quality:corruption, structural:summarization, information:filtering, information:extraction
Design

These adjustments are done at two different scales. At the small scale (within a township) it is done by starting the sectional surveys (township "subdivisions") in the southeast corner and moving progressively toward the northwest corner. The algorithm used is to move northward to establish the six easternmost sections (and quarter-sections), then move west at one mile intervals, parallel to the eastern boundary of the township, repeating this process, until the western side of the township is reached. The result of this is that the northernmost and westernmost tiers of sections—11 in all—are thus allowed to deviate from one square mile, but the other (southeasterly-most) 25 sections are not. This method accommodates the curvature problem within a township and also allows for any errors made during the surveying—which were nearly unavoidable because of the physical difficulty of the work and the crude equipment used—without overly compromising the basic rectangular nature of the system as a whole. At the larger multiple township scale, the standard parallels developed at the establishment of the baseline, so that townships widths do not continually decrease as the grid proceeds north (and is in fact the primary reason for their establishment). Thus, corrections for curvature of the Earth exist at two separate spatial scales—a smaller scale within townships and a larger scale between multiple townships and within standard parallels.