GEO 433 lecture # 2.
Map Use &
Creation.
What is a map
A representation drawn to scale of a portion of the
earths surface.
Could also be of subsurface, oceans, skies, other
planets or in 3D.
Types of maps:
Topographic.
Chloropleth.
Isoline.
Dot distribution
Thematic.
Specialized Maps:
Specialized thematic
maps are frequently needed. These thematic maps must provide info on theme
of interest plus context: Context: Roads, rivers, topography possibly.
Themes: Soils,
geology, land-use, locations of dead dogs...
Components of maps:
Thematic content.
Scale Bar.
Legend.
North arrow.
Title.
Source.
Coordinate grid (optional)
Design of a Map:
Contour
lines/interval.
Map symbols
Choice of colors.
Scale.
Projection.
Symbols:
Standard set of
symbols used by USGS in topographic maps.
Schools, oil wells,
mines, airports, swamps, have their own symbols.
Some features lack
symbols: landfills lack a symbol although there are more of them around here
than mines.
Color:
Color is one of the
most powerful means of presenting information.
Most people can discern 1,000 shades, some
can differentiate 1000,000 colors.
Colors designed to
convey meaning
Water is blue, vegetation is green, bare rock is brown, built
environment is black...
Patterns& Lines:
Fill patterns can also convey meaning; such as for swamps and sand
dunes.
Line type can provide information: road type or nature of steam
(i.e. permanent or intermittent).
Scale:
relationship between
distance on a map compared to distance on ground of area portrayed by the map.
1:24,000 means one
inch on map = 2,000 feet on ground this is a medium scale map
Maps that are
1:24,000 or smaller scale (i.e. 1:100,000, 1: 1,000,000) are small scale maps.
Maps that are larger
scale than 1:24,000 (i.e. 1:1,000) are
large scale maps.
Significance of Scale:
Scale is important
since details on maps must be generalized when moving from larger to
smaller scales.
Projection:
The mathematical
techniques called projection is used to convert locations on curved
surface of the earth to corresponding points on a flat surface of a map.
Projection causes
distortion of true shape, area or orientation of mapped features.
________________________________________________________________________
Break for 10 min.
Coordinate systems:
Since earth is
curved, all coordinate systems must deal with spherical geometry problems.
Locations are determined either in degrees, min., sec. or in a Cartesian
coordinate system with a origin in one corner.
Latitude and longitude.
Grids the earth with parallels
and meridians. Parallels range east- west of Greenwich U.K., meridians
range north-South of the equator. Uses degree, minute and second
convention to locate a point on earth=s surface.
State Plane Coordinates:
Divides each U.S.
State into 1-10 zones and uses best projection in each. We are in Central Zone
of 5 in Texas. Distances are feet east and north of origin (in Mexico or New
Mexico), so all values are positive numbers.
Universal Transverse Mercator:
Divides worlds into
120 zones each with a Mercator projection and an origin in lower left corner.
Uses metric system units (meters) normally.
Common in
international mapping projects
Public Land Survey System:
Used to track land
ownership. Uses Townships(N/S) and Ranges(E/W) with 36 1 square
mile sections within each pair.
Sections are
subdivided into fours based on north, south, east and west corners.
Not used in most of
Texas. Why? No public lands.
Units:
Units can be U.S.
Customary or metric. Metric is mostly easier to use but still not
adopted in U.S. (Also in Liberia and Brunei).
Length and area are
important. Meter, Kilometer and Hectare. Foot, Mile Square Foot, Acre and
Square Mile.
Using maps
Topographic maps are a good way of learning about the physiography
of an area.
Good info. on topography & hydrography.
Less information on
built infrastructure, political boundaries (often out of date).
Less information on
land-use/land cover.
No information on land ownership. No
information on geology, soils.
Working with a topographic map:
What scale is it?
Available at 1:24,000 (7.5 minute). 1: 67,5000 (15 min) (Rare). 1: 100,000,
1:250,000.
Interpretation of
legend.
Finding the right
map.
Choice of Map:
Use a map of an
appropriate scale for your needs. For most field work the largest scale
available topographic is best. But for
getting to field work a thematic map of a smaller scale may be appropriate.
For special projects
other maps may be needed, GIS can help...
Obtaining maps:
USGS publishes
1:24,000 topographic maps for lower 48 states (Alaska at 1:100,000 for whole
state).
Maps can be up to 50
years out of date but usually no more than 15 years out of date.
DRGs are now
available for your computer.
