GIS Test 1
student grade in a class (e.g., A, B+)
ordinal because it ranks student by their performance.
How can scale affect how a particular feature ( a city or a river, for example) is portrayed on a map, or in a GIS?
Larger scales (i.e., larger representative fractions) allow for more feature detail to be depicted on a map Smaller scales allow for less feature detail to be depicted, and may also require: --feature movement --simplification --other compromises that affect map precision and accuracy
Point symbols
Point Symbols can show a change in categories like representing a well. You can change the size or color of the point to indicate size.
Who created an early atlas that was widely used for several centuries, and what type of information did it contain?
Ptolemy, a Greco-Roman astronomer and geographer from the 2nd century B.C.
What is the Difference Between Real Maps and Virtual Maps?
Real Maps: Tangible --permanent form --can be viewed directly Include: Conventional drawn or printed maps --road maps, topographic maps, etc. Aerial photographs, remote sensing images, etc. Block diagrams, relief models and globes
Describe the following broad categories of map type.
Reference Maps Symbols used to identify prominent landmarks and other pertinent features --useful for looking up the location of specific geographic features --no particular feature is emphasized over the others Examples: Topographic Maps Remote Sensor Images --orthophotomap, orthophotograph, and aerial photograph, Satellite Imagery -Globes -Atlases -School Wall Maps -Road Maps -Recreation Guides Often produced in national mapping series (USGS topographic map series)
What should you do if the area you wish to map falls on the boundary between two State Plane or UTM zones?
Sometimes the region to be mapped falls close to a UTM or State Plane zone boundary or spans two zones. In this case, a customized coordinate system is desirable. Typically, one starts with a UTM or State Plane zone and adjusts the central meridian and/or the standard parallels to minimize the distortion. The central meridian should bisect the map extent, and the parallels for secant conic maps should divide the north south extent into thirds.
Spatial reference
The complete description of how the spatial data are stored for a feature class that includes the coordinate system, the X/Y domain, and the precision.
Proportional symbol map
a symbol whose size differs in relation to the phenomenon being mapped.
Briefly describe each of the following generalization operations, using diagrams to illustrate your points. c)Displacement d)Smoothing and Enhancement
c) Separating objects to depict their locations relative to one another d) Smoothing Reduce angularity of angles between lines to reduce blocky appearance. Enhancement Enhancing certain features to elevate the message portrayed
ratio data
data having a regular scale of measurement and a natural zero point like the population.
categorical data
data that place objects into unranked groups. Example: land use
ordinal data
data values that indicate a rank or ordering system.
Rectify
to rotate, resize, or wrap an image to match a map base using a selected set of ground control points.
Interval data
values that follow a regular scale but have no natural zero point like temperature.
nominal data
values that name or identify an object, like the name of a state.
Internet Data services: Cloud-based services
A cloud consists of warehouses of computers and hard drives managed by a company that rents processing power and disk space to clients --allows organizations to perform GIS-related tasks without needing to purchase all of the required hardware, software, and data
Explain what a divergent color set is, and what it can be used for
A set of colors with a neutral middle value that grades to increasingly saturated colors of different hues above and below. It can be using for showing a climate change.
Who founded the art of remote sensing?
French photographer and balloonist Gaspard Felix Tournachon carried large format cameras into the sky.
What does GIS stand for?
Geographic Information System or Geographic Information Science
Why are map projections necessary for making maps?
A GCS is a 3D coordinate system, but maps are flat. It is necessary because you have to convert degrees of lat and long into x-y coordinates.
What pathname refers to?
A pathname refers to the location of a file by listing the folders down to a file. The different file locations are separated by backslashes and the location progresses down to more specific file locations. For instance the pathname F:\gisclass\mgisdata\usa\States.shp would indicate looking on the F drive for a folder named gisclass containing a folder named mgisdata containing a folder named usa containing a file named States.shp. If a user wants to know where the shape file States.shp is located, the pathname would direct them where on the computer (or flash drive to find it). This could be likened to a map. For instance a geographical "pathname" to McNeese State University could be E:\northamerica\usa\louisiana\lakecharles\mcneesestateuniversity. When provided with a pathname, you know "where" to find a file.
Affine transformation
A process to translate, rotate, or skew an image to fit a new coordinate system. this transformation scales, rotates, skews, and/or translates images or coordinates between any two spaces. It is used to transform maps between coordinate systems. In affine transformation, the parallel lines remain parallel, the midpoint of a line segment remains a midpoint, and all points on a straight line remain on a straight line.
Ground control points
A set of points that match easily identifiable locations on two different data layers to enable georeferencing of one layer to another. An accurately surveyed coordinate location for a physical feature that can be identified on the ground. Control points are used in least-squares adjustments as the basis for improving the spatial accuracy of all other points to which they are connected. Control points are used in digitizing data from paper maps, in geoeferencing both raster and vector data and in performing spatial adjustment operations.
Georeferenced raster
A spatial data layer that is tied to a specific location on the earth's surface for display with other data.
