12 Review and Outlook

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12.1 Review 12.2 Outlook

12 Review and Outlook

(2)

• What are the basic functions of a geographic information system?

12.1 Review

(3)

• What are spatial objects?

• What are the two main distinctions of spatial

objects on basis of their contour?

12.1 Review

http://worboys.duckham.org/

(4)

• What are the two main models of space?

• What are the basic concepts of geometry and topology?

• What are the main topological relationships?

12.1 Review

Spatial Framework

Attribute Domain

spatial field

Object Domain

Spatial Embedding

spatial reference

(5)

• What are the characteristics of the raster model?

• What are the main compression techniques for raster geometry?

12.1 Review

(6)

• What are the characteristics of the vector model?

• What problems arise during discretization?

12.1 Review

(7)

• Which methods for rasterization of vector shapes are there?

• Which methods for vectorization of raster shapes are there?

12.1 Review

1 3

2 2 1

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1

(8)

• What are the main topology models for vector geometry?

• Which interpolation methods for fields

are there?

12.1 Review

//skagit.meas.ncsu.edu/~helena/gmslab/interp/

(9)

• How to intersect vector geometry segments efficiently?

• Which

operations on fields are there?

12.1 Review

x₁ a₁

a₄ a₃

a₂

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e₂ e₄

S_2, S₃

x₁, e₃, e₂, a₄, e₄

Q (events):

T (active segments):

(10)

• What is a (thematic or topographical) map?

• Which means for designing maps are there?

12.1 Review

http://www.wiedenbruegge.net/

(11)

• Why is cartographic

generalization necessary at all?

• What are the basic operations of generalization?

12.1 Review

http://maps.google.de/

(12)

• How can polylines be smoothed?

• How does the Douglas/Peucker algorithm work?

• The Douglas/Peucker algorithm does not preserve right angles. Why?

12.1 Review

(13)

• What procedures exist for the transition from polygons to lines?

• What is the

challenge in the placement of text?

12.1 Review

http://upload.wikimedia.org/

(14)

• Is it possible to evaluate spatial queries with core SQL?

• On which level is SQL extended in order to become spatial SQL?

12.1 Review

(15)

• How to formulate with spatial SQL the query

"Through which parcels do brooks flow"?

• What are the main differences between Oracle Spatial and PostgreSQL?

12.1 Review

(16)

• What are the two steps in the evaluation of spatial queries?

• What are the differences between conservative and progressive approximations?

12.1 Review

http://dbs.mathematik.uni-marburg.de/teaching

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• Can conventional B/B+-trees be used for indexing spatial data?

• How are points in the plane ordered according to the Z-order?

• How good is the Z-order as a spatial index?

12.1 Review

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11 17

10 20

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• How does the data-driven point quadtree work?

• How does the R-tree work?

12.1 Review

A C B

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• When does the R-tree become increasingly inefficient as index structure?

• How in principle does the linear split method work with the R-tree?

12.1 Review

e

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j m

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(20)

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• What are the characteristics of the K-d tree?

• What are the characteristics of the BSP tree?

• What are the characteristics of the Grid File?

12.1 Review

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• For what purpose can XML be used?

• What are the main components of a document type definition (DTD)?

12.1 Review

(22)

• What concepts for integrating different XML

documents are there?

• What are the advantages of XML schema in

contrast to DTDs?

12.1 Review

[EE04]

</restriction>

</simpleType>

(23)

• For what purpose can GML be used?

• What are some

important SVG commands?

12.1 Review

(24)

• What are the special features of the combination of PostgreSQL and JDBC?

12.1 Review

/** * @param c PGpoint describing * the circle’s center * @param r radius of circle

*/

public PGcircle(PGpoint c, double r) { this();

this.center = c;

this.radius = r;

}

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• What are the special features of the combination of Oracle Spatial and JDBC?

• How can GML based data be processed

with Java?

12.1 Review

XML Parsing

Object Based (e.g. DOM)

Event Based

Push Parsing Pull Parsing

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• Which are the architectures of geographic information systems?

• What are the typical functions

of a GIS client (GIS server)?

12.1 Review

(27)

• How can photogrammetry be characterized?

• Which kinds of scanner are used in Earth exploration

satellites?

• How does LIDAR work?

12.1 Review

http://www.uni-potsdam.de/.../febasis/febasis06_04-1206.pdf

(28)

• What are the typical geometric errors in photographic systems?

• What are the elements of image

interpretation?

12.1 Review

invisible space invisible space reference plane

side view http://homepage.univie.ac.at/.../lba_fe_28102004.pdf

(29)

• How does GPS work?

• What are the functions of a location transponder ?

12.1 Review

http://www.uni-giessen.de/.../2.6-GPS.pdf

(30)

• What kinds of automotive navigation are there?

• How does

quadtree spatial cloaking work?

12.1 Review

[St12]

(31)

• How can environmental data be characterized?

• What are the properties of monitoring

networks?

