L7 –Maps & Data Entry

Chapter 4 – pp 153-End

Lecture 7 1

When do we need a transformation?Digitizing from legacy maps

Digitizing from suitable aerial photos

Lecture 7 2

Coordinate Transformation

• Also called registration, as it registers the map layers to a map coordinate system.

• Requires a set of control points.– Must be as accurate as the desired outcome.– Evenly distributed over the area.– Sufficient number.

• Commonly used to convert newly digitized data to a standard coordinate system.

Lecture 7 3

Control Points

How many are enough? – 12 to 30 recommended

How should they be distributed? – at least 3 in each quadrant

Best to have an independent, higher order set – the control data should be at least as accurate (hopefully 10 times more accurate) than the data to be transformed. Lecture 7 4

Equiarea Transformation

• Equiarea (congruence) Transformation:– The method allows rotation of the rectangle

and preserves its shape and size.

Lecture 7 5

Similarity Transformation

• Similarity Transformation:– The method allows rotation of the rectangle

and preserves its shape but not size.

Lecture 7 6

Projective Transformation

• Projective Transformation:– The method allows angular and length

distortion, thus allowing the rectangle to be transformed into an irregular quadrilateral.

Lecture 7 7

Topological Transformation

• Topological Transformation:– The method preserves the topological properties of an

object but not shape, thus allowing the rectangle to be transformed into a circle.

– Also called rubber sheeting

Lecture 7 8

Affine Transformation

• Affine Transformation:– The method allows angular distortion but

preserves the parallelism of lines.– While preserving line parallelism, the affine

transformation allows rotation, translation, skew, and differential scaling on the rectangular object.

Lecture 7 9

Developing the Transformation Equations

Coordinates in the source system

Coordinates in the target system

Estimate equations that allow us to calculate the target coordinates given any set of source coordinates Lecture 7 10

Affine TransformationTarget coordinates a first-order linear function of source coordinates

Known as an Affine Transformation:

Easting = Te + a1x + a2y

Northing = Tn + b1x + b2yT shifts originbi & ai changes scale & rotation

Lecture 7 11

Example

• Road intersection:– Real world coordinates: E=500,000 & N=4,800,000– Digitized coordinates: x=125 & y= 100

• Each control point provides two equations.

)100()125(4800000

)100()125(500000

21

21

bbT

aaT

N

E

Lecture 7 12

Lecture 7 13

RMSE = e21 + e2

2 + e23…

n

Lecture 7 14

Lecture 7 15

Lecture 7 16

Higher order polynomial transformation

• Named for the largest exponent in the transformation equation.

• ArcMap supports first to third order transformation.

• Command line supports first to twelfth order transformation.

• Use the lowest order transformation that provides acceptable results

Lecture 7 17

Lecture 7 18

Raster Geometry and Resampling

• Data must often be resampled when converting between coordinate systems or changing the cell size of a raster data set.

• Common methods:– Nearest neighbor– Bilinear interpolation– Cubic convolution

Lecture 7 19

Lecture 7 20

What if the cells aren’t “well behaved”

Lecture 7 21

Orientation and/or Cell Size May Differ

Lecture 7 22

Resampling - Distance-weighted averaging

bilinearinterpolation

Lecture 7 23

Map Transformation - Summary

• From 2-d to 2-d system

• Requires mutually identified control points

• Linear (affine) transformation is best

• Sufficient, well-distributed control points

• Should not be used in place of a map projection!

Lecture 7 24

Types of GIS Output

• Maps: Everyone recognizes this most common output from a GIS.

• Cartograms: These special maps that distort geographic features based on their output values rather than their size.

• Charts: GIS can produce pie charts, histograms (bar charts), line charts, and even pictures in addition to maps.

Lecture 7 25

Types of GIS Output

• Directions: Another common output, directions show you how to get from one place to another.

• Customer lists: Business GIS applications often produce customer lists, sometimes with printed mailing labels.

• 3D diagrams and movies: These forms of GIS output help you see the results of your work realistically and dramatically.

Lecture 7 26

Maps as Output

• The map is still the most common form of output.

