Presentation on theme: "“Public Land Survey System (PLSS)” Surveys of the Public Lands Lecture 18."— Presentation transcript:
“Public Land Survey System (PLSS)” Surveys of the Public Lands Lecture 18
Lecture Outline Introduction System Outline and Units System Components Designations PLSS and LIS Required readings: 22-1 to 22-13, 22-17, 22-20, Required Figures: 22-1 to 22-3, 22-6, 22-8
Introduction Public Lands : areas that have been subject to administration, survey, and transfer of title under the public-lands laws of the US since 1785 only 72% of the US in 30 states constitute the public land surveys. See fig 22-1 Why was the system created ? Low accuracy reasons: inexperienced surveyors, budget, no check up or supervision, instruments, non permanent objects for corners. Two legal principles: Boundaries are unchangeable Corners are the true locations, whether or not in the place shown in the field notes.
System Outline and Units Boundaries are meridians and parallels. Area is divided into quadrangles (tracts) 24 mi x 24 mi Each quadrangle is divided into 16 townships, 6 mi x 6 mi Each township is divided into 36 sections, 1 mi x 1 mi division of sections into fractions, 1/2, 1/4, etc. as needed Surveys proceeded from south to north, and from east to west, errors accumulate in the north and west sections. Units: 1 ch = gunter’s chain = 66 ft = 100links (lk) 1 mile = 80 ch 10 ch 2 = 1 acre 1 section = 80 ch x 80 ch = 640 acres
System Components Initial Point : A point of precise location, done with astronomical means. Starting point in a new area. Principal Meridian (PM): A line in the direction of the true north passing by the Initial point and extended to area limits, marked each 1/2 mile (40 ch) Base Line : A true parallel of latitude extended east and/or west to area limits. Marked each 1/2 mile (40 ch) Standard Parallels: True parallels of latitude, 24 mi apart, marked each 40 ch. Numbered north or south of Base line: third standard parallel north. Guide Meridians (GM) : Meridians at 24 mi intervals from principle meridian, numbered east/west of PM, Fourth guide meridian west. They run north from Base line or standard parallels, not south.
Closing Corner(CC): intersection of GM and standard parallel or Base Line Standard Corners (SC) : corners at 24 mi from PM or GM. Will not coincide with CC because of meridian convergence. All the above mentioned components are on tract boundaries Range Lines : meridians each 6 mi, run north, marked each 1/2 mi Township Lines : east-west, connect 6 mi marks on PM, GM, and ranges, they are not necessarily parallel to latitude. Range and Township lines are township boundaries Sections are formed by connecting the marks at 1 mi intervals. Quarter sections are formed by connecting the 1/2 mi marks. Witness Corners (WC): Markings on adjacent objects. Lost Corners: Restored by equation: x = X (d/D), example 23-3
Designations Townships: think of the system as X, Y. The X being R (range) either E or W of certain Principle Meridian. The Y being the T (township or tier) either N or S of base line. For Example: T7S, R4E, 6th PM Sections : There are 36 section in a township, numbered 1 to 36 starting at the NE corner. Designated by numbers. For example: Sec 6, T 2 S, R 3 E, 6th PM Half, quarter, and quarter-quarter sections: designated by their location in the section: N S, or E W. Examples: The SE1/4, NE1/4, Sec. 14, T 3 S, R 9 W, SBM. E1/2 of NE1/4 of sec 20, T 5 N, R10 E, Indian PM.
PLSS and LIS The Bureau of Land Management is developing a LIS system to facilitate the management of the public lands. The PLSS point locations will serve as the positional components necessary for correlating all other information in the LIS.