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Public Land Survey System
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==Survey design and execution== [[File:Systemic numbering in the Public Land Survey System.svg|thumb|400px|Illustration of the system from the National Atlas]] ===Commonly used terms=== * ''Aliquot part'': A terse, hierarchical reference to a piece of land, in which successive subdivisions of some larger area are appended to the beginning of the reference. For example, SW1/4 NW1/4 S13, T1SR20E refers to the southwest quarter of the northwest quarter of section 13 of Township 1 South Range 20 East (a 40-acre parcel). See further discussion below. * ''[[Baseline (surveying)|Base Line]]'': A parallel of latitude, referenced to and established from a designated initial point, upon which all rectangular surveys in a defined area are based. Also spelled ''baseline''. * ''BLM'': Bureau of Land Management, the successor agency to the General Land Office * ''[[Cadastral]]'': Having to do with the boundaries of land parcels. * Corner: The point of intersection of any two actual or potential survey lines, defining one corner of a rectangular land parcel. * ''Lot'': A subdivision of a section which is not an aliquot part of the section but which is designated separately. A lot is typically irregular in shape, and its acreage varies from that of regular aliquot parts. * ''[[Initial point]]'': The starting point for a survey; the intersection point of the Principal meridian and the Base line in a given region. * ''[[Land grant]]'': Historically a land grant is an area of land to which title was conferred by a predecessor government, usually English/British, Spanish or Mexican, and confirmed by the U.S federal courts after the territory was acquired by the United States. * Monumentation: Placement and/or marking of physical objects on the ground to mark survey points and lines. * ''Original survey:'' The first official government survey in a given area. Unless fraud is proven, the original survey is legally valid and binding, regardless of any surveying errors that may have occurred. All subsequent subdivision, sale, etc. must proceed from the original survey. In the United States, most original surveys were done under contract with the General Land Office. * ''[[Principal meridian]]'' (PM): A true meridian running through an initial point, which together with the baseline form the highest level framework for all rectangular surveys in a given area. The list of all principal meridians is given below. * ''[[Public domain (land)]]'': Land owned and managed by the Federal government. Synonymous with public lands. [[National Park Service|National Parks]] and [[National forest (United States)|National Forests]] are a large part of the public domain land today. The original public domain included the lands that were turned over to the Federal Government by the original thirteen states and areas acquired from the native Indian tribes or foreign powers. * ''Range'' (Rng, R): A measure of the distance east or west from a referenced principal meridian, in units of six miles. * ''[[Section (United States land surveying)|Section]]'': An approximately one-square-mile block of land. There are 36 sections in a survey township. * ''[[Survey township|Township]]'' (Twp, T): A square parcel of land of 36 square miles, or a measure of the distance north or south from a referenced baseline, in units of six miles. * ''Witness'': Any marker set on the ground that marks or represents some other nearby object or location of surveying importance, such as a corner. For example, a bearing tree is a witness to a survey corner. ===Design=== The surveying of any regional area, such as a state or multiple states, is a multi-step process. First, two controlling survey lines are established: a baseline which runs east–west and a principal meridian which runs north–south. The locations of the two are determined by a previously chosen [[Geodetic datum|initial point]], where they originate and thus intersect. Next, at a defined distance interval, commonly 24 or {{convert|30|mi|km}} depending on the year and location, standard parallels of latitude are established parallel to the baseline. The meridian, baseline and standard parallels thus established form a lattice upon which all further surveying is then based. Subsequent work divides the land into [[survey township]]s of roughly {{convert|36|mi2}} or {{convert|6|mi}} on each side. This is done by the establishment of township and range lines. Township lines run parallel to the baseline (east-west), while range lines run north–south; each are established at 6-mile intervals. Lastly, townships are subdivided into 36 [[section (United States