Reexamine Figure 2.6 and its description in the text. The table on p. 58 (Chapter Review Questions) contains four actions. Below each is the list of the map documents in Figure 2.6. For each one, indicate whether the pathnames in the map document would still work (yes/no) after the action was taken, depending on whether the map document is saved with absolute (Abs) or relative (Rel) pathnames.
Absolute path: When the file is stored in an absolute path it starts with the drive letter e.g. "C": For sharing a file stored in absolute path they need the exact same path for the map layers. Relative path: it specifies the current location of the map in the disk. It has two special symbols a dot (.) and a double dot(..). A single dot represents the location of the directory while the double dot indicates moving up in the hierarchy. For sharing the map documents especially this is the most preferred path because even when the map documents and associated folders moved to a new drive their data can be traversed.
Why does the author strongly recommend that you turn off background processing in the Geoprocessing>Geoprocessing Options window?
Background processing is slower to start and finish a task, and it may not run as reliably as foreground processing.
Explain why it might cause problems to run ArcCatalog and ArcMap simultaneously.
Both programs can put file locks on data to signify it is in use; if the other program tries to modify a file locked by another, an error will result, and the action can't be completed.
Examine Figures 3.6 through 3.9 and explain why conic projections usually conserve area and distance but cylindrical projections typically preserve direction.
Conic projections have decreasing lengths of the parallels as you approach the poles, which mimics the decrease in the circumference of the earth towards the poles. Hence the distances do not get distorted with increasing distance from the equator. Since distance is not distorted, areas generally aren't either. In a cylindrical projection the longitudes are always projected straight up and down, so direction won't be distorted.
The difference between Define Projection and Project
Define Projection" in ArcGIS is what you use when the data has no defined coordinate system. The ArcGIS error message would look like: "Unknown Spatial Reference". When you run the "Define Projection" tool, the tool does not change the projection.
True or False: A shapefile of the United States with a GCS coordinate system would have an x-y extent that contains entirely positive values. ________ Explain your answer.
False. The extent is the range of x-y values, and the United States in GCS would have positive decimal degrees for y because it is north of the equator, but negative degree values for x because it is west of the Prime Meridian.
You need to create a map for the entire state of Idaho. What options do you have? How could you get the most accurate map possible?
Idaho is split between UTM Zones 11 and 12, and has three State Plane Zones, so one single predefined coordinate system is not available. You could (1) start with a UTM zone and redefine the central meridian through the center of the state, (2) just use the central State Plane zone (which would almost be the same thing). The state is more north-south, so UTM is better than a conic projection.
What does a GIS allow its users to do?
It allows them to collect, manage and analyze spatially-referenced data--produces information for better decision-making
What purpose is served by labeling coordinate systems?
It documents the characteristics of the coordinate system and it helps GIS display and manage data.
If a data set's features have x coordinates between -180 and +180, what is the coordinate system likely to be? In what units are the coordinates?
It is likely to be the Geographic Coordinate System in which the longitude measures the horizontal angles east or west of the Prime Meridian from -180 to +180 Degrees and measures the latitude vertically above or below the equator from -90 degrees at the south pole and +90 degrees at the north pole. As previously stated the all the measurements in the Geographic Coordinate System are in units of Degrees.
Who made the first explicit reference to map overlay techniques, who was one of the early implementer of the technique, and what did he use it for?
Jacqueline Tyrwhitt made the first explicit reference to the technique. Ian McHarg implemented it for highway planning.
Briefly list, and discuss, some different applications for which GIS can be used.
Land use planning Sociological analysis Business marketing Wildlife Habitat Studies Farm Management
Which of the following is the smallest scale?:
Large and Small Scale In terms of map scale (general rule of thumb): Large Scale: Scales of 1:50,000 or larger 1:24,000; 1:10,000, 1:5,000, etc. Intermediate Scales: 1:50,000 to 1:250,000 Small Scales: 1:250,000 to 1:7,500,000 Very Small Scales: Scales smaller than 1:7,500,000 Textbook maps as small as 1:100,000,000 Now, explain why you came up with this answer. General Rule of Thumb: Think of representative fraction as an actual fraction --1:1,000 = 1/1,000 (one one-thousandth) --1:1,000,000 = 1/1,000,000 (one one-millionth)
What does latitude measure, and what are the lines that are used to demarcate latitude called?
Latitude measures the angular distance from the equator to a feature's location --parallels are lines used to mark this angular distance --all points along a parallel have the same latitude
Line symbols
Line symbols can be uses to show rivers or roads. By changing the line type, you can show different types of roads like highways and interstates. By changing the thickness, that can indicate the discharge of the river.
What are some other GIS systems currently being developed, and who is developing them?
MAPINFO (Pitney Bowes), Intergraph MGA, IDRISI (Clark University), GRASS (open-source), and QMAP (also open-source)
What are some of the drawbacks of paper maps that make GIS so much better for creating, manipulating, storing, and analyzing data?
Manual techniques of spatial analysis have several drawbacks: 1. They are inaccurate 2. Data updating is time-consuming and laborious 3. It is difficult to extract relevant data 4. It is difficult to analyze data 5. The data storage media (paper maps) is inflexible, and can be degraded with continual usage. Difficult to perform analysis for more than a few different siting criteria --best sites are often missed. GIS techniques allow for quick remodeling for slight changes in siting criteria --produce results as maps --well-suited for presentation for a variety of situations
What are Map Elements?
