copies to the title company and client Other copies as negotiated Durable, dimensionally stable Digital copies allowed Produced in recordable form and recorded when required or requested

63 Table A Optional Items Requested with order Negotiated Surveyor may need to qualify Items 5 and 11b do not equate to an engineering design survey

64 Table A Item 1 (Monuments) Monumentation Required in most states (see introductory paragraph to the standards)

65 Table A Item 2 (Addresses) Address(es) If disclosed in Record Documents If observed

66 Table A Item 3 (Flood zone) Flood zone by graphic plotting

67 Table A Item 4 (Land area) Gross land area Other areas if specified by client

68 Table A Item 5 (Elevations) Vertical relief Source Contour interval Datum Originating benchmark

69 Table A Item 6 (Zoning) 6(a)- Zoning classification as provided by title company 6(b)- Zoning classification and setback, height, floor space area restrictions as provided by title company

70 Table A Item 7 (Bldg dimensions) 7(a) - Building dimensions 7(b) Square footage of buildings 7b(1) exterior footprint 7b(2) other areas as specified 7(c) Measured height at a defined location

71 Table A Item 8 (Other features) Substantial features in addition to those required in Section 5 Parking lots Billboards Signs Swimming pools Landscaped areas

72 Table A Item 9 (Parking spaces) Striping Number of parking spaces Types of parking spaces

73 Table A Item 10 (Party walls) 10(a)- Information on party walls as designated by client 10(b)- Plumbness of certain walls as designated by client Client to provide for access

74 Table A Item 11 (Utilities) Location of utilities 11(a) Based on observed evidence 11(b) Based on observed evidence together with plans and markings obtained from utility companies or provided by client A note to clients qualifying what surveyors can depict

75 Table A Item 11 (Utilities)

76 Table A Item 12 (other requirements) Governmental agency requirements as specified by the client. e.g HUD BLM leases

77 Table A Item 13 (Platted adjoiners) Names of adjoining owners of platted lands

78 Table A Item 14 (Nearest Intersecting street) Distance to nearest intersecting street as specified by client

79 Table A Item 15 (use of other technologies) Use of alternative technologies and tools Parameters of use (a) Prior discussion with client, title company and lender (b) Note on face of survey explaining source, date, precision, etc.

80 Table A Item 16 (HUD) Current earth moving, building construction or building additions

81 Table A Item 17 (HUD) Proposed changes in street right of way lines, if info available from jurisdiction Observed evidence of recent street or sidewalk construction or repairs

82 Table A Item 18 (HUD) Observed evidence of site use as a solid waste dump, sump or sanitary landfill

83 Table A Item 19 (Wetlands) Location of wetland areas as delineated by appropriate authorities

84 Table A Item 20 (Offsite Easements) 20(a)- Locate improvements within appurtenant easements 20(b)- Monument appurtenant easements Client to provide access

85 Table A Item 21 (Insurance) Client may require professional liability (E & O) insurance in a specified amount Certificate of Insurance may be requested

86 3.E.i. - Relative Positional Precision We know that every point located on a survey has an uncertainty in its location that can be represented by an error ellipse.

87 Relative Positional Precision Target Measured angle and distance Occupied Station

88 Relative Positional Precision Target Occupied Station Uncertainty in the angle measurement (exaggerated)

89 Relative Positional Precision Target Occupied Station Uncertainty in the distance measurement (exaggerated)

90 Relative Positional Precision

91 Relative Positional Precision

92 Relative Positional Precision

93 3.E.i. - Relative Positional Precision The size (length of the semi-major and semi-minor axes), and orientation of the error ellipse is a function of: (1) the uncertainties in the measurements that were made and, (2) the confidence level we are using (95%).

94 3.E.i. - Relative Positional Precision Think about the Bell Curve If we want a high probability (confidence) in our measurements, our uncertainty will be larger

95 3.E.i. - Relative Positional Precision 95% Probability, but large uncertainty

96 3.E.i. - Relative Positional Precision Think about the Bell Curve If we want a lower amount of uncertainty, we can accomplish that, but with a lower probability (i.e. a lower percentage of the time)

97 3.E.i. - Relative Positional Precision Smaller Uncertainty, but only with 5% probability

98 3.E.i.- R.P.P. defined the length of the semi-major axis, expressed in feet or meters, of the error ellipse representing the uncertainty due to random errors in measurements in the location of the monument, or witness, marking any corner of the surveyed property relative to the monument, or witness, marking any other corner of the surveyed property at the 95 percent confidence level (two standard deviations).

99 Relative Positional Precision The length of the semi-major axis in this error ellipse

100 3.E.v.- Relative Positional Precision The maximum allowable Relative Positional Precision [the maximum length of the semimajor axis] for an ALTA/ACSM Land Title Survey is 2 cm (0.07 feet) plus 50 parts per million (based on the direct distance between the two corners being tested)

101 Relative Positional Precision Note that R.P.P. is not expressed at a point, but rather it is related to the relationship between the two points being tested The size of the error ellipse is a function of the error ellipses at each of the two end points of that line.

