Environmental GIS

1. Environmental GIS Nicholas A. Procopio, Ph.D, GISP nick@drexel.edu

2. Map Review • A map is defined as a representation, normally to scale and on a flat medium, of a selection of material or abstract features on, or in relation to, the surface of the Earth.

3. Map Characteristics • Usually out of date • Show only a static situation – one slice of time • Often elegant/artistic (much more so in distant past, more functional in recent times)

4. History of Maps • Earliest direct evidence of mapping comes from the middle east. • Thought to be Babylonian clay tablets that depict the earth as a flat circular disk • Most date it as 2,300-2,500 B.C.

5. Early Views of the Earth • Thales (625-547 BC) proposes a disc on an ocean • Anaximander (611 – 554 BC) proposes a cylinder with the land curving on its surface • Pythagoras (6th century) – proposes a sphere due to geometrical perfection.

6. Early View of the Earth • Cartography became considerably advanced in ancient Greece. • The concept of a spherical Earth was well known among Greek philosophers by the time of Aristotle (ca. 350 B.C.) and has been accepted by geographers since.

7. Conceptualizing the Earth • Eratosthenes (276 – 195 BC) first calculated the circumference of the earth. • Value was determined to be 24,663 - 27,967miles • Actual value is 24,902 miles

8. Conceptualizing the Earth • Ptolomey • Defined the elements and form of scientific cartography • Created first projection in 150 AD

9. Ptolemy’s Projection

10. Ptolemy’s View of the World • Ptolemy promulgated a value for the circumference of the earth much less than the actual number • This would have a significant impact on human history • By observing Ptolemy’s work, it appeared to Columbus that Asia was much closer to Europe

11. Early Map Forms • As Europe entered the Dark Ages, the ideas about the shape of the earth were gradually lost. • In Europe, the view of the earth is based primarily on theologic premises. The map became a religious statement as opposed to a geographic tool. • Many outlying areas are decorated with religious symbols and mythical figures.

12. Early Arabic Maps • Al-Idrisi was the leading mapmaker of the Middle Ages • His world map (shown with south oriented at the top) was world renown

13. Early Maps • Early European explorers often drew maps of newly discovered coastlines.

14. Mercator • In the 16th Century, Mercator created the Mercator projection • Allows mariners to sail to their destinations by following a rhumb line

15. A rhumb line is a line or direction on the surface of the earth that follows a single compass bearing and makes the same angle with all meridians, resulting in a curved spiraling toward the poles

16. Early Maps • Waldseemüller's world map, 1507 • The first map to incorporate New World discoveries.

17. Advancements in Cartography • In the late 17th Century, Newton proposes that the earth is not a true sphere but an oblate spheroid • Proposal submitted as a corollary to his theory of gravitation

18. Advancements in Cartography • In the late 17th Century and early 18th century, measurements of degrees of latitude support Newton’s proposal that the earth is an oblate spheroid • The length of a degree of latitude decreases northward, suggesting the earth flattens toward the top • Soon after the establishment of degrees of latitude, degrees of longitude are established

19. Greenwich Prime Meridian • The Prime Meridian, the first line of longitude, was established in 1884 • The prime meridian was established as a means of developing a navigational and timekeeping standard, as the pace of development and travel accelerated in the 19th century

20. Greenwich Prime Meridian • In 1884, 25 countries reached agreement at a conference in Washington, USA, that the Greenwich Meridian would be adopted as the `Prime Meridian' (zero degrees) from which time could be set and from which other points of longitude could be calculated

21. Greenwich Prime Meridian • Before the establishment of the prime meridian in 1884, almost every town in the world kept its own local time!

22. Advancements in Cartography • In the 18th Century, there is a rapid expansion of thematic mapping • Various layers of spatial data on a series of similar base maps • 18th Century maps of the Battle of Yorktown, drawn by French cartographer Louis-Alexandre Berthier contained hinged overlays to show troop movement.

23. Types of Maps • Reference map • Shows the simplest properties of the map data • Often display political boundaries, streams, roads, and towns • Thematic map • Show colored, grouped, or coded information on a particular theme

24. Types of Maps • Topographic - a reference tool, showing the outlines of selected natural and man-made features of the Earth

25. Types of Maps • Thematic map - a tool to communicate geographical concepts such as the distribution of population densities, climate, movement of goods, land use etc.

26. Chloropleth Maps • Choropleth map - uses reporting zones such as counties or census tracts to show data such as average incomes, percent female, or rates of mortality

27. Isopleth Maps • Isopleth map - shows an imaginary surface by means of lines joining points of equal value, "isolines"

28. Area Class Maps • Area class map - shows zones of constant attributes, such as vegetation, soil type, or forest species

29. Other Types of Maps • Graduated symbol map • Symbols locate features and the size of the symbol correlates to the value of the feature

30. Other Types of Maps • Dot map • Dots depict locations of features

31. Map Features • Title • Symbols • Legend • North Arrow • Place-names • Credits • Inset • Scale

32. Symbols • Map symbols are the representations of the real-world features. The mapmaker can assign a certain symbol to represent a feature but most maps follow a specific guideline for representing features.

33. Map Representations

34. Legend • The legend lists the symbols used on a map and what they depict • The symbols should appear on the legend exactly as they do on the map

35. North Arrow • The question of “what is north” can be an issue on some maps • The earth has a “true” north and a “magnetic” north • Most maps reference true north

36. Inset • Occasionally, data and observations may be densely cluttered in small sections of a map. • The mapmaker provides insets to zoom in to these cluttered locations

37. Scale • The amount of reduction that occurs when taking the real world and expressing it as a map • In most maps, scale is extremely important • Scale can be indicated by • Verbal (1 inch equals 2000 feet) • Numeric (1:24,000) • Graphic

38. Scale • Large scale map features are relatively large. Small scale map features are relatively small. • Large Scale 1:1000 • Small Scale 1:250000

39. More Detail <--------- ----------> Less Detail 1:24,000 1:100,000 1:500,000 1:1,000,000 Scale Small Scale Large Scale