Geospatial Data

Question 1

metadata

Answer 1

information that describes the content, quality, condition, origin and other characteristics of data or other pieces of information

Question 2

Federal Geographic Data Committee (FGDC)

Answer 2

format for metadata - who, what, when, where, why and how - include title, abstract and date, geographic extent and projection info, attribute label definitions and domain values - Content Standard for Digital Geospatial Metadata (CSDGM)

Question 3

ISO 19115

Answer 3

developed for documenting vector and point data and geospatial services (web-mapping, data catalogs, and data modeling applications)

Question 4

ISO 19115-2

Answer 4

adds elements to describe imagery and gridded data as well as data collected using instruments (monitoring stations and measurement devices)

Question 5

Quality Assurance

Answer 5

process oriented and focuses on defect prevention - establishment of good quality management system and assessment of its adequacy - periodic audits - managerial tool

Question 6

Quality Control

Answer 6

product oriented and focuses on defect identification - finding and eliminating sources of quality problems through tools and equipment - corrective tool

Question 7

Archiving

Answer 7

captures, manages, and analyzes data changes - most often done with gdbs

Question 8

Retreival

Answer 8

Similar to a backup

Question 9

Join

Answer 9

Combine two attribute tables into one using a common key between tables

Question 10

Merge

Answer 10

Combines multiple input datasets of the same data type into a single new output

Question 11

Append

Answer 11

Combines datasets of same data type into an existing dataset

Question 12

Union

Answer 12

Combines input features with another feature dataset

Question 13

Clip

Answer 13

Extracts input features that overlay the clip features (keeps input attributes)

Question 14

Intersect

Answer 14

extracts features which overlap in all layers to new feature class (joins attribute tables)

Question 15

Geomatics

Answer 15

science and technology of gathering, analyzing, interpreting, distributing, and using geographic information (includes surveying, mapping, remote sensing, GIS, GPS)

Question 16

Remote Sensing ( Field Data Collection)

Answer 16

3 resolutions - spatial, spectral (electromagnetic spectrum measured), temporal (repeat cycle)

Question 17

Ground Survey (Field Data Collection)

Answer 17

expensive and time consuming

Question 18

Field Data Collection methods

Answer 18

planning, preparation, digitizing and transferring, editing and improvement, evaluation

Question 19

GPS (Field Data Collection)

Answer 19

24 satellites - orbit earth twice a day - revolution every 12 hours - altitude to about 12,000 miles - started by US Department of Defense (DOD) in the 1970’s for military

Question 20

Space Segment

Answer 20

NAVigation Satellite Timing and Ranging (NAVSTAR) constellation - GPS satellites which transmits signals on two phase modulated frequencies - transmit a navigation message that contains orbital data for computing the positions of all satellites

Question 21

Standard Positioning Service (GPS)

Answer 21

signal broadcast for civilian use

Question 22

Horizontal location (GPS)

Answer 22

3 satellites are required

Question 23

Vertical Position (GPS)

Answer 23

min 4 satellites are required

Question 24

How does GPS calculate distance?

Answer 24

by measuring the time interval between the transmission and reception of a satellite signal

Question 25

Trilateration

Answer 25

used to determine position of GPS receiver

Question 26

How is GPS accuracy determined?

Answer 26

type of GPS receiver, field techniques, post processing of data, error from various scenarios

Question 27

3 Types of GPS Receivers

Answer 27

Recreational Grade, Mapping Grade, Survey or High Accuracy Grade

Question 28

Multipath (GPS Error)

Answer 28

errors caused by reflected GPS signals arriving at the GPS receiver - nearby structures and other reflective surfaces

Question 29

Atmosphere ( GPS errors)

Answer 29

GPS signals can experience delays when traveling through the atmosphere - common atmospheric conditions can affect GPS signals such as tropospheric delays and ionospheric delays

Question 30

Distance from Basse Station (GPS errors)

Answer 30

differential correction will increase the quality of the data, accuracy is degraded slightly as the distance from the base station increases

Question 31

Selective Availability (GPS errors)

Answer 31

Intentional degradation of the GPS signals by the department of defense (DOD) to limit accuracy for non-US military and government users - currently turned off, but can turn it back on whenever

Question 32

Noise (GPS errors)

Answer 32

error is the distortion of the satellite signal prior to reaching the GPS receiver and or additional signal piggy backing onto the GPS satellite signal

Question 33

PDOP

Answer 33

Position Dilution of Precision - collect data when there is an optimum satellite availability (four or more) and when satellites are in an appropriate configuration to produce an acceptable (lower) PDOP value - higher PDOP values are bad

Question 34

PDOP values

Answer 34

set to 6 or less - Higher levels will be less reliable data

Question 35

Signal to Noise Ration (SNR) mask

Answer 35

set the value of the SNR mask higher to help minimize noise error - use manufacturer recommendations

Question 36

Elevation Mask

Answer 36

set it to 15 degrees - default angle to minimize the amount of atmosphere through which the satellite signal has to travel

Question 37

Data Collection Rate (sync rate)

Answer 37

recommended to collect point data at 1-second interval - collect polygon and line data at a 5 second interval - collect point data at the same data collection interval as the base station

Question 38

Datum (GPS)

Answer 38

GPS receivers are designed to collect GPS positions relative to the WGS84 datum - can designate what datum to be used