Geographical Movement

Transcription

1 Today s Topic Geographical Movement is critically important. This is because much change in the world is due to geographical movement. The movement of ideas, people, disease, money, energy, or material. 1

2 An Exciting Movement Map World Soccer Final: Italy against France 2

3 3

4 Slide all trips to a central point, keeping their directions fixed, and measure dustances. 4

5 Store Customers (From an ESRI business program) 5

6 Sort by distance to see distance decay. 6

7 The friction of distance 7

8 There are several simple implications of this friction as shown by the distance decline. One is to define trade areas or areas of influence. Consider two places at different locations: where the curves cross (intersect) is the place of equal influence. This is easily extended to the spatial case of influence zones and leads, inter alia, to central place theory. Another implication is the ability to estimate movement (migration, communication, etc.) between places. 8

9 Geographers sociologists, economists and others have used models to take these distance effects into account. Most common is the so-called gravity model. In this model the movement from place a to place b is proportional to the sizes of the places and inversely proportional to the distance between the places: Mij= kpapb/dij. Use is also made of the entropy variant: Mij= kaibjoidj exp -ß dij. 9

10 How well does it predict? 10

11 The form of the movement tables Mij In the case of migration from place i to place j these are square non-symmetric tables 11

12 The 9x106 numbers in a county to county table are not a lot for a computer. But for humans? This quantity of information could not be comprehended without some visualization techniques or without a model. Most of the cells in the county to county table would be empty. If the US county migration table has only 5% of the cells with non-zero entries that is still almost half a million numbers! I do not think that I could cope with that much information without some aids in the form of techniques or theory. 12

13 16 Million People Migrating An ensemble average. Note the distinct migration domains. 13

14 A common technique used to explain migration is a multiple regression. Mij = βx + ε, where β is a vector of parameter estimates relating to the several postulated causes X, and ε is an error term minimized by the least squares technique. Some of the many causes are properties of the ith place, others of the jth place, others are of the differences between the places. Here properties of the migrants themselves are typically not modeled. Instead different regressions are applied to difference classes of movers. The list of the X s is chosen in advance, on the basis of some theoretical conjectures, is often rather long, but can never be exhaustive. Also notice that no auto-correlation is assumed. 14

15 Gaining and loosing states. Based on the marginals of a 48 by 48 migration table data Sketch in the boundary between leaving and arriving places. 15

16 My original training was in geographical and mathematical cartography. But I find that too many maps are static depictions. I particularly abhor chorpleth maps. Therefore I have spent more time since the 1970 s studying and modeling movement, specially migration. This is the reason for the work on the flow mapping program. If interested in other aspects of this work, including modeling, a recent summary can be seen in the power point presentation A Flow Talk on the CD and in the publications under migration.. 16

17 Flow Mapper Tutorial In order to save time I have removed a portion of the tutorial. The full tutorial contains more detail. As you know the Flow Mapper program and tutorial can be copied from csiss.org/spatial tools/ Flow Mapper. Some supplementary materials are also on the distributed CD. 17

18 Some nice properties of the program Simple and quick flow map preparation - GIS Not Needed! Extensive color styles available. Black & white too. Hovering over a band or arrow gives the magnitude. Hovering over a centroid gives its label. Two-way, total, or net movement maps. Many to many, one to many, or many to one maps. Easy threshold choice. Some statistics made available. Size dependant only on memory availability. Multiple output formats. Non-geographic flows within firms, industries, organizations, too. Help file included. Microsoft Windows compatible. 18

19 The first steps You will need to have the coordinates available. And an interaction table, or an origin - destination list. The order in which you load these is not important. I usually load a background map first to make certain that I am working with the correct area. Then I load the place names and locations, then the interaction table. 19

20 The form of the movement tables Mij In the case of migration from place i to place j these are square non-symmetric tables 20

21 Having found an interaction matrix, the next step is to get it into the computer If the table is small you can enter it by typing it into notepad. Larger tables can be entered using a spreadsheet. Excel tables can be used directly or by converting them to space or comma delimited ASCII files (do not use tab delimitation). 21

22 Interaction table loaded 22

23 If you have an origin - destination - list instead of a complete flow table Then look under data_sets\programs\moves\input help programs and choose the appropriate program to convert your data. (do not use tab delimited lists - only comma or space delimited will work) The program should convert your list to a table in the correct form for use in Flow Mapper. In order to do this you will need to exit the Flow Mapper program, convert and save the data, and then restart the Flow Mapper program using the movement table that was created.. 23

24 Flow types: Gross, net, two-way; single row or column or all Sort: Large/small on top, large recommended Line Width: fixed, proportional, maximum size 24

25 Flow band properties Solid color, gradient, arrowhead style, edge color options 25

26 Color selection menu Note RGB values. Click OK after choosing. 26

27 Threshold None (all flows), average, percent, specific, maximum expected. Note that the average calculated from the interaction table is of all array entries and that the gross flows may exceed this and net flows can be much smaller. 27

