PolyU LSGI2223 Geographic Information Science
Q&A revision list (answer by Otto Yu)
L1
What is map scale and how to calculate map accuracy?
To calculate the map accuracy, the minimum distance on the map divided the scale is the map accuracy.
All the object smaller than the “map accuracy” cannot been mapped
Minimum distance on the map means “cannot see and visualize”
What are the three types of maps in Hong Kong according to map scales?
The three types of maps are small, middle, and large-scale map, the small scale is 1:50,000 and smaller, the middle scale is 1:10,00 to 1:50,000 and large scale is 1:10,000 and larger.
What are the primary and secondary map symbols?
For the primary visual variables, it includes three geometric variables and color variables respectively, and for the secondary visual variables, it includes three types of visual variables.
About the primary visual variables: Shape, size orientation are the geometric variables
Hue, value and chroma are the color variables
About the secondary visual variables: Texture, pattern orientation and arrangement
What are the basic questions of geographic thinking?
Location, attribute, trend, routing, pattern, modelling
What are the two parts in spatial data and the data types.
Coordinate plus attributes are the two parts in spatial data.
Quantitative data and qualitative data types.
For the Quantitate data would be the description, place name, mobile and address.
For the Quantitative data would be the coordinate, distance, and area.
What is the first law of geography?
Everything is related to everything else, but near things are more related than distant things.
What are the basic types of geographic data models?
Vector, raster, and hybrid.
Vector data models’ basic logic unit in a geographic context are correspond to a line (such as contour lines)
Raster data models’ basic logic unit is a single cell or unit of a space in the mesh/grid
Hybrid make use of both vector and raster
What are the four types of spatial data sources?
Ground surveyed data, remotely sensed data, cartographic data, and the Administrative and statutory
What is VGI?
VGI means the volunteered geographic information, which are based on people who volante to make the GIS and map system themselves and provide an open-source platform, such as the OSM.org OpenStreet map.
Who developed the first GIS software, and who first coined GIScience?
Roger Tomlinson and Michael F. Goodchild
What are the five components in GIS?
Hardware, software, data, people, and methods
What are the two types of GIS software?
Commercial and open sources
L2
Compare the users, function and price between Desktop GIS, Web GIS and Mobile GIS
User increase when price increase, user decrease when function complexity increase
Desktop GIS < Web GIS < Mobile GIS (most popular)
What is the difference between spatial dependency and spatial heterogeneity?
Spatial dependency means things may affect by their surroundings (all are correlated) which is not dependent. It reflects a situation where value at one location depended on the value of neighboring observations at nearby location.
Spatial heterogeneity means the location data are independent, it changes one to another one, it is a property generally ascribed to a landscape to a population.
How to measure spatial autocorrelation?
Moran’s Index can aid the spatial autocorrelation measurement, the Moran’s Index 0 mean the dataset is randomly distributed, -1 mean the dataset is dispersed and 1 mean the dataset is clustered.
What is spatial scaling?
Spatial scaling mean fractal, self-similarity (such as Koch curve) part of itself that similar to the whole one
What is MAUP, and how it affects regression analysis?
MAUO mean the modifiable are unit problem, it is a type of statistical information. It helps to divide the data in different units and perspective, still the justification of unit may affect the data analysis.
What is spatial interaction, and what is the relationship between interaction and attribute?
Spatial interaction means the aggerate flow movement of something (such as the traffic flow, population, and capital flows) that interact with the geographic area/ space.
Attributes is the first order of spatial unit and interaction in the second order of mutuality, the attribute of spatial unit contributes to static quantity, while the interaction between spatial unit matter for spatial structure identification. Attributes and interaction affect each other’s, interaction matters, and attributes refines.
L3
What is the different between a single layer network and multilayer network?
Multilayer network contains more layer, and they interact with each other, unlike the single layer network. For example, each node can belong to any subset of the layers.
What are the complexity and geo-complexity?
Complexity is the phenomena that arise due to interaction among the parts of a complex system, such as the self-organized. Geo-complexity is the use of mathematical techniques to models the complex geological system (such as natural hazards).
What are the components in LBS?
Mobile devices (User), Positioning, communication network, service, and content providers
How to divide positioning technologies in different groups?
