GEO 221 L3& L4

NAD stands for ______________________ and the number refers to ___________________________ (for example, NAD 27 was adopted in 1927). As its name implies, this datum is only applicable to North America.

"North American Datum," the year it was adopted

USBGN has 3 categories for name changes:

1. Changes that conform to local usage 2. Changes from a derogatory name 3. Changes to eliminate duplication

The 4 aspects of developable surfaces:

1. Equatorial/normal 2. Transverse 3. Oblique 4. Polar

There are two main components of a planar coordinate system:

1. The map projections that make the conversion from the three-dimensional to the flat representation 2. The datum, which is where the coordinate system is centered.

Scale can be represented in three ways on a map, as a:

1. representative fraction (for example, 1:100,000), 2. scale bar 3. statement (also known as, verbal scale) (for example, one inch equals 1000 miles).

The west coast of the US is _____ time zones to the west of the Prime Meridian (PM) and ____ to the west of the US east coast

8, 3

Lambert conformal conic

A conic projection i which a cone intersects Earth as 2 parallels. The distortion on the map is reduces as you get closer to lines of tangency and increases the farther away you move from them. - It's commonly used for geospatial data about the US

Transverse mercator

A cylindrical projection with the tangency being the intersection between cylinder and Earth. Measurements are most accurate at that point and distortions are worst in the areas of the map farthest away from that point, to the east or west.

United States National Grid (USNG)

A grid system of identifying locations in the US. It measures coordinates in Meters, using values derived from UTM northing and easting. It also uses the UTM zone numbers in conjunction with smaller 100,000 meter gridded zones to derive location information. USNG accuracy ranges between 1000 meters and 1 meter. This is also known as the Military grid reference system (MGRS)

International Date Line

A line of longitude that uses the 180th meridian as a basis (but changes away from a straight line to accommodate geography). It marks the division between 24-hour periods and divides 1 day from another.

Affine transformation

A linear mathematical process by which data can be altered to align with another data source. * Calculates real-world X&Y coordinates * x=Ax+By+C * Y=Dx+Ey+F (74) * A,B,C,D,E,F are the values calculated initially by the procedure and applied to the mathematical formulae as coefficients. * First-order transformation

Easting

A measurement of so many units east or west of some principal meridian.

Northing

A measurement of so many units north or south of a baseline

Time zones

A method of measuring time around the world, created by dividing the world into subdivisions of longitude and relating the time in that subdivision to the time in Greenwich, England (Greenwich Mean Time (GMT))

Geographic Coordinate system (GCS)

A set of global latitude and longitude measurements used as a reference system for finding locations.

Root mean square error (RMSE)

An error measure used in determining the accuracy of the overall transformation of the unreferenced data

Features on the earth's surface, when represented on a globe, have four spatial characteristics:

Angles, projections, areas, distance

Compromise projections

Attempt to optimize all earth surface features, but do not preserve any of them. For this reason, compromise projections are used for visualization purpose only. Ex: The Robinson projection and the Winkel-Tripel projection

3 types of developable surfaces:

Conic, cylindrical, azimuthal

The State Plane Coordinate System (SPCS)

Grid-based system for measuring and determining coordinates of locations within the US. It uses NAD83 datum.

Contact for developable surfaces

How the surface 'touches' the reference globe is called contact. The point of contact is the location of least distortion - the projection is most accurate at that location.

Angles-conformal projections

If a projection preserves angles, it is call a conformal projection. These projections preserve angular relationships and shapes over small areas (the angles in a feature ultimately create its shape). In a conformal projection, any two lines on the map follow the same angle as the corresponding lines on the earth's surface. Conformal projections are used when angular relationships are important, such as for navigational or meteorological charts.