land surveying)|sections]] of approximately {{convert|1|mi2|acre km2}} and sections into four quarter-sections of {{convert|0.25|mi2|acre km2}} each. The intersection of a township line (or baseline) with a range line (or principal meridian) constitutes a ''township corner'', of a section line with any other type of line a ''section corner'', and a point halfway between any two section corners a ''quarter corner''. The federal government typically surveyed only to this quarter-section level, the subdivision of smaller parcels being carried out subsequently by private surveyors after original sale. Because the survey design is two-dimensional (rectangular), while the actual Earth is three-dimensional (approximately spherical and topographically), adjustments to land areas must be made periodically to prevent error propagation; not all sections can be one square mile nor can all townships be exactly 36 square miles. More specifically, all north–south running lines (all range lines and half of all section lines), as with the prime meridian, are always established with reference to true, geodetic north. But it is a physical impossibility to meet this condition and still maintain a rectangular land grid, because such lines converge on the north pole. 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. [[File:Theoreticaltownshipmap.gif|thumb|left|200px|Figure 2. This [[United States General Land Office]] diagram shows the theoretical sectioning of a standard [[survey township]].]] A specific and terse location descriptor is always used, in which the townships and sections are indexed based on (1) the township's position relative to the initial point, (2) the section's location within the designated township, and (3) the principal meridian reference. Township, range, and section are abbreviated as T, R, and S, respectively, and [[Cardinal direction|cardinal bearings]] from the initial point by N, S, E, and W; each principal meridian also has its established abbreviation. Thus, for example, the description "T1SR20E S13 MDM" reads as follows: Township 1 South, Range 20 East, Section 13, Mount Diablo Meridian. That is, the 13th section in the first township south of the baseline (in this case, the Mount Diablo Baseline) and the 20th township east of the principal meridian (the Mount Diablo Meridian). Since township and range lines are six miles apart, the "T1SR20E" part of the designation instantly places the location somewhere between zero and six miles south of the baseline, and 114 and 120 miles east of the principal meridian. Knowing how sections are numbered within townships, section 13 is identified as therefore occupying the one square mile located 2 to 3 miles south, and 119 to 120 miles east, of the Mount Diablo initial point (in central California). Note that the sections within a township are numbered in an unconventional, [[Boustrophedon]] pattern (Fig. 2), in which alternating rows are numbered in opposite directions, starting from section 1 in the northeast corner and ending with section 36 in the southeast corner, as per Figure 2. Therefore, section 13 is adjacent to the eastern range line of the designated township. Numbering in this pattern ensures that numerically sequential sections within the same township are physically adjacent and share colinear boundaries. [[File:Kent-1885-twp-co.jpg|thumb|left|Figure 3. [[Kent County, Michigan]] in 1885 as a PLSS example, showing 24 named townships and sectional subdivisions.]] ===Measurement=== Distances were always measured in chains and links, based on [[Edmund Gunter]]'s [[Chain (unit)|66-foot measuring chain]]. The chain – an actual metal chain – was made up of 100 links, each being {{convert|7.92|in}} long. Eighty chains constitute one U.S. survey mile (which differs from the international mile by a few millimeters). There were two chainmen, one at each end, who physically made the measurements, one of them typically also acting as "compassman" to establish the correct bearing at each chain placement. In forested areas, it was essential for rapid progress and accuracy that the lead chainman follow the correct bearing at all times, since no straightening of the chain was possible without backtracking around trees and re-measuring. It was also necessary to keep the chain level, since all surveying distances are based on the horizontal, not slope, distance. In steep terrain, this meant shortening the chain, raising one end of the chain relative to the other, or both. In areas where measuring by chain was not possible, such as extremely steep terrain or water obstructions, distances were calculated by [[triangulation]]. ===Monumentation=== Monumentation is the establishment of permanent on-the-ground objects that