Map elements refer to the various visual components of a map layout --allow the transfer of information The cartographer arranges the visual elements of a map --into a functional composition --to facilitate communication Typical Elements That Appear on Maps 1) Typographic Elements 2) Legend 3) Map Scale 4) Mapped Areas 5) Map Symbols
Briefly discuss how the State Plane Coordinate System (SPCS) is set up, including the following items in your discussion: a. Why the system was created. b. State Plane Zones c. Projections Used, and how each is used in the SPCS d. Units used
Most state plane zones are based on either a transverse Mercator Projection or a Lambert Conformal Conic Projection. The choice between the two map projections is based on the shape of the state and its zones. States that are long in the east-west direction are typically divided into zones that are also long east-west. These zones use the Lambert Conformal Conic Projection, because it is good at maintaining accuracy along an east-west axis, due to the projection cone intersecting the earth's surface along two lines of latitude. Zones that are long in the north-south direction use the transverse Mercator Projection because it is better at maintaining accuracy along a north-south axis, due to the circumference of the projection cylinder being oriented along a meridian of longitude. The panhandle of Alaska, whose maximum dimension is on a diagonal, uses an Oblique Mercator projection, which minimizes the combined error in the X and Y directions. d.The standard unit of measure for SPCS 27 is the U.S. survey foot. For SPCS 83, the most common unit of measure is the meter.
Describe the following broad categories of map type.
Persuasive Maps Used to persuade readers to choose a particular product or support a certain position --persuasive maps that deliberately distort or misrepresent information become propaganda maps
Polygon symbols
Polygons can represent different geologic units.
Why does ArcGIS create lock files, and how can the user remove a "spurious" lock on a file?
Programs keep track of which documents are being used by creating a small lock file on the same folder as the document while it is open in an application. When the program releases the file, the lock is deleted and another program is free to access the file. When the you open a document, the application checks for the file lock. If it is present, you will get the "in-use" message.
If each of the following data were stored as rasters, state which ones would be discrete and which ones would be continuous: Rainfall Soil type Voting districts Temperature Slope Vegetation type
Rainfall: continuous. Soil type: discrete. Voting districts: discrete. Temperature: continuous. Slope: continuous. Vegetation type: discrete. The rasters representing rainfall, temperature, and slope would be considered continuous rasters because the values range smoothly into one another, forming a continuous surface or field. This type of representation works well for constantly changing values that it would be hard to represent with vectors. The discrete rasters representing voting districts, soil type, and vegetation type are so called because they are used to show vector features. For example the voting districts have a line demarcating the different districts, and the soil and vegetation types have clearly discernible boundaries unlike rainfall, temperature, or slope.
What extra step is performed when projecting rasters that is not needed when projecting vector data? What happens during this step?
Rasters must be resampled to a new cell grid after transforming or projecting them. New cell values are generated for the new grid based on one of three resampling methods. Nearest neighbor grabs the value of the cell closest to the center of the new grid. Bilinear and cubic convolution interpolate values based on the four or sixteen closest cells.
Text symbols
Text Symbol variations usually indicate categories like towns versus rivers, although font size can indicate qualitative differences in value like the town size.
Briefly discuss how the Universal Transverse Mercator (UTM) coordinate system is set up, including the following items in your discussion: a. Lines of tangency b. Zone dimensions and number of zones, including the effect that this has on distortion c. Central meridian d. False northing and false easting e. How UTM coordinates are written f. Main usage in mapping g. Units used
The Universal Transverse Mercator (UTM) system is a specialized application of the transverse Mercator projection. The UTM system is based on a secant transverse cylindrical projection. Two lines of tangency of the cylinder to the sphere fall about 180 km to each side of the central meridian The globe is divided into 60 north and south zones, each spanning 6° of longitude. Each zone has its own central meridian. Zones 1N and 1S start at 180° W. The limits of each zone are 84° N and 80° S, with the division between north and south zones occurring at the equator. The polar regions use the Universal Polar Stereographic coordinate system. The origin for each zone is its central meridian and the equator. To eliminate negative coordinates, the coordinate system alters the coordinate values at the origin. The value given to the central meridian is the false easting, and the value assigned to the equator is the false northing. A false easting of 500,000 meters is applied. A north zone has a false northing of zero, while a south zone has a false northing of 10,000,000 meters. UTM is convenient because users need only know the zone number and hemisphere. In the United States and in ArcGIS, each zone is indicated by a number and the designation N for the northern hemisphere or S for the southern hemisphere, for example, UTM Zone 14N. The worldwide UTM system uses letters C to X to represent different latitudinal zones. Usage in mapping: Used for United States topographic quadrangles, 1:100,000 scale. Many countries use local UTM zones based on the official geographic coordinate systems in use. Large-scale topographic mapping of the former Soviet Union. The unit used in UTM is meters.
What do the equator and poles represent, in terms of latitude?
The equator is the base reference for latitude --i.e., zero degrees latitude The poles represent maximum values for latitude --north pole = 90 degrees north latitude --south pole = 90 degrees south latitude
What are the three basic types of map symbols, and what type of spatial information is each used to convey? Provide examples of spatial information that can be represented by each type of symbol.