102 Relative Positional Precision

103 Relative Positional Precision The RPP for the line is compared to the allowable RPP (0.07 feet (2 cm) plus 50 ppm). The 50 ppm is based on the length of the line connecting the two points being tested.

104 Relative Positional Precision Example: If the line being tested is 1,000 feet long, the allowable RPP for that line is: 0.07 feet+(50*1,000)/1,000,000 = 0.12 feet Can we achieve this?

105 3.E.iv.- Measurement Procedures To achieve a low level of random error uncertainty, the surveyor must: (1) use appropriately trained personnel (2)compensate for systematic errors, including those associated with instrument calibration

106 3.E.iv.- Measurement Procedures The surveyor shall: (3) use appropriate error propagation and measurement design theory (selecting the proper instruments, geometric layouts, and field and computational procedures) to control random errors such that the maximum allowable Relative Positional Precision is not exceeded.

107 Relative Positional Precision If the RPA for the line being tested exceeds the allowable 0.07 feet and 50 ppm, we can make redundant measurements use higher precision equipment develop a different survey design to decrease the size of the error ellipses at the endpoints of the line

108 3.E.v.- Relative Positional Precision It is recognized that in certain circumstances, the size or configuration of the surveyed property, or the relief, vegetation or improvements on the surveyed property will result in survey measurements for which the maximum allowable Relative Positional Precision may be exceeded. This must be explained (see Section 6.B.ix)

109 Relative Positional Precision A simple 3-step process to address R.P.P. on your survey: 1. Understand: What are the primary sources of random errors in your measurements?

110 Relative Positional Precision 2. Develop reliable estimates of the magnitude of those random errors from each of those sources

111 Relative Positional Precision 3. Use a correctly weighted Least Squares adjustment to process your data

112 Estimating R.P.P. 1. What are the primary sources of random errors in your measurements?

113 Estimating R.P.P. What are the primary sources of random errors in your measurements? In an angle (with electronic total station): Pointing Centering the instrument Centering the target Reading (straight out of the manual)

114 Estimating R.P.P. What are the primary sources of random errors in your measurements? In a distance (with EDM): Centering the instrument Centering the target Reading (straight out of the manual)

115 Estimating R.P.P. What are the primary sources of random errors in your measurements? With GPS: Centering the instrument Centering the target Reading (this is a function of the quality of your observation (PDOP, SNR, length of observation, etc.) and the length of your baseline)

116 Estimating R.P.P. 2. Develop reliable estimates of the magnitude of the random errors from each of those sources.

117 Estimating R.P.P. Develop reliable estimates of the magnitude of the random errors from each of those sources These cannot be WAGs They need be statistically based (Note that random reading errors for angles and distances come directly from the equipment manual; and random reading errors for GPS will be generated by the processing software)

118 Estimating R.P.P. 3. These uncertainties are used in the least squares program for a weighted (best fit) solution.

119 Uncertainty in Conventional Measurements Following is an example of the determination of the magnitude of significant random errors in a conventional measurement

120 Uncertainty in Conventional Measurements Analyze the angular measurement at station 2 (BS station 1 and FS station 3). Analyze the distance measurement from 2 to 3

121 Uncertainty in Conventional Measurements Significant sources of Uncertainty (random error) in Angle Measurements Significant sources of Uncertainty (random error) in Distance Measurements

122 Significant Sources of Uncertainty in Angular Measurements Pointing* Centering the instrument Centering the target Reading * * These two are a function of how many pointings & readings we make. Let s assume we are turning 1 direct & 1 reverse (or turning the angle and closing the horizon) with an electronic total station (where the standard deviation is 2 DIN from the manual). This is 4 pointings & 4 readings.

123 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Pointing Ed Mikhail and Gordon Gracie in their book Analysis and Adjustments of Survey Measurements, estimate the standard deviation of a single pointing (σ p ) to be 1 to 4 seconds. We will assume σ p = 2 seconds. But we need the standard deviation for 4 pointings (n = 4). σ for 4 pointings = σ p /(n) 1/2 = 2/(4) 1/2 = 1.0

124 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Centering the instrument Mikhail and Gracie estimate the standard deviation of the instrument centering (σ c ) to be 0.5 to 3 mm. We will assume σ c = 1 mm ( feet). But we need to know how this impacts the angle. (Where D 1 = length of backsight. D 2 = length of foresight. D 3 = Distance between backsight) σ = (σ c D 3 )/(D 1 D 2 ) =( )/( ) = 5.65 X 10 6 rads = 1.2

125 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Centering the target What is the standard deviation of your target centering (σ T )? If the target is on a tripod, it should be the same as the standard deviation of your instrument centering. But what if your target is a prism on 8 feet of range pole on a windy day? What is σ T then?! We will assume the target is on a tripod (σ T = 1 mm). Again, we need to know how this impacts the angle.

