UTM
UTM
Uniform strips
Scalable coordinates
Globally consistent, most popular projection/coordinate system for regional to global
scale geospatial data (i.e. satellite images global scale datasets USGS/EDC)
UTM
UTM Zones for the US
UTM coordinates on topo maps are usually abbreviated (false northing-easting removed)
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UTM
State Plane Coordinate System (SPC)
UTM coordinates on 1:24,000 7.5’ USGS topo maps shown with blue tics
SPCS was developed by US Coast and Geodetic Survey (Coastal Survey)
and was based on US land surveys (1933)
- Most popular planar coordinate system for County/City data, US only
- Muehrcke claims in its “now largely obsolete” – NOT!
Base: North American Datum 1927/83 [NAD27 (ft) / NAD83 (m)]
local (NAD27) vs. geocentric (NAD83: GPS compatible)
125 State Plane zones (for CA: zones I-VI)
Orientation dependent on state shape (CA: Lambert Conformal Projection)
- Each state is broken into zones to minimize distortions
- Zones defined based on state boundaries
- Each zone is a planar grid with a max. error: 1 part in 10,000
False origin 2,000,000 feet west of central meridian, State Plane coordinates
are always positive values
Used by primarily government/land surveyors, permanent recording of land
surveys, state planners, highway engineers, utility companies
Most “accurate” locational reference system, best for working with local to
state-sized areas
State Plane
State Plane
Each state define with zones, WI shown
below for example
• Black tic marks outside of map neatline,
usually not abbreviated
• Notation
Zones are irregular shape, delimited based
on US land survey baselines and state
boundaries
– 1 440 000 feet E, 330 000 feet N, CA, Zone V
– Always positive, in feet, and increase to the East
and to the North
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Metes-and-Bounds
State Plane (SPCS)
(Zonal locational reference system)
Used to define boundaries for settled land in America prior to US land survey
- Prior to 1800 the US was mostly unoccupied areas
- Unsystematic, sometimes very unsystematic, asymmetric parcel boundaries
Land partitions were defined as they became available for settlement in the West
- “homesteads” occupied the best land
Base: North American Datum
NAD27 (ft) / NAD83 (m)
Properties were defined based on boundaries and points apparent in the environment
- Trees, rocks
- Streams, Rivers (French “Long Lots” of Louisiana)
Local (27) vs. Global (83)
GPS can read SPCS zones
but are only comparable with
NAD83 (meters)
Metes and Bounds (Louisiana “Long Lots”)
Boundaries translated into bearings and distances formed legal land claims and were
incorporated into deeds and records, and later into the surveys of US land survey
baselines.
- Contemporary issues arrise regarding interpretations of descriptions
- “cartographic archiology”
- Streams move, trees grow, and magnetic compass headings change!
Metes and Bounds
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USPLS
Metes and Bounds
•
Initiated by the 1785 Land
Ordinance Survey Act after the
Revolutionary War and the cession
of western territories
•
Ohio was the first state to adopt it,
applies to areas West of Ohio
•
USPLS was the first systematic wide
aerial coverage survey for the US
•
USPLS was created out of the need
to inventory public lands for
distribution to settlers and for
taxation
•
Conducted in 34 separate surveys
which remain legal today
•
Based on the original “Metes and
Bounds” land partitioning system
Linklater, A. 2002. Measuring America.
Walker & Co. NY. ISBN 0-8027-1396-3
PLS
US Public Land Survey (USPLS)
Each survey zone consists of:
- Baseline running E-W = “Township”
- Prime meridian running N-S = “Range”
* Zonal locational reference system (“Township and Range”)
Township and Range lines divide the US
every six miles E-W and N-S
Each US survey zone has:
US was mapped with systematic survey zones, subdivided like a grid
- A base-line running E - W = “Township”
- A prime meridian running N - S = “Range”
- 6 mi x 6 mi blocks are called Townships
(just to add distinctly American duality!)
Township and Range
- The 1 mi x 1 mi blocks (within each 6 mi
x 6 mi Townships) are called Sections
-
Range lines: every 6 miles N - S along the base line
Township lines: every 6 miles E-W along the prime meridian
6 x 6 mile area = a “township”
Township is further subdivided into 36 “sections”, each section is
broken down into quarter sections
- ¼ x ¼ section = ~ 40 acres (Homestead Act., “forties”)
- “Lots” are the smallest subdivision, 40s are broken into lots where there
are streams/lakes or irregularities
- The 1 mi x 1 mi Sections can be
subdivided into “Quarter Sections” ( ¼ mi
x ¼ mi) which are ~ 40 acres (as per
Homestead Act.)
Properties, parcels, in PLS are
usually specified by N-S-E-W within
Quarter Sections
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Not all Townships match the idealized measurements
- Errors in measurement from many sources necessitated “adjustments”
- “Correction lines” (standard parallels) were used to compensate for
measurement distortions
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34 USPLS Principal Meridians and Baselines
USPLS integrated previous ownership boundaries from Metes-and-Bounds
property boundaries (East of Ohio)
USPLS Township & Range offset to accommodate boundaries, so resulting
coordinates and regular
Why surveyors are expensive, why property
disputes can occur
US Public Land Survey (USPLS)
Who uses USPLS?
- Primarily used by surveyors, tax assessors, land registers etc.
- BLM (Bureau of Land Management) for surveying public land
Shown as red-black lines, and red numbers, on USGS 7.5’ minute topo maps
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Cadastral Map
(Muerke and Campbell differ on this, but not seriously)
• Records of legal land ownership are recorded in the “register”, which
references the cadastral map for the city (or county)
• Tax Assessor’s Office usually maintains the register, and updates the map
• Most cadastral maps are now in CAD but gradually being converted to GIS
Latitude (parallels)
• Measured 90˚ N (+) and 90˚ S (-) from the equator
• Degree are subdivided: 60 seconds in a minute, 60 minutes in a degree
• Equator is 0˚ for latitude measured (0˚ to 90˚) N or S
Note: The equator is a great circle
• 1˚ latitude is ~ 69 mi (111 km)
CAD -> GIS conversion is a small industry in and of itself due to the costly
mess of resolving discrepancies
- State certified surveyors are expensive (time = $)
- Needs to be periodically revised and updated
Graticule (Lat/long grid)
The axis of earth’s rotation points towards Polaris
North, or “up”, provides the basis for our reference system
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Earth is not a perfect sphere
Ellipsoid
Rotation generates centrifical force, earth’s
insides are fluid
The sphere swells at the equator, the pulling
force from earth’s spin decreases towards the
poles
- flattening
Longitude
Length (km) of
Length of (km)
1 degree latitude 1 degree longitude
Meridians converge at poles, longitude is
measured by ...
1˚ longitude at the equator ~ 69 miles (111 km)
1˚ longitude at the poles = 0 miles/km (a point)
x˚ distance: cosine of (x˚ lat.) * length (Eq.)
The “reference ellipsoid” is used for surveying
heights, reference to a standard enforces
uniformity and compatibility among
measurements
Geoid
The ellipsoid is not smooth either, earth is actually lumpy
Geodesist, and Geophysicists, measure variations in earth’s gravitational field to
better define the Geoid
- Earth’s “equigravitational surface” varies over space and time
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