EAS 531 Midterm

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Raster extent

# of cols, # of rows

In row and column space, the upper left cell is usually

1,1

ArcGIS representation of projections

Geographic, aka GCS

Observed element (2types)

Object model, field model

3 common ellipsoid shapes

Clarke 1866, GRS 1980, WGS 1984

3 uses of multispectral satellite images

Classification of land cover or other features, biophysical parameters (continuous data), others (real time monitoring ,weather)

Fields

Earth is a continuous surface characterized by a number of properties (elevaiton, pH)

Longitutde is measuring _____ relative to _____

East West relative to the Greenwich Meridian

location in raster

coordinates assigned to the entire grid and also to each cell

what dataset has arc attribute tables?

coverages

digitizing polygons with autcomplete

create a new polygon by snapping to an existing one

Plate Carree Projection

cylindrical projection that distorts areas and shapes

3 families of projections

cylindrical, conic, azimuthal

3 uses of GPS

field digitizing, navigation, tracking

computer map window projection defined by ____-

first data source added, subsequent data will be reprojected on the fly

Object model

focus is on the object (objects can have different attributes)

Field model

focus on the attribute (varies over space)

in the US state plane system, projected origins and coordinate origins are established -__

for each zone

data structure

formal symbolic representation of specific things in the data model (coordinates, attribute data) Organized set of files for managing entities/fields defined in the data model

domains are defined at hte level of hte

geodatabase

spatial sample

geographic measurements based on a sample of space

All layers are precisely ____

geolocated

connectivity and adjacency

geometric relationships between features in a single GIS layer (no overshoots or undershoots)

Raster cells have X, Y locations that are

georeferenced

remote sensing

getting info about an object/area through analysis of data acquired by a device that is not in contact with the object

GADM

global administrative boundaries available by country

GNSS

global navigation satellite systems

SEDAC

global or national, social, environmental, and health themed data

Open street map

global road data

ASTER GDEM

global, from aster sensor, elevation data

symbolization for ordinal

gradations in color or symbol size

2 ways to select by location

graphical interaction pointer (clicking on what you want) topological relationships to features in the same or a different data set

Projections

mathematically defined conversions from location on 3D earth to 2D space

spatial census

measure or count every object or location in an area

RMSE

measures the fit of transformation

why does GIS need simplification or sampling framework

measuring everything everywehre all the time is impossible!

Balance

minimize blank space, efficient use of space

why use relational database?

more efficient, makes updating easier, can mix and match data from various tables

best if you have ____ georeferenced points

more than 15

feature dataset

multiple feature classes with the same projection/datum can be combined into this

Each spatial feature in a vector data set can have _____

multiple values

geodatabase contains _____

multiple vector feature datasets and/or vector feature classes. can also contain raster

NLCD

national land cover database, created from landsat

USGS

national map of the US

natural color and fake color

natural - assigning RGB . to their true values fake - assigning other values to RGB

3 resampling methods for raster

nearest neighbor, bilinear interpolation, cubic convolution

vector is prefered for ____ analysis

network

is there a single set of topology rules or relationships across software packages or data formats?

no

dangling nodes

node connection to only one arc (overshoot or undershoot)

Shapefiles are ______ and use a _____ objected approach

non topological, use disconnected object approach

NAD83 best fit for, based on

north america, GRS80

NAD 27 best fit for, based on

north america, clarke 1866

1st order transformation

not warped. rescaled, rotated, etc

number of bands

number of layers

difference between feature and object

object does not have a known location, feature is an object with a location

line in vector is an ______

ordered set of points

database

organized collection of tables, files, data. formall defined and centrally controlled colleciton of data

spatial cognition

our understanding of hte geographic world

How to make a distance raster?

perform GIS functions on vector data to output a raster

spatial resolution and extent

pixel size and image extent

ESRI GIS coverage enforces

planar topology

Thematic map example

population change map by district

5 uses for GIS

Platform for collecting data Database and data repos Tool for analysis Visualization Land, resources, and infrastructure management tool

Coordinate origins in the UTM

X = 500,000 west of central meridian (false easting) Y = one for northern hemi (equator), different one for southern hemisphere

in cartesian coordinate space, the lower left cell is

X min Y min

Layers have their own internal ____

abstraction and logic

Lidar sensing

active, aircraft mounted, cannot see through clouds, records geo location and height

radar sensors

active, light and clouds irrelevant, most are space borne, use radio

datum location information corresponds to

actual surveyed coordinates at Earth Locations

Non-map representations of the earth

air photos and satellite images, photos and drawings

snapping

allows you to create features that automatically connect to others

attributes can be measured using

almost any measurement device

TIGER

census geography. Census tracts, block groups, blocks geogrpahic data. can be joined to census data

line of contact in UTM

central meridian

flat bed scanner

cheap, limited in size

Thematic raster maps are created from

classification of remotely sensed images

polygon is a single _____ or a set of ____

closed line, connected lines forming an enclosed area

______ are commonly used for continuous raster data with ratio attributes

color ramps

legibility

common font throughout, less is more

symbolization for nominal

common symbol for all features or a unique color or symbol for features with a different value