• Map design elements to be considered:– Frame of reference– Projection– Features to be mapped– Level of generalization– Annotations– Symbolism

• Maps should show only as much detail as necessary to get the point across.

Lecture 7 27

Cartographic Design

• Most design choices are compromises• Design is a process

– Stage 1 – type of map, data to be represented, size, shape, basic layout.

• Data type is the most important factor in determining map type and symbols

– Stage 2 – kinds of symbolism, number of classes, class limits, color, line weights.

– Stage 3 – define all symbols, typography (font, size, positions etc.)

Lecture 7 28

Making Great Maps

Lecture 7 29

https://www.youtube.com/results?search_query=ArcGIS+making+great+maps

Making Better Map Layouts with ArcGIS (1 hour)

Lecture 7 30

Qualitative Data

Make symbols as intuitive as possible

Use professional standards whenever possible

Legends

Lecture 7 31

e

e

e

e

Contrast – bad example

Lecture 7 32

e

e

e

e

Contrast – good example

Lecture 7 33

Typography & Lettering

Use concise formulated captions• Avoid using more than four fonts• Establish a typographic hierarchy• Develop legibility

• Black lettering on yellow ---- most legible• Red lettering on green ---- least legible

Lecture 7 34

Example:Example:

hello worldhello world

Hard to read betterHard to read better

Lecture 7 35

Text Placement

• Placing text on a map is one of the most time consuming tasks, as much as 50% of the final map production time.

• Poor placement of text affects the readability of the map, this is especially true in regions where map symbols are densely clustered.

• Situations often arise in which text must overwrite other symbols with which it has no logical association.

Lecture 7 36

Automated Name Placement

• Components of name placement systems:– Specification of map features and text characteristics.– Generation of trial name positions.– Selection of optimal labels.– Scale at which labels will be displayed

• Font type, color and size must also be specified.• It is desirable to name as many features as

possible, while recognizing that some features will remain unlabeled.

• Named features should be ranked in some way to resolve conflicts.

Lecture 7 37

Non-Traditional Maps

• Cartogram

• Multimedia output

• Hybrid – Map overlaying an image

• 3D

• Virtual GIS

Lecture 7 38

Cartogram

Lecture 7 39

Cartogram

http://www-personal.umich.edu/~mejn/election/2008/

2008 Election Results by StateResults on A Population

Cartogram

Lecture 7 40

http://amphibiaweb.org/amphibian/cartograms/Lecture 7 41

Figure 8.9 Example of multimedia content in GIS displaysSource: Screenshot shows ESRI Graphical User Interface (GUI). ArcMap, ArcView and ArcInfo Graphical User Interfaces are the intellectual property ofESRI and is used herein with permission. Copyright © 2005 ESRI all rights reserved Lecture 7 42

Maps and Images

Lecture 7 43

3D Maps

http://www.vidiani.com/?p=10431Lecture 7 44

THE OUTPUT FROM GIS ANALYSIS

TABLES AND CHARTS

• Used with maps or alone to improve understanding of cartographic results

• Whenever map output is less immediately understood by audience– Tables and charts are generally more understood by general public

than maps are

• Map is not appropriate for the output

• Show summaries of attribute data and relationships among them– Explicitly spatial– Implicitly spatial

Lecture 7 45

THE OUTPUT FROM GIS ANALYSIS

TABLE AND CHART DESIGN

• Should be readily understood with minimal explanations

• Appropriate titles for each table and chart presented

• Label axes on all graphs

• Provide legends wherever appropriate

• Use fonts types and sizes that are easily read – Arial

• Chose colors wisely as not to mislead audience– E.g. human eye is drawn to reds much more readily than to whites

• Using red lines against white ones will draw the eye towards one and away from the other – is that what you wish?

• Avoid plotting more than 3 distinct attributes per plotLecture 7 46

Good for comparing values and showing trends

Bar Chart

Lecture 7 47

Good for comparing values and showing trends

Column Chart

Lecture 7 48

Good for showing the relative value for each category as well as the total.

Area Chart

Lecture 7 49

Combines features of both the bar and area charts

Cumulative Bar Chart

Lecture 7 50

Shows relationships between the parts and the whole, particularly useful for showing proportions and ratios.

