Gu Gis Midterm Prep

Front 1

GIS tool box definition

Back 1

emphasizes the storage and retrieval functions of a GIS system - in retrieving the data (which is geographic), it can be transformed and displayed in a way that suits our purposes

Front 2

GIS IS definition

Back 2

emphasizes its design to work with data that correspond to a particular geographic coordinate and the way it is oriented systematically toward spatial/geographic information, especially "points, lines, and areas"

Front 3

GIS approach-to-science definition

Back 3

GIS is used in scientific research-used to pinpoint locations of epidemic hotspots and to infer sources of contamination. Also GIS is used in a lot of ecological research where scientists map the location of different populations of interest

Front 4

What is the difference between data and information?

Back 4

there are all sorts of data out there, but it only becomes information when it is useful to inform our understanding about a particular questions that we have

Front 5

What is the difference between non-spatial and spatial information?

Back 5

Spatial information shows a physical relation between objects as they exist in the real world. An example is a blueprint, which shows the parts of a structure as they relate to each other. Non-spatial information would be something like a list of all the components of a structure with no information about where they are located.

Front 6

What is the difference between non-geographic and geographic information?

Back 6

Geographic information is "geo-referenced" to a specific spot on the Earth's surface. Information can be spatial and not geographic if it is not geo-referenced.

Front 7

How do “activity space”, “migration”, and “residence” affect the study of population at risk?

Back 7

Someone's activity space is not limited to where they live - it also allows for the various activities they normally do. When migration occurs (a change of residence), a person (population) is exposed to an different set of risks.

Front 8

Explain the difference between incidence and prevalence.

Back 8

Incidence refers to the number of new instances (mnemonic device?) of a disease. Prevalence refers to the total number of cases at a particular time. Someone might talk about the HIV incidence in March being 0.1% of the population (that many more people contracted the disease) and a prevalence of 10% (that many people have the disease).

Front 9

Define relative risk (or risk ratio) and odds ratio.

Back 9

Risk, basically, expresses the number of times something will happen relative to the general population or a study group. So someone who smokes has a 10% risk of lung cancer happening - that's their risk - and someone who doesn't smoke has a 1% risk of lung cancer happening. So the risk ratio is exactly that - the ratio of the risks - 10% to 1% = 10 times more likely. Odds measures the "number of times the health event occurs relative to the total number of times it does not occur" - so in our example that would be 10:90 odds of lung cancer for a smoker, or 1/9, over the odds of the non-smoker developing lung cancer - 1/99, coming out to 11.

Front 10

What is the difference between space and place?

Back 10

Space is more of a purely geographical concept that defines certain boundaries and attributes of an area, while place incorporates the importance to humans of those boundaries and attributes for life activities and social interactions - like the concept of a 'home', a 'workplace' or a 'commute'.

Front 11

GIS is technology among a constellation of computer technologies that process geographic data. Name two and briefly describe what they are.

Back 11

1. GPS, which references a specific spot on the Earth and geo-references its user using satellites and triangulation

2.remote sensing, which includes aerial photography (detecting light reflectivity)

3. digital image processing (detecting invisible radiation emanating from the Earth's surface).

Front 12

What are the four levels of measurements? Can you give examples?

Back 12

Nominal (just giving it a name, like the states); Ordinal (setting something up in a ranking, like the US News college rankings, but with no information about the distance between the ranked elements), Interval (like ratio scale, but with an arbitrary zero point like the Fahrenheit and Celsius temperature scales that can use negative numbers), Ratio-scale (has an arbitrary zero - so height measurements fall under this category, can't use negative numbers)

Front 13

There are 4 cartographic elements (point, line, area, surface). What are they and what are their respective dimensions?

Back 13

The 4 cartographic elements and their dimensions are:
Point 0, line 1, area 2, surface 3

Front 14

What is geodesy?

Back 14

Geodesy is the science of observation and measurement of the shape, size, and dimensions of the earth as a whole and of the earth’s surface. The use of GPS is closely linked to geodesy.

Front 15

Why are ellipsoid and datum important information in cartography and hence GIS?

Back 15

The Ellipsoidal earth model is important because it allows for accurate range and bearing calculations over long distances. Reference ellipsoids include the semi-major (equatorial radius) and semi-minor (polar radius) axes.
Geodetic datum is important to cartography because it defines the reference system that describes the size and shape of the earth (currently the ellipsoidal model)

Front 16

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In terms of map projection, there are 3 flat surfaces (developable/plotting surfaces) on which the spherical earth is projected. What are they?