Latitude (parallels)

Imaginary lines on a globe north and south of the equator that serve as a basis of measurement in GCS.

another conformal projection, and perhaps one of the most recognizable projections

Mercator projection

Michigan GeoRef coordinate system

Michigan GeoRef was designed to be an alternative to the Michigan State Plane Coordinate System. Unlike the Michigan State Plane Coordinate System, which divides the state into three zones, Michigan GeoRef only has one zone. As mentioned earlier, the State Plane system uses a different projection depending on the shape/orientation of the state. However, Michigan GeoRef uses the Oblique Mercator projection, which represents the northwest/southeast orientation of the shape of the State of Michigan with greater accuracy.

Planar coordinate system

Model the earth as a plane, a flat surface. In a planar coordinate system, the irregular shape of the earth, which can be modeled as an ellipsoid, spheroid, or geoid is converted to a flat representation.

Two datums commonly used in the United States are

NAD27 & NAD83

NAD27

North American Datum of 1927 was developed for measurements of the US and North America.

What are the 2 types of coordinate systems?

Planar and geographic

An example of Distance- Equidistant projections

Plate Carrée projection, one commonly-used equidistant projection

Distance- gnomonic projections (also known as, true-direction or azimuthal)

Preserve direction from a central point. This point is where the projection is centered, which is also the tangent point. All gnomonic projections preserve direction from a central point. These projections are also called true-direction or azimuthal.

Areas-Equidistant projections

Preserve relative distances between points on the earth's surface. As you know, all maps 'shrink' the size of the earth, and scale is the measure of this reduction. However, the scale is not altered by the same amount at different locations. In other words, the ratio of distances between two points on the earth's surface and the distance on a map will vary at different locations. In an equidistant projection, scale along some lines will be preserved.

Projections- equivalent (equal-area) projections

Projections that preserve areas are known as equivalent (or equal-area) projections. In a map using an equivalent projection, the ratio of the actual size of two features, such as countries, is equivalent to the ratio of their sizes on the map.

Toponyms

Reflect important characteristics of the land and the people who inhabit it. In other words, place names are an important part of the cultural landscape, which geographers study to learn about people's influence on the natural and built environment. You can see that __________ reflect a place's history, culture, and physical geography.

When you're georeferencing an image, new locations for the image's pixels will need to be calculated, and in some cases new values for the pixels will need to be generated as well. This process is referred to as _______________.

Resampling

There are two types of contact for developable surfaces:

Secant and Tangent

United States Board on Geographic Names

Standardize the procedure for naming places in the United States.

An example of Areas-- equivalent (equal-area) projections

The Mollweide projection This is a classic example of distortion in maps

NAD83

The North American Datum of 1983 was developed for data for the US and North America.

WGS84

The World Geodetic System of 1984 datum used by the Global Positioning System for locating points worldwide on Earth's surface.

Geoid

The actual shape of Earth. It is a model that describes the true physical figure of the earth. It does not indicate the actual surface of the earth's crust (for example, it does not account for Mount Everest or the Mariana Trench) but instead, it is an imaginary reference figure that would be taken up by a worldwide sea level. In essence, it describes the shape of an imaginary ocean over the earth's surface with no topography, no waves, and no weather.

Secant

The developable surface intersects the reference globe at two lines.

Polar

The developable surface is centered on one of the poles.

Transverse

The developable surface is oriented east/west.

Olbique

The developable surface is oriented in a direction other than due north/south or due east/west.

Equatorial/normal

The developable surface is oriented north/south.

Tangent

The developable surface touches the reference globe along a single line (or a point if it is a planar projection).

Graticule

The grid of latitude and longitude lines.

Equator

The line of latitude that runs around the center of Earth and serves as the 0 degree line from which to make latitude measurements.

Degrees, minutes, and seconds (DMS)

The measurement system used in GCS

Geodesy

The science of the exact size and shape of planet earth.

Toponymy

The study of place names, including their origins, meanings, use, and standardization (referred to as applied ___________).

Map projection

The translation of locations on the 3D Earth to a 2D surface. It is a translation of coordinates and locations from their places in the real world to a flat surface

Universal Transverse Mercator (UTM) Coordinate System

This coordinate system applies to the entire world, which it divides into 60 north/ south zones. Additionally, the UTM system divides the United States into 10 zones.

