GIS Spatial Analysis and Lecture 3 Flashcards
Spatial analysis
Spatial analysis is the process by which we turn raw data into useful information. Transformations of spatial analysis are ways in which the sender tries to inform the receiver by:
- Adding greater informative content and value, and
- Revealing things that the receiver might not otherwise see
Spatial analysis exists as the interface between the human and computer, both play important roles
- Human intuition: vague and informal
- Spatial Analysis: formal, precise
The concepts human understand, navigate and exploit in the world are mirrored in the concepts of spatial analysis.
Geographical/Spatial analysis plays a vital role in many parts of daily life
- Directly: in the use of maps for navigation
- Indirectly: where we use resources like water or gas, we are dependent on where these things are located and their attributes.
Before GIS
- Some methods of spatial analysis were developed long before GIS was introduced
- They were carried out by hand or by the use of measuring devices like the ruler
- Analytical cartography is used to refer to methods of analysis that can be applied to maps
to make them more useful and informative - Spatial analysis using GIS is a logical successor to this.
Spatial Analysis in GIS
It is the crux of GIS. Includes:
- Transformations
- Manipulations
- Methods that can be applied to geographic data to add value, support decisions, reveal patterns and anomalies that are not immediately obvious.
In the context of LBS this means that there is no one-size-fits-all approach to map design.
GIS is an ideal platform for spatial analysis because its data structures accommodate the storage of object locations. Can be used to further aims in science by revealing patterns that hint at undiscovered generalities and laws. Patterns in the occurrence of a disease may hint at the mechanisms that cause the disease. Ex. This is how the cause of cholera was found.
Geospatial Analysis
Domain of geospatial analysis is the surface of the earth:
- Extending upwards: in the analysis of topography and the atmosphere
- Downwards: in the analysis of groundwater and geology
Scale:
- Most Local: locations of items to the nearest millimeter or centimeter
- Global: ex. in the analysis of sea surface temperatures
Time:
- Extends backwards: historical analysis, discovery of patterns, detailed mapping of movement of continents
- Future (predictions): track hurricanes, melting icecaps, growth of areas
Methods of spatial analysis are robust and capable of operating over a range of spatial and temporal scales.
Geospatial analysis concerns
- What happened where
- makes use of GI that links features and phenomena on Earth’s surface to their location.
The richness of geospatial analysis is in the structures and arguments that can be built what seems to be simple and straightforward techniques.
In principle, there is no limit to the complexity of spatial analytic techniques that might find some application in the world, and might be used to tease out interesting insights and support practical actions and decisions. In reality, some techniques are simpler, more useful, or more insightful than others.
The importance of spatial data
- Making use of spatial data requires a whole set of approaches to:
- Extract info from data and make them useful
- GIS plays a key role in context
- GIS provides a means of generating, modifying, managing, analyzing and visualizing spatial data.
Types of Spatial Analysis
- Queries and Reasoning
- Most basic of analysis operations
- No changes occur in the database, and no new data is produced
- Simple, well-defined queries “how many houses are found within 1KM of this point”
- Vaguer questions “which is the closest city to LA to the north”
- Measurements
- Simple numerical values that describe aspects of geographical data
- Anomalous shape is the primary means of detecting gerrymanders of political districts.
DEMs
Most versatile and useful representation of terrain in GIS. In a raster representation, each grid cell:
- records the elevation of the earth’s surface
- reflects a view of terrain as a field of elevation values
Knowing the exact elevation of a point asl is important for some applications, including prediction of the effects of global warming and rising sea levels on coastal cities. For many applications the value of a DEM lies in its ability to produce derivative measures through transformation, specifically measures of slope and aspect, both of which are conceptual fields.
Transformations
Simple geometric, arithmetic, or logical rules, include operations that convert raster data to vector data or vice versa.
Buffering
- One of the most important transformations available to the GIS
- any set of objects by identifying all areas within a specified distance of the original objects.
Geofencing
Geofencing is the use of the Global Positioning System (GPS) satellite network and/or local radio-frequency identifiers (such as Wi-Fi nodes or Bluetooth beacons) to create virtual boundaries around a location.
Geo Targeting
In geo marketing and internet marketing is the method of determining the geolocation of a website visitor and delivering different content to that visitor based on his or her location, such as country, region/state, city, metro code/zip code, organization, IP address, ISP or other criteria.
Spatial Interpolation
A process of intelligent guesswork, in which the investigator and the GIS attempt to make a reasonable estimate of the value of a field at places where the field hasn’t been measured.
The one principle that underlies all spatial interpolation is Tobler’s Law: “all places are related but nearby places are more related than distant places”
The best guess as to the value of a field at some point is the value measured at the closest observation points.
Examples of Spatial Interpolation
Inverse Distance Weighting (IDW)
Inverse Distance Weighting (IDW)
- Most often used by GIS analysts
- Employs Tobler’s Law
- Provides a simpler way of guessing the values of a field at locations where no measurement is available
- Creates a smooth surface whose value at any point is more like the values at nearby points than the values at distant points.
Maps
Visual representations of a geographic space. Relations of events and objects depicted in that space. Cartographic representations developed to encode geographic relationships between real world objects, which enable map reader to build geographic understanding.
Maps are active. They are involved in achieving a goal, but also define and identify that goal
- They frame the narrative a map is a description of the way the world is.
- a map is a prescription of what might be done about the problem as identifier.
Cartography
art and science of map making. The totality of scientific and artistic activities aiming at the production of maps and data. Cartography includes the study of maps as scientific documents and their use. Based on knowledge that has evolved over many years.
Cartography is a process associated with
- Conception
- Production
- Dissemination
- Study of maps in addition with geospatial technology
- Human-Computer Interaction (HCI)
Cartographer’s Role
Decide how real world objects should appear on the map through an approximation of geometric objects, alongside are objects, and their relations.
Decide on: shapes, colours, other graphic variables.
