GIS

the art and science of producing maps

political, reference, topographic

US geological survery started in 1879

maps made by planetable surveying

photogrammetry (science of measuring and interpreting photos) in 1940s

defined by their contour lines to portray shape and elevation of the land

lines drawn representing constant vertical height above sea level

CONTOUR INTERVAL - change in vertical height between two adjacent contours; same on a simgle map

change in vertical height between two adjacent contours; same on a simgle map

computer system for capturing, storing, quering, analyzing, and displaying geospatial data

science

the theory behind the development, use, and application of GIS

technology

always changing and improving

spatial data, attritube data

strength is it handles and processes geospatial data

geospatial data: describes both the locations and characteristics of spatial features

describes both the locations and characteristics of spatial features

computer system, GIS software, people, data, infrastructure

points, lines, polygons

uses x,y coordinates to represent point features

• points: have no dimenstions; single x,y coordinate
• lines: have one dimension, length, with beginning and ending nodes and intermediate points called vertices
• polygons: have two dimensions, length and area; consist of a  group of verticies that define a closed area

uses cells in a grid to represent point features

• discrete data (usually thematic or categorical data)
• thematic raster: land use and land cover
• continuous data: temp, elevation, aspect

• Small Scale: map that covers a large area, but gives little detail
• 1:2,000,000

• Large Scale: map which covers a small area and provides a lot of detail
• 1:50,000

Babalonian Clay Tablet World Map

600 bc

• early maps were hand drawn 
• wood carvings were used to reproduce the early maps

Gaspard Nadar Tournachon

father of GIS

developed GIS for the Canadaian Land Inventory

Environmental Systems Research Institute

formed in 1969 by Dangermond

GPS made public in 2000

• today, more than 90% of GIS market uses ESRI
• 3+ billion anual revenues-debt free company

Aspatial Data- data that is not tied to a location on the earths surface


Spatial Data- information that is tied to a specific location on the earths surface

• create maps, graphs, reports
• manage map data
• analyze spatial relationships
• overlay map data from different sources
• manage and display database info
• locate addresses
• analyze utility and transportation networks

a graphic representation of the spatial relationships of entities within an area

a depiction of all or part of the earth or other geo phenomenon as a set of symbols and at a scale whose representative fraction is less than 1:1

coverage and shapefiles use split systems to store geometries and attributes

• dbf: database
• prj: projection
• sbx: spatial index
• sbn: spatial index format
• shx: shape index
• xml: metadata

diagrams or graphs are used in topology to study the arrangements of geometric objects and the relationships between objects

• ensures data quality
• are lines connecting?
• coincident boundaries have no gaps or overlays

it can enhance GIS analysis when using geocoding

stores geometries and attribues seperately in a split system

examples being coverage and shapefiles

standard, nontopological data format used in ESRI

treates a point as a pair of x,y coordinates, a line as a series of points, and a polygon as a series of line segments, but there are no files to describe the spatial relationships between these geometric objects

display more rapidly on a computer monitor than topo based data

more nonproprietary and interoperabe, meaning that they can be used across different software packages

part of ArcObjects, a collection of thousands of objects, properties, and methods that provide the foundation for ArcGIS 

defines topo as relationship rules and lets user choose the rules, if any, to be implemented in a feature dataset

data orginization and management: create feature dataset to hold all feature layers for specific areas; new data has same coordinate system

provides object oriented tech such as domains and validation rules

on the fly topology to ensure data integrity and optimize data analyses

can develop customized application using Python

triangulated irregular networks

approximates the terrain with a set of nonoverlapping triangles

a linear feature such as a highway, a bike path, or a stream but unlike other linear features, a route has a measurement system that allows linear measures to be used on a projected coordinate system

uses a grid to cover the area

value of each grid cell represents value of characteristic at that cell location

data storage: divided into rows, colums, and cells

can represent a discreet or continous surface

represents points by single cells, lines by sequences of neighboring cells, and areas by collections of contiguous cells

Cell Value: represents characteristic of a spatial phenomenon at location denoted by its row and column

• cell value can be integer or floating point
• intergers used for discrete (land use or habitat suitability)
• floating used for continous (temp, precip, elevation)

Cell Size: determines resolution of raster data model

• smaller cell size gives greater ability to distinguish features on the landscape
• 3 meters per cell = high resolution
• 30 meters per cell = not as good resolution

Raster Bands: singular or multiple

Georeferenced Raster: one that has been processed to match a projected coordinate system

Spatial Reference: aligned spatially with other data sets in a GIS

• sttellite imagery
• digital elevation modesl DEM
• digital orthophotos quads DOQ
• digital orthophoto quarter quads DOQQ
• bi level scanned files
• digital raster graphics DRG
• digital line graphics DLG 

contains info required by ArcGIS

• data structure
• extent (rows and columns and spatial extent)
• cell size
• number of bands
• value for no data

raster data are usually large files and require large computer storage

data compression refers to the reductin of data volume

a variety of techs are available for image compression.  compression techs can be lossless or lossy

• TIFF - lossless
• Jpeg - lossy

converstion of vector data to raster data is called rasterization

• creation of raster grid with specific cell size
• change values of cells that correspond to points, lines, or polys
• fill the interior of polys with poly value

• line thinning (lines may be more than one cell)
• line extraction (determine where lines begin/end)
• topological reconstruction (make certain all lines are connected)
• line smoothing (remoes step like fetures)

• title
• map
• legend
• scale bar
• north arrow
• source
• ancillary info

• maximize size of map relative to other components
• balance elements on the page
• avoid blank or cluttered areas
• align straight edges 
• use neatlines to enhance clean lines
• choose quite patterns (dont use same pattern for land and water)
• use natural colors
• emphasize import info

2 Dimensions:

Lat and Long

North/South Pole are the fixed reference points

Equator and poles most important when dealing with the Corrdiante system

Measured in Degrees, Minutes, Seconds

Prime Meridian located in Greenwich, England

• Total of 360 Degrees
• 60 Minutes in each Degree
• 60 Seconds in each Minute

3600 seconds in each degree

Converts into Decimal Degrees

• add decimal to degrees
• 38 degrees becomes .38

• divide mintes by 60
• 48/60
• .8

• divide seconds by 3600
• 41.17/3600
• .011436

• Add all together
• 38+.0+.011436
• 38.81144

Topographic Variations

Polar Flattening

Gravitational anomalies

ground measured spheroid used for mapping til the late 1980s

satellite determined spheroid

shape, size and measurements of earth determined through Doppler satellite

mathematical model of earth used as reference for calculating geogrpahic coordinates

includes point of origin that models earth in a regional context

used to reduce discrepencies

• NAD27
• based off clark 1866
• used for digital and paper maps
• origin is Kansas lol

• NAD83
• based on GRS80
• used for paper maps
• origin is center of earth

• WGS84
• used by DOD
• based on GRS80
• most precise
• used for GPS data
• Origin is center of earth

uses linear measurment of meters