GEOG 221 EXAM 1 STUDY GUIDE

What are three main subfields in geospatial technology?

-GIS: Geographic Information System Computer-based mapping, analysis, and retrieval of location-based data -Remote Sensing Gathering info (using satellites, aircrafts, UAVs) about an object or phenomenon w/put making physical contact. EX: Taking pics -GPS: Global Positioning System Gathering real-time location info from a series of satellotes in Earth's orbit.

Geospatial data is the heart of geospatial technology applications. What is the definition of geospatial data? Give three examples of how geospatial data is used in various fields and disciplines. Refer to my lecture slides #10-15.

-Homeland Security Geospatial tech can be used to examine the risk assessment of everything from evacuation plans to smoke-plume modeling. Geospatial technology can be used to enhance disaster mitigation and recovery efforts. -Health and Human Services Geospatial tech can be used to monitor diseases, track the sources of disease, and map health-related issues. (COVID TRACKING) -Environmental Monitoring Geospatial tech can be used to assess and track the various processes that affect Earth's environment in diff ways.

Chap 3: Explain three major steps in georeferencing. Explain how each step is done

1. Choose a source need a source of real world coords against which to align unref data source has to be scientifically reliable and cover same geographic data as unref data 2. Select control pts ctrl pts: pt locations where coords are known find common pt to "tie" unref data to source data want places that have heterogenous land covers. Good GCPs: building corners, large trees, street intersections Bad GCPs: cars, rocks, shoreline of beach Want at least three GCPs, the more GCPs the more accurate 3.Transformation Rotate, Skew (distort or slant), Translate, Scale 4. Check accuracy affine transformation and RMSE root mean square error

Chap 2: How many degrees of longitude does each time zone cover? Why time zones don't exactly follow the lines of longitude? Where is the International Date Line located? How many time zones does the United States cover (including Hawaii and Alaska)?

15 degrees, time zones are asymmetrical bc of the irregular nature of political/geographical boundaries IDL: "a line of longitude that uses the 180th meridian as a basis (but deviates away from a straight line to accommodate geography)" USA covers 9

Chap 3: What is the indicator used to evaluate how well a georeferenced image matches with the source? How to use this indicator?

Affine transformation: calculates the RMSE that measures how will GCPs fit into particular affine equation Lower the overall RMSE the better the fit

Chap 2: What type of map projection is the Lambert equal-area projection? What property does this projection preserve and what is the distortion?

Azimuthal, accurately reps area in all regions of sphere but it does not accurately rep shape

Chap 2:What type of map projection is the Albers conic equal-area projection? What property does this projection preserve and what is the distortion?

Conical; maintains size but distorts shape

Chap 2: What are three major types map projection?

Cylindrical, Conical, Azimuthal

Chap 2: What type of map projection is the Mercator projection? What property does the Mercator projection preserve and what is the distortion?

Cylindrical, maintains shape but distorts size

Chap 2:What is a datum transformation? A datum transformation is required in what situation?

Datum Transformation is necessary when two maps are created in diff datums

Chap 4: What are two popular methods used to improve GPS accuracy? How they work?

Differential GPS uses one or more ground stations to provide a correction for GPS position determination in addition to satellite signals Satellite Based Augmentation Systems (SBAS): uses correction info sent from an additional satellite to improve location accuracy

Chap 2: Know the degrees of latitude of the Equator, the Tropic of Cancer, the Tropic of Capricorn, the Arctic Circle and the Antarctic Circle.

Equator: 0 degrees lat Tropic of Cancer: 23.5 N Tropic of Capricorn: 23.45 S of Equator Arctic Circle: 66.5 N Antarctic Circle: 66.5 S

Chap 2: How to describe a location using latitude and longitude? How to convert a DMS measurement to DD? Practice using examples in the slides.

GCS coords made in DMS (is degrees minutes seconds) Towson's location would be 39 degrees 23' 36" N, 76 degrees 36'26" W DD is DMS in decimal form Using above ex 1. Convert sec into mins: 36" = 36/60"= 0.6' 2. Calc total mins: 23'+0.6'= 23.6' 3. Convert total mins into deg: 23.6'= 23.6/60' = 0.3933 degrees 4. Calculate total degrees: 39 degrees + 0.39.3933 degrees north 5. Do the same thing for W

Chap 2: Define GCS, latitude, longitude, the Equator and the Prime Meridian.

GCS: Geographic Coordinate System -> global ref system for determining the exact position of a point on Earth based on the ellipsoid model. Equator- Line of Latitude that runs around center of Earth and serves as the 0 degree line from which to make lat measurements Prime Meridian: line of longitude that runs thru Greenwich England and serves as the 0 degree line of longitude from which to base measurements.

Chap 4: What is a GPS constellation? What is the minimum number of satellites for a full constellation? How many orbit planes are in a constellation? How many satellites are in each orbit? How many orbits around Earth does a GPS satellite make every day? What is the flying altitude of these satellites?

GPS Constellation is a group of satellites working together as a system. min number for full constellation is 24 bc 6 constellation orbit planes and 4 satellites in each orbit GPS satellites orbit 2x around Earth a day GPS satellites fly at an alt of 20,200 km

What is the definition of geolocation? How does an electronic device determine your location? What is W3C geolocation API?

Geolocation: The technique of determining where something is in the real world. An electronic device can determine your location by using geolocation and plotting your location on a digital map W3C Geolocation API: javaScript programming technique that enables the web application to obtain user location info

Chap 4: What is GPS? What are three essential components/segments in GPS?

