Geospatial Science Exam 1

Geography

study of earth surface as the space within human population lives

has natural and human components

Spatial data

data related to an object'

location (latitude, longitude, and elevation)

geometry (size, length, shape)

topology (relationship of neighbors)

Non-spatial data

data that adds up to, or describes information about the spatial data

road names, population, city names

information not specified by location, geometry, or topology

GIS

computer based tools used to store, visualize, analyze, and interpret geographic data

remote sensing

acquisition of data and imagery from satellites, aircrafts, or ground stations

wiki

open database available to anyone to edit and utilize

Wikipedia is most famous but not geospatial

spatial pattern

The arrangement or placement of features on the earth, as well as the space between them. The repetitive or structured arrangement of features on the ground or map.

spatial arrangement

the overall arrangement, spread, or location of a phenomenon, object, or population across the Earth’s surface

three main datums historically utilized by geography field

NAD27, NAD83, WGS84

absolute location

stand alone

such as coordinate system, street address

relative location

depends on external factors

such as where you are relative to a building or neighborhood

measure latitude

equator is 0

north and south are 90N and 90S

parallels

measuring longitude

prime meridian is 0

180 degrees

meridians

how to express coordinates in degrees, min., sec

42 degrees 23’15’’ N, 72 degrees 35’ 38’’ W

How to express coordinates in decimal degrees

north and east expressed as positive

south and west expressed as negative

How to convert from degrees to decimal coordinates

divide minutes by 60

divide seconds by 3600

add degree value and two decimal values together

add negative if appropriate

how to convert decimal coordinates to degrees

multiply decimal portion by 60 (minutes)

multiply minutes by 60 (seconds)

express whole number of initial decimal expression in degrees, add minutes and seconds

add NSEW

number of time zones

24

earth rotates

1 zone per hour

15 degrees

1 time zone is

1 hour time difference

what happens when you cross the IDL to the east

gain a day

what happens when you cross the IDL to the west

lose a day

when is it appropriate to use a cylindrical projection

global maps, equatorial projections, navigation

preserves local shapes and angles and renders compass bearing as straight lines

when is it appropriate to use a conic map projection

mid latitude regions that run east to west

scale and shape are very accurate along standard lines

when is it appropriate to use a planar (azimuthal) projection

polar regions or displaying global hemispheres centered on specific point of interest

accurately preserve directions from central point and represent radial distances correctly

what is being preserved/distorted when using a conformal map

shape is preserved, size is not

what is being preserved/distorted when using an equal area map

size is preserved, shape is not

how do you find a location using the civilian UTM coordinate system

zone number - latitude and longitude designated zones

false origins are Central Meridian and equator/south pole

eastings - middle of each zone is 500,000m, so it is ± meters from it

northings - northern hemisphere meters from north of equator, south hemisphere negative meters from the equator + 10,000,000

how do you find a location using the civilian SPC coordinate system

instead of using lines of longitude, follow state/county lines

reprojection

the process of changing a dataset from one measurement or mapping system to another

georeferencing

the process of aligning an unreferenced dataset or map with one that does have an assigned spatial reference

what is the significance of control points during the georeferencing process

user may need to manually place control points to align the unreferenced map to the spatially referenced map

they should be spread out and you need 4 at the very minimum

rotated

clockwise, counterclockwise rotation

skewed

image being pulled and distorted

scaled

reducing or enhancing the size

translated

altering location of data without altering data dimensions

affine transformation

automated process where GIS software will utilize a formula to automatically rotate, skew, scale, and translate unreferenced image as appropriate

control points

points digitally created by user to identify same location on two maps

RMSE

root mean square error

measure of identifying control point distance discrepancies between easting and northing coordinates from the source and unreferenced maps following the transformation process

the lower, the better

when georeferencing two map images, what mapping characteristics can pose problems

