Hawth's Analysis Tools for ArcGIS

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 Summary

PLSS POINT FINDER
Input: a table containing distances to the southern and western section boundaries in a PLSS layer, and a polygon PLSS layer
Output: a point shapefile of the resolved locations
Features:

  • (this is a specialist tool designed to perform a specific function and may not be more generally useful)
  • given a PLSS (township, range, section) polygon layer, and a table of measured distances to the southern and western edges of a specific section, this tool will resolve the x and y coordinates of this point

Limitations:

  • the reference layers MUST be in a projected coordinate system (this tool will produce biased results if a geographic coordinate system is used)
  • this tool is designed to work with shapefiles, other vector formats have not been tested

 Help

Getting started The polygon PLSS reference layer and the table containing surveyed distances must be loaded into ArcMap before starting this tool. The PLSS layer must have the following three integer fields: one coded with the township number, one coded with the range number, and one with the section number. The table of surveyed distances must have these same three integer fields (they may be named differently, but they must represent the township, range and section numbers). The surveyed distances table must also contain: i) a unique ID field (integer) that will replicated in the output point shapefile so that a join can be made between the two tables, ii) the distance from the western boundary of the section (in meters or feer) in a due east direction, iii) the distance from the southern boundary of the section (in meters or feet) in a due north direction.

Output The output of this tool is a point shapefile ("survey_points.shp") representing the resolved coordinates of the surveyed distances. A secondary output is a line feature layer ("validation_lines.shp") that is intended to be used as a validation tool and contains two straight lines for each resolved point: one line depicting the distance from the southern boundary of the section, and one line depicting the distance from the western boundary of the section. By displaying these lines with the resolved points, it will be possible to visually inspect the output of the tool for consistency in an expedient manner. This may be particularly useful for identifying problematic records, for instance where a highly irregular section boundary must be resolved manually. The tool also creates an error log ("error_log.txt") to record any problems encountered during processing, which is also intended to be useful for validating the results of the tool. Because there are three output to this tool, the form requires the user to specify a new, empty folder to which the output is directed.

How this tool works This tool will process all records in the surveyed distances table (which can be a DBF file, a CSV file, or an Access database table that has been loaded into ArcMap). For each record in that table, the tool begins by locating the correct section using a tabular query on the township, range and section numbers (this should return a single polygon). The tool then identifies the southern and western boundaries of the polygon, shifts those lines by the two distances specified in the table (a eastern distance for the west boundary, and a northern distance for the southern boundary), and finds the resulting intersection of the shifted lines. This is the resolved point location that is written to the output shapefile.

If the section does not exist, than an error message is written to the error log so that this record can be verified. If more than one polygon is returned as having the same township, range and section number, then the first polygon returned is used, but a records is also written to the error log so that this result can be verified.

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