E.G. please always turn off your cell phone or put it on vibrate mode for class

A kind reminder on distractions such as phone use, noise (see syllabus). Please allow fellow students to focus.

GIS for environmental management Dr. William James Smith, Jr.

Assistant Professor of Environmental Studies, UNLVAdjunct Assistant Professor in Geography, The University of Iowa

GRADUATE STUDENTS MUST PUT THEIR FINISHED PRODUCTS

FOR LABS 7, 8, 9

ON THEIR OWN WEB SITE – OPTIONAL FOR UNDERGRADS.

YOU NEED YOUR BOOKS NEXT WEEK! UPDATE ON SOFTWARE ISSUES

I am able to setup the first opening hour for Spring 2006.

Every Friday from 1:30pm to 5pm.

State of your labs and exercises and databank

http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u27.html#SEC27.6.1

Cartographic roots and map projections

Cartography

The science that deals with the construction, use, and principles behind maps and map use.

Old fashioned cartographers worked strictly on paper…but they are not the oldest --

ancient Greek Ptolemy (father of latitude and longitude and map projections).

Ch 2clarke

How could we map these stats (provide x, y, z coords?)

Map scale and projections

The shape of the earth

But paper is!

Nevertheless, earth is a oblate ellipsoid or spheroid (not a sphere since it is a little wide around the equator than tall from pole to pole.

Remote sensing and improving global position technology has improved ellipsoid estimation, allowing better measurement of the elevation of every point on earth, including sea level! This is calledthe datum.

Newer datums have been calculated using the center of the earth as the reference point (instead of a point on the ground).

In mapping the US we will often use the datum introduced in 1983 called the North American Datum (NAD 83) -- there is still some error.This is part of the geodetic reference system (GRS80) used internationally.

The U.S. military adopted much of this work but refined the values tocreate the world geodetic system (WGS84).

This matters to you because when you use or compare maps you need to know the datum and ellipsoid reference information, as atlarge scales (more detailed) there can be significant differences, especially in elevation.

You also need to know this when using a GPS receiver due to differences in coordinates.

But what if I need extra accuracy?!

The science of geodesy, which measures the earth’s size, shape, and gravitational fields exactly has resulted in mapping out of local variationsfrom the ellipsoid and calls the surface it produces a geoid.

Truth is cartographers often use the sphere as the reference base. For finer detail (large scale) maps and maps that are very much smaller(e.g. around 1:100,000) this can produce big differences.

What is map scale?

EVERY map has scale -- be it paper or digital, and every map you usewill represent a REDUCED representation of the world… or of what use would it be (1:1)?!

Representative fraction is the term used for defining the amount of scaling. This is the ratio of distances on the map to the distances on theground.

A model train is usually about 1:40 scale, meaningevery distance on the model is one-fortieth of its size on the real train.

But the world is so big we have to get some small values for the representative fractions!

1: 100,000

According to various measurements the distance around the “averageworld” is 40,078,346.23 meters (24,903.22 miles).

Representative fraction map distance (m) distance in feet (approx)1:400,000,000 .10002 .328 (3.9 inches)(earth mapped onto a gumball) 1:40,000,000 1.0002 3.28(earth mapped onto a basketball) 1:24,000 1,666.99 5,469 (1.036 miles)

http://convert.french-property.co.uk/

The original definition of a meter was one ten-millionth of the distance from the equator to the north pole measured along a meridianpassing through Paris. No wonder metric is easier to make computationswith!

* A 1:1,000 map with lots of detail would mean the equator on the mapwould be twice the length of Manhattan Island.

http://convert.french-property.co.uk/

The original definition of a meter was one ten-millionth of the distance from the equator to the north pole measured along a meridianpassing through Paris. No wonder metric is easier to make computationswith!

* A 1:1,000 map with lots of detail would mean the equator on the mapwould be twice the length of Manhattan Island.

Most national GIS mapping for the U.S. is between 1:1,000,000 and1:24,000.

Understanding the right scale for the level of detail needed is vital.

GIS allows one to zoom in and zoom out, but you still must make good choices in map making, and if the details come from data you pulled from a map at, say, 1:100,000 scale, then zooming in on the same data might make them look bigger, but there is not the data ofa 1:10,000 map!

Demo on NV Quad

But, even with the right scale, we still have to fit a ellipsoid to a flatscreen or piece of paper!

The part of cartography that deals with this is called map projections.

You can’t memorize every potential map projection and where it is appropriate for in the world, but we can define general groups and explore examples together.

Distance between Lines If you divide the circumference of the earth (approximately 25,000 miles) by 360 degrees, the distance on the earth's surface for each one degree of latitude or longitude is just over 69 miles, or 111 km.

Minutes and Seconds For precision purposes, degrees of longitude and latitude have been divided into minutes (') and seconds ("). There are 60 minutes in each degree. Each minute is divided into 60 seconds. Seconds can be further divided into tenths, hundredths, or even thousandths.

