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) 1
UTM UTM coordinates on 1:24,000 7.5 USGS topo maps shown with blue tics State Plane Coordinate System (SPC) 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 Black tic marks outside of map neatline, usually not abbreviated Notation 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 Each state define with zones, WI shown below for example Zones are irregular shape, delimited based on US land survey baselines and state boundaries 2
State Plane (SPCS) Metes-and-Bounds (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) Local (27) vs. Global (83) GPS can read SPCS zones but are only comparable with NAD83 (meters) Properties were defined based on boundaries and points apparent in the environment - Trees, rocks - Streams, Rivers (French Long Lots of Louisiana) 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 (Louisiana Long Lots ) Metes and Bounds 3
Metes and Bounds USPLS 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 Each survey zone consists of: - Baseline running E-W = Township - Prime meridian running N-S = Range Township and Range lines divide the US every six miles E-W and N-S - 6 mi x 6 mi blocks are called Townships (just to add distinctly American duality!) - The 1 mi x 1 mi blocks (within each 6 mi x 6 mi Townships) are called Sections - 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? US Public Land Survey (USPLS) * Zonal locational reference system ( Township and Range ) US was mapped with systematic survey zones, subdivided like a grid Each US survey zone has: - A base-line running E - W = Township - A prime meridian running N - S = Range Township and Range - 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 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 4
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 34 USPLS Principal Meridians and Baselines 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 5
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 6
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 The reference ellipsoid is used for surveying heights, reference to a standard enforces uniformity and compatibility among measurements 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.) Length (km) of 1 degree latitude Length of (km) 1 degree longitude 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 7