1. Introduction to Geographic Information Systems and Sample Applications

2. Overview Role of a GIS Parts of a GIS Spatial Data
Relational Databases
Geodesy and Map Projections
ArcView and Sample Applications
Scale and Resolution

3. What is GIS???? Standard definition: Sound efficient??????
An organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.
Sound efficient??????

4. GIS: Simplified
A computer-based tool for mapping and analyzing things.
Geospatial Database: a set of compatible data layers or themes

5. The Role of GIS
The advanced modeling programs and technologies used in water resources studies are increasingly GIS-based.
Examples include:
Floodplain Assessments
Land Use Planning
Demographic and Economic Data
Hydrologic and Water Quality Data Display
Rainfall Analysis with NEXRAD Radar

6. Digital Hydrologic / Hydraulic Processing
HEC-RAS
Water
surface
profiles
HEC-HMS
Flood
discharge
HEC-GeoHMS
HEC-GeoRAS
ArcView
Digital
Elevation
Model
ArcView
Flood
plain maps
Digital Map Database

7. Parts of a GIS A GIS should be able to:
Take in spatial data - both maps and attributes
Establish logical linkages between the data elements
Put data into a storage system in which the data, and the places on the map that the data represents, are directly linked
Perform analysis
Produce and display information
Take in spatial data - both maps and attributes
Establish logical linkages between the data elements
Put data into a storage system in which the data, and the places on the map that the data represents, are directly linked
Perform analysis
Produce and display information

8. Spatial Data Spatial data is what goes into a GIS
Maps are one of the most common forms of spatial data
Features represented by areas
Alphanumeric data to describe areas
Descriptive data is known as attributes
Spatial data – Existing within space. In a GIS, spatial data are the geographic relationships between features based on their locations.
Attributes, or attribute data - is descriptive information about features or elements of a database. A GIS stores attributes in tables and links them to the map features they describe.
Attributes of a river might include its name, length, average depth, and so on.

9. Attributes GIS stores more than just maps
Relationship between map features and attributes within a GIS
Dynamic interactive maps
In general, all map data is made up of point, line, and area features. Some combinations or special cases of these three types of features represent complex real-world objects. For example, a school could be represented by a combination of areas (buildings and playgrounds), lines (sidewalks and driveways), and points (individual trees and trash bins).

10. Data Entry and Storage Store data in a logical way
Maps and data are stored in digital form
Digital layers with attributes attached
Layers are stored together in a relational database using a database management system (DBMS).
One of the primary capabilities of a GIS is data storage.
The maps and other data you enter are stored in digital form. Imagine them as digital layers with their attributes attached

11. Database Management System
DBMS
Inside the DBMS, spatial data is stored as digital layers with their associated attributes

12. Analysis Why should spatial data be stored in a GIS?
Want to use the power of the computer to ask questions of the spatial data
Analyze data and produce new information
Convey technical data non-technically
If you asked why spatial data should be stored in a GIS, a casual answer would be "so that it can be taken out again." If this were literally true, there may be no need for a GIS. Perhaps a filing cabinet would suffice. You can hang up the maps in a filing cabinet and be done with it.
input, editing, and management of data; data query, analysis, and visualization; and output operations.

13. Discrete and Continuous Space
Discrete Space: Vector GIS
Lumped models
Continuous Space: Raster GIS, Tin
Distributed models

14. Spatial Data: Vector format
Vector data are defined spatially:
(x1,y1)
Point - a pair of x and y coordinates
vertex
Line - a sequence of points
DRM
Node
Polygon - a closed set of lines

15. River Reaches
Flow along lines through the landscape

16. River Basins
Hydrologic features containing several different types of flow processes

17. Spatial Data: Grid (Raster) format
Raster data are described by a cell grid, one value per cell:
Number of
rows
Number of Columns
(X,Y)
Cell size
NODATA cell