The three basic map symbol types are Marker Symbols, Linear Symbols, and Polygon Symbols. Marker Symbols are basic on point data such as the location of a city or airport. Linear symbols represents data that follows a linear path; for example, contour lines and streets and highways. Polygon Symbols are used to show data that is contained within an area and represented with patterns and/or colors, examples of data that could be represented with such symbols are counties and land divisions.
What are the x-y coordinates of a map's origin? ___________ What is the x coordinate along the central meridian?______________________
The x-y coordinates of a map's origin are (0,0). This will be the assumed basis of all the other dimensions and coordinates throughout the map. The x-coordinate along the central meridian is 0, and the central meridian is chosen based on its position near the center of the area being mapped. Thus, coordinates will be given as positive or negative on the map based on which quadrant they lie in.
What do the tropics of Cancer and Capricorn depict? Why might this be important, from an environmental perspective?
They depict the latitudes at which the sun is directly overhead at noon on June 21 and December 21 (solstices) --this marks the latitudinal extent of the tropics, which receive the highest amount of solar radiation on an annual basis.
RGB
This is a method based on mixing red, green, and blue light on a computer screen.
CMYK
This is a method often used for printing and specifies mixtures of inks used in printers or plates (cyan, magenta, yellow, black).
HSV
This method is instructive for discussing the use of color in portraying features on a map. Stands for hue, saturation, value.
Define projection tool
This tool overwrites the coordinate system information (map projection and datum) stored with a dataset. The only use for this tool is for datsets that have an unknown or incorrect coordinate system defined. All geographic datasets have a coordinate system that is used throughout ArcGIS to display, measure, and transform geographic data. If the coordinate system for a dataset is unknown or incorrect, you can use this tool to specify the correct coordinate system. You must know the correct coordinate system of the dataset before using this tool.
What was the original ellipsoid used as the best fit for North America (pp. 10-11)? What ellipsoid replaced it, which is still in use today?
Until recently, the US used the Clarke 1866 ellipsoid --reference ellipsoid --datum (starting point) for horizontal control in large-scale mapping --now use WGS 1984 ellipsoid
You have a shapefile with a UTM Zone 10 NAD 1983 coordinate system, and you want to bring it into your state database, which uses the Oregon Statewide Lambert coordinate system. What is your next step?
You will use the Project tool to convert the shapefile to a new shapefile with the Oregon Statewide coordinate system.
Graduated color symbol map
a map on which a range of colors indicates a progression of numeric values. ex. increase in population density might be represented by the increased saturation of a single color.
Briefly discuss each of the following projection classes, and subclasses, including what properties each preferentially preserves, and which properties tend to be the most distorted, by each: a. Cylindrical projections 1) Transverse variant 2) Oblique variant b. Conic projections 1) Standard parallel 2) Secant variant c. Azimuthal projections
a. Cylindrical projections- a projection that transforms points from a spheroid or sphere onto a tangent or secant cylinder. 1) Transverse variant- A map projection whose line of tangency is oriented along a meridian rather than along the equator. 2) Oblique variant- A planar or cylindrical projection whose point of tangency is neither on the equator or at a pole. b. Conic projections- A projection that transforms points from a spheroid or sphere onto a tangent or secant cone that is wrapped around the globe in the manner of a party hat. The cone is then sliced from the apex (top) to the bottom and flattened into a plane. 1) Standard parallel-The line of latitude in a conic or cylindrical projection in the normal aspect where the projection surface touches the globe. A tangent conic or cylindrical projection has one standard parallel, while a secant conic or cylindrical projection has two. At the standard parallel, the projection shows no distortion. 2) Secant variant-A projection whose surface intersects the surface of a globe. A secant conic or cylindrical projection, for example, is recessed into a globe, intersecting it at two circles. At the lines of intersection, the projection is free from distortion. c. Azimuthal projections- A map projection that transforms points from a spheroid or sphere onto a tangent or secant plane. The azimuthal projection is also known as a planar or zenithal projection.
Briefly discuss each of the following aspects of GIS project management: b)The importance of developing a well-designed GIS. c)Choosing a methodology or model
b) A well-designed system will adapt easily to future modification --a haphazard system may be constantly redoing previous work when changes arise. c)Models convert the raw data of the project into useful information using a well-defined series of steps and assumptions
Briefly discuss the roles of GIS professionals in the following aspects of GIS, including why such expertise is important: c)Development GIS d)Distributed Database GIS
c)Skilled software and hardware engineers --build and maintain GIS software and hardware d)Computer science professionals with a background in networking, internet protocols, and/or database management systems --maintain complex server and network systems --allow data services, Server GIS , and Enterprise GIS to operate
Briefly discuss each of the following aspects of GIS project management: d)Data collection phase
d) The needs dictate which data layers (roads, soil types, vegetation, etc.) are required and how accurate they must be --an appropriate source must be found for each data layer --open-access sources --some may have to be created in-house, or through a data contractor --spatial detail and accuracy of data must be evaluated to ensure that they are able to meet project needs
Briefly discuss the evolution of the following aspects of GIS: e) Customization f)Enterprise GIS
e) Due to emphasis on open-source solutions --customized applications can now be based on a fundamental set of GIS tools (hydrology tool or wildlife management tool) --smartphone and tablet applications programming growing f) Integrates a server with multiple ways to access the same data --traditional GIS software, web browsers, and wireless mobile devices --goal to meet data needs of many different levels of users and provide access to non-traditional users of GIS
How can maps be used to deceive or, more specifically, to promote a particular political or economic perspective?
