WEEK 2 FNR 210

A Map is..

graphical depiction of all or part of a geographic
rgraphical depiction of all or part of a geographic
realm; a symbolic interpretation of a place

Where the real world features are

replaced by symbols

at their correct spatial location

at a reduced scale

Maps

Should have 4 parts

• title

• scale bar

• compass rose

• key/legend

Maps store and communicate geospatical data

Maps are paper or digital storehouses of the spatial information we use as sources of data for GIS

Maps are the final stage of GIS work, the means by which GIS data and analysis is communicated to its intended audience

Reference maps

• convey general geographic information

• emphasize the location of spatial phenomena

Thematic maps

• show distribution pattern of data across geography

• emphasize the spatial pattern of geographic attributes or statisitcs about places and relationships between places

Effective maps

1, purpose

why is the map being made? this will determine what to map and how to portray the information

2, reality

the phenomenon being mapped will impose constraints on map design

Available data

specific characteristics of data - amount of data, resolution of the data, data model will affect the design

Map scale

Controls how many data appear in the map frame resolution, the size of symbols, overlap and much more

Audience

different audiences expect different information on a map and expect to see information presented in different ways

conditions of use

the environment in which a map will used will be imposed will impose significant constraints

Technical limits

whether digital or hardcopy, there are technical limits on map design

Many ways to convey meaning:

size, value, hue, saturation, orientation, shape, arrangement, texture, and foucs

Border shape

size

shape

Overall location and orientation

orientation

arrangement

What happens inside borders

value

hue

saturation

texture

focus

Many ways to convey meaning

size

value

hue

saturation

shape

orientation

arrangement

texture

focus

area

size

value

hue

saturation

orientation

shape

arrangement

texture

focus

Geographic feature?

Natural

rivers, vegetation, climate

Constructions

roads, pipelines, wells, and buildings

Social constructs

countries, political divisions, land parcels

Three types of geographic features:

Discrete

Continuous

Aggregated by area

Two ways to represent features in GIS:

• Vector

• Raster

Discrete

Actual location can be pinpointed, feature is present

Continuous

Blankets an entire area with no gaps, value can be determined at any location

Aggregated by area

Represents count or density within area boundaries, applies to entire area but not to any specific location

2 ways of representing geographic features

vector- points, lines, areas

raster- gridded cells

What is an attribute?

Non-spatial information about geographic features in a GIS,
usually stored in a table and linked to the feature by a unique
identifier
u In raster datasets, information associated with each unique
value of a raster cell

In general, attributes fall into 5 basic categories:

• Nominal

• Ordinal

• Interval

• Ratio

• Cyclic

Nominal attributes

• tells us the names of values

• may be numbers, letters or even colors

Ordinal attributes

Values have a natural order

• tell us the order but not the differences between the values

• Adding, dividing, or averaging ordinal attributes produces nonsense results

Interval attributes

• Tell us the order and exact differences between the values

• These don’t have a true zero point

• can be added or subtracted

• Cannot be multiplied or divided

Ratio attributes

Ratios are based on a zero-point and permit comparisons such as being twice as high, or one-half as much

• these do have a true zero

• ex

• Age

• Distance, Height

• Volume

• Weight

Cyclic attributes

Directional or cyclic in nature

arithmetric operations can be challenging

ex:

time of year

compass direction

Summary:

• Nominal-identify or distinguish

• Ordinal- have nature order

• Interval- differencing makes sense

• ratio-ratios makes sense

• cyclic-directional

.mxd

Arc map document

.aprx

Arc project file

.shp

Shapefile

.shx

shapefile index

.dbf

Mandatory. A standard database file used to store attribute data and object IDs

.prj

an optional file that contains the metadata associated with the shapefile’s coordinate and projection system

.xml

extensible markup language contains the metadata associated with the shapefile. if you delete this file, you essentially delete your metadata.

.dat

Database tables

.gdb

Arc geodatabase

.kml/.kmz

Keyhole markup langauge

.csv

Comma separated values

.txt

text

.tif

geotiff

When moving shapefiles

use the catalog pane

Features

A representation of objects/phenomena located on or near the surface of the earth. Can
be natural, social/physical constructions. Are discrete, continuous, or aggregated by
area. (Week 1)
u Refers to geography not “bells and whistles

Attribute Tables

• A database file containing information about a set of geographic features, usually arranged so that each row represents a feature and each column represents one attribute of the features

• In raster datasets, each row of an attribute table corresonds to a certain zone of cells having the same value

• In raster datasets, each row of an attribute table corresponds to a certain zone of cells
  having the same value.
  u In a GIS, attribute tables are often joined or related to spatial data layers, and the
  attribute values they contain can be used to find, query, and symbolize features or
  raster cells.

  
  

Feature class (ArcGIS

A collection of geographic features with the same geometry type (such as point,
line, or polygon), the same attributes, and the same spatial reference.
u Feature classes can be stored in geodatabases, shapefiles, coverages, or other data
formats.
u Feature classes allow homogeneous features to be grouped into a single unit for
data storage purposes. For example, highways, primary roads, and secondary roads
can be grouped into a line feature class named "roads

layer

A visual representation of a geographic dataset (raster or vector) in any digital map
environment.
u Conceptually, a layer is a slice of the geographic reality in a particular area, and is
more or less equivalent to a legend item on a paper map.
u Example: On a road map, roads, national parks, political boundaries, and rivers
might be considered different layers.

Shapefile

A
vvector data storage format for storing the location, shape, and attributes of
geographic features.
- A shapefile is stored in a set of related files and contains one feature class.
- “Shapefile” is never a raster, but raster data can be converted to vector and stored
as a shapefile

These are all parts of a system of organizing and managing data
- Features (have attributes) < Feature class (multiple features, stored as a shapefile
with an attribute table)
- Often shapefile and layer are used interchangeably, but a raster can also be a data
layer.

population

attributre