18. NEXRAD Rainfall Intensity Image
October 18, 3:00 AM (CST)

19. NEXRAD Rainfall Intensity Image
October 18, 4:00 AM (CST)

22. Raster and Vector Data Vector Raster Point Line Polygon Zone of cells
DRM
Zone of cells
Polygon

23. Points as Cells

24. Line as a Sequence of Cells

25. Polygon as a Zone of Cells

26. Vector Data Uses positions to represent real world entities
Points, lines, polygons
Vector representation of a reservoir and highway. The small squares are nodes—point locations specified with latitude and longitude coordinates. Line segments connect nodes to form line features. In this case, the line feature colored red represents the highway. Series of line segments that begin and end at the same node form polygon features. In this case, two polygons (filled with blue) represent the reservoir. The vector data model is consistent with how surveyors measure locations at intervals as they follow a property boundary. Computer-aided drafting (CAD) software used by surveyors, engineers, and others, stores data in vector form.
Reservoir and Highway

27. Raster Data Samples attributes at fixed intervals
List of numbers, one number per cell
The raster approach, by contrast, involves sampling attributes at fixed intervals. Each sample represents one cell in a checkerboard-shaped grid.
The graphic above illustrates a raster representation of the same reservoir and highway. The area covered by the aerial photograph has been divided into a grid. Every grid cell that overlaps one of the two selected entities is encoded with an attribute that associates it with the entity it represents. Raster data consists of a list of numbers, one number for each grid cell, each number representing an entity. For example, grid cells that represent the highway might be represented with the number 1 and grid cells representing the reservoir might be coded with the number 2.
Digital remote sensing systems, which are gradually replacing cameras as primary sources of geographic data, produce raster data by scanning the Earth’s surface pixel-by-pixel, one row at a time.
The raster data model is a smart choice for representing phenomena that lack clear-cut boundaries, such as terrain elevation, vegetation, and precipitation.
Reservoir and Highway

28. Hydrologic Cycle Atmospheric water Surface water Subsurface water
Connecting processes in the hydrologic cycle
involves linking spatial features of various kinds

29. Concept Summary
A region can be considered spatially discrete or spatially continuous
Discrete space is represented by features (vector data) and continuous space by elements or cells(raster data)
Atmospheric water, surface water and subsurface water have a variety of continuous and discrete space representations with different boundaries

30. Levels of Analysis: Relational Database
Relational Linkages
Spatial Attributes
Water Right
Locations
Descriptive Attributes

31. Feature Attribute Table
Fields
Records

32. Value Attribute Table
Attributes of grid zones

33. Linked Tables

34. Tables: Edit, Join and Link

35. Relationships in Linking and Joining Tables
Source Table
(new information
to be added)
Destination Table
(existing information)
Many to one
relation
Primary Key field
(each record must
have a unique value)
Relate field
(can have one or many
records for each value)

36. Concept Summary
Grid or raster representation is used to link hydrologic processes at the element or cell level
Grid data model is based on square cells
Point, line, area and network features have a corresponding grid cell representation which forms the basis of the raster-vector data model

37. Concept Summary
Features have descriptive attributes stored in an attribute table
Attribute tables can be linked or joined to related tables using a key field

38. Break Time

39. Geodesy and Map Projections
Geodesy - the shape of the earth and definition of earth datums
Map Projection - the transformation of a curved earth to a flat map
Coordinate systems - (x,y) coordinate systems for map data

40. Types of Coordinate Systems
(1) Global Cartesian coordinates (x,y,z) for the whole earth
(2) Geographic coordinates (f, l, z)
(3) Projected coordinates (x, y, z) on a local area of the earth’s surface
The z-coordinate in (1) and (3) is defined geometrically; in (2) the z-coordinate is defined gravitationally

