GIS UPDATE!
http://forecast.weather.gov/MapClick.php?lon=-124.16121&lat=40.85186#.U_1mcfldV9j
TODAY:
• What is GIS?
• Map Scale
What is GIS?
A geographic information system
(GIS) is a computer system for
capturing, storing, checking, and
displaying data related to positions
on Earth’s surface. GIS can show
many different kinds of data on
one map. This enables people to
more easily see, analyze, and
understand patterns and
relationships.
GIS software uses relational
database management
technologies to assign a series
of attributes to each spatial
feature. Common feature
identification keys are used to
link the spatial and attribute
data between tables. A soil
polygon, for example, can be
linked to a series of database
tables that define its mineral
and chemical composition,
crop yield, land use suitability,
slope, and other
characteristics.
GIS provides the capability to
combine various data into a
composite data layer that may
become a base layer in a
database. For example, slope,
soils, hydrography,
demography, wetlands, and
land use can be combined
to
http://
develop a single layer of
suitable hazardous waste
storage sites. These data, in
turn, may be incorporated
into the permanent database
of a local government and
used for regulatory and
planning decisions.
www.epa.gov/region5fields/gis.html
Projections
The three families of map projections. They can be represented by a)
cylindrical projections, b) conical projections or c) planar projections.
http://docs.qgis.org/2.0/en/docs/gentle_gis_introduction/coordinate_reference_systems.html
Map projections determine how
people view the world, the
political and economic
relationships between different
countries, and the importance of
certain regions on a global level.
We rely on them for navigation,
for international research and
analysis, and for reference
purposes. Since different types
of projections skew different
aspects of the globe, it is of
critical importance that we are
aware of these distortions.
http://aswgeog7.blogspot.com/2011/05/projections-in-arcgis.html
Coordinate Systems
http://www.geo.hunter.cuny.edu/~rdatta/gis2/lectures/Lecture2/lecture2.htm
Can anyone think of a use
for a GIS?
TODAY:
• What is GIS?
• Map Scale
Map scale refers to the relations (or ratio)
between distance on a map and the
corresponding distance on the ground. For
example, on a 1:100,000 scale map, 1cm on the
map equals 1km on the ground. (or 1 cm on the
map equals 100,000 cm on the ground)
Verbal Scale
Relative Fraction Scale
Bar Scale
Verbal Scale ?
Relative Fraction Scale ?
Bar Scale ?
"one cm represents six km"
Large scale maps or Small scale maps?
A large scale map shows greater detail
because the scale is a larger fraction
than a small scale map.
• Large scale maps have a scale of
1:50,000 or greater (1:24,000,
1:10,000, ...).
• Small scale maps are those with scales
smaller than 1:250,000.
Which is larger scale ?
Which is larger scale ?
1:50,000 or 1:500,000
5 cm represents 1 km or 1
cm represents 10,000 m
–––––––––
–––––––––
0
1 km 0
1 cm
Express the following verbal scales
as representative fractions:
2 cm represents 5 km
100 cm represents 2500 km
0.4 cm represents 0.1 km
Given a map scale of 1:30,000, how
many cm would represent 9 km?
Given a map scale of 1:10,000, how
many km are represented by 2.5 cm?
Picture a 2 cm by 2 cm area
2 cm
taken from three maps,
each with the different
2 cm
scales listed below.
1:500,000
___________ km2
1:250,000
___________ km2
1:1,000,000
___________
2
km
Metric standard units
1 centimeter (cm) = 10 millimeters (mm)
1 meter (m) = 100 cm
1 kilometer (km) = 1,000 m
American customary system standard units
1 foot (ft) = 12 inches (in)
1 yard (yd) = 3 ft
1 rod (rd) = 16.5 ft
1 chain (ch) = 4 rd
1 furlong = 10 ch or 220 yd
1 mile (mi) = 5,280 ft
1 acre (ac) = 43,560 square feet (ft2)
Converting from Metric to American
Inch to centimeters – multiply inches by 2.54
Centimeters to inches – multiply cm by 0.3937
Feet to meters – multiply feet by 0.3048
Meters to feet – multiply meters by 3.281
Miles to kilometers – multiply miles by 1.61
Kilometers to miles – multiply km by 0.62
BREAK TIME!