126 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Centering the target (where D 1 = length of backsight. D 2 = length of foresight and σ T is 1mm ( feet)(target is on tripod) σ = σ T (D 12 + D 22 ) 1/2 /(D 1 D 2 ) = ( ) 1/2 /( ) = 4.69 X 10 6 rads = 1.0

127 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Centering the target But what if our target was on 8 feet of range pole on a windy day? Estimate σ T is 2 cm (0.066 feet) [Is this even a reliable estimate??] (Where D 1 = length of backsight. D 2 = length of foresight and σ T is 2 cm (0.066 feet) σ = σ T (D 12 + D 22 ) 1/2 /(D 1 D 2 ) = ( ) 1/2 /( ) = 9.39X 10 5 rads = 20.0

128 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Reading From manufacturer the Standard Deviation is 2 for one D&R (2 DIN). Remember, we turned a direct and reverse (or turned the angle and closed the horizon) either way, we had 4 readings, so the DIN out of the manual is the number we need. The equation (which we do not need to solve in our case, is): σ= σ R /(n) 1/2 (where n = number of readings)

129 Develop reliable estimates of the magnitude of the random errors in Angular Measurements Pointing = 1.0 Centering the Instrument = 1.2 Centering the Target (on a tripod) = 1.0 Reading = 2.0

130 Develop reliable estimates of the magnitude of the random errors in Angular Measurements σ = ( ) 1/2 = 2.7 seconds standard deviation in our angle measurement

131 Develop reliable estimates of the magnitude of the random errors in Angular Measurements But what if we used 8 feet of range pole? Pointing = 1.0 Centering the Instrument = 1.2 Centering the Target = 20.0 Reading = 2.0

132 Develop reliable estimates of the magnitude of the random errors in Angular Measurements σ = ( ) 1/2 = 20.2 seconds standard deviation in our angle measurement

133 Significant Sources of Uncertainty in Distance Measurements Centering the instrument Centering the target Instrument error

134 Develop reliable estimates of the magnitude of the random errors in Distance Measurements Centering the instrument If our instrument is on a tripod, remember we already estimated the standard deviation as 1 mm ( feet). There is no equation to use; the impact of the standard deviation of the instrument centering on the distance is simply that number (1 mm or feet)

135 Develop reliable estimates of the magnitude of the random errors in Distance Measurements Centering the target If our target is on a tripod, remember we already estimated the standard deviation as 1 mm ( feet). There is no equation to use; the impact of the standard deviation of the instrument centering on the distance is simply that number (1 mm or feet)

136 Develop reliable estimates of the magnitude of the random errors in Distance Measurements Centering the target But what if our target was on 8 feet of range pole on a windy day? We estimated (guessed) the standard deviation as 2 cm (0.066 feet). Again, there is no equation to use; the impact of the standard deviation of the instrument centering on the distance is simply that number (2 cm or feet)

137 Develop reliable estimates of the magnitude of the random errors in Distance Measurements Instrument Error From the manufacturer, Standard Deviation is 2 mm and 2 ppm

138 Develop reliable estimates of the magnitude of the random errors in Distance Measurements Centering the Instrument = 1 mm Centering the Target (on a tripod) = 1 mm Instrument Error = 2 mm + 2 ppm

139 Develop reliable estimates of the magnitude of the random errors in Distance Measurements σ = ( ( *2) 2 /1,000,000 2 ) 1/2 σ = feet standard deviation in our distance measurement

140 Develop reliable estimates of the magnitude of the random errors in Distance Measurements But what if we used 8 feet of range pole? Centering the Instrument = 1 mm Centering the Target = 2 cm Instrument Error = 2 mm + 2 ppm

141 Develop reliable estimates of the magnitude of the random errors in Distance Measurements σ = ( ( *2) 2 /1,000,000 2 ) 1/2 σ = feet standard deviation in our distance measurement

142 Total Uncertainty in this Conventional Measurement (1σ) Using the semi-major axis as the defining factor for Relative Positional Precision, we check to see which is greater, the angular error or the distance error (target on tripod) Angular: X sin 2.7 = feet Distance: feet Therefore, angular error is greater

143 Total Uncertainty in this Conventional Measurement (1σ) But this is for 1σ. What about 95% or 2σ? 1σ = feet 95% C.I. (1σ) = feet for course 2-3 (target on tripod)

144 Total Uncertainty in this Conventional Measurement (1σ) Using the semi-major axis as the defining factor for Relative Positional Precision, we check to see which is greater, the angular error or the distance error (target on 8 feet of range pole) Angular: X sin 20.2 = feet Distance: feet Therefore, angular error is greater

145 Total Uncertainty in this Conventional Measurement (1σ) But this is for 1σ. What about 95% or 2σ? 1σ = feet 95% C.I. (1σ) = feet for course 2-3 (target on 8 feet of range pole)

146 Allowable Relative Positional Precision in this Conventional Measurement 2σ = ppm (from the Standards) 2σ = *50/1,000,000 2σ = = 0.13 feet for course 2-3

147 Questions and Answers

148 The Schneider Corporation Gary R. Kent, L.S. Director, Integrated Services 8901 Otis Avenue Indianapolis, IN Phone Fax gkent@schneidercorp.com