Other Sources:
Internet Altavista,
go.com, etc.
Buy from Maplink or
similar vendor if in a hurry.
Other maps from NRCS, FWS, Local city etc.
Map making:
Four methods:
Manual.
Photogrammetry.
Computer Graphics
programs.
GIS.
Manual.
Uses tools like grid
& tracing paper, pencil, protractor, lettering sets. Used in real world until 1980's. No longer
used in Mongolia.
Slow, hard to copy,
mistake prone. Of primarily historical interest today.
But sketch maps are
handy.
Photogrammetry:
Uses aerial
photography and tools such as zoom transfer scope to rectify images and
estimate topography and identify features.
Widely used to up
date topographic maps, and as a basis for GIS.
Computer Graphics.
Programs like Adobe
Illustrator, Aldus Freehand have great graphics and can generate adequate maps.
Maps lack scale bars,
north arrows also unlike GIS have no attribute data.
Therefore GIS is the
best method for creating maps although not the easiest.
GIS:
A technology that
combines graphics with descriptive attribute data and spatial analysis
functions.
Most powerful
approach but requires more work if a map is all one is after.
IN CONCLUSION:
Making a map:
Scale is a key, all
things represented need to be scaled by the same factor.
Simplification is
also necessary.
Symbolization is
useful.
Wise use of color,
fill, line type is important.
Put just enough not
too much content in.
REMEMBER:
Essential map components:
Every map should have
six components:
Content (thematic)
information,
Title,
Legend,
Scale,
North Arrow,
Source info (including date, projection if any).
Lecture # 3
Aerial
photography.
Aerial photography is limited to capture of images on film from a
aerial platform.
Other less common variants include aerial imaging (which uses digital
sensors).
And aerial videography which can be done using a plane or helicopter or
other platform.
Photography
Can be either in the visible spectrum or the invisible infrared.
Visible light photography is the most common and can be color or black
and white with B & W being most common.
Infrared
The next most common aerial photography type after B&W.
This is because vegetation and water appear very strongly on infrared
film and hence land-use classification is simplified.
Can be B&W or false color.
Orientation of
platform:
The image can be a vertical image or a oblique image.
High or low...
Aerial photography can be high or low level (high level; is shot from
10,000-20,000 or more feet while low level is 500 to 5000 feet up).
Usual platform id a two seat single engine plane.
High level uses U2s or SR71s.
Gathering
aerial photography:
Flight plan,
Path,
Legs,
Overlap.
Distortion.
Caused by curvature of lens, convergence of light, irregular
topography, uneven flight path.
Distortion induced these many factors can be removed or ortho-rectified
with manual or computer means.
Registration.
To be useful, aerial photography needs additional data to provide a
frame of reference.
Registration to points on the ground is best.
Also ground-truthing.
Rectification:
To be accurately registered and rectified points of reference visible in the photo
with a known location are used.
If landmarks such as street intersections are absent, panels are
set out at known pre-surveyed locations on the flight path.
Panels appear as cross marks on the photo.
Digital
sensors:
Other non-photographic digital sensors are available in the other
frequencies of the electromagnetic spectrum such as ultraviolet and radio
(radar) frequency.
Radar is lower resolution but can penetrate clouds.
Photogrammetry
principles:
Need to capture a stereo pair.
Edge match pair and align correctly
Compensate for distortion in image by using principle point and
adjusting for shift and other distortion.
Use stereoscope, zoom transfer scope or digital methods to detect
topographic relief
Photogrammetry
is now an automated process.
Use ground control points & computer algorithms to create best fit
model of topography and adjust all points to fit model.
More control points greater precision.
Can be inaccurate since computers cannot think thus mistake canopy for
ground surface, etc.
Air photo
interpretation:
What you think you see is not always what you get.
The implies need for ground truthing
Topographic mapping most common application.
Looking at many photographs develops ability to interpret, but some
creativity and imagination is handy.
10 Minute
Break.
Field
applications
Environmental: Detecting pollution & historical land use.
Mapping: For remote areas & geologic structure.
In Archeology.
In Urban Planning.
Military applications.
Infrastructure
& planning applications
Land-use change analysis
Re-mapping areas where change has occurred.
Other
applications:
Archaeology
Crop science.
Geologic mapping.
Long history of
military applications...
Interpretation needed because ground-based mapping of enemy territory is not always so easy
they
might shoot your field worker as a spy.
Goes back to U.S. Civil War (Balloon based photography)
Pigeons, rockets
U2, Spy satellites.