Intro to Digital Mapping

Connects spatial data and list data to answer geographical questions and solve geographical problems

Coordinate system

Distance, intersection, adjacency, containment

Visualization, spatial modeling, social science and policy, planning and infrastructure, natural sciences, information technology

Has clear boundaries

States, cities, countries, bodies of water

Has no clear boundaries (except the edge of the data)

How we encode a geographic phenomenon, be it discrete or continuous into a digital data on a computer

Points, lines or polygons defined by x, y coordinates (lat/longs) and an attribute table

Vector data tends to be stored as

Political boundaries, building sites, roads, train lines

A grid of cells with values

Raster data tends to be stored as

Satellite/aerial imagery, elevation

More fundamental than maps, GIS, or even writing

Humans have the (apparently unique) ability to think about geography abstractly

1. How people understand geography varies across different places and times

   1. There are multiple kinds of legitimate geographic knowledge

• A graphic representation of the environment

• A geographical proposition/argument

  • Visual, abstract, geographic practice

Involve multiple topics or themes and no one theme is most prominent

• Focus on one theme

  • Any of a huge variety of specific themes

The shape of Texas is an example of

Parallel lines also known as y

Meridian lines also known as x

Of or related to 60

N 40° 46’ 7”, W 73° 58’ 11”

A) Degrees become the whole number

B) Calculate the total number of seconds (minutes * 60 + seconds)

C) Divide by the possible number of seconds (# from B/3600)

D) Add to the whole number

A) Degrees become the whole number

B) Multiply the decimal by 60 (decimal * 60)

C) Multiply the remaining decimals by 60

Are South and West negative or positive?

Are North and East negative or positive?

• Space-based global navigation system that in which a receiver unit calculates its location and time

  • Satellites emit radio signals. A receiver takes the signals from multiple satellites to calculate the receiver’s location

The device that gathers GPS satellite signals and uses them to calculate your location

An accurately defined location identified with a GPS unit

A recorded GPS fix that is part of a series

Global navigation systems require at least _________ for full world-wide coverage.

Name the 3 GPS parts

1. Satellites broadcast current time and location. They are synchronized

2. GPS receiver gets the signal and records the time delay between when the signal was sent vs the time the receiver got the message; indicating the time

   1. Uses space trilateration to calculate its location on time delays

A method for determining positions using the geometry of sphere in 3 dimensions

Trilateriation uses known locations of at least ___ GPS satellites

• GPS are weak

• GPS chips break

• If you drop your phone or have an old one

• Relativity

• Clock bias

• Number of visible satellites

• Dilution of precision

Can anticipate this and reduce it

Impossible to eliminate

Using external information to improve the accuracy of GPS readings

• Can be as good as 1 to 5 meters

• Uses two GPS receivers

  • One at a base station

  • A second moving about in a field

• Continuous geographic phenomena

• Discrete geographic phenomena

  • Stored digitally in raster and vector datasets

• Categories of data measurement

  • Nominal

  • Ordinal

  • Interval

  • Ratio

• Stored digitally in attribute data

Named types

Hierarchy of types

Measured difference between types based on an arbitrary zero point

Measured difference between types based on an absolute, known zero point

• Only one corner of the grid has a latitude and longitude (the origin: usually the upper left)

• Cells are regularly sized with no gaps

  • Latitude and longitude is not stored for each cell

The geographic size of a cell on the ground

Beginning points and ending points

• Lines: beginning and ending are different

• Polygons: beginning and ending are the same

Connecting points in the middle

Line connecting points

• X, y, z values

• Network of points defining triangles

  • Best for continuous data

Originally Environmental Systems Research Institute, replaced by ArcMap

A single set of GIS data is called this. Appears as layers in the contents of Arc GIS.

Raster data storage is

Vector data storage is

Stores 1 feature class

Can store multiple feature classes and other stuff