Global Positioning System: geospatial tech that uses signals broadcast from satellites for navigation and position determination on Earth 1. Space segment (satellites) 2. Control Segment (Master Station) 3. User Segment (Phones etc)

Geospatial technology has been widely used in many fields. Name at least five fields

Government, Engineering, Military, Academic, Agriculture, Transportation

Chap 4: What is the use of ground control stations?

Ground Stations collect satellite data, make corrections, and upload new data for the satellites to make sure satellites broadcast correct info

Chap 2:How is the angle of latitude/longitude measured? Describe the procedure.

Latitude Straight line from center of Earth to your location Straight line from center of earth to Equator Angle in between Longitude straight line from your location thru N and S pole straight line from center of Earth to where the line from your location intersects with equator another straight line wherePM and Equator intersect Angle in between

Chap 2: What is map projection. Why does map projections always have distortions?

Map projections are the presentation of 3D info about Earth on a 2D map. Always distorted bc it is impossible to perfectly translate a 3D surface onto a 2D surface

Non-spatial data is another essential component in geospatial technology. What are examples of nonspatial data? Name at least three.

Non Spatial Data: Data not directly linked to a geospatial location. EX: person's height, mass, and age

What are the cons and pros of geolocation?

PROS -if you are lost, you can let others know here you are -Can find things to do near you -Can geotag locations CONS -can very easily give away a lot of data

Chap 3: What is reprojection? Why is reprojection necessary when working with multiple geospatial data layers in different map projections?

Reproject: transform all datasets to a common datum, coord sys, and projection. mult data layers in diff map projections wont properly align w/ eachother

Chap 4: Name three GNSS used by other countries/regions.

Russia: GLONASS China: BeiDou-2 Navigation Satellite System Euro Union: Galileo System

Chap 2: What is SPCS? Where is this grid-based system mainly used? What are the similarities and differences between UTM and SPCS grid systems?

SPCS: State Plane Coordinate System-> another grid based sys for determining locations and measuring distances in the USA. Uses a projected coord sys that uses a translation method like the UTM does but SPCS only covers USA

Chap 4: What is a multipath effect? How does it influence GPS accuracy?

Signals can be blocked by buildings, bridges, trees, etc. Signals may be reflected off buildings or walls before reaching receiver Multipath effect can introduce additional delays into the reception of the signal bc the signal is reaching the receiver later than it should

Chap 2:Why are there hundreds of datums in use? Why shouldn't we just use one datum for all different places on Earth? Why does a datum have to be determined before using a geographic coordinate system?

The Earth is shaped like a lumpy potato. Not all Datums cover certain areas. Some datums are better fit for other areas

Chap 2: Which map projection does the UTM grid system use? How many zones are in the UTM system and how many degrees of longitude does each zone cover?

UTM uses the Transverse Mercator Projection. Only covers Earth above 84 north and 80 south. cant be used for polar regions. 60 zones.

Chap 2:Understand the differences between NAD27, NAD83 and WGS84 datums. Which datum should be used for the globe? Which datum should we use for the United States? Which datum do most digital maps (e.g. Google Earth Pro, Google Maps, Bing Maps, etc.) use?

WGS84 Datum: World Geodetic System of 1984 is a gen model for the whole planet. Used for GPS. Google Earth NAD27: North American Datum of 1927, based on clarke ellipsoid of 1866 w/ fixed center @ Meade's ranch in Kansas. Developed for measurements of USA and the rest of NA NAD83: North American Datum of 1983 based on Geodetic Reference System (GRS80) ellipsoid that is referenced at the center of Earth's mass.Developed as datum for USA and the NA content as whole

Chap 4: What does a "12-channel" GPS receiver mean?

channel is the number of satellites from which the receiver can get signal from at one time. More channels = higher accuracy.

Chap 3: What are control points (or ground control points)? What are the standards of selecting control points? What are good/poor examples of control points? What is the minimum number of control points required for georeferencing?

ctrl pts: pt locations where coords are known find common pt to "tie" unref data to source data want places that have heterogenous land covers. Good GCPs: building corners, large trees, street intersections Bad GCPs: cars, rocks, shoreline of beach Want at least three GCPs, the more GCPs the more accurate

Chap 2: What is a geoid? What is an ellipsoid? What is a datum? What are the relationships between geoid, ellipsoid and datum?

geoid- model of Earth using mean sea level as a base and takes mountains and trenches into account as an Earth Model ellipsoid: rounded model of shape of Earth assuming Earth's surface is flat and smooth. Datum- math model that approximates shape of Earth to enable acc position, length and area calculations DATUM IS THE WAY WE USE THE ELLIPSOID TO TRY AND FIT THE GEOID

Chap 4: Which two atmospheric layers can cause GPS signal delays? Why?

ionosphere: (above troposphere) can alter the speed of satellite signals which can cause an inaccurate timing measurement. troposphere: the amount of water in it can interfere w/ signals and can cause delays.

Chap 3: What are the standards of choosing a georeferencing source? What is a commonly used source?

must be scientifically reliable. GEP google earth pro is commonly used

Chap 4: Describe the process of trilateration in determining a location on Earth. What is the minimum number of GPS satellites needed to determine a location?

need three satellites. uses three points of ref.

Chap 3: What are four transformation methods?

rotate, skew, translate, scale

Chap 3: Why does not a scanned historical map match up with georeferenced data layers? What technique do you use to solve this issue?

scanned map doesn't have spatial reference. the software doesn't know how to match it up with other data sets that are georeferenced. so you have to georeference the data.

Chap 4: What is the difference between a single frequency and dual frequency GPS receiver?

single: only picks up L1 frequencies dual: picks up both L1 and L2