Intro to digital mapping Final

 Remote sensing

the acquisition of information about an object or phenomenon using devices not in direct physical contact with what is being measured (ex. SONAR, LIDAR, Xrays)

Passive remote sensor

collects sunlight that bounces off the earths surface (space telescope with cameras)

Electromagnetic radiation EMR

energy emitted and absorbed by charged particles that exhibits wave-like behavior through space 

Active remote sensors

send out a signal and detects the bounce back. Data tends to be continuous and raster  (LiDAR- light detection and ranging)

Swat width

the measurement of the width of ground the satellite can image during one pass

Capabilities of a satellite sensor

temporal resolution, spatial resolution, spectral resolution, radiometric resolution 

Temporal resolution

how often the sensor can return to image the same spot on earth’s surface. TIME

Spatial resolution

the size of the smallest object that the remote sensor camera can detect. HOW ZOOMED IN CAN YOU BE

Spectral resolution

the bands and their wavelengths measured by the sensor along the electromagnetic spectrum. REFLECTANCE 

Radiometric resolution

a sensor's ability to distinguish between very small differences in the amount of electromagnetic energy (light, heat)

Relief displacement

the effect in aerial imagery in which tall items appear to lean outward from the photos center toward the edges. Stretching the natural effect of earths circular form

Orthophoto

image that has been corrected for the perspective of camera. Uniformed

Spectral resolution

the bands and their wavelengths measured by

the sensor along the electromagnetic spectrum

Thermal infrared

part of the electromagnetic spectrum that measures heat emitted from the Earth’s surface rather than reflected sunlight. It is used to determine surface temperature and works even at night

reflective infrared

shorter-wavelength infrared energy that comes from sunlight reflected off surfaces, similar to visible light

How does NDVI show data

Healthy vegetation appears in greens, stressed or sparse vegetation in yellow to brown, and water or non-vegetated areas in blue or very dark colors.

what reflects infrared the strongest

vegetation reflects the strongest

Ground truthing

verifying measurements at sample sites on the ground to ensure that you are interpreting images correctly

Visual image interpretation

 the process of examining information to identify objects in an aerial image

pattern

 the arrangement of objects in an image, used as an element of image interpretation

Site and association

 information referring to the location of objects and their related attributes in an image, used as elements of image interpretation

size

physical dimensions of objects, used as an element of image interpretation

Shape

the distinctive form of an object, used as an element in image interpretation

texture

 repeated shadings or colors in an image 

Tone

the grayscale levels or range of intensity of a particular color discerned as a characteristic of particular features present in an image

mean sea level

zero elevation, the baseline in sea level and vertical land

abosulte relief

refers to actual numeric heights and their differences. ex- spot elevations, benchmarks

spot elevations

a distinct point with an elevation

benchmarks

high accuracy spot elevation used by surveyors 

Contour interval

the vertical difference between contour lines

how to know if a contour line is a waterway

if a line goes through a contour line

if contour lines are close together

this means it is a steep slope

if contour lines are far apart

this means a flat land

hypsometric tinting

elevation by color

Isobaths

depth curves, are lines of equal water depth below the mean sea level

Soundings

use electronic depth measuring instruments such as SONAR to measure the time an acoustic pulse takes to reach the bottom and return to the instrument

Aspect

the direction in which the steepest slope of a terrain surface faces, measured in terms of azimuth or the angle clockwise from true north

Relative relief

refers to the height of one point in relation to the height of another point. Gives elevations and measurements in relation to other features nearby

Hachures

Short lines that run directly downhill. These tend to appear on contour lines to denote depressions

Hill shading

Apply a light source to highlight peaks and shade depressions

Shading Issues

Relief shading is not the same as the shadowing that appears on real-earth features

Relief reversal

the exact opposite effect from what was intended. Hills look like valleys and valley bottoms look like ridgetops 

Digital elevation model

represents the bare earth surface, removing all natural and built features

Digital surface model

captures both the natural and built/ artificial features of the environment

Digital terrain model

typically augments a DEM, by including vector features of the natural terrain, such as rivers and ridges

z value

elevation point assigned to an x.y coordinate 2D. 2.5D, 3D

viewshield

Shows us what is visible from a given point

Cartographic partition

outcomes of history. Process of dividing territory into separate parts to create new political entities or administrative boundaries

Ex. marking people as others. British empire

Satellite radar

tends to be low or medium resolution over large areas

LIDAR- tends to be high resolution, local scale

Redlining

discriminatory practice, originating from 1930s U.S. government maps, where banks and federal agencies denied or limited financial services (like mortgages, insurance) and investment to neighborhoods primarily inhabited by racial minorities, often drawn with a "red line" on maps,

Gerrymandering

the manipulation of electoral constituency boundaries so as to favor one party or class

Cracking

spreading voters of an opposition party across multiple districts to deny them a large voting block in any one district

packing

concentrating voters of an opposition party into a single district to reduce their influence elsewhere

Consequences of gerrymandering

a majority of votes does not mean a majority of seats in a legislature/congress

A map’s topic is

 the map’s subject matter- but a topic is not enough of a reason to invest time and work into making and publishing a map. The proposition is what the map’s authors want you to believe or accept.