To divide them in the coverage size (such as the long and short range) and coverage area (indoor and outdoor).
What is GNSS, and what are the two GNSSs with full operational capability?
GNSS is the generic term for global satellite navigation system that provide three-dimensional positioning and timing information at a global scale.
The two GNSSs with full operational capability are the (1) GPS developed by the US government and the (2) GLONASS developed by the former Soviet Union.
What is the relationship between the coverage and accuracy for indoor positioning technologies?
The lower the technologies coverage, the higher the accuracy; vice versa the higher the technologies, the lower the accuracy.
What is user modeling in LBS?
User modeling, location modeling, context modeling and integration
What are communication forms in LBS, and what is AR?
LBS can communicated to their users by graphical, verbal, and haptic forms. Such as the mobile map “Google map” is the LBS that communicated as a graphical form.
AR means the Augmented Reality, that superimposes a computer-generated information on a user’s view of the real world and thus providing an “augmenter” view
What are the three issues in LBS?
Standardization issues, Legal issue, and social issue
How to define location privacy in LBS?
The concept of privacy can be described as the protection and control of our personal information, it is both an openness and a closeness dialectic.
L4
What is visual illusion and how does it occur?
Illusion occurs when visual signals lead to internal inconsistencies within an image, it also occurs when conclusions are reached that are clearly contradictory to our preconceived notion or reality.
What are the four types of visual illusion?
Ambiguity, distortion, paradox, and fiction
What is Gestalt psychology?
It is a concept that “the whole picture is greater than the sum of its parts”, which implies humans mind tend to perceive object as part of a greater whole and as element of a more complex system.
What is the law of figure/ ground?
It means the human mind tend to use element of the scene while are similar in appearance, shape
and group them together as a whole.
What is the law of simplicity?
It means the human mind tend to simplify the complex pictorials (objects) by line and logos.
What is the law of similarity?
It means the human mind tend to group the complex pictorials (objects) together.
What is the law of continuity?
It means the human mind tend to predict the preference as continuous surface.
What is the law of closure?
It means the human mind tend to group the pictorials (objects) together and complect the missing part to forms a continuous surface (which is an illusion). It is because the human mindset reacts to patterns that we are familiar with, when we receive some incomplete pictorials, it will become speculated, and we will group and complect the missing part -> law of closure.
What are the two types of schematic map in transport?
(1) From segment to stroke and (2) re-orientate strokes
What are the main steps to create a schematic map?
The main step of schematization is to simplifies lines to basic shapes, orientate lines along grid line (we can have the four basic orientations or even set more orientation to eight or sixteen), lastly to enlarge the congested areas.
What are the main steps to create a concentric map?
The main step to create concentric maps is to choose a center point, set up the polar gridline and put the selected center point in the middle of the pole, to enhance the line importance (such as reducing the bending of lines in the drawing map.
L5
What is Map generalization? Why we need it?
It means transforming Earth geographic features by setting map scale and purpose (cartographic generalization). The map scale is a main factor which indicate the generalization process.
The reason for generalization is to update the large-scale map frequently, the updated large-scale maps can be a reference to generate and update the small-scale maps, for example from detailed information (polygon) to abstract (lines or points).
What is subjectivity in generalization?
The subjectivizes in generalization would be exaggeration and characteristics in the generalization process. Exaggeration and characteristics are mainly caused by the human, as it involves personal judgements, the generalization may include some bias (such as the smaller and larger sizes misjudgments).
What is the operation for transformation of features in the process of generalizations?
The operation calls Geometric transformation. Geometric transformations mean the process of using a set of control points and transformation equations to register a digitized map, in GIS it may include map-to-map transformation and image to map transformation.
To ensure the spatial information, how to calculate the number of features according to principle of selection?
According to the Principle of selection:
And how to calculate the spatial entropy of a map?
The spatial entropy can be calculated by:
For the step for calculation:
(1) Sum up the total symbol to be the “P” denominator
(2) Calculate the symbols (such as road and building) to be the “P” nominator
(3) Then, calculate the “P”
(4) Use the sequence , then change it into the
Douglas Peucker algorithm is used for what kind of map generalizations.
Douglas Peucker algorithm is for the line (contour line and slope) generalization.