12.1 Review

http://www.wald-online-bw.de/

(32)

• ACM

– Founded in 1947 as

– The world's first scientific and educational computing society

– More than 100,000 members (2014) – Headquarters in New York City

– 37 Special Interest Groups (SIGs) – ACM SIGSPATIAL

• International Conference on

Advances in Geographic Information Systems

12.2 Outlook

http://www.acm.org/

http://www.sigspatial.org/

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• Sessions

– Map Generation – Predictive Analysis

– Localization and Road Networks – Route Planning and Ride Sharing – Query Processing on large

– Mining and Planning – Traffic and Travel Time – Geo-Social Data

– Vision Papers

12.2 Outlook

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• Spatial-temporal Data

12.2 Outlook

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• An Algorithmic Framework for Segmenting

Trajectories based on Spatio-Temporal Criteria

– Authors: Maike Buchin, Anne Driemel, Marc van Kreveld, Vera Sacristán

– URL: http://dx.doi.org/10.1145/1869790.1869821

12.2 Outlook

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• Trajectory

– Continuous mapping from a time interval [t0; tn] to the plane (or a higher-dimensional space)

– Usually represented by a discrete sample of time- space positions

12.2 Outlook

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• Segmentation

– Aim: obtain segments where movement characteristics inside each segment are uniform in some sense.

– Useful

• to understand the behavior of animals from animal trajectories

• to find and analyze patterns in movement of sports players

• for content-based motion retrieval tasks.

– An optimal segmentation of a trajectory is a segmentation into a minimum number of subtrajectories (segments)

according to one or more criterion

12.2 Outlook

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• Movement characteristics

– Speed – Heading – Velocity – Sinuosity – Curvature – Curviness

– any combination of such characteristics

12.2 Outlook

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12.2 Outlook

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• Characteristics of algorithmic framework

– Specify criteria formally that should hold for any attribute within each segment of the segmentation – No artificial structures like bounding boxes

– Result is guaranteed to satisfy the criteria and be optimal

– Algorithmic technique: randomized incremental construction

– O(n log n) time segmentation for a trajectory with n vertices in many case

12.2 Outlook

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• A Traffic Flow Approach to Early Detection of Gathering Events

– Authors: Xun Zhou, Amin Vahedian Khezerlou, Alex Liu, Zubair Shafiq, Fan Zhang

– http://dx.doi.org/10.1145/2996913.2996998

12.2 Outlook

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• Detecting gathering events based on human mobility data

• Given:

– Spatial framework (grid)

– Traffic flow between neighboring grids

– Thresholds for distance, p-value and result size

• Challenge: Exponential growth of possible event footprints

12.2 Outlook

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• Smart Edge Algorithm

– Candidate root filter

• Cells with significant flows within given distance

• Create index of roots, linked to flows

– Building G-Graph

• Dynamic programming

• Breadth–first retrieval

– G-Graph pruning:

• Gscore upper-bound

• Sorted by number of significant incoming flows

12.2 Outlook

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• Case study

– Trajectories of over 10000 taxis in Shenzhen, 08/2013 – Grid size 500m * 500m (128 by 64 grids)

– GPS signal every 40 seconds

– Flow function: occupied taxis crossing boundaries – Baseline:

Monthly average traffic flow during same time and weekday

12.2 Outlook

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• Top-5 G-Graphs, 19:30-19:40, 8/16/2013

12.2 Outlook

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• Experimental evaluation on the efficiency

– Examine how each design decision impacts the running time

– Varying number of grids,

distance threshold, result size and p-value threshold

12.2 Outlook

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• Optimal and Topologically Safe Simplification of Building Footprints

– Authors: Jan-Henrik Haunert, Alexander Wolff – http://dx.doi.org/10.1145/1869790.1869819

12.2 Outlook

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• Simplification of polygonal rings

– Selecting a subsequence of its original edges

– The vertices are defined by intersections of consecutive (and possibly extended) edges

• Aim: minimize the number of all output edges subject to a user-defined error tolerance

• Problem is NP-hard → use integer program (IP)

– Large, O(m

⁶

) constraints (m: number of input edges) – Start with O(m) constraints for a smaller running time – Add neglected constraints whenever a new solution

violates them

12.2 Outlook

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• Requirements

– R1restricts the creation of new edges

• Extend or shorten an old edge (at both ends)

• No turn of its direction

– R2 means no change of the order of the edges

– R3 is similar to the bandwidth criterion that is often applied to line simplification – R4 ensures the simplicity of the output

rings

12.2 Outlook

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• Shortcut

– Pair of edges in the same original ring.

– Selecting shortcut (e, f) means that in the solution

there will be an edge a that corresponds to e, an edge b that corresponds to f, and no edge that corresponds to an edge between e and f

12.2 Outlook

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– Pairs of consecutive and feasible shortcuts can be infeasible

– A shortcut violating the constraints with regard to the original edges may still be part of a feasible solution

12.2 Outlook

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12.2 Outlook

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