--maps are very persuasive due to implied precision of lines, scales, symbols and information content All maps distort the truth --sometimes unknowingly Sometimes for propaganda purposes --Nazi and Cold War propaganda maps exaggerated importance of certain spatial relationships
You are using a map that depicts Moss Bluff that is in such bad condition that you can no longer see the supplementary information (map scale, etc.). However, it does show a football field, which measures ½ inch long on the map, from goal to goal. What is the map's scale?
0.5 inches = 100 yards 0.5" = 300 feet 1" = 600 feet 1" = 7200" 1:7200
Provide at Least Five Examples of Graphic Elements that Can Appear on a Map, and Briefly Describe Each Type of Graphic Element.
1) A Neatline Frames mapped area --separates map from supporting information (titles, legends, etc.) 2) A border --similar to a neatline --often a design element --usually encompasses entire map document 3) A Map Scale Ratio between size of features on map and size of same features on Earth's surface Three Types Representative Fraction (1:24,000) Written Scale One inch equals 2000 ft. Graphic Scale (scalebar)
Briefly list, and describe, the three types of scale that can appear on a map. Include in your answer the benefits and drawbacks of each. 1
1) Written scale a. Provides a quick idea of size relationships b. Awkward to use, limited by language & units Examples: One inch equals 2,000 feet One inch equals one mile One inch equals two miles
What does data source refer to in ArcGIS?
1) a spatial data file that provides the features for a map layer. 2) the original info used to develop a spatial data set.
List, and briefly describe, each of the components that constitute a GIS.
1)Computer hardware platform 2)GIS software 3)Data storage 4)Data input hardware -Digitizer tablets, scanners, internet connection, gps 5)Information output hardware 6)GIS data 7)GIS personnel
What is the minimum set of functions that a GIS should provide?
1)Data entry from a variety of sources 2)Data management tools 3)Thematic mapping 4)Data analysis functions 5)Map layout functions
What is a database management system (DBMS)?
A set of computer programs used for organizing information that is stored in a database. A database is a collection of data that is usually stored as a single or multiple files that are associated with a single general category--usually stored in tabular format
Briefly describe the following programs associated with ArcGIS, including their principle functions within the ArcGIS desktop platform: a. ArcCatalog b. ArcToolbox c. Model Builder d. ArcMap
A) ArcCatalog- facilitates viewing and managing of spatial data files. B) ArcToolbox- a collection of tools and functions for operations in ArcCatalog and ArcMap, such as converting between data formats, managing map projections, and performing analysis. C) Model Builder- lets users graphically arrange and run sequences of steps, and save them to be used over and over. D) ArcMap- provides the means to display, analyze, and edit spatial data and data tables.
How can this affect the user's decisions concerning analysis performed using maps and/or geographic information systems?
An Important Consideration: Always choose the appropriate scale of map for your analysis Smaller scale maps involve greater compromise in terms of : 1)number of features depicted 2)feature detail shown displacement of features 4)Feature size
What are the advantages of the raster data model, and thus what type of spatial data is the raster data model best suited for working with? What are its drawbacks?
In its simplest form, a raster consists of a matrix of cells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information, such as temperature. Rasters are digital aerial photographs, imagery from satellites, digital pictures, or even scanned maps. Data stored in a raster format represents real-world phenomena: Thematic data (also known as discrete) represents features such as land-use or soils data. Continuous data represents phenomena such as temperature, elevation, or spectral data such as satellite images and aerial photographs. Pictures include scanned maps or drawings and building photographs. The drawbacks (disadvantages) are inefficient use of computer storage errors in perimeter, area, and shape difficult network analysis inefficient projection transformations loss of information when using large cells less accurate (although attractive) maps The advantages are simple data structure easy and efficient overlaying compatible with RS imagery high spatial variability is efficiently represented simple for own programming same grid cells for several attributes
What Does Cartography Involve?
Involves defining rules for: --transfer of features from a spherical planet onto flat maps --use of symbols to portray real-world features --reducing size of real-world features (map scale) --the need to remove unimportant details (generalization)
John and Mary are collecting GPS data together. John's GPS says their location is at (631058, 4885805). Mary's GPS says their location is at (1204817, 663391). Explain what is going on. What must be done to make the GPS units agree?
John and Mary are not using the same coordinate system. In order to make the GPS units agree, all they need to do is to set up their GPS in the same coordinate system and the units will match.
Who founded ESRI (the company that created ArcGIS)? a. What powerful concept did they first introduce, which served to revolutionize the industry? b. What is the main GIS product that they developed?