Mercator Projection is ______, has correct ______, exaggerates _____, designed for______

conformal, correct shapes, exaggerates high latitutde area, navigation

with coverage, features are __

connected

Attribute domains

constrains values to values you specify Coded value or range

records in an attribute table

contain a set of values for a single entity

Raster is prefered for ___ data analysis

continuous

can't do attribute table for _____ data, only for _____

continuous, integer

CORS

continuously operating reference stations - allows for differential correction post processing

issues of trilateration

position dilution of precision (PDOP) based on geometric arrangements of satellites when satellites are closer together, there is a large area of uncertainty

vector spatial precision is limited by____

positional measurements

Objects

present a view of hte world in which the earth's surface is populated by a number of discrete entities

JPEG is only good for

presentation, not looking at data

measurement

process of extracting data about the world

normalization

process of identifying redundancies and storing them in separate tables

another word for cartesian coordinates

projected coordinates

prj

projection information

US state plane coordinate system

projects the 3D earth into separate projections for each state, some have more than one zone

How does GPS work?

pseudo random code (radio signal) generated by satellite and decoded by receiver. Receiver compares signals and determines the time it took to travel from satellite to receiver

ratio attribute

quantitative values, equality of units, non-arbitrary 0 measurement, ratios between values makes sense

Interval attribute

quantitative, equality of units, arbitrary 0 measure

domain

range of values that features may take

ESRI GRID is a _____ format

raster

raster is good for _____ output, vector is good for _____ output

raster - images vector - maps

difference in reclassification between raster and vector

raster - just recode vector - recode, then dissolve

raster is ____ in coordinate conversion, vector is _____ in coordinate conversion

raster - slow vector - simple

Path of less abstract to more abstract

real world --> data model --> data structure --> machine code

in the attributre table, the rows are the ____ and the columns are the _____

records, fields

hierachry

relative importance should be clear, use placement

georeferencing a raster image file

resample the image pixel values to fit the new raster geometry

graphic scale uses

scale bar

MMU dependent on

scale over original source and goals of cartographers

topology

science and math of spatial relationships

Real-float numbers use ___

scientific notation

5 ways to increase GPS precision

select satellites that are not low to the horizon select low PDOP threshold take multiple readings at a point and average them apply differential correction use more expensive carrier phase receivers

set-based approach for retrieving data

select subset of records based on a logical expression

Map content is ____

selective, maker has control

relational databases store ______ connected by _____

separate types of entities in separate tables, connected by a key variable

shp

shape format, feature geometry itself

shx

shape index format, positional index of the feature geometry

Every projection distorts ____

shape, area, or direction

SRTM GDEM

shuttle radar topography mission, NASA, global. Elevation data

Atmospheric interference with signal sent from GPS

signal is delayed, solution: mask out low angle satellites

keep roughly ______ for hues of all categories of nominal

similar saturation and value

simple vs compound data query

simple - one conditional statement compound - use Boolean logic

raster are ____ and _____ than vector as data models

simple and larger

domains advantage

simplify entering data, validate entered data

Vector point is made of a _____

single coordinate pair

sliver polygon

small spurious polygon between two others as a result of overlap

Reference map communicates

spatial assc between various phenomena

Vector data uses ___

spatial features - points, lines, and polygons

Location in vector

spatial features with coordinates assigned to points

feature classes inside a feature dataset inherit ____ from dataset

spatial reference

spatial operation data can be ___, ____, ____

spatial, non spatial, used for another operation

database management system

specialized computer program for organiziang and managing data

hue

spectral color

Geographic framework for michigan

standardizes basic info for the state features include roads, lakes, streams, school districts. uses Michigan GeoRef

NAVSTAR GPS

started in 1995, continually improving

node

starting and ending points of the line

Data from FAO of the UN

stat data, broad range land, forest, agri, food, pop

in ArcGIS, coordinates are stored _____ and define _____

stored in the permanent spatial portion of GIS, define projection of hte data

arc attribute table

stores relationships between points, lines/arcs, and polygons. preserves topology

DBMS main function

storing and retrieving data as requested by software

GCS is useful for

storing large, global dataset files, project as needed

Pyramids

subsample data to be displayed more rapidly

WGS 84 is the best fit for ____, origin is

the globe, origin is the Earth's center of mass

Real world abstraction

the real world physical entities or continuous fields

Geoid

the shape that the surface of the oceans would take under the influence of Earth's gravitation and rotation alone, in the absence of other influences such as winds and tides.

