Classifications of ALTA/ACSM

Land Title Surveys as adopted by

American Land Title Association and

American Congress on Surveying & Mapping

1997

Introduction

These Accuracy Standards address Positional Uncertainty and Minimum Angle, Distance and Closure Requirements for ALTA-ACSM Land Title Surveys. In order to meet these standards, the Surveyor may either: (1) Apply the within table of “Minimum Angle, Distance and Closure Requirements for Survey Measurements Which Control Land Boundaries for ALTA-ACSM Land Title Surveys” to the measurements made on the survey or (2) Compute the Positional Uncertainty for the physical points on the survey to assure that those uncertainties do not exceed the Positional Tolerance for the specified Class of Survey.

The lines and corners on any property survey have uncertainty in location which is the result of (1) availability and condition of reference monuments, (2) occupation or possession lines as they may differ from record lines, (3) clarity or ambiguity of the record descriptions or plats of the surveyed tracts and its adjoiners and (4) Positional Uncertainty.

The first three sources of uncertainty must be weighed as evidence in the determination of where, in the professional surveyor’s opinion, the boundary lines and corners should be placed. Positional Uncertainty is related to how accurately the surveyor is able to monument or report those positions.

Of these four sources of uncertainty, only Positional Uncertainty is controllable, although due to the inherent error in any measurement, it cannot be eliminated. The first three can be estimated based on evidence; Positional Uncertainty can be estimated using statistical means.

The surveyor should, to the extent necessary to achieve the standards contained herein, compensate or correct for systematic errors, including those associated with instrument calibration. The surveyor shall use appropriate error propagation and other measurement design theory to select the proper instruments, field procedures, geometric layouts and computational procedures to control and adjust random errors in order to achieve the allowable Positional Tolerance or required traverse closure.

If radial survey methods are used to locate or establish points on the survey, the surveyor shall apply appropriate procedures in order to assure that the allowable Positional Tolerance of such points is not exceeded.

Definitions:

“Positional Uncertainty” is the uncertainty in location, due to random errors in measurement, of any physical point on a property survey, based on the 95% confidence level.

“Positional Tolerance” for a specified Class of Survey is the maximum acceptable amount of Positional Uncertainty for any physical point on a property survey relative to any other physical point on the survey, including lead-in courses.

Survey Classes by Land Use

The degree of precision and accuracy necessary for a particular property survey shall be based on the intended use of the land. If the client does not provide information regarding the intended use, it shall be based on the present use of the land.

The following four survey classes for ALTA-ACSM Land Title Surveys are defined using land use classifications:

Urban Surveys - Surveys of land lying within or adjoining a city or town, and including commercial and industrial properties, condominiums, townhouses, apartments and other multi-unit developments, regardless of geographic location..

Suburban Surveys - Surveys of land lying outside urban areas and developed for single family residential use.

Rural Surveys - Surveys of land such as farms and other undeveloped land outside urban and suburban areas which may have a potential for future development.

Mountain and Marshland Surveys - Surveys of land normally lying in remote areas with difficult terrain and normally having a limited potential for development.

Computation of Positional Uncertainty

The Positional Uncertainty of any physical survey monument on a survey, whether the location of that point was established using GPS or conventional surveying methods, may be computed using a minimally constrained, correctly weighted least squares adjustment of the points on the survey.

Positional Tolerances for Classes of Survey

Application of Minimum Angle, Distance and Closure Requirements

The combined precision of a survey can be statistically assured by dictating a combination of survey closure and specified procedures for a particular class of survey. ACSM, NSPS and ALTA have adopted specific procedures in order to assure the combined precision of a particular survey class. The statistical base for these specifications is on file at ACSM and available for inspection. The surveyor shall employ, in his or her judgement, proper field procedures, instrumentation and adequate survey personnel in order to achieve accuracies comparable to those adopted for a designated class of survey.

American Congress on Surveying and Mapping

Minimum Angle, Distance and Closure Requirements for Survey Measurements Which Control Land Boundaries for ALTA-ACSM Land Title Surveys (Note 1)

Note (1) All requirements of each class must be satisfied in order to qualify for that particular class of survey. The use of a more precise instrument does not change the other requirements, such as number of angles turned, etc.