T/F The inconsistent pulls of gravity cause the shape of the geoid to be dynamic - the geoid is always changing, and its undulations vary over time.

True

T/F The more accurate our geoid is, the better our GPS will operate and the more accurate our coordinate systems will be.

True

Military grid reference system (MGRS)

Used extensively by the military and by disaster relief organizations like the Federal Emergency Management Agency (FEMA)

State Plane Coordinate System (SPCS)

Used only in the United States. Used to provide a common reference system for surveyors and mappers. It divides the United States into 126 zones.

Ellipsoid

What the Earth's shape resembles- a smooth mathematical surface resembling a compressed sphere.

False easting

a measurement made east (or west) of an imaginary meridian set up for a particular zone

False northing

a measurement made north (or south) of an imaginary line such as is used in measuring UTM northings in the southern hemisphere.

First-order transformation

a type of transformation that's usually utilized in this procedure.

Developable surfaces

basic geometric shapes (a cone, cylinder, and plane) onto which the earth's shape is projected

Statement of scale

can be easy to understand, as it is just a written sentence of the ratio. As with all cartographic decisions, the map's purpose and potential audience are considerations for choosing how scale will be represented.

Representative fractions

can be useful because they do not have units. People can use distance measures such as miles or kilometers, and the scale would still be valid.

Datum transformation

changing measurements from one datum to measurements in another datum.

Meridians are the ________________ origin lines, yet they run _________________.

east-west, north/south

Universal Transverse Mercator (UTM)

grid system works by dividing the world into a series of zones (1-60) and then determining x and y coordinates for a location in that zone.

Longitude (meridians)

imaginary lines on a glove east and west of the Prime Meridian that serve as a basis of measurement in GCS.

A site's location is listed with the degree of ____________(N/S hemisphere) first, then ______________ (E/W hemisphere)

latitude, longitude

Planar coordinate system

models earth as a 2D object

Geographic (spherical) coordinate system

models the earth as a 3D object

Baselines are the ______________ origin lines, yet they run_____________.

north-south, east/west

UTM zone

one of the 60 divisions of the world set up by the UTM system, each zone being 6 degrees of lon. wide.

Control points

point locations where coordinates are known, used to align the unreferenced image to the source

Parallels and meridians cross at

right angles

Principal meridian

serve as origin lines for the township and range system in the surrounding area (similar to how the Prime Meridian serves as the east/west origin line for the latitude/longitude system).

Datum

specifies the model of the earth that was used to create the coordinate system, and where the coordinate system is centered. Datums essentially 'match' a coordinate system to a model of the earth's shape, such as an ellipsoid.

Decimal Degree (DD)

the fractional decimal equivalent to coordinates found using degrees, minutes, and seconds.

Prime meridian

the line of longitude that runs through Greenwich, England, and serves as the 0 degree line of longitude from which to base measurements.

A a scale bar is useful if

the map will be reproduced at a different scale (for example, imagine using a photocopy machine to enlarge or shrink the map). Because the scale bar would be enlarged or shrunk simultaneously with the map, the ratio represented on the scale bar would remain valid.

Georeferencing

the process of aligning an unreferenced dataset with one that has spatial reference information

Scale

the ratio of the size of objects on the earth's surface to their representation on a map.

Aspect for developable surfaces

the relationship between the axis of the earth and the axis of the projection.

Great circle distance

the shortest distance between 2 points on a spherical surface.

Spatial reference

the use of a real-world coordinate system for identifying locations.

Reproject

transform all of the datasets to conform to a common datum, coordinate system, and projection.

Conic

using a cone as their developable surface

Cylindrical

using a cylinder as their developable surface

Azimuthal

using a plane as their developable surface

Scaled

when the unreferenced images is altered during the transformation.

Skewed

when the unreferenced images is distorted or slanted during the transformation.

Translated

when the unreferenced images is shifted during the transformation.

Rotated

when the unreferenced images is turned during the transformation.