41. Global Cartesian Coordinates (x,y,z)
Greenwich
Meridian
Equator •

42. Geographic Coordinates (f, l, z)
Latitude (f) and Longitude (l) defined using an ellipsoid, an ellipse rotated about an axis
Elevation (z) defined using geoid, a surface of constant gravitational potential
Earth datums define standard values of the ellipsoid and geoid

43. Origin of Geographic Coordinates
Equator
(0,0)
Prime Meridian

44. Latitude and Longitude
Longitude line (Meridian) N W E S
Range: 180ºW - 0º - 180ºE
Latitude line (Parallel) N W E S
(0ºN, 0ºE)
Equator, Prime Meridian
Range: 90ºS - 0º - 90ºN

45. Latitude and Longitude in North America
120 W
60 W
90 W
0 N

46. Shape of the Earth
It is actually a spheroid, slightly larger in radius at the equator than at the poles
We think of the
earth as a sphere

47. Geographic Coordinates (f, l, z)
Latitude (f) and Longitude (l) defined using an ellipsoid, an ellipse rotated about an axis
Elevation (z) defined using geoid, a surface of constant gravitational potential
Earth datums define standard values of the ellipsoid and geoid

48. Ellipsoid or Spheroid Rotate an ellipse around an axisZ b O a a Y X
Rotational axis

49. Horizontal Earth Datums
An earth datum is defined by an ellipse and an axis of rotation
NAD27 (North American Datum of 1927) uses the Clarke (1866) ellipsoid on a non geocentric axis of rotation
NAD83 (NAD,1983) uses the GRS80 ellipsoid on a geocentric axis of rotation
WGS84 (World Geodetic System of 1984) uses GRS80, almost the same as NAD83

50. Representations of the Earth
Mean Sea Level is a surface of constant
gravitational potential called the Geoid
Earth surface
Ellipsoid
Sea surface
Geoid

51. Geoid and Ellipsoid Gravity Anomaly Earth surface Ellipsoid Ocean

52. Vertical Earth Datums A vertical datum defines elevation, z
NGVD29 (National Geodetic Vertical Datum of 1929)
NAVD88 (North American Vertical Datum of 1988)
takes into account a map of gravity anomalies between the ellipsoid and the geoid

53. Length on Meridians and Parallels
(Lat, Long) = (f, l)
Length on a Meridian:
AB = Re Df
(same for all latitudes) R Dl
30 N R D C Re Df B
0 N Re
Length on a Parallel:
CD = R Dl = Re Dl Cos f
(varies with latitude) A

54. Geodesy and Map Projections
Geodesy - the shape of the earth and definition of earth datums
Map Projection - the transformation of a curved earth to a flat map
Coordinate systems - (x,y) coordinate systems for map data

55. Map Projection Flat Map Curved Earth Cartesian coordinates: x,y
(Easting & Northing)
Curved Earth
Geographic coordinates: f, l
(Latitude & Longitude)
DRM

56. Earth to Globe to Map Map Projection: Map Scale: Scale Factor
Representative Fraction
Globe distance Earth distance =
Scale Factor
Map distance Globe distance =
(e.g. 1:24,000)
(e.g )

57. Geographic and Projected Coordinates
(f, l)
(x, y)
Map Projection

58. Projection onto a Flat Surface (Three Broad Classes by Light Source)

59. Gnomonic Projection

60. Stereographic Projection

61. Orthographic Projection

62. World from Space – Orthographic Projection

63. Types of Projections
Conic (Albers Equal Area, Lambert Conformal Conic) - good for East-West land areas
Cylindrical (Transverse Mercator) - good for North-South land areas
Azimuthal (Lambert Azimuthal Equal Area) - good for global views

64. Conic Projections (Albers, Lambert)

65. Azimuthal (Lambert)

66. Projections Preserve Some Earth Properties
Area - correct earth surface area (Albers Equal Area) important for mass balances
Shape - local angles are shown correctly (Lambert Conformal Conic)
Direction - all directions are shown correctly relative to the center (Lambert Azimuthal Equal Area)
Distance - preserved along particular lines
Some projections preserve two properties