28 To save the map Use the little flagged box at the upper left corner; name it with with an extension. All of the map must be on view on the screen! Later cropping may be desirable. 28

29 Moves to the South Atlantic Division Notice choice of arrowhead type 29

30 The moves to the South Atlantic Division 30

31 Or moves from the South Atlantic Division 31

32 Study area in Pennsylvania Ten counties containing five parks 32

33 Much of Computer Cartography is a Dot-to-Dot Just replace the dots by coordinates. 33

34 Getting coordinates Area outline and centroids, using graph paper.the results go into an ASCII file. Or use a digitizer but only if you have lots of experience with it. 34

35 Visits by county residents to parks 35

36 Two-way, Total (Gross), and Net Migration 36

37 Showing the majority of inter-provincial moves in China Using the flow mapper program 37

38 Total Migration Variable width bands, and parsing by quantity. 38

39 Net Migration Complete and simplified. 39

40 Migration from and to California Flows from CA Major flows to CA 40

41 Net Migration by two age groups, and movement size. 41

42 Two Variants Same Data 42

43 Net Migration in the United States Migration patterns persist for a long time. US Census Data

44 Migration Patterns Persist the Netherlands

45 Migration by Census Divisions Top: Migration, Total and Net Bottom: Birth to 1970 Residence, Total and Net 45

46 Variations in style With islands, showing centroids, and title. 46

47 Legend Box A legend box (an island ) with gross moves. Numbers added later. 47

48 London Inter-borough migration from 33 boroughs. Exploration of map styles, especially colors, 48

49 Commuting Pattern in Roanoke, VA, 1965 By Census Tract 49

50 Movement between French Regions Data courtesy of Mr. C. Calzada of Paris 50

51 51

52 Transfers between eleven schools in Santa Barbara School locations adjusted for clarity. Courtesy of Dr. Stuart Sweeney. Open Alternative S.B. Academy Adams 87 Roosevelt Washington Peabody Franklin Monroe McKinley Cleveland Harding 52

53 Thank You For Your Attention Experiment with your own data or try some of the files that came with the program in the Data_Sets folder., Questions?. 53

54 Comments or samples of your work done with the flow mapper program are appreciated. Send them to: Waldo Tobler Professor Emeritus Geography department University of California Santa Barbara, CA

55 Today s Topic Geographical Movement is critically important. This is because much change in the world is due to geographical movement. The movement of ideas, people, disease, money, energy, or material. 1

56 An Exciting Movement Map World Soccer Final: Italy against France 2

57 3

58 Slide all trips to a central point, keeping their directions fixed, and measure dustances. 4

59 Store Customers (From an ESRI business program) 5

60 Sort by distance to see distance decay. 6

61 The friction of distance Click to add an outline Click to add an outline 7

62 There are several simple implications of this friction as shown by the distance decline. One is to define trade areas or areas of influence. Consider two places at different locations: where the curves cross (intersect) is the place of equal influence. This is easily extended to the spatial case of influence zones and leads, inter alia, to central place theory. Another implication is the ability to estimate movement (migration, communication, etc.) between places. 8

63 Geographers sociologists, economists and others have used models to take these distance effects into account. Most common is the so-called gravity model. In this model the movement from place a to place b is proportional to the sizes of the places and inversely proportional to the distance between the places: Mij= kpapb/dij. Use is also made of the entropy variant: Mij= kaibjoidj exp -ß dij. 9

64 How well does it predict? 10

65 The form of the movement tables Mij In the case of migration from place i to place j these are square non-symmetric tables 11

66 The 9x106 numbers in a county to county table are not a lot for a computer. But for humans? This quantity of information could not be comprehended without some visualization techniques or without a model. Most of the cells in the county to county table would be empty. If the US county migration table has only 5% of the cells with non-zero entries that is still almost half a million numbers! I do not think that I could cope with that much information without some aids in the form of techniques or theory. 12

67 16 Million People Migrating An ensemble average. Note the distinct migration domains. 13

68 A common technique used to explain migration is a multiple regression. Mij = βx + ε, where β is a vector of parameter estimates relating to the several postulated causes X, and ε is an error term minimized by the least squares technique. Some of the many causes are properties of the ith place, others of the jth place, others are of the differences between the places. Here properties of the migrants themselves are typically not modeled. Instead different regressions are applied to difference classes of movers. The list of the X s is chosen in advance, on the basis of some theoretical conjectures, is often rather long, but can never be exhaustive. Also notice that no auto-correlation is assumed. 14

69 Gaining and loosing states. Based on the marginals of a 48 by 48 migration table data Sketch in the boundary between leaving and arriving places. 15