Laura and Jack Dangermond a) Linking spatial representation of features with attributes in a table. --a core concept in GIS b) Arc/Info, which formed the basis for the modern ArcGIS platform
What Do Maps Do That Makes Them So Useful for Analyzing Spatial Phenomena?
Maps allow us to: 1. Reduce scale 2. Isolate spatial phenomena 3. Combine or recombine spatial interactions and distributions --reveals relationships not directly measurable in the landscape
Why Do We Need Maps?
Maps are the Primary Tool for Spatial Analysis. Spatial phenomena not easy to observe or interpret in the landscape Because: 1.Too extensive 2.Many are neither tangible nor visible Examples: Language or religious patterns 3.Dynamic qualities of spatial interaction not directly observable
When Did Modern Cartography Develop?
Maps long used to convey spatial information --scratchings in sand --formal cartographic traditions established ~2000 y.a. in Greece, Rome and China Cartography re-discovered during the Renaissance --discipline dedicated to map-making --the science and art of making maps
Describe the following broad categories of map type.
Navigation Maps Also known as charts --created specifically to help navigators plan voyages and follow planned travel routes Examples: Nautical Charts Topographic Maps Aeronautical charts
What three basic vector objects exist, and what types of objects is each used to represent (provide examples)?
Points: shows objects that have no dimensions -Like a well or a sampling locality Lines: shows objects in one dimension -Like a road or a utility line Polygons: shows objects in 2D of a bounded area. -Like parcels or a state.
What is map (i.e., cartographic) generalization, and why is it used in cartography?
Process of removing detail Used because --too much complexity often obscures important patterns --too much detail in a map can be confusing
What was the U.S. Bureau of the Census' contribution to the development to the development of GIS?
Produced first geocoded census in 1970 --developed the early DIME data format based on CGIS and POLYVRT --later developed into the TIGER format
Briefly list, and describe, the three types of scale that can appear on a map. Include in your answer the benefits and drawbacks of each. 2
2) Arithmetic ratio (representative fraction) a. Map units expressed as ratio or fraction b. Units on left (map units) always same as units on right (ground distance) c. Scale not dependent on units used d. Awkward to use + not readily visualized
Imagine you are looking at a geodatabase that contains 50 states, 500 cities, and 100 rivers. How many feature classes are there? How many features? How many attribute tables? How many total records in all the attribute tables?
3 feature classes 650 features 3 attribute tables 650 records
Briefly list, and describe, the three types of scale that can appear on a map. Include in your answer the benefits and drawbacks of each. 3
3) Graphically 1) Graphic scale or bar scale (scalebar) 2) Map distance directly translated into correct Earth distance 3) Often includes more than one set of units 4)Applicability depends on projection used and units that appear on scalebar
Provide at Least Five Examples of Graphic Elements that Can Appear on a Map, and Briefly Describe Each Type of Graphic Element.
4) Map Orientation How a map is aligned, relative to Earth's surface North arrows, graticules or locational grids can provide orientation 5) Map Insets Small additional maps included within the main map --an enlargement of a portion of main area --locator maps showing where mapped area located Note: A locator map is only considered to be an inset map if it actually appears within the main body of the map.
Internet Data services: ArcGIS Online and web maps
A cloud-based platform that provides an environment to create and share maps --makes data available to users with little or no GIS training --also addresses needs of professional users Based on a web map --interactive map based solely on GIS services --perform a restricted set of basic functions such as zoom and query --device independent and can be used in ArcMap, in web browsers, on mobile devices (smartphones or tablets, and even within social media sites
Coverages
A coverage is the oldest vector format, developed for Arc/Info. ArcGIS Desktop has limited functions for managing coverages, so most users will encounter them simply as an old data format that must be converted into a shapefile or exported to a geodatabase.
How does a GIS differ from a conventional DBMS?
A database management system is designed to store manipulate, analyze and protect tabular data of all kinds. DBMS work with any kind of data, whereas a GIS is designed specifically to work with both spatial data and aspatial data
Explain the difference among the terms feature, feature class, and feature dataset.
A feature is a spatial object composed of one or more x-y coordinate pairs and having one or more attributes in a single record of an associated table. A feature class is a set of similar objects with the same attributes stored together in a spatial data file. A feature dataset is a set of feature classes in a geodatabase that shares a common coordinate system and can participate in networks and topology
Briefly discuss the decisions that the GIS user must make when creating maps of the following areas: Local and regional maps
Any region that fits inside a single UTM or State Plane zone can use either. The United States uses the State Plane Coordinate System. Similarly, other nations have their own specifically designed state or province coordinate system for better projection. The preferred system would place the region to be mapped close to the center of the zone, where the distortion is least. However, other factors may take precedence, such as the existing coordinate system of one's data sources, or the decision of the agency that oversees the project.
CAD files
CAD stands for computer aided design, and is used primarily for drafting or drawing maps. They can be read, but not edited or analyzed, without first being converted to shapefiles or geodatabase files.
What is a cartogram, what are cartograms used for, and why do they look so odd.
