Survey Retracement & Analysis Software

Typical Applications

BOUNDARY RETRACEMENT - When a retracement of a previous survey is required, existing monuments must be verified and lost monuments replaced. If a map or deed exists for which some corresponding monuments have been found in the field then it is possible to analyze how the found monuments relate to the map. A field survey is performed locating existing monuments from which coordinates are calculated for the monuments based on the field measurements. The map may be calculated on some arbitrary coordinate system based on the record bearings and distances. This establishes map coordinates at the corners and verifies the mathematical correctness of the map. The points and the map points are now available on unrelated coordinate systems with a dual set of point numbers for common locations. All of the points from the two systems are combined in a coordinate data text file.

Run the Triad program and enter the point numbers of corresponding locations. Triad will pair up the coordinates of the map points with the coordinates of the found monuments and instantly find the best fit for rotation, scale, and translations. The solution for the transformation will indicate the best rotation between the map and the field survey and the best scale factor to be applied to the map distances that correspond to the field measured distances. You may then analyze the residuals, use the error detection routine, reject bad monuments, and re-process the solution as necessary. After a solution is determined that represents the best retracement of the survey, Triad can create new points by transforming all of the points from the map to the field survey coordinate system. Alternately, the field coordinates may be best fit to the map.

CORNER SEARCHING - In the course of a BOUNDARY RETRACEMENT, as described above, it may be helpful to use the found monuments to develop search areas for monuments not yet located. Triad will allow you to estimate the accuracy of the search area from the Radial Standard Deviation.

PUBLIC LAND SURVEYS - Triad can be used in the retracement of sectionalized lands to determine the proportional length of the government chain and the deviation of the compass (known as indexing). This may be very useful for estimating the proximity for corner searching. Note, calculate the map (plat) coordinates in chains then the resulting scale factor determined by the program will be equivalent to the length of the government chain.

GRANT BOUNDARY ADJUSTMENT - Triad automatically performs a Grant Boundary Adjustment as described in the Manual of Instructions for the Survey of Public Lands when new points are calculated that begin and end at two fixed points in a solution. Triad will rotate, translate, and proportionately adjust record measurements in the same manner as prescribed for public land surveys.

GPS & CONVENTIONAL CONTROL SURVEYS - Adjusting field measurements to fit existing control points without verification may distort good work. Avoid this by computing a minimally constrained adjustment of the field measurements to obtain preliminary coordinates. Then, use Triad to fit these coordinates to the published or accepted coordinates of found control points to verify consistency and check for problems before performing a constrained adjustment.

SUBSIDENCE & EARTH MOVEMENT - Establish a control network outside of the study area on stable ground. Perform a field survey from time to time locating the monitoring points to track subsidence relative to the outside control network. Using Triad, fix the outside control and set the monitored points inside the study area free. Compute a transformation solution to fit earlier observed positions to later observed (new positions) of monitored points. The actual movement of the monitored points will be indicated by the residuals.

DATUM TRANSFORMATIONS - Use Triad to compute local transformations in state plane coordinates from the North American Datum of 1927 (NAD27) to North American Datum of 1983 (NAD83). Assuming sufficient common control points, this will provide an accurate and quantifiable solution.

GIS - Use Triad to create a mosaic of parcels by hooking subdivision maps and boundary surveys together via common points. Then, constrain the composite mosaic to best fit known ground control.

Triad can determine the positions on a best fit straight line for a row of monuments.

Tel. 805-964-3520