too far apart in geographic area coverage

not clear image detail and clarity

don’t utilize similar mapping projections

heads up digitizing

using a mouse or digital pen to sketch over an aerial photo or satellite image

how is heads up digitizing related to georeferencing

you can use heads up digitizing after you georeference to convert to vector datawha

what is NAVSTAR GPS system

United States global positioning system

part of GNSS (global navigation satellite system)

roughly 24 satellites orbiting

constellation

full pattern of orbits compromised by 24 NAVSTAR GPS satellites

trilateration

GPS receiver identifies location relative to three orbiting satellites

what kind of clock do space segment satellites use

atomic clock

what GPS radio band are used for civilian use

L1 and L2

almanac

information transmitted by satellites that includes status, speed, and location

not precise

ephemeris

precise satellite location broadcast every 30 seconds, valid for 30 min

user segment

GPS receiver, do not submit

control segment

global network of ground stations

L1 carrier

C/A (course acquisition) code

causes frequency to be transmitted at random intervals to all GPS receivers

L2 carrier

P (precise) code

status messages, regulates random electric pulse intervals

may also be encrypted to Y code to prevent potential hacking

pseudorange

distance between GPS receiver and transmiting satellite offset by clock precision errors

PDOP

position dilution of precision

wider spacing by satellites allows for greater locational accuracy

differential GPS

satellites may broadcast location errors of ground control stations to the stations

control stations broadcast erroneous location difference to GPS receivers to account for error

Geocaching

practice of finding location of hidden object using GPS

vector data

data in GIS utilized to represent discrete objects or features (a variable or feature that is present only in specific locations)

appropriate for point line and

raster data

data in GIS utilized to represent continuous variables or features that are present at all locations of the earth

nominal data

data (alpha or numeric) providing a unique characteristic or identity to a certain feature

ethnic background, color of car, type of material

numeric values carry no significance with respect to: magnitude, differences in value, order, direction

runner ID, jersey number

ordinal data

data used to represent some form of ranking system

racing contest outcomes, mapping symbols of small roads vs highways

interval data

numerical data based without a fixed absolute zero value as a starting point, but differences in value are significant

Celsius temperature, time values

ratio data

data consisting of values based on an absolute zero value as starting point

differences in value are also significant

records

rows in attribute table

fields

columns in attribute table

joining two tables

allows non-geospatial data to be linked with geospatial data on an attribute table

what do you need to join two tables

each data set must have a common field (key) for join command to work

metadata

information or data about specific data layer

topology

set of rules and behaviors that address how points, lines, and polygons share coincident geometry in GIS

digitizing

process of manually creating new vector data (points, lines, polygons)

shapefile

primary vector mapping file that can store data only in one vector format

geodatabase

single file which stores multiple files and/or layers of data pertaining to common theme

feature class

vector mapping files consisting of geographic features of the same geometry, attributes, and spatial reference

intersect

new mapping feature created which corresponds to where two or more mapping features occupy same space on ArcGIS

identity

1st input layer - all geometric features retained

2nd input layer - geometric features are retained only where 2nd layer intersects 1st

symmetrical difference

all geometric features of all mapping layers are retained except where features intersect together

outcome is direct opposite of intersection

union

all geometric features that are input are combined together, the union functions as merge between two or more mapping layers

what do addition map algebra operations on raster data sets select

union function allowing to identify raster grid cells where all, some, or none of desired set are met

what do multiplication map algebra operations on raster data sets select

an intersection function allowing to identify raster grid cells where multiple desired criteria are met

query

identify and highlight mapping features that have specific attribute that is specified by user

compound query

consists of query search based on multiple criteria, not just one

Boolean operators

programming construct using simple words (AND, OR, etc.) as conjunctions to combine or exclude keywords or numerical values in search

relational operators

programming construct which tests equality and inequality between two variables

=, <, >

suitability analysis/index

raster overlay combining multiple criteria and “ranking” individual cells as to how well each cell location fits a desired criteria

multi criteria evaluation

integration of multiple data layers that are weighted to determine overall suitability score for specific purpose