Back 16

Spherical earth is projected on 3 flat/developable/plotting surfaces: cone, cylinder, azimuthal (plane).

Front 17

What is a secant projection? Can you draw a diagram to illustrate how it is different from other projections?

Back 17

A secant projection consists of a cylinder cutting through a sphere vertically so that there are two tangent lines (small circles) formed along the parallels of the sphere.

Front 18

What is a transverse projection? Can you draw a diagram to illustrate how it is difference from others?

Back 18

A Transverse projection consists of a 90 degree rotation of a secant projection, so that the cylinder cuts through the sphere horizontally and the tangent lines run north-south (small circles), but are not parallel to the meridians.

Front 19

Projections are classified according to their distortion. Any examples? What property does each of these projection types preserves?

Back 19

Conformal projections preserve shape but not areas.
Equal area projections preserve areas but not shapes.
Cylindrical projections preserve true directions and angles but not shapes and areas. They are most appropriate for navigation, analyzing, guiding, or recording motion. Examples of cylindrical projections include Mercator and UTM

Front 20

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What are the key characteristics of Transverse Mercator Secant and Lambert Conformal projections? What spatial relationship they preserve? What are the plotting surfaces they use?

Back 20

Transverse Mercator secant and Lambert are both conformal projections that accurately illustrate equal areas, distance, shape of geographical features, and true direction. They are often used in state projections. The Transverse Mercator is used for states that run north-south, like Illinois, while the Lambert projection is used for states running east-west, like Tennessee.

Front 21

There are many coordinate systems one can use. Describe the characteristics of geographic coordinates.

Back 21

The geographic coordinate system consists of latitudes and longitudes which create a grid and allow for a location to be specified using degrees as units. These are stated in reference to the main longitude—the Prime Meridian (E/W) and in reference to the main latitude—the Equator (N/S).

Front 22

Know the following terms: longitude, latitude, parallel, meridian.

Back 22

Longitude: the position of a place east or west of the prime meridian. It is measured as the arc of the parallel between that place and the prime meridian, and ranges from 0 to 180 degrees E/W
latitude: the position of a place north or south of the Equator. It is measured as the arc of the meridian between the place of intersect and the equator, and ranges from 0 to 90 degrees N/S
meridian: all points having the same longitude. true north-south lines connecting the poles. Each is half a great circle.
parallel: all points having the same latitude. They are true east-west lines, and intersect meridians at right angles. (The equator is a parallel that is a great circle)

Front 23

What is the use of UTM coordinate system? Describe the characteristics of the UTM coordinates.

Back 23

The UTM coordinate system is set up as a grid which divides the earth’s surface into 60 rectangular zones which span 6˚ each in the West-East direction extending from 80 degrees South latitude to 84 degrees North latitude (designated by UTM zone numbers) and 8˚ each in the North-South direction (designated by UTM Zone Designators: letters). Within each of these zones, there is a central meridian, and x and y coordinates are used to describe locations with regards to this meridian and the equator. It is possible to state distances within zones in meters, and by extension to state these distances with regards to the equator. Eastings are measured from the central meridian of the zone and northings are measured from the equator. For this reason, it is important to describe a location using UTM with the correct zone, cardinal direction, and meters or degrees N/S and E/W of the zone meridian or equator.

Front 24

Why do we concern ourselves with map scale?

Back 24

1. Map scale tells us a) Resolution of data (tells how much smaller the map is from the area it is representing) 2) The amount of detail you are showing c) And it affects the type of analysis that you can do
2. This is important in analyzing health data when you are researching the clustering of diseases or other factors in a specific region. The scale of the clustering (e.g. by city vs. by state) can influence the inferences you can draw from your data. Also, clustering at larger scales of region or states can result from larger factors like climate or culture while clustering in cities or communities can reflect localized factors like a point source of environmental contamination. The scale at which a health issue is studied should reflect some understanding of the disease in question and some possible factors.

Front 25

What are the three types of map scale often found on a printed map?

Back 25

1. Graphical/Visual (i.e. bar scale: looks like this
2. ______________________________________
_____16________0________16_________32_ miles
3. Representative fraction (i.e. 1:24,000 which means that one unit of measure on the map is equal to 24,000 units of the same units of measure in real life)
4. Verbal scale (i.e. 1 inch equals 16 miles)

Front 26

Which of the followings has larger map scale? 1:24,000 versus 1:100,000

Back 26

1. 1:24,000 (think in terms that you are dividing by a smaller number so this will give you a larger map scale; larger map scale means that you are zoomed in and are seeing a smaller area but with more detail)

Front 27

In your own word, define the term georeferencing.