Pie Charts

Lecture 7 51

Emphasizes rate of change. Particularly good for representing trends over a period of time.

Line Charts

Lecture 7 52

Reveals trends or patterns in the data. Can help reveal associations, sometimes cause-and-effect relationships.

Scatter Charts

Lecture 7 53

The Geodatabase

Lecture 7 54

What is the geodatabase?

• An ArcGIS geodatabase is a collection of geographic datasets of various types held in a common file system folder:– a Microsoft Access database, – A multiuser relational database (such as

Oracle, Microsoft SQL Server, PostgreSQL, Informix, or IBM DB2).

Lecture 7 55

Fundamental datasets in the geodatabase

• A key geodatabase concept is the dataset.• It is the primary mechanism used to

organize and use geographic information in ArcGIS.

• The geodatabase contains three primary dataset types:– Feature classes – Raster datasets– Tables

Lecture 7 56

Lecture 7 57

A feature class is stored as a table. Each row represents one feature. In the polygon feature class table below, the Shape column holds the polygon geometry for each feature. The value Polygon is used to specify that the field contains the coordinates and geometry that defines one polygon in each row.

Data in a Geodatabase

Lecture 7 58

Feature Class

• Conceptual representation of a category of geographic features.

• Includes point, line, poly & annotation• When shapefiles are added to a GDB their

computer representation is changed• This is why you cannot drag and drop a

shapefile into a GDB.• You have to load it or Import it.

Lecture 7 59

Feature Dataset

• A collection of feature classes that share the same spatial reference.

• It is because they share the same spatial reference that they can participate in topological relationships with each other.

• Several feature classes with the same geometry may be stored in the same feature dataset.

• Object geometry and relationship classes can also be stored in a feature dataset

Lecture 7 60

Lecture 7 61

Geodatabase

Feature Dataset

Lecture 7 62

} Cover

Line(arc)

point

poly

Anno

Table

Lecture 7 63

Catalog View

WE view

Lecture 7 64

Catalog View

WE view

Advantages

• Can be moved as a unit, regardless of how much stuff is in it.

• Faster

• Can get at it through Microsoft Access, if you know what you are doing,

• Stores topology

Lecture 7 65

Advantages

• TOPOLOGY? = the arrangement that defines how point, line, and polygon features share coincident geometry.

• Examples:

– Fire hydrants must fall on water mains,

– Adjacent soil polygons must share their common boundaries.

Lecture 7 66

Topology

• Many datasets have features that could share boundaries or corners

• By creating a Topology you set up rules defining how features share their geometries.

• Editing a boundary or vertex shared by two or more features updates the shape of all of them.

Lecture 7 67

Topology Rules

• Govern the relationships between between features within a FC or features in different FCs

• Example: moving a slope boundary in in one FC could update two slope class polys AND update a forest stand boundary in another FC.

• Topology editing tools in ArcMap are used to create and change the rules

Lecture 7 68

Geometric Networks

• Some vector datasets need to support connectivity tracing and network connectivity rules– Communications– Pipelines– Transportation (roads, railroads, canals)

• Geometric networks allow you to turn simple point and line features into network edge and junction features

Lecture 7 69

Creating a Geodatabase

• In ArcCatalog!

• Point to where you want to put the new GDB

• Click New>Personal GDB

• Type in a new name

Lecture 7 70

Adding Data

Lecture 7 71

• In Catalog…Right click and select New

• You get

Copying Data

• You can copy/paste data between GDBs

• OR

• You can import shapefiles, coverages, computer-aided drafting (CAD) data, and GeoDatabase FCs into a GDB

Lecture 7 72

Importing Shapefiles

Lecture 7 73

• feature class that's in another coordinate system. – You MUST project to the spatial definition

of the GDB– Then right click on

GDB and select Import ---------

Planning for Your Geodatabase

• What is the problem?

• What data is needed (scale, extent, etc.0?

• What kinds of relationships are needed between FC?

• How will the data be organized (FDS)?

Lecture 7 74

Summary

• The Geodatabase is a container for all types of geographic data.

• A feature dataset contains features that share a projection and geographic space.

Lecture 7 75