Questions Flashcards
(22 cards)
Geographical data vs spatial data
Spatial data are all the data that somehow can be localised in a spatial reference system.
Geographical data are all the data
that somehow can be semantically identified and localised in a spatial reference system about the earth.
What is management ?
Management is the set of activities in an organization where ressources are coordinated and directed towards the efficient and effective acomplishment of commonly decided goals.
What is a GIS ?
A geographic information system (GIS) is a framework for gathering, managing and analyzing data which are spatially referenced to the Earth.
What problems can GIS help to answer?
GIS can help to answer questions related to : location, patterns, trends, condition and implication. Some example for these types of questions are :
Location : Where is the library ?
Patterns : What is the distribution of crime incident in London ?
Trends : how are patterns of retailing changing in response to the Development of out of town superstores ?
Conditions : Where can i find holiday accommodation that is within 1km of a windsurfing beach and accessible by public transport.
Implication : if we build a New theme park here what will be the effect on traffic ?
Components of a GIS ?
A GIS has five key components : hardware (computer equipment), software, people, data, methods (business rule)
What are the 3 components of spatial data ?
Temporal : when ? Refers to the time of an event or data collection
Thematic : what ? Describes characteristics of data
Spatial : where ? Geographic location of data
What are the two types of spatial coordinate system ?
GCS : (geographic coordinate system) features located on Earth’s surface using latitude and longitude in degrees based on reference like WGS84 system.
PCS : (Projected coordinate system) represents objects on a 2D plane, PCS is GCS + map projection (Lambert, mercator)
In meters
What are the four types of attribute data ?
Nominal : classifies features into groups (Soil types; city names)
Ordinal : orders data into ranked categories (sizes)
Interval : provides values with equal units allowing distance interpretation
(Temperatures in celsius)
Ratio : like interval but with a fixed zero (weight, lenght)
What are the five types of spatial entities in conceptual data modeling ?
- Points (represents a unique location : a well, a weather station)
- Lines (represents linear entities : roads, rivers)
- Areas (Polygon) (represents closed surfaces : lakes, forests)
- Network (Represents connected flows (road network, distribution network)
- Surface (Represents continuous phenomena : elevation, temperature)
What are Raster and Vector data ? What are the common data formats of Raster and Vector data ?
Raster data used grid of cells to represent spatial features. Common Raster data formats include GEOTiff and ERDAS image (.IMG).
Vector data uses points, Lines and polygons to represent spatial features. Common Vector data formats include : Shapefiles (.SHP; .DBF ; .SHX) ; GeoJSON (.GEOJSON ; JSON) ; Geography markup language (.GML); Google keyhole Markup Language (.KML ; KMZ)
What is a layered approach ?
The layered approach in GIS involves representing different types of features as separate layers. Each layer represents a set of features with the same thematic characteristic. This allows for the flexible combination and analysis of different types of data.
What is geodataframe in geopandas in python ?
In the python library geopandas, a geodataframe is a data structure that combines the capabilities of a dataframe (from the pandas library) with geometry. This means it can store both tabular data and spatial data in the same structure, making it well suited for working with geospatial data in Python.
What is a minimum bounding box (MBB) ? Why is it useful for spatial indexes ?
A minimum bounding box, also known as a minimum bounding rectangle (MBR) is the smallest rectangle that completely encloses a spatial feature : MBBs are useful for spatial indexes because they allow for quick and efficient spatial queries.
For example, if you want to find all the points that intersect a given Polygon, you can first use the MBB of the Polygon to quickly narrow down the set of candidate points, and then perform more detailed calculations only on the points that fall within the MBB.
What are the Common spatial topological relations in postgis ?
- ST_Equals
- ST_Disjoint
- ST_Intersects
- ST_Crosses
- ST_Overlaps
- ST_Touches
- ST_Within
- ST_Contains
What is buffering ? What is an Inward Buffering ? What is an outward buffering ? What is a Bi-directional buffering ?
- Buffering is the creation of a zone of interest around an entity or set of entities.
- Outward buffering extends the buffer zone Outward from the boundary of the entity.
- Inward Buffering creates a buffer zone inside the boundary of the entity.
- Bi directional buffering creates a buffer zone that extends both Inward and Outward from the boundary of the entity.
What is a map overlay analysis ?
The ability to integrate data from two sources using map overlay is perhaps the key GIS analysis function.
- For simply visual comparaison of data layers.
- Overlays where new spatial data sets are created.
- Vector/Raster Overlay.
What is a spatial interpolation ? Some existing methods ?
Spatial interpolation is the process of using points with known values to estimate values at other unknown points.
Step 1 : Collect point data at sampling location within the map area.
Step 2 : Interpolation
Step 3 : (optional) Connect locations of equal values using (smooth) Lines (isolines/contours) .
Many methods exist :
Linear triangulation, inverse distance weighted (IDW), Kriging …
What are the classic applications of network analysis ?
- Optimal route search : Finding the shortest or fastest path (GPS nav)
- Connectivity analysis : Identifying connections between different points in a network. (Electrical grids)
- Flow analysis : Studying movements within a network (roads traffic, logistical flows)
- Resource optimization : Planning deliveries or interventions (véhicule routing, service scheduling)
What is Geographic interoperability ?
Is the ability of information system to :
- Freely share spatial data about the Earth (surface, subsurface, phenomena)
- Use cooperative software over networks to manipulate this data without technical difficulties between systems.
It ensures that different systems can exchange, execute and interpret geospatial data without additional effort from the user.
What are WMS, WFS, and WCS ? What are the typical operations/functions they offer ?
- WMS (Web Map Service) Provides maps as images
✓Getmap : Display a map.
✓Getcapabilities : retrieve metadata about the service.
✓GetFeatureInfo : Retrieve information about a point on the map. - WFS (Web Feature Service) : Provides Vector data.
✓GetFeature : Download Vector features.
✓Transaction : Modify data (add, update, delate) - WCS ( Web Coverage Service) : Provides raw Raster data.
✓GetCoverage : Download Raster data.
✓Describe Coverage : Retrieve details about data Coverage.
✓ GetCapabilities : Retrieve metadata about the service.
What is metadata ? Why is it important for spatial data sharing ?
Metadata is descriptive information about spatial data, such as its origin, quality, format or coordinate system.
Its important because :
- It make data easy to find
- It allows users to assess data quality and suitability.
- It facilitates sharing and using data between different systems.
What is INSPIRE ?
INSPIRE (Infrastructure for Spatial Information in the European Community) is a European initiative aimed at :
- Harmonizing geospatial data to ensure compatibility and ease of use across Europe.
- Facilitating data sharing among member states for environmental policies and other public domains.
It relies on open standards to ensure interoperability and accessibiliy to data