Back 27

To reference the location of a point using a predefined coordinate system to establish the relationship between page coordinates on a planar map and real-world coordinates

Front 28

In terms of data file, there are flat and hierarchical file. What is the difference?

Back 28

Prof. Cheung talked about flat and hierarchical files in terms of the data structure of vector data structures.
Flat files: "An attribute file that contains all of the points". One sheet of data
vs. Hierarchical files: Data is expanded into another layer and sheet

Front 29

There are two main data structures in GIS. They are vector and raster structures. How are they different? Discuss in terms of the conceptualization of the “real world”, ie the concepts of object-view and field-view. What are their respective advantages and disadvantages?

Back 29

1. Raster: represent geographic features by pixels (a square grid cell that represents the generalized or the average view of an area of specific size on or near the earth's surface)
2. Pixel size affects the size of the object that can be seen in a digital image which determines the spatial resolution of the data (hi resolution means a small pixel size)
3. Every raster layer corresponds to a single attribute for a unit of space (i.e. elevation at a particular place)
4. Raster structure treats geographical features as surfaces, regions or segments -->FIELD-based view
1. This data is often captured by remote sensing imaging devices (spatial resolution of resulting image depends on the sensor) and digital cartography (i.e. digital cameras, image scanners, etc.)
2. Every raster layer corresponds to a single attribute
3. Advantage: raster data structures make it easy to overlay data layers BUT the corresponding pixels must be registered to the same position on the surface of the earth
4. Disadvantage: Requires geographical features that are CONTINUOUS rather than discrete(represented by an integer) (exp: elevation, temp, rainfall)
1. Spatial resolution dependent on sensor
2. cell size determines resolution at which the data is represented
3. most data is in vector form so there must be a conversion to raster structure

1. Vector structures: represent geographic features by the basic graphical elements (cartographic elements) of points, lines, and polygons
1. The vector structure treats geographical objects as though they are discrete objects on the earth's surface --> OBJECT-based view
2. Every vector layer corresponds to a single class of objects that have the same dimensionality (point, line, or area)
Advantages: most data (e.g. hard copy maps) are in this form so conversion isn't always needed
1. aesthetically pleasing graphic output
3. Disadvantages: continuous data can't be effectively represented in this form

Front 30

Please understand the information Figure 2.6 illustrates with respects to topological vector data model.

Back 30

Textbook, p.44. Topological vector databases contain information on the neighborhood relationships among objects. A line or arc is defined by a start node and an end node which together indicate the arc's direction. Regions to the right or to the left of this arc are then identified and compiled to give an index of the spatial relationship between these arcs.
I emailed him about this one and he said: You should take a look at that figure and see how schematically
points lead to lines/arcs and lead to areas/polygons; also pay attention to how they look not just in terms of map but also the data tables behind it

Front 31

What is tessellation? Which of the two data structures is directly related to this process?

Back 31

Tessellation is when a plane is divided into areas so that the plane is filled with no overlaps or gaps. Tessellation is associated with the raster data structure which subdivides space into a regular matrix of square or rectangular pixels with no gaps and no overlaps.

Front 32

What is the difference between absolute and relative location?

Back 32

Absolute: position with respect to an arbitrary grid system like the geographic grid of parallels and meridians. This tells us the position of a point so its unique position on the earth is clear. "The burner stack is 41degrees48'N and 72 degrees15'W"

Relative: position with respect to other objects in the geographic space. "The burner stack is 300' northwest of the intersect of Park and Broad streets"

Front 33

What are the four types of accuracy? Give a brief description and perhaps example for each. (He said we should know 4 of 5)

Back 33

GIS data quality issues in which accuracy is important:
1: Lineage (the information needed to assess data quality based on other factors. It describes data at various stages in its existence, the source material from which the data were derived, the methods of derivation, and all the transformations needed to produce the final digital files)
-->describe data at various stages of its existence
2: Accuracy
spatial: how close the values describing the position of a real-world object to the object's "true" position-->important when locating objects)
attribute: nearness of the values describing the real-world entity-->i.e. this becomes an issue in definitions of what constitutes a health event (is it really malaria or just malaria-like symptoms?)
3: Completeness (measure of the absence and presence of data for the specified universe)
-->are all relevant objects captured in the database? (i.e. voluntary vs. mandatory screening programs may have varying levels of completeness in representing the true story of an issue)
-->are all the records for an individual unit in the database complete? (not just the presence or absence of a unit that is important, but also how complete the information for this unit is)
4: Logical (structural integrity of a database)
-->are all of the attribute data consistent with the requirements of the selected vector or raster data models? want to make sure that all of the data is modeled in the same way (as fields or objects) and described by the same attribtue data to ensure consistency in data handling
-->consistency within and across data layers is important (records from different time periods can present this problem)
5: Temporal (modeling data from across different time periods)
-->i.e. some data is more recent than others
-->important to model the data as an attribute (importance of historical data when looking for trends and noting when and attribute "expired" or began, i.e. public drinking well data)