You are here - http://www.geocode.com/modules.php?name=TestDrive_Eagle

Map projections are attempts to portray the surface of the earth or a portion of the earth on a flat surface.

Some distortions of conformality, distance, direction, scale, and area always result from this process. shape

Some projections minimize distortions in some of these properties at the expense of maximizing errors in others.

Some projection are attempts to only moderately distort all of these properties.

* Conformality - When the scale of a map at any point on the map is the same in

any direction, the projection is conformal. Meridians (lines of longitude) and parallels (lines of latitude) intersect at right angles. Shape is preserved locally on conformal maps.

* Distance - A map is equidistant when it portrays distances from the center

of the projection to any other place on the map.

* Scale - Scale is the relationship between a distance portrayed on a map

and the same distance on the Earth.

* Area - When a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the Earth that they represent, the map is an equal-area map.

shape

Different map projections result in different spatial relationships between regions.

Four major classes of map projections:

1. Cylindrical projections result from projecting a spherical surface onto a cylinder.

2. Conic projections result from projecting a spherical surface onto a cone.

3. Azimuthal projections result from projecting a spherical surface onto a plane.

4. Miscellaneous projections include unprojected ones such as rectangular latitude and longitude grids and other examples of that do not fall into the cylindrical, conic, or azimuthal categories.

The line(s) on the map where the cut falls on the projection act like a globe, that is, that is an area with no distortion -- the nearer the line the less problems. If the line coincides with a parallel of latitude then it is a standard parallel.

PP 42-44 ClarkeAt http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.htmlReview from “Map projections fall into four general classes.”

Map projection options continued

http://www.lib.utexas.edu/maps/cartographic_reference.html

http://www.swopnet.com/waypoints/

Bottom line

-Larger area mapped = more important the errors due to proj are.

-The proj should fit the application (e.g. calculating areas vs dist.)*Many GIS can convert geographic coordinates to several map projections (you will do this next), some can go backwards fromfrom map coordinates in a projection to lat/long.

-Do not unintentionally mix. E.G. in the U.S., until recentlymost 1:24,000 topographic map series of the USGS used a polyconicprojection, the Clarke 1866 ellipsoid, and NAD27 datum

but now, you see a continued shift to NAD83 datum and ellipsoid named GRS80.

This has “moved” features by as much as 300 meters on the groundor 12.5 milimeters (.49 inch) on 1:24,000 maps.

Datum and coordinate systems overviewshttp://www.colorado.edu/geography/gcraft/notes/datum/datum.html

STOP HERE

http://ccs.unlv.edu/scr/support/labs/questions.aspI have copied the section of creating web site.How to create a website using your SCR Computer Labs account?

You can host web pages over the World Wide Web using your Home Directory.

Log into your SCR Computer Labs account.

Browse to the Home Directory or H:\ drive.

Create a folder titled: public_html.

Place all images and .htm/.html files inside the public_html folder.

Make sure to name the first page or homepage index.htm.

The URL for your website will be http://complabs.nevada.edu/~username.

Substitute username for your SCR Computer Lab account username (what you use to login).

Demo philippinefamily and GIS Café email me for it Arcview list

Truly,Pak-Kwan (John) NgComputer Facilities SupervisorStudent Computing ResourcesUniversity of Nevada, Las VegasEmail: Pak-Kwan.Ng@unlv.eduOffice phone:(702)895-5370

NAME, ISBN, PURCHASED FROM

TEST ALL COMPUTERS

New data on computers

Normal progression to these topics v. cliff notes puzzle version

Samples of MP from book

Why study these issues?

Maps sharing the same coordinate systems, datum and projected the same can align with each other.

Vs digitizing off varying data

Geodetic datums define earth’s size and shape, and thus, how best to apply coordinate systems that will fit that surface (resulting in maps).E.G. the right datum makes it possible to figure the elevation at a point.

If the earth was a perfect sphere, knowing the center would do what for distance?

Knowing the shape and size also allows us to fit map projections better.

Hundreds of different datums have been used to frame position descriptions since the first estimates of the earth's size made by Aristotle.

Remember, mapping the US we will often use the datum introduced in 1983 called the North American Datum (NAD 83) (300ft)

The U.S. military adopted much of this work but refined the values tocreate the world geodetic system (WGS84).

North American datum 83 associated with this earth shape

Coordinate system

Map projection

NZ in ArcView

Absolute location is in reference to an origin or “zero point” (e.g. theequator and prime meridian for lat/long).

To convert maps into numbers, standard ways to encode locations as numbers are key -- these are coordinate systems.

(you can’t just say relative location, like, not far from the post office,)!

Computers and plotters can understand distance from a zero point in ax,y format (easting going east-west, northing north-south) -- this is called a coordinate pair, put into standard coord systems.

P 47 Clarke fig. 2.11 and 2.12

Demo align vs non.

Placing the frame on the clay, so the picture/map can be hung.

Where is theorigin or zero pt?