Cartograms are maps that use variations in size and shape to depict quantitative differences in the phenomenon being depicted --created by substituting a different standard of measurement (time, cost, or population) for distance measures --distorts sizes shapes and distances significantly
Define What A Map Is
Definition: Any concrete or abstract representation of features that occur on or near the surface of the earth or oher celestial bodies Two Types: Real maps Virtual maps
Define what map scale is.
Definition: The ratio of map distance to the distance represented on Earth's surface
Describe the following Types of Thematic Maps:
Dot-Density Maps Use dots to represent a specific quantity of a certain variable --show distribution patterns Choropleth Maps Show distributions summarized by specifically bounded areas Isoline Maps Show numerical values for continuous distributions --use lines that join points of equal value Flow Maps Show direction and amount of movement What is being moved May show: --actual routes --quantities moved
Who is called the "Father of GIS", and what were his contributions to the development of GIS?
Dr. Roger Tomlinson --promoted idea to use computers for mapping --helped develop Canadian Geographic Information System (CGIS)
Explain some ways that GIS services are different from data that reside on your hard drive.
GIS services can store many types of information, from vector and raster data to geodatabases, which can be manipulated. Information from Internet-based data services can also be used for spatial analysis. GIS servers can only be accessed over the Internet, so a connection must be available. Many GIS servers provide only the data requested rather than the entire data file. GIS services can be used by many kinds of devices, not just a Windows computer. GIS servers have more sophisticated security measures than local data
How does this differ from GPS?
GPS stands for Global Positioning System. A series of 24-30 satellites used for precise location of features
What is Earth's true shape (pp. 18-19)? What geometric shape best approximates this shape?
Given the uneven nature of Earth's surface, the shape that best approximates the Earth's true shape at a given location is called a GEOID Geodesists and cartographers do not use a true geoid, but instead use a geometric shape called an ellipsoid --created by rotating a flattened ellipse about its narrow axis to approximate Earth's true shape Different countries use different ellipsoids --each selects an ellipsoid that best fit the Earth's true shape for that particular region
Internet Data services: GIS servers 1) Map service 2) Layer package or map package 3) Image service
Provide geospatial data over the Internet --contain software that responds to requests from users for specific maps or data in the user's current window --some are public access, meaning they are open and free to the public --some may be proprietary, meaning that they are only open to members of a particular organization or group of users 1) Map service Renders map layers as tiles and sends to the user as static images --faster --user cannot modify map symbology A feature service shares requested data features --slower --user can change symbology and potentially edit or analyze them 2) Layer package or map package Sends the data to the client --stored locally during use 3) Image service Provides access to large mosaics of satellite imagery or aerial photography
Shapefiles
Shapefiles Spaghetti data models containing a feature class composed of points, lines or polygons, but never mixed. Attributes are stored in a dBase file. Can store multipart features meaning an island state or nation like Hawaii or the Philippines can consist of multiple polygons stored as a multipart feature that has one record in the attribute table, rather than many.
What two basic vector models exist? How is each used to store spatial data?
Spaghetti: stores features of the file as independent objects, unrelated to each other. It is commonly used to transfer vector features from one GIS system to another. Topological: Stores features, but it also contains info about how the features are spatially related to each other. Example: whether two parcels share a common boundary, whether two water lines are attached to each other.
Explain the difference between spatial data and aspatial data
Spatial data have spatial or geographical reference --enables them to be located in two- or three- dimensional space. Aspatial Data--data that is either not tied to location, or only incidentally tied to location
How are the equator and poles associated with Earth's movement, and how does that make them ideal "features" with which to develop one part of a geographic grid, such as that of latitude and longitude (often simply referred to as the Geographic Grid).
Spherical Earth rotates once every 24 hours --poles are endpoints of rotation axis Equator is a line around Earth's circumference --midway between two poles --creates a great circle (divides Earth into two equal halves) Locational System To portray place locations with a map --need to define locations using spatial referencing system --most apply a geographic grid --others use a rectangular grid to transfer features to flat map --use projections to control distortions
What reference datum was used for surveying in North America from the 1920s through the 1980s? a) What reference datum replaced it? b) What effect did that have on maps created after that time, when compared to maps created using the earlier datum?
The North American Datum of 1927 --based on the Clarke 1866 Ellipsoid a) Recent advances in satellite geodesy --led to the establishment of a new Datum --North American Datum of 1983 b) Resulted in shift of up to 300 meters. Maps created after 1983 noted new datum in the corners --maps created after 1994 have been re-surveyed, and redrawn to the new datum Two Early Decisions Made When Deciding How to Depict an Area of Earth's Surface Using a Map: 1) What is the appropriate Map Scale 2) How much information to include --Generalization
Imagine a feature class of agricultural fields with attributes for the crop and the organic matter content of the soil. What issues might impact the thematic accuracy of each attribute?
The crop field can be well defined for a single moment in time as it is very clear what is growing. However, the crop type could change from year to year. Organic matter value of soil probably changes from place to place within the field & may also vary from year to year, so can only be considered a representative value. Knowing how it was determined might be important. However, If the crops are on a rotation, the crop type that is recorded may not match up with the one that is currently planted in the field. Organic matter of the soil may also vary with time, and it is also difficult to draw a distinct boundary across things like soil types, which may gradually change from one to another. Better answer: The agricultural field can be well defined for a single moment in time as it very clear what is growing. However, the crop type could change from year to year. The organic matter of the soil may also change from place to place within the field, and may also vary year to year, and so can only be considered a representative value. Knowing how it was determined might be important.