mark exact locations of surveyed points and lines. They are the legally binding markers used for setting property lines and as such are the culminating work of any survey. They consist of both corner monuments as well as nearby accessory objects that "witness" to them. Witness objects allow subsequent surveyors and landowners to find the original corner monument location should the monument be destroyed. It was not uncommon for [[Squatting|squatters]] or [[Homestead Acts|homesteaders]] to destroy corner monuments if they felt the [[Land patent|patenting]] of the land would threaten their residence on it. For this reason, destruction of corner monuments, or their accompanying witness objects was, and still is, a federal offense. At corners, ''corner monuments'' are established to mark their exact location on the ground. As with most PLSS specifications, those for corner monumentation also changed over time. In the 19th century, monuments were commonly a rock pile, a wooden post, or a combination of the two. Trees could be used if the corner happened to fall at the exact spot where one grew. In the 20th century, steel pipes with caps, supported by mounds of rock, became required (for example, see Fig. 4). Witnesses can be trees, rocks, or trenches dug in the ground; their exact locations relative to the corner, and the markings made on them, are also recorded in the surveyor's official [[fieldnotes]]. Witness trees at corners are more commonly referred to as bearing trees because the exact distance and bearing from the corner, to them, was required to be recorded (as well as the [[taxon]] and diameter). [[File:YoseBoundaryMon.JPG|thumb|200px|right|Figure 4. The cast and stamped cap on a corner monument pipe, in western Yosemite National Park, placed in 1905 during the Park boundary resurvey.]] On each bearing tree, two blazes were typically required, one about chest height and easily visible, and one at ground level (in case the tree were illegally cut, the stump remaining). On the exposed wood of the blaze, surveyors were required to inscribe, with wood chisels, township, range and section information, on typically either two or four bearing trees, if they were within some reasonable distance of the corner (unspecified early on but later set at a maximum of 3 chains (178 feet, 60 meters) away). Bearing trees are of vital importance not just for these land boundary purposes but also for their use by ecologists in the estimation of historic forest vegetation conditions before settlement and large scale human disturbance of the land. The data provided in these surveys provide a definitive estimate of original forest composition and structure, and the data have accordingly been used heavily. Along survey lines, monumentation was much less elaborate, consisting primarily of only the blazing and some simple scribing of trees directly on, or very close to, the survey line. The purpose was to help retrace a surveyed line should that become necessary. It was also additional proof that the line had in fact been run correctly, especially in those cases where the blazed line tree's pertinent information (species, diameter and distance from previous corner) was recorded in the fieldnotes, as was often required. ===Information to be recorded=== Records kept by the surveyors during the execution of the work varied over time. Furthermore, how well individual surveying parties actually met the requirements or recommendations at the time, also varied. The following is a list<ref>{{cite book |url= https://books.google.com/books?id=1X1VAAAAMAAJ&q=theory%20and%20practice%20of%20surveying%201913&pg=PP1 |first1= J. B. |last1= Johnson |first2= Leonard S. |last2= Smith |title= The Theory And Practice of Surveying |publisher= Wiley & Sons |location= New York |edition= 17th |year= 1913 |oclc= 221005352 |access-date= 2020-10-19 |archive-date= 2022-04-18 |archive-url= https://web.archive.org/web/20220418163608/https://books.google.com/books?id=1X1VAAAAMAAJ&q=theory%20and%20practice%20of%20surveying%201913&pg=PP1 |url-status= live }}</ref> of the more commonly required landscape and surveying items that were either required or requested be noted, over much of the nineteenth century. * The precise length of every line run, noting all necessary offsets therefrom, with the reason and mode thereof. * The species and diameter of all "bearing trees", with the course and distance of the same from their respective corners; and the precise relative position of witness corners to the true corners. * The kinds of materials (earth or stone) of which mounds are constructed—the fact of their being conditioned according to instructions—with the course and distance of the "pits", from the centre of the mound, where