67. Geodesy and Map Projections
Geodesy - the shape of the earth and definition of earth datums
Map Projection - the transformation of a curved earth to a flat map
Coordinate systems - (x,y) coordinate systems for map data

68. Coordinate Systems
Hydrologic calculations are done in Cartesian or Planar coordinates (x,y,z)
Earth locations are measured in Geographic coordinates of latitude and longitude (f,l)
Map Projections transform (f,l) (x,y)

69. Coordinate System A planar coordinate system is defined by a pair
of orthogonal (x,y) axes drawn through an origin Y X
Origin
(xo,yo)
(fo,lo)

70. Universal Transverse Mercator Coordinate System
Uses the Transverse Mercator projection
Each zone has a Central Meridian (lo), zones are 6° wide, and go from pole to pole
60 zones cover the earth from East to West
Reference Latitude (fo), is the equator
(Xshift, Yshift) = false easting and northing so you never have a negative coordinate

71. Cylindrical Projections (Mercator)
Transverse
Oblique

72. Mercator
Projection

73. UTM Projection (Zone 15)

74. UTM Zone 14
-99°
-102°
-96° 6°
Origin
Equator
-120°
-90 °
-60 °

75. Universal Transverse Mercator Projection

76. Summary Concepts
Two basic locational systems: geometric or Cartesian (x, y, z) and geographic or gravitational (f, l, z)
Mean sea level surface or geoid is approximated by an ellipsoid to define an earth datum which gives (f, l) and distance above geoid gives (z)

77. Summary Concepts (Cont.)
To prepare a map, the earth is first reduced to a globe and then projected onto a flat surface
Three basic types of map projections: conic, cylindrical and azimuthal
A particular projection is defined by a datum, a projection type and a set of projection parameters

78. Summary Concepts (Cont.)
Standard coordinate systems use particular projections over zones of the earth’s surface
Types of standard coordinate systems: UTM, State Plane, Texas State Mapping System, Standard Hydrologic Grid

79. What is ArcView? Desktop geographic information system (GIS) from ESRI
Uses scripting language called Avenue
Customize GUI
April 20, 2002 – ArcGIS released

80. Below is a typical ArcView project
Below is a typical ArcView project. A map, chart, and table have been used to depict migration patterns in the United States.
The ArcView interface consists of windows that present information in different ways. Rows of menus, buttons, and tools at the top of the main application window allow you to view and perform analytical operations on the data in the database.
We’ll look at each thing individually.

81. Geographic Features
Points, lines and polygons

82. Feature Attributes

83. Feature Attributes

84. Feature Attributes

85. Sample Applications

94. Site Selection Example
At least five acres in size
Vacant or for sale
Zoned commercial
Not subject to flooding
Located not more than one mile from a heavy duty road
Situated on terrain whose maximum slope is less than ten percent

95. Parcel > 5 Acre

96. Parcels Zoned for Commercial

97. Within Distance ‘x’ of Highway

100. segments and their watersheds
Trinity River Basin
Continuous Space
Representation
Discrete Space
Representation
Digital
Elevation
Model
(30m cells)
River reaches
and their watersheds
TNRCC
water quality
segments and their watersheds

102. Soil Map of TNRCC Management Segment 841 Lower West Fork Trinity River

103. Lumped Models  Discrete flow systems e.g. watersheds,
streams
 Ordinary differential equations
 Spatially averaged properties
 Network of connected flow systems dS dt
= I - Q
Input, I(t) A A A 1 2
Storage, S 1 A C
Output, Q(t) 2 1 S C 1

105. 30m DEM of Lower West Fork, Trinity River
Both regions and features can
be represented using elements

106. Distributed Models  Continuous flow systems e.g. groundwater,
air
 Spatially distributed properties
 Vertically averaged or integrated flows
 Partial differential equations
 Must solve both the continuity and momentum
equations y x