70 My original training was in geographical and mathematical cartography. But I find that too many maps are static depictions. I particularly abhor chorpleth maps. Therefore I have spent more time since the 1970 s studying and modeling movement, specially migration. This is the reason for the work on the flow mapping program. If interested in other aspects of this work, including modeling, a recent summary can be seen in the power point presentation A Flow Talk on the CD and in the publications under migration.. 16

71 Flow Mapper Tutorial In order to save time I have removed a portion of the tutorial. The full tutorial contains more detail. As you know the Flow Mapper program and tutorial can be copied from csiss.org/spatial tools/ Flow Mapper. Some supplementary materials are also on the distributed CD. 17

72 Some nice properties of the program Simple and quick flow map preparation - GIS Not Needed! Extensive color styles available. Black & white too. Hovering over a band or arrow gives the magnitude. Hovering over a centroid gives its label. Two-way, total, or net movement maps. Many to many, one to many, or many to one maps. Easy threshold choice. Some statistics made available. Size dependant only on memory availability. Multiple output formats. Non-geographic flows within firms, industries, organizations, too. Help file included. Microsoft Windows compatible. 18

73 The first steps You will need to have the coordinates available. And an interaction table, or an origin - destination list. The order in which you load these is not important. I usually load a background map first to make certain that I am working with the correct area. Then I load the place names and locations, then the interaction table. 19

74 The form of the movement tables Mij In the case of migration from place i to place j these are square non-symmetric tables 20

75 Having found an interaction matrix, the next step is to get it into the computer If the table is small you can enter it by typing it into notepad. Larger tables can be entered using a spreadsheet. Excel tables can be used directly or by converting them to space or comma delimited ASCII files (do not use tab delimitation). 21

76 Interaction table loaded 22

77 If you have an origin - destination - list instead of a complete flow table Then look under data_sets\programs\moves\input help programs and choose the appropriate program to convert your data. (do not use tab delimited lists - only comma or space delimited will work) The program should convert your list to a table in the correct form for use in Flow Mapper. In order to do this you will need to exit the Flow Mapper program, convert and save the data, and then restart the Flow Mapper program using the movement table that was created.. 23

78 Flow types: Gross, net, two-way; single row or column or all Sort: Large/small on top, large recommended Line Width: fixed, proportional, maximum size 24

79 Flow band properties Solid color, gradient, arrowhead style, edge color options 25

80 Color selection menu Note RGB values. Click OK after choosing. 26

81 Threshold None (all flows), average, percent, specific, maximum expected. Note that the average calculated from the interaction table is of all array entries and that the gross flows may exceed this and net flows can be much smaller. 27

82 To save the map Use the little flagged box at the upper left corner; name it with with an extension. All of the map must be on view on the screen! Later cropping may be desirable. 28

83 Moves to the South Atlantic Division Notice choice of arrowhead type 29

84 The moves to the South Atlantic Division 30

85 Or moves from the South Atlantic Division 31

86 Study area in Pennsylvania Ten counties containing five parks 32

87 Much of Computer Cartography is a Dot-to-Dot Just replace the dots by coordinates. 33

88 Getting coordinates Area outline and centroids, using graph paper.the results go into an ASCII file. Or use a digitizer but only if you have lots of experience with it. 34

89 Visits by county residents to parks 35

90 Two-way, Total (Gross), and Net Migration 36

91 Showing the majority of inter-provincial moves in China Using the flow mapper program 37

92 Total Migration Variable width bands, and parsing by quantity. 38

93 Net Migration Complete and simplified. 39

94 Migration from and to California Flows from CA Major flows to CA 40

95 Net Migration by two age groups, and movement size. 41

96 Two Variants Same Data 42

97 Net Migration in the United States Migration patterns persist for a long time. US Census Data

98 Migration Patterns Persist the Netherlands

99 Migration by Census Divisions Top: Migration, Total and Net Bottom: Birth to 1970 Residence, Total and Net 45

100 Variations in style With islands, showing centroids, and title. 46

101 Legend Box A legend box (an island ) with gross moves. Numbers added later. 47

102 London Inter-borough migration from 33 boroughs. Exploration of map styles, especially colors, 48

103 Commuting Pattern in Roanoke, VA, 1965 By Census Tract 49

104 Movement between French Regions Data courtesy of Mr. C. Calzada of Paris 50

105 51

106 Transfers between eleven schools in Santa Barbara School locations adjusted for clarity. Courtesy of Dr. Stuart Sweeney. Open Alternative S.B. Academy Adams 87 Roosevelt Washington Peabody Franklin Monroe McKinley Cleveland Harding 52

107 Thank You For Your Attention Experiment with your own data or try some of the files that came with the program in the Data_Sets folder., Questions?. 53

108 Comments or samples of your work done with the flow mapper program are appreciated. Send them to: Waldo Tobler Professor Emeritus Geography department University of California Santa Barbara, CA