Persuading map readers

 something appears on a map, visual hierarchy, graphic elements, good story

Earths shapes

geiod (earth without topography)-ellipsoid (simplification of geoid

map projection

 a coordinate system that is flattened (stretched/shrunk/torn) for a flat medium such as paper or computer screen

Datum

a reference surface, or model, of Earth that is used for plotting locations anywhere on the actual surface of Earth

NAD 27

This datum was developed for measurements of the United States and the rest of North America. It has its center point positioned at Meades Ranch in Kansas

NAD 83

Key improvement over NAD27: Adjusted to fit the entire Earth, not fixed to a single point.

WGS84

the world geodetic system of 1984

NAVD88

north american vertical datum 1988, Standard vertical reference for elevation in North America

Datum transformation

 required to alter the measurements from one datum to another (for instance, changing the measurements made in NAD27 to NAD83)

Geographic coordinate system

use latitudes and longitudes to represent locations on a spherical or ellipsoidal model of the earth

DMS (degrees, minutes and seconds)

GCS measurements are not made in feet or meters or miles

Decimal degrees

GCS coordinates can also be expressed in their decimal equivalent

Standard lines

points or lines where theoretically the plane meets the sphere, making for no distortion. When the surface touches the globe, there is no spatial distortion (cylindrical, conic, azimuthal/planar)

Shape distortion

this occurs when the features on earths surface are altered on the map compared to their true shapes

Area distortion

refers to the size of features of the earths surface, alters our perspective about some of these areas

Direction distortion

refers to the inaccuracies in the angles or bearings between points on the earths surface when projected

Distance distortion

distances between points on earths surface are inaccurately represented on the map

Tissots indicatrix

 if there were no distortion at all the ORANGE DOTS would be the exact same size and shape

Common projections mercator

a cylindrical map projection seen in classrooms that preserves angles and direction

Universal transverse mercator

grid system works by dividing the world into a series of zones, and then determining the x and y coordinates for a location in that zone. The grid is set up by translating real-world locations to where their corresponding places would be on a two-dimensional surface State plane coordinate system

Classification

ordering or grouping attribute data into classes to be presented on a map so that similar things are grouped together and different things are split into different classes

Qualitative map

nominal, ordinal. varying classes differentiated by type

Quantitative map

interval, ratio. Show differences in shape, color , text

Nominal data

unique identifier (phone number, SSN)

Ordinal data

ranking ( gold, silver bronze)

Interval data

temperature, can fall below zero

Ratio data

values with fixed zero, age or weight

Three decisions of classification

1. How many classes?

2. What method to use for placing the values into classes? (how do we draw the lines between categories?)

3. What kind of graphic symbology?

Equal interval

each class has an equal attribute value range (pro- easy to understand, con- may not effectively represent data with uneven distribution) 

Quantile

rank by attribute value. Putting an equal number of states in each class

Natural breaks

selects breakpoints between sections of low and high attribute values. Can be good for thematic mapping, con- makes assumptions

Manual

fit the case, or an outside standard

Visual variables

the property of a symbol/graphic mark that denotes a type of information

Thematic maps

focuses on one or a few themes

Choropleth maps

different colors to fill polygons by class and represent variations across an area

Normalization

ensures that variables can be compared meaningfully on the same level. Promotes fairness and enhances interpretability of results

Graduated symbols map

data classed into symbol size classes, symbols of varying sizes are used to represent different values of a variable. Size or shape of the symbol shows magnitude

Dot density maps

each dot represents a specific amount. Uses dots to represent spatial distribution of an attribute or phenomenon

Six core cartographic elements

Legend, Neatline, Directional indicator ,Scale ,Credits, Title

Legend

what the symbols and colors mean in terms that the readers understand 

Scale

uses absolute distance units 

Directional indicator

usually a north arrow

Neatline

framing line indicating the edge of geographic space

Web map services

map is center of the application ( google maps, arcgis, waze)

Location based service

technologies that perform a function based on being at a location. tends to focus on consumption