necessity exists for deviating from the general rule. * The name, diameter, and distance on line to all trees which the line intersects. * The distance at which the line first intersects and then leaves every settler's claim and improvement; prairie; river, creek, or other "bottom"; or swamp, marsh, grove, and wind fall, with the course of the same at both points of intersection; also the distances of ascents, summits, and descents of all remarkable hills and ridges, with their courses and estimated height, in feet, above the level land of the surrounding country, or above the bottom lands, ravines, or waters near which they are situated. * All streams of water which the line crosses; the distance on line at the points of intersection and their widths on line. In cases of navigable streams, their width will be ascertained between the meander corners, as set forth under the proper head. * The land's surface, whether level, rolling, broken, or hilly. * The soil, whether first, second, or third rate. * The several kinds of timber and undergrowth, in the order in which they predominate. * Bottom lands were to be described as wet or dry, and if subject to inundation, state to what depth. * Springs of water, whether fresh, saline, or mineral, and the course of the stream flowing from them. * Lakes and ponds, describing their banks and giving their height, and also the depth of water and whether it be pure or stagnant. * Towns and villages; Indian towns and wigwams; houses or cabins; fields, or other improvements; sugar tree groves, sugar camps, mill seats, forges, and factories. * Coal banks or beds; peat or turf grounds; minerals and ores; with particular description as to quality and extent, and all diggings therefore; also salt springs and licks. All reliable information that could be obtained respecting these objects, whether they be on the immediate line or not, was to appear in the general description at the end of the notes. * Roads and trails, with their directions, whence and whither. * Rapids, cataracts, cascades, or falls of water, with the height of their fall in feet. * Precipices, caves, sink-holes, ravines, stone quarries, ledges of rocks, with the kind of stone they afford. * Natural curiosities, interesting fossils, petrifactions, organic remains; ancient works of art, such as mounds, fortifications, embankments, ditches, or objects of like nature. * The variation of the needle must be noted at all points or places on the lines where there is found any material change of variation, and the position of such points must be perfectly identified in the notes. The following table indicates some distance and area conversions in the PLSS: {| cellpadding="2" cellspacing="5" style="margin:3px; border:3px solid #99aacc; margin:auto;" |- !bgcolor="#99aacc" colspan="7"| |- ! !align="right"|Dimensions<br/>(miles) !align="right"|<br/>(mi<sup>2</sup>) !align="right"|Area<br/>(acres) !align="right"|<br/>(m<sup>2</sup>) !align="right"|<br/>(km<sup>2</sup>) !align="left"|Notes |- ! bgcolor="#87ceeb" colspan="7" | |- valign="top" !align="right"|Quadrangle/check |align="right"|24 by 24 |align="right"|576 |align="right"|{{convert|576|mi2|acre|0|disp=number}} | |align="right"|{{convert|576|mi2|km2|sigfig=3|disp=number}} |Usually 16 townships |- valign="top" !align="right"|Township |align="right"|6 by 6 |align="right"|36 |align="right"|{{convert|36|mi2|acre|0|disp=number}} | |align="right"|{{convert|36|mi2|km2|sigfig=3|disp=number}} |Usually 36 sections |- valign="top" !align="right"|Section |align="right"|1 by 1 |align="right"|1 |align="right"|{{convert|1|mi2|acre|0|disp=number}} | |align="right"|{{convert|1|mi2|km2|sigfig=3|disp=number}} |- valign="top" !align="right"|Half-section |align="right"|1 by {{frac|1|2}} |align="right"|{{frac|1|2}} |align="right"|{{convert|1/2|mi2|acre|0|disp=number}} |align="right"|{{convert|1/2|mi2|m2|sigfig=3|disp=number}} |align="right"|{{convert|1/2|mi2|km2|sigfig=3|disp=number}} | |- valign="top" !align="right"|Quarter-section |align="right"|{{frac|1|2}} by {{frac|1|2}} |align="right"|{{frac|1|4}} |align="right"|{{convert|1/4|mi2|acre|0|disp=number}} |align="right"|{{convert|1/4|mi2|m2|sigfig=3|disp=number}} | |- valign="top" !align="right"|Half of quarter-section |align="right"|{{frac|1|2}} by {{frac|1|4}} |align="right"|{{frac|1|8}} |align="right"|{{convert|1/8|mi2|acre|0|disp=number}} |align="right"|{{convert|1/8|mi2|m2|sigfig=3|disp=number}} |- valign="top" !align="right"|Quarter of quarter-section |align="right"|{{frac|1|4}} by {{frac|1|4}} |align="right"|{{frac|1|16}} |align="right"|{{convert|1/16|mi2|acre|0|disp=number}} |align="right"|{{convert|1/16|mi2|m2|sigfig=3|disp=number}} | | |}
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