Front 34

What is the NMAS horizontal position accuracy standard for published map scale of larger than 1:20,000?

Back 34

Not more than 10% of all points on the map should have an error by more than 1/30th of an inch
(the larger the map scale, the higher the horizontal positional accuracy required)

Front 35

What is the importance of foundation spatial data?

Back 35

All the recordable and/or observable data that will be used in creating a gis must be spatially referenced to this underlying layer, so it must be developed for the specific purpose and type/availability of data that will be supported by the foundation spatial data. This is what defines the geographical extent of the database, or the bounding rectangles of the study area in terms of xmin, xmax, and y min, ymax.

Front 36

What factors tend to influence the selection of foundation spatial data?

Back 36

The foundation spatial data is what determines the scale, resolution, positional accuracy, display of features, and raster or vector structure of the database. In determining these factors at the foundation level, it is important to consider the surface area being captured by the maps and the level of detail desired, as well as the level of complexity and detail of the data sets that will be linked to the foundation data, since all attributes will rely on this underlying configuration. For example, a national or large regional area of study would be better suited to satellite imagery or digital line graph data, which are both considered intermediate-scale foundation data. By contrast, a study of a smaller area that deals with smaller units such as specific addresses in a community would necessitate a more detailed view and consequently a DOQQ database for foundation spatial data would be preferred. Of course deciding which type of database to use involves evaluating what resources are available to create the map in the first place, since certain types of foundation spatial data may be impossible to create based on the resources available.

Front 37

Use a satellite imagery product (such as ETM+ or IKONOS) to illustrate the following four concepts: spatial, temporal, spectral, and digital/radiometric resolutions.

Back 37

Spatial resolution refers to the ability to sharply and clearly define the extent or shape of features within an image. It describes how close two features can be within an image and still be resolved as unique, discrete entities. Temporal resolution concerns the frequency with which images/attributes of an exact location are updated. Data should include an attribute describing when the data were observed, since often different layers of a map may be observed with different frequency. Spectral resolution refers to how many spectral bands are featured in a map, where spectral bands are "a well-defined, continuous wavelength range in the spectrum of reflected or radiated electromagnetic energy. A map may only have bands that include types of visible light, whereas other maps can have spectral bands of infrared light at well.The more bands you have, the larger the file size and the more costly it is to develop. Digital/radiometric resolutions refers to how sensitive the sensor is when it records variations in the electromagnetic spectrum. Higher values mean that more subtle appearance changes in the image can be detected. (Definition found online).


IKONOS compared to other satellite imagery products has a higher spatial resolution of 1 meter, making it very detailed and accurate. Regarding spatial resolution, it is panchromatic which means it can capture more than one band of electromagnetic energy (in the case of IKONOS this means 4 bands of visible light). Other satellite imagery products have lower spatial resolution, so they can cover a larger amount of area at a time, and have more spectral bands represented, including wavelengths such as TIR (thermal infrared) or MWR (medium range coverage). Since IKONOS covers such a small area at a time with high accuracy, the temporal resolution is such that updates to a given unit area are infrequent, sometimes taking years. For digital resolutions, this involves calibration but I don't understand what <10% calibration is. Calibration in the GIS sense is defined as "the process of choosing attribute values and computational parameters so that a properly represents the real-world situation being analysed" and often this means comparing the measurements to a standard. So perhaps <10% calibration means that less than 10% of the map is subject to any level of distortion or inaccuracy? What do you think

Front 38

Know the sources and data structures of the foundation spatial data introduced in class.

Back 38

Geodetic control: Data is transparent/never displayed or connected with attribute informationyet is crucial for ensuring consistent, accurate data linkage. It has growing uses in GPS receivers

DOQQ: Digital Orthorectified Imagery that consists of raster images generated from aerial photography or satellites. It's tied to geodetic control [how so?]and does not include any feature or sttribute information.