Four major systems1. Geographic coordinates

2. Universal transverse Mercator (UTM) favored for many efforts

3. Military grid system (alt. Form of UTM) adopted by some countriesand used for world mapping.

4. State plane (basis of most surveying in the U.S.)

Geographic coordinatesStorage of locations as numbers using lat/long aka geographic cords.This system was standardized in 1884. Greenwich Observatory

Demo Mt. Charleston gas stations open or closed

- add graphic over projected data - add lat/long- change theme name- display by id and value 1 vs. 0

Demo

world label lat/long overlay and countries unprojgraphic to shp add xy = same

In a GIS lat and long are nearly always geocoded, or captured from themap into the computer in 1 of 2 ways.1. Degrees, minutes, and seconds (DMS)2. Decimal degrees (DD)

Latitude goes from 90 degrees south (-90) to 90 degrees north (+90)

Long is the same except range is -/+180 degrees.

1 of 2 formats1. DMS as a +/- DD.MMSS.XX here DD are degrees, MM are minutesand SS.XX are decimal seconds. Or,

DD

DD.XXXX aka decimal degrees (like time 60 min has 60 secs)

At the equator 40,000km per 360 degrees = 111.11km, so .001 degree = 111 meters resolution (accuracy relative to perfect coastline of Africain fig. 2.12 in Clarke).

The major advantage to “unprojected” geographic coordinates is that if many maps are captured the data can be transformed in a projection “onthe fly” so they overlay in whatever projection you choose. If maps already projected are changed to GC then they could overlay.

Unprojected maps include those that are formed by considering longitude and latitude as a simple rectangular coordinate system. Scale, distance, area, and shape are all distorted with the distortion increasing toward poles.

Universal Transverse Mercator Coordinate System (UTM) -- includedon USGS topo maps since the late 1950s. 60 pole to pole zones, each 6 degrees of long wide, within each zone we draw a transverse mercator projection centered on the middle of the zone oriented N-S toform a central meridian (the equator meets it at right angles, with a secant along 2 lines parallel to the central meridian.

http://www.colorado.edu/geography/gcraft/notes/coordsys/gif/utm14det.gif

In 1772 Lambert modified the Mercator projection into transverse formto make the “equator” run north-south to form narrow strips to mitigatedistortion. That form was used to map Mars too.

For N. Hemisphere0 northings is the equatorruns to 10,000,000 to N. Pole(don’t use over 84 degrees)

For eastings the origin is set at 500,000 west of the central meridian.

We will skip the Military Grid Coordinate System

State Plane Coordinate SystemYou will use this often in the U.S. Used for surveying and engineeringpractices (e.g. utility marking underground electric cables). A differentmap exists for each state, except Alaska.

States elongated N-S (CA) drawn on a Lambert conformal conic proj.

States elongated E-W (NY) drawn on a Transverse Mercator proj.

States are then divided into as many as 5 zones to reduce distortionbetter than UTM).

Each zone has an arbitrarily determined origin some number of feet westand south of the southwestern-most point on the map (so eastings andnorthings [in feet] come out as positive numbers).

Slightly more precise than UTM and so good in small areas, but lacksUTM universality -- imagine mapping over 2 states and 2 zones, so youwould be working with 4 coordinate systems on 2 projections.

You often find grids and tic marks on maps to help for conversion intoGIS. See Clarke p 54 figure 2.18.

Points, lines and polygons (areas) can build on one another and spatial patterns can be investigated or created only if you address these thingsand mitigate things like distorting direction.

P56 Clarke Fig. 2.20.

Coordinate systems overviewhttp://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys.html

Good sources for more information in brief text and with pictures is

http://www.lib.utexas.edu/maps/cartographic_reference.html

http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj.html

http://www.ilstu.edu/microcam/map_projections/index.htmlAlso has papers on various topics.

http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html

http://everest.hunter.cuny.edu/mp/

http://www.uncc.edu/~lagaro/cwg/mapproj/index.html

http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj.html#Refsfor more references

http://mcmcweb.er.usgs.gov/DSS/Requires JAVA plug-in

* Bugayevskiy, Lev M. and John P. Snyder. 1995. Map Projections: A Reference Manual. London: Taylor and Francis.

* Muehrcke, Phillip C. and Juliana O. Muehrcke. 1998. Map Use: Reading-Analysis-Interpretation, 4th ed. Madison, WI: JP Publications.

* Snyder, John P. 1987. Map projections: a working manual. USGS Professional Paper 1395. Washington, DC: United States Government Printing Office.

Key termsUse those in this lecture, no separate section in this PPT.

END

What you do on this space once you have made all the right choicesregarding what you have seen already in this PPT

Attributes of phenomena inside these spaces can be categorized by level of measurement1. Nominal-assign a lable or a class e.g. ski resort2.Ordinal-rank assigned e.g. roads as trail, unsurfaced road, single ln3.Interval-measure on a relative scale e.g. elevations on a datum4.Ratio-measured on an absolute scale e.g. total precipitation You can put all of these to work in GIS

Continuity refers to maps like contour maps assuming a continuous distribution -- we discuss raster later.

Choropleth maps assume a discontinuous distribution like taxes by state