pg. 1 GIS Exam/ Practice Questions with Correct Verified Answers/ Rated A+ / Latest Update 2024
What is remote sensing? Give examples. - ANSWER - Collecting information from a distance; ex.photographs or radar/LiDAR. Typically satellite or air plane. Offer great detail over a continuous surface
How is remote sensing imagery stored? - ANSWER - Great detail = large file sizes. Stored using raster data models - typically, three rasters superimposed together to get color (one each for Red, Green, and Blue
value: RGB)
How can we pull information from remote sensing? - ANSWER - Can often be detected by the human eye and then digitized or classified based on type; but is very time consuming and expensive. Plus, humans can make mistakes. So we increasingly use computers to pull out the information correctly. Computers use automatic processing, being trained to write rules to automatically pull out information. This is hugely beneficial for large datasets. Not ideal for small areas.
How do buffers work? - ANSWER - Create distances around objects (points, lines or polygons). A powerful analysis tool that is useful for showing proximity and can be done on raster or vector data but is more common on vector data, where the buffer output is displayed as a new polygon.
What are the 3 different buffer types? - ANSWER - Dissolve none: each object has its own distinct buffer and overlap is clear.
Dissolve all: all overlapping buffers from objects are combined.
Nested buffers: or multiple ring buffers. Buffers at varying distances, like a bull's eye.
Define vector overlays. - ANSWER - Involve combining spatial and attribute data from two or more data layers. Can be numerous variations where each gives a different output.
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pg. 2 Define clip analysis. - ANSWER - Using one shape, called the clip feature, to cut out another from the input, creating the output. Raster or vector data can be clipped. Basically involves cutting out data.
What is clip analysis in raster used mainly for? - ANSWER - To look at specific areas, and is less for analysis and more for storage/processing reasons.
What is the erase analysis tool? - ANSWER - Opposite to the clip function, removes a shape (erase feature) from the input to create the output where only the areas outside of the erase feature remain
What is the intersect analysis tool? - ANSWER - Finds overlapping features, and only these features that overlap from both layers occur in the output.
What happens if you mix inputs with the intersect tool? - ANSWER - The output will be features with the lowest geometry. For ex., intersection of points and lines will result in a new points layer.
What is the union tool? - ANSWER - Brings different features together into a new layer as one.
What is the dissolve tool? - ANSWER - Erases internal boundaries to specify larger groups by combining smaller ones with similar attributes.
What are the applications of networks analysis? - ANSWER - Flow of resources through a set of interconnected lines with centres connected by network links. used in traffic, sewer lines, electrical networks. Must follow along links to get from one centre to the next.
What is artificial intelligence? - ANSWER - Show computer what to look for and it figures it out; E.g.cancer on a brain scan, gentrification on street view. Cutting edge of computer technology - but humans are unsure of how it actually works. Computer is literally thinking for itself (training itself). Huge potential moving forward - perhaps someday replace all humans
What is LiDAR? - ANSWER - Light Detection and Ranging - similar to SONAR, but uses laser rather than sound waves. Device sends out a laser pulse, and records how long it takes for it to bounce off surface
and return to detector. Benefits: Highly Accurate; can penetrate foliage
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pg. 3 How are drones used in RS and what is their benefit - ANSWER - Similar to RS from air photos or satellite.However, much cheaper to collect the information and can be collected by user at will, rather than relying on someone else's satellite.
How can smart phones be used for data collection? - ANSWER - Because they are hugely powerful data collection devices, with a large number of sensors (accelerometer, GPS, gyroscope, microphone, barometer, thermometer). Have lots of storage for data, cloud connections, and high processing speed.The fact that our phones are constantly collecting data about us creates massive privacy issues.
Define projections and coordinates. - ANSWER - Projections compensate for the earth being spherical but being represented on a flat surface (map) Coordinates allow us to accurately and reproducibly locate features on the earth's surface
Define geodesy - ANSWER - Science of measuring the shape of the earth - humans have been refining the model for thousands of years
Describe earth's shape. - ANSWER - Earth is an Ellipsoid, not a perfect sphere. Two radii: •r1, along semi-major (through Equator) •r2, along semi-minor (through poles). More specifically, its shape is a geoid, because it is rough, not smooth, due to differences in internal gravitational pull. This causes some areas to bulge out while others are sunken.
What is essential for defining x/y coordinates? - ANSWER - The poles and equator
Define datum. - ANSWER - A model of the earth's size/shape (ie a model of the Geoid). Applied to a specific origin/reference point. Different datums created for places around the world. Continually refined over time (ex: NAD 27 vs 83). Not much change in recent decades. Horizontal and Vertical datums exist
With projections, is there more distortion on small scale or large scale maps? - ANSWER - Small scale maps
Projections typically only maintain 1 or 2 of what following features, and must distort at least one feature? - ANSWER - Area, shape, distances, and angles 3 / 4
pg. 4
Define spherical coordinates. - ANSWER - Use the length of a vector originating at the ellipsoid center to define the location on the surface
Define latitude and longitude. - ANSWER - Latitude: Lines running parallel east to west; Equator is the baseline Why can getting points from a GPS into ArcGIS be problematic? - ANSWER - Poor connection - hardware and software issues; different companies/products/versions Difficult to find the specified datum/projection
Longitude: Lines running from pole to pole; Meridians; Greenwich (Prime) Meridian is the baseline from which measurements are made
Define UTM. - ANSWER - Divides the world into 60 zones (including North and South). Each zone has an origin based on False Easting/Northing
Describe the relationship between GIS, coordinate systems, datum and projections and what happens in GIS when they differ. - ANSWER - Each layer has a coordinate system, and datum (usually projection) - even if it is not defined. All layers on the map must be in the same system to allow them to line up (superimpose). Thus, GIS projects on the fly to one system for all of the different layers. Data frame has one projection/coordinate system which is defined by first file added. All others that differ are re- projected on the fly to match this one.
GIS - ANSWER - geographic information system software - allows you to envision the geographic aspects of a body of data.
ESRI - ANSWER - is Environmental Systems Research Institute - the developer and supplier of GIS
how does computer hardware performance change - ANSWER - the performance doubles every 18 months.
ArcReader - ANSWER - allows one to view and query maps created with other ArcGIS products
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