resolution

the smallest resolvable unit

use two colors in a blended hue ramp if

the variable range has a center

four ways to represent ratio attributes in raster

total value over the cell, average value, extreme value, cell center

Universal Transverse Mercator (UTM)

transverse mercator projection for each of 60 different zones, each 6 degrees of longitude wide

in shapefile, boundaries are recorded _____

twice

what to do if your datum/projection is defined in your GIS layer but you want to convert it?

use a projection - reprojecting, converting between projections and datum use PROJECT in ArcMap Geographic transformation - changes the datum

symbolization for ratio

use gradations in colors or symbol size, color ramps, proportional symbols

what to do if your layer is neither defined nor projected

use ground control point method and a statistical transformation (georectification) to match the geometry of a digital reference map or images taht has a known datum/projection using least squares regression

How do geodatabases store vector data?

uses feature class and feature datasets to store vector data

generalization

values from a census are generalized over geographic units

Ordinal attribute

values that have a natural order or rank

attributes are considered____ and are often stored in _____

variables, stored in a data table called an attribute table

2nd order transformaiton

warping, most often used

your choice of scale affects

what can be measured and how it's represnted

Abstraction in map making

what is important for the map? extent vs purpuse

WAAS

wide area augmentation system - allows for correction on the fly

In Raster, each grid cell is coded ____

with a single value

geodatabases have topology ______

within and between feature classes

raster spatial precision is set by ____

cell size

spatial operation

manipulates or calculates based on coordinates or attribute values

WWF ecoregions

825 terrestrial ecoregions in 14 biomes

if one bit is used to indicate sign, what is the range of values?

-128 to 127

3 benefits of Geodatabase

1. allows for data models to be formalized before creation. predefine all feature classes etc 2. is topological within and between classes 3. topology can be defined by rules and stored as a component of a feature dataset

3 things GIS uses topology for

1. enforce the geometry of vector features in a single GIS layer 2. define geometric relationships between vector features in a single GIS layer 3. enforce spatial relationships between GIS layers

topology rules can do two things

1. monitor spatial relationships of features in a single feature class. 2. restrict the relationships that exist between feature classes

2 solutions for if you need a single coordinate system for an area that spans multiple UTM or state plan zones?

1. project all to one 2. create a new single custom projection for the entire area

3 things GIS requires

1. system for precise measurement of location 2. attribute scheme and acceptance of attribute defs 3. spatial, thematic, and temporal simplification or sampling framework

CCI global land cover

12 classes of data

Cartesian/projected : location referenced relative to _____

2 perpendicular axes (x,y)

8 bit max storage

256 values (0-255)

How many zones does Michigan hvae in the US state plane coordinate system?

3 - north, central, south

single precision floating can be represented wit

32 bit

how many satellite signals do you need to locate yourself?

4

when you ½ the cell size the file size is ____

4x as large. 4 times as many cells

CEP

50% of the GPS fixes fall within this area circle's radius around the true mean

double precision floating can be represented with

64 bits

16 bit max storage

65,536 values

1 byte =

8 bits

coordinate systems in ArcMap have 5 things

A projeciton an ellipsoid/datum projection lines of contact (central meridian or standard parallels) units coordinate system origins

characters are coded with

ASCII coding

Equal area conic (1 type, what does it preserve)

Alber's Equal Area preserves area at the expense of shapes

4 advantages of DBMS in large enterprise

Control simultaneous multi-user access Data independence (structured independently of the apps) Multiple applications centralized control and maintenance

2 units for angles and the conversion between them

Decimal degrees and degrees-minutes-seconds 1 degree = 60 minutes

3 non-lossy

ESRI GRID, ERDAS/IMAGINE, TIF

units of distance measure in projected data

English : inches, feet Metric

multipath errors

GPS is line of sight technology signal bounces of nearby objects can screen via signal to noise ratio

GIS acronym

Geographic Information System

fine spatial resolution (3 examples, time)

Ikonos, quickbird, WorldView. infrequent coverage, pointable

Lossy format

JPEG

coarse spatial resolution (2 examples, frequency)

MODIS, AVHRR daily data

Do pyramids alter your data?