Satellite Imageries: Landsat and Spot are types of satellite imagery, the former is land-based.

DLG: Digital Line Graphs are vector databases showing transportation lines, water bodies, political boundaries, and elevation contour lines. This type does inclue attribute information (every line appearing on the map has attributes associated with it), but often runs into accuracy and recency concerns

TIGER/Line data: Topologically Integrated Geographic Encoding and Referencing data set. It features street centerline spatial data, connecting street addresses with specific locations on the ground. This is made possible due to the fact that TIGER is topologically integrated. However, in some places the positional accuracy of these specific locations is better than in others (a weakness of TIGER).
Cadastral: This data is associated with land ownership as it is legally defined. As such, there is a high level of positional accuracy covers a large spatial scale. Nevertheless, there is a large amount of variation in accuracy and availability of this type of spatial data.

What are the typical vital statistics? What are the two types of address-based information associated with vital statistics? Give examples. What are the challenges/limitations associated with the use of vital statistics in GIS?

Typical vital statistics are birth and death records, and these records are address-based, either to the individual's home (which may aid in linking the residential environment to mortality outcomes) or to the place of death (which considers health outcomes in the context of a facility's service utilization). When dealing with this sort of information, there are issues regarding innacurate or incomplete information, which can stem from any number of causes, such as miswriting an address or misdiagnosing the ultimate cause of death, particularly when many causes were involved. There are also issues of privacy and how many are willing to have their information reported, making availability of info a problem. A third problem is that tying everything may give a false sense of causal relationship, when exposure to the illness occured somewhere other than in the community.

Front 39

What is the difference between morbidity and mortality? Give examples in the US that are good examples of morbidity data.

Back 39

Mortality records are generated from death certificates and include demographic characteristics of the decedent and information about the cause of death and contributing factors to the death. Morbidity data concerns disease surveillance, i.e monitoring distributions and trends for a specified population and geographic area. Morbidity data can include anything from info gathered by government agencies and health care providers to info from survey research projects and subject-wise can concern wide variation of content, % of the population, and geographic scale.

Sentinel health events are cases of illness that signal a need for immediate public health intervention, and are monitered closely as such.

Front 40

Using health services data as an example, illustrate the two approaches we can use to illustrate spatial distribution of such services using GIS.

Back 40

Symbols are used that can either be geometric, consisting of simple shapes like circles or squares, or they can be pictorial, featuring simple pictures. For instance, for health services, a hospital may be indicated with a particular shape, or can be miniature buildings that in some way resemble a hospital (maybe with a medical cross on it).

Front 41

How do we typically represent point features and their attributes in GIS?

Back 41

Point features tend to be connoted by a specific symbol indicating what that point represents (i.e a symbol for a hospital) Besides the pictorial v. geometric methods of illustrating point features as discussed above, they are handled differently in point symbol maps and proportional symbol maps. On a point symbol map, point symbols correspond to 1+ event(s) and concentrations of point symbols reveal clusters of events.These maps can help in creating hypotheses about links to environmental hazards. Proportional symbol maps have symbol size be proportional to the number of events at a place.

Front 42

What are choropleth maps? What are the four key issues associated with making choropleth maps.

Back 42

Choropleth maps are where each region has a shade of color depending on where it stands on some spectrum (i.e percentage of population diagnosed w/ cancer). This is one of (if not THE) most common type of map used in the media.
The first issue is in determining where the natural breaks should be, which is determined by how many classes there are and built-in algorithms.The next issue is how to use color shading to convey information the most meaningful way on the map. The third is trying to keep consistency over time and not fragmenting maps into separate classes because they occur at different times. Maps shouldn't be made into too many separate chunks for comparison purposes. The fourth is the number of classes that should be used, and this issue is closely related to the previous ones.

Front 43

Briefly explain how modifiable area unit problem (MAUP) occurs, what it is, and how we may deal with it.

Back 43

Book: "The map's appearance and the message it conveys vary depending on the size, number, and configuration of area units", and these can be manipulated. This presents such problems as gerrymandering where the location of area boundaries are concerned. When health issues are being depicted in a map, this makes it possible that area units can divide up clusters of health events or concentrate them. Another way MAUP manifests itself has to do with the differences between areas that are densely v. sparsely populated to begin with, since any variation will be much more apparent over areas with fewer people. Similarly, the scale of a map will have a big impact on the extent to which an health issue appears to be a problem. To deal with this, a cartogram can be created where the sizes of areas are proportional to their population (i.e the red and blue US state map we saw in class)