GTECH 709 Principles of GIS Spatial relationships Scale Time Earth from above The acronym Disciplinary background Representation Geo-relational principle Maps vs. Geography 1

GTECH 709 Thinking like a geographer Space is everywhere 2

Tobler's First Law (Waldo) Tobler'sFirst Law of Geography

Tobler's First Law (Waldo) Tobler'sFirst Law of Geography Everything is related to everything else, but those things closer to each other are also more related with each other

Spatial Thinking Making a decision on where to take your next vacation Determining whether or not you can make it to the next rest area

Tabular Data # Annoying People Total Population Average Age Average Income # of SUVs County State 72 998 26 48,000 Hatchback Wholefood 48 2,000 65 32,000 Dialupia 776 2,250 44 72,000 750 Sriracha Traderjo 789 3,500 36 12,000 700 Muffintown 469 1,200 31 22,500 461 Fixieplaid 525 1,400 42 66,000 400 Burb-on-Burb 62 33 92,000 59 Bluetooth Village 230 16,450 51 35,000 1,950 Pabsto 9,654 52,510 49,000 8,192 University Collegeville 779 1,459 41 61,000 398 Kingo 6

Thinking Like a Geographer

Thinking Like a Geographer Choropleth Map = areas filled with colors to represent a range of values

Space is Everywhere!

Twitter Locations

GTECH 709 Spatial relationships Topological relationships .. and their importance

Spatial Relationships (1) Equals A is the same as B Touches A touches B Overlaps A and B have multiple points in common Contains A contains B

Spatial Relationships (2) Disjoint A shares nothing with B Covers A covers B Crosses A and B have at least one point in common B A A B A B

Ignore at your Own Risk What would happen if we ignored them? Mapquest and Google Maps would be useless Consider 500 road segments of your neighborhood collected with a GPS

GTECH 709 Scale Map scale Spatial resolution Scale of analysis

Map Scale The scale you learned about in Geography / cartography

Spatial Resolution The smallest element discernable / stored in your database

Scale of Analysis Specific geographic context used to understand a problem

All three influence each other Scale All three influence each other

GTECH 709 Time in GIS Integral component of geographic data Hard in/for GIS

Time Almost everything geographic involves a dynamic process of one type or another

Time Almost everything geographic involves a dynamic process of one type or another Geography = ƒ (space, time, attributes)

Time Almost everything geographic involves a dynamic process of one type or another Geography = ƒ (space, time, attributes) Static maps make it hard to see time as an explicit factor

Time

GTECH 709 Locations Where are we? How do we get out location?

Locations Where are we now? Used to be a hard question involving complicated instruments and specialist training

How Do We Get Our Location Smartphones and consumer-grade GPS Often augmented by wifi and cellphone tower data Positional accuracy between ten and 1,000 feet Professional surveying-grade systems provide sub-feet accuracy Hunter Geography lab is at a point defined as -73.9647298 / 40.7683774

How Do We Get Our Location Classroom is at a point defined as -73.9647298 / 40.7683774 If I walked to the elevator, we would create a path line If we walked around the block, we could create a polygon Point, lines and polygons form spatial vector data

GTECH 709 Earth From Above Reference to parallel course Raster data Data sources Application examples

GTECH 711 Virtual globe tools like Google Earth Most geographic image data comes from satellites and airborne sensors, but you can even make your own DIY drone now Geographic image data is raster data, which captures information by assigning values to cells in a grid

Raster Format The size of raster grid cells determines how much resolution you have for the image

Example 1

Example 2

Example 3

GTECH 709 GIS – the acronym G I S

What is GIS? Geographic Information System Scale 1:1K to 1:100M On or near Earth’s surface Information Data and the methods to transform them into information, aka analysis System Software People and institutional settings

GTECH 709 Disciplinary background Core disciplines Original application areas

GIS Core Disciplines Geography Surveying engineering cartography Surveying engineering geodesy Computer / information science Databases and graphics systems

Inventors of GIS (Canadian) forestry Landscape architecture US Census  Military

GTECH 709 GIS layers Themed layers Geometry types

GIS Map Organization Layers

GIS Map Organization Layers Organized by “theme”

GIS Map Organization Layers Organized by “theme” One geometry at a time

GIS Map Organization Layers Organized by “theme” One geometry at a time Act as a legend in a separate window

Map and Legend Windows

GIS Map Organization Layers Organized by “theme” One geometry at a time Act as a legend in a separate window Borrowing from map making / printing history

GTECH 709 Representation Points, lines, polygons

Representation Features Points Lines Polygons

GTECH 709 Geo-relational principle Geometries Attributes

Georelational Principle Combining map geometries with attributes that describe the geographic characteristics of those geometries

Georelational Principle

GTECH 709 Maps vs. geography Revisiting the relationship game

Maps versus Geography Remember the relationship game We use geometries to describe locations on the Earth’s surface We use attributes (e.g. spreadsheets) to describe what interests us about each of those locations We use maps to communicate visually about the relationship between locations and what can be found at these locations

Maps versus Geography Remember the relationship game Maps depict usually only one or a small number of attributes at a time There are as many maps about an area of interest as there are attributes to describe the area Even with the same attributes, there are myriads of ways to visualize them;  even more maps

Maps versus Geography Remember the relationship game One geographic data set can produce many maps The map is a visual index to geographic data The map prompts us to reason about spatial relationships, such as … You will provide the answer in the quiz

GTECH 709 Geographic data Geo-relational principle - again Geographic data organization Back to the map

What is Geographic Data? Following the geo-relational principle, geographic data has to have A locational reference Check for yourself about all the different ways we can specify a location Data that describes what can be found at that location: Income, temperature, party affiliation, soil type, etc.

Geographic Data Organization We will have whole sessions on this Location and attributes in one file Latitude Longtitude Precision Address City State ZIP Name Description 51.514 -0.0936 109 Cheapside London UK EC2V 6 GIS Cloud Web-based GIS 38.967 -77.380 555 Grove St Herndon VA 20170 Juice Analytics Data analysis 37.416 -122.02 701 First Ave Sunnyvale CA 94089 Yahoo Address matching 37.423 -122.08 1600 Amphitheater Pkwy Mountain View 94043 Google Google Earth 47.643 -122.13 Street One Microsoft Way Redmond WA 98052 Microsoft Excel 41.132 -73.704 1 New Orchard Rd Armonk NY 10504 IBM You tell me

Geographic Data Organization Location and attributes in multiple files ESRI “shapefile” A collection of .shp, .dbf, .shx files Location and attributes in a database (file) ESRI geodatabases PostGIS database Web services

Back to the Map A digital map is a set of instructions on how to arrange visual representations of geography Items such as a Google map or a satellite image may serve as context We can turn map layers on or off Label map elements Change appearances

GTECH 709 GIS as a process GIS as a sequence of steps GIS as a process of inquiry

GIS as a Process 1 Capture data Store data Query data Analyze data Display data Present data

GIS as a Process 2 Ask a geographic question Acquire geographic data Explore geographic data Analyze geographic information Act on geographic knowledge

GTECH 709 Week 2 summary

Summary A GIS organizes and stores information about the world as a collection of thematic layers. Each layer contains features with the same shape and attributes, all located within a common geographic area. Each feature is assigned a unique numerical identifier and is characterized by a unique location in space and a corresponding record in a table. Features can be stored in a GIS as three primary shapes: points, lines, or polygons. Features have spatial relationships with other features, and with a GIS you can find features based on their spatial relationships. The geographic inquiry process provides a framework for solving problems with GIS.