No!

is your data projected in GCS

No! Simply based on datum/ellipsoid, uses angular units

3 attribute types in GIS and how they're stored

Nominal -text field or integer Ordinal - text field or integer Ratio - integer or real number

Latitude is measuring _____ relative to _____

North South relative to the Equator

SQL query format

Select ____ from -____ where _____ and/or/not _____

3 steps in building map model

Spatial cognition measurement symbolization

GPS

US satellite segment

How does differential correction work?

a base station at a precisely known location records its own GPS location. Different between the recorded and true value = error in GPS estimated location. can adjust post data collection or real time

each feature class in a geo db is available as ____-

a layer for display, like a shapefile

Radial coordinates: location referenced relative to _____

a single axis (x)

Each vector data layer in GIS contains ___

a single feature class

geographical coordinates : reference is made using ____

angle positioned at the center of th earth

Radial coordinates : measurement is ____

angular displacement from x and linear distance (r) from origin (0,0)

____ within a feature class inside a geodatabase can use a domain inside that geodatabase

any attribute

Object model empty space

any space between the entities

if you want your projection to preserve: area, shape, direction

area - equal area shape - conformal direction - conformal or azimuthal

Equal area cylindrical

areas are correct, shapes distorted

UTM is best for

areas with longer NS extents and not EW extents

dbf

attribute format, columnar attributes for each shape

Fields are defined by

attribute name, type (text, integer, float, etc)

fields in attribute table hold

attributes or variables describing all entities

point samples dependent on

average sample spacing

Pro and con of equal interval

bad for highly skewed data, easier to interpret

natural breaks

balance between equal and quantiles

figure ground

be clear what is the information highlighted and what is the background, contrast and color

2 ways to select features in ArcGIS

by attribute, by locaiton

attribute range in raster is determined by

bytes

3 options for when 2 vector polygons span one raster cell

can do largest share rule or central point rule, presence or absence

Resolution in raster

cell size

In GIS, information is organized into data ____ that represent ____

data layers, single theme

simplest form of spatial operation

data query

Compression is basically

data storage

resolution of polygons

defined by "minimum mapping unit"

Michigan GEOREF

defined to allow referencing locations throughout the state of michigan on a single projection and coordinate system

prj file

defines projections

Attributes

describe characteristics of either locations/cells or geographic features

Can use infrared to ___

differentiate between surfaces ,differnet sufraces have different spectral reflectance curves

heads up digitizing

digitizing on screen with a georeferenced map or image displayed and use a mouse to record locations

non-lossy compression is good for

discrete data with large homogenous areas

Cartesian measurements are in _____

distance along each axis from the origin (0,0)

Thematic map communicates

distribution of a single property or relationship among several

quantiles

divides range into n categories with the same number of features

Equal interval

divides the range into categories that all have the same value range

Empty space in field model

does not exist

Most zones in the US state plane coordinate system use

either a ™ projection (cylindrical) or a lambert projection

DEM

elevation data

datums

ellipsoids with location information (lat and long)

planarity

enforcing geometry requires that all features occur on a 2d surface. No overlapping

manual digitizing tablet

enter points through map document placed on digitizer and use mouse to record locations

data model

entities or fields represented in a spatial database and hte relationships among them (raster, vector, object based)

symbolization

established rules for relating marks to real world entities or continuous fields

Satellites know their (3)

exact altitude, position in orbit, and position wrt the WGS84 ellipsoid

drum scanner

expensive, accurate, can handle large documents

tissot indicatrix

graphically displays distortion. Helps you see what type of distortion occurs in the size, shape, and orientation of ellipses that would be circles were they located on the spherical Earth's surface

Raster data uses ____

grid cells

feature class

group of features of the same type (analogous to vector layer in the geo db)

pro and con of quintiles

highlights differences in the values of features, hard to read

spectral resolution

how many bands (Wavelengths) can the sensor collect simultaneously

temporal resolution

how often does a location get sampled?

saturation

how rich or vivid a color is, deep/saturated

Nominal attribute

identifier value, names, letters, numbers (phones, SSN)

why use pyramids?

improves the performance of rasters

if your data is not projected, it will display ...

in a plate carree projection with coordinates in Lat/long

Selective availability

in the 1990s, intentional degradation of public GPS. reduces precision

high accuracy in UTM occurs

in zones less than a few degrees in east west extent

Maps are a form of _____, because they can be interpreted

information storage

value

intensity (lightness or darkness)

vertices

intermediate points on the line

join vs relate

join - appends the attributes to the table based on a common field relate - defines a relationship between the two tables based on a common field, does not append

conformal conic (1 type, preserves)

lambert conformal - preserves shapes at the expense of areas

MODIS

land cover map from NASA, 17 land cover classes

moderate spatial resolution (1 example, time)

landsat, 16 days

1:5000 is a ____ scale map than 1:500,000

larger

large scale map covers ____ area, has ___detail , and ____ denominator

less area, more detail, smaller denom

Connectivity applies to ____ and adjacency applies to _____

lines, polygons

______ and ______ between marks on maps and what the refer to

logical and scientific correspondence

selecting by attribute

logical expression to interact with attribute table

Non-lossy format

maintains original cell values


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