What is meant when Dr. Price tells that both of these vector and raster data systems are georeferenced?
The information is tied to a specific location on the earth's surface using a coordinate system.
Describe the following broad categories of map type.
Thematic Maps Show a single type of feature that is the map's theme --stress the geographical distribution of this one theme Examples: Climate Maps Language Maps Population Maps Precipitation Maps Vegetation Maps Historical Maps Use base maps that provide geographic reference information --not for use as an actual reference map --used only to locate area of interest
Why was it more difficult to come up with the location for the Prime Meridian than those of the equator and the poles?
There are no good natural references like the equator or poles for measuring east-west locations Longitude measures east-west distance from the Prime Meridian --passes through Greenwich, England --extended to form a great circle Meridians imaginary lines that intersect the equator & meet at the poles (all are Great Circles) International Date Line --passes through the Pacific Ocean 180º from the Prime Meridian A feature's longitude is its arc distance east or west of the Prime Meridian
Would raster or vector be a better format for storing land ownership parcels? Give at least 3 reasons for your choice.
Vector would be the better format for storing land ownership parcels. Vectors are used to define objects in the real world with specific locations or boundaries in which suites the parcels. Vector model features contain polygons which represent two dimensional areas and would best describe /feature the land ownership parcel. you would also be able to put the parcels in a singular feature class along with their attributes.
What is the Difference Between Real Maps and Virtual Maps?
Virtual Maps Maps that do not exist as tangible objects (that you can touch, or hold in your hands) Three Primary Types of Virtual Maps: 1) Images that can be directly viewed but are not permanent --maps on a computer display --these maps that are displayed on the wall 2) Mental Maps—images of the world that each of us holds in our minds Provide mental references of --location --distance and direction --size and characteristic of regions Affected by: --familiarity --proximity --similarity to one's own environment --standard of living --physical environment --amenities (entertainment, shopping, parks, etc.) 3) Geographic Data—collected data that refer to Earth surface features Field Data--fieldnotes, written books, computer Printouts
What Does the Term Typographic Elements Refer to?
Written Elements that Appear on the Map, and which are used to explain various aspects of the map Describe at least four examples of typographic elements which may appear on a map. Title—Indicates the purpose for which the map was prepared Legends—show map symbols & explain their meanings Names—names of feature types shown on the map Credits—usually an explanation of the map's information source , author, map accuracy, dates, or other explanatory material
Briefly describe each of the following generalization operations, using diagrams to illustrate your points. a) Selection b) Simplification
a) Involves deciding which features to keep for map and which features to remove b) Shapes of map features are simplified --river bends removed --bays and inlets removed Overall character must be retained
Briefly discuss the roles of GIS professionals in the following aspects of GIS, including why such expertise is important: a)Primary data providers b)Applications GIS
a) Create base data for many GIS installations.Surveyors and land-planning professionals—precise measurement of boundaries. Photogrammetrists—develop elevation and other data from aerial photography or LIDAR. Remote Sensing Professionals—extract cultural artifacts and natural information from satellite and airborne measurement systems. GPS experts provide base data and format it properly for GIS. b) Professionals trained in fields such as geography, hydrology, land use planning, business, civil engineering and utilities --use GIS in their work. Mathematics and statistics specialists—develop new ways to analyze and interpret spatial data.
Briefly discuss the evolution of the following aspects of GIS: a) Data storage and data-sharing associated with GIS. b)Options for working with GIS data.
a) More people are serving large volumes of data over the Internet to remote locations within an organization, across organizations, and to the general public --now moving toward cloud-based storage and file-sharing b) Used to have to purchase a large, expensive program and learn how to use it. Now can purchase scaled applications that serve user needs --servers for viewing and printing maps, freeware for viewing interactive map publications, and scaled-down versions of the full program with fewer options --server-based GIS provides data and a customizable set of viewing and analysis functions to users w/o a GIS license via a web browser.
Briefly discuss each of the following aspects of GIS project management: a)Important questions to ask before beginning a GIS project.
a)What specific issues must be studied? What kind of information is needed to support decision making? What functions must the GIS perform? How long will the project last? Who will be using the data? What funding is available for start-up and long-term support?
Briefly discuss the evolution of the following aspects of GIS: c)Expansion into wireless technology d) New emphasis on open-source solutions
c) More people collecting and sharing data via handheld wireless devices --handheld computers, smartphones, and GPS units --cell phone technology is advancing rapidly with new geolocation options, web access, and geo-applications becoming available d) More GIS functions now implemented within open-source software and hardware, rather than proprietary, specialized software --data now more often stored using engines from commercial database platforms and utilize same development environments as rest of computer industry
Briefly discuss each of the following aspects of GIS project management: e) Analysis phase f) Presentation of results
e) Problems during this phase may require making changes to the model and/or data --final result must be checked carefully against reality --recognize shortcomings and provide guidelines for improving future work f) Project completion requires communication of the results --to head of project, to client, to public
