TPC provides the tools necessary to perform a survey that meets the 2011 MINIMUM STANDARD DETAIL REQUIREMENTS FOR ALTA/ACSM LAND TITLE SURVEYS (effective February 23, 2011) as adopted by American Land Title Association and National Society of Professional Surveyors.
These surveys are described as follows on the ALTA web site www.alta.org/standards/standards.cfm.
"For a survey of real property and the plat or map of the survey to be acceptable to a title insurance company for purposes of insuring title to said real property free and clear of survey matters (except those matters disclosed by the survey and indicated on the plat or map), certain specific and pertinent information shall be presented for the distinct and clear understanding between the client (insured), the title insurance company (insurer), and the surveyor (the person professionally responsible for the survey)."
ALTA.drt - this template includes many of the minimum drawing requirements such as north arrow, scale bar, etc. It also contains the certificate required if your survey precision complies with the minimum standard of 0.07 FT +- 50 PPM. If the relative positional accuracy of your survey exceeds these limits, you can replace the certificate included in this template with the certificate found in the pre-defined ALTAExcd.dxf drawing object.
The program folder\Blocks\ALTA\ folder contains blocks you can insert into your drawing as part of the minimum requirement.
ALTACert.dxf - The certificate of compliance with the minimum standard. You will need to edit the text in this block for each survey. This certificate is already included in the ALTA.drt template.
ALTAExcd.dxf - The certificate of exceeding the minimum standard. You will need to edit the text in this block for each survey. If the relative positional accuracy of your survey exceeds the minimum limits, you can replace the certificate included in the ALTA.drt template with this block.
The 2011 standard defines RPP in section 3E as follows: "Relative Positional Preceision" means the length of the semi-major axis, expressed in feet or meters, of the error ellipse representing the uncertainty due to random errors in surveyed property relative to the monument, or witness, marking any other corner of the surveyed property at the 95 percent conficent level.
Section 3Ev further states that "The maximum allowable Relative Positional Precision 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)."
The Least Squares adjustments include pre-defined APriori values that contain the Least Squares solution to this stated Relative Positional Accuracy at the 95% confidence level. If you do a Least Squares traverse or network adjustment using these pre-defined APriori values, the solution TPC computes will meet this standard.
Both the Adjusted Coordinates and Ellipse reports include the semi-major ellipse value (Su) at the 95 percent confidence level.
You should check this value to ensure it meets the 2 cm (0.07) limit.
Since RPP includes a parts per million component, TPC includes a Relative Positional Precision report that accounts for the line of sight distance between each corner be adjusted and the fixed control points in the survey. Although this does not allow the flexibility to compute RPP between any 2 corners, it does give a more accurate estimate of RPP. See Relative Positional Precision.
The 2005 ALTA/ACSM referred to RPP as 'Relative Positional Accuracy' stated as 0.07 feet (or 20 mm) + 50 PPM. It describes two tests as:
(1) comparing the relative location of points in a survey as measured by an independent survey of higher accuracy or
(2) the results of a minimally constrained, correctly weighted least square adjustment of the survey.
The 2011 standard is more explicit about RPP and therefore is the preferred standard.
Adjusting a Traverse
Least Squares APriori Settings
Personal, Premium, Professional - include templates and blocks
Premium, Professional - include traverse and network Least Squares Adjustment