Note (2) Instrument must have a direct reading of at least the amount specified (not an estimated reading), i.e.: 10” = Micrometer reading theodolite, <1'> = Scale reading theodolite, 10" (boldface) = Electronic reading theodolite, 20" (italic)= Micrometer reading theodolite, or a vernier reading transit.

Note (3) Instrument must have the capability of allowing an estimated reading below the direct reading to the specified reading.

Note (4) D & R means the Direct and Reverse positions of the instrument telescope, i.e., Urban Surveys require that two angles in the direct and two angles in the reverse position be measured and meaned.

Note (5) Any angle measured that exceeds the specified amount from the mean must be rejected and the set of angles re-measured.

Note (6) Ratio of closure after angles are balanced and closure calculated.

Note (7) All distance measurements must be made with a properly calibrated EDM or Steel tape, applying atmospheric, temperature, sag, tension, slope, scale factor and sea level corrections as necessary.

Note (8) EDM having an error of 5mm, independent of distance measured (Manufacturer’s specifications).

Note (9) EDM having an error of 10mm, independent of distance measured (Manufacturer’s specifications).

Note (10) Calibrated steel tape.

Table A

OPTIONAL SURVEY RESPONSIBILITIES AND SPECIFICATIONS

NOTE: The items ______of Table A must be negotiated between the surveyor and client. It may be necessary for the surveyor to qualify or expand upon the description of these items, e.g. in reference to Item 6, there may be a need for an interpretation of a restriction. The surveyor cannot make a certification on the basis of an interpretation.

If checked, the following optional items are to be included in the ALTA/ACSM LAND TITLE SURVEY:

1.___ Monuments placed (or a reference monument or witness to the corner) at all major corners of the boundary of the property, unless already marked or referenced by an existing monument or witness to the corner.

2.___ Vicinity map showing the property surveyed in reference to nearby highway(s) or major street intersection(s).

3.___ Flood zone designation (with proper annotation based on Federal Flood Insurance Rate Maps or the state or local equivalent, by scaled map location and graphic plotting only.)

4.___ Land area as specified by the client.

5.___ Contours and the datum of the elevations.

6.___ Identify, and show if possible, setback, height and bulk restrictions of record or disclosed by applicable zoning or building codes (in addition to those recorded in subdivision maps). If none, so state.

7.___ (a) Exterior dimensions of all buildings at ground level

___(b) Square footage of:

___(1) exterior footprint of all buildings, or gross floor area of all buildings, at ground level;

___(2) other areas to be defined by the client

___(c) Height of all buildings above grade at a defined location.

8.___ Substantial, visible improvements (in addition to buildings) such as signs, parking areas or structures, swimming pools, etc.

9.___ Parking areas and, if striped, the striping and the type (eg. handicapped, motorcycle, regular, etc.) and number of parking spaces.

10.___ Indication of access to a public way such as curb cuts, driveways marked.

11.___ Location of utilities serving or existing on the property as evidenced by on-site observation or as determined by records provided by client, utility companies and other appropriate sources (with reference as to the source of information) (for example):
(a) railroad tracks and sidings;
(b) manholes, catch basins, valve vaults or other surface indications of subterranean uses;
(c) wires and cables (including their function) crossing the surveyed premises, all poles on or within ten feet of the surveyed premises, and the dimensions of all crosswires or overhangs affecting the surveyed premises; and
(d) utility company installations on the surveyed premises.

12.___ Governmental Agency survey-related requirements as specified by the client.

13.___ Significant observations not otherwise disclosed.

14.___ Observable evidence of earth moving work, building construction or building additions within recent months.

15.___ Any changes in street right of way lines either completed or proposed, and available from the controlling jurisdiction. Observable evidence of recent street or sidewalk construction or repairs.

16. ___Observable evidence of site use as a solid waste dump, sump or sanitary landfill.

17. ___________________________________________________

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Note: This set of brochures is also available from the National Society of Professional Surveyors, a Member Organization of ACSM. The first set is complimentary and additional sets are available at U.S. $3.00 per set.

To obtain a set, please contact:

National Society of Professional Surveyors
c/o American Congress on Surveying and Mapping
5410 Grosvenor Lane, Suite 100
Bethesda, MD 20814-2144
Phone: 301-493-0200   Fax: 301-493-8245

E-mail address:  mailto:nsps@mindspring.com#nsps@mindspring.com