1. Bringing Historic Maps into GIS
Patrick Florance
Digital Cartographer
Harvard Map Collection
Harvard University

2. Purpose Demonstrate how historical maps can be used within a GIS.
Illustrate the techniques used to bring historical maps into GIS
Show types of maps that are useful to bring into GIS
Convey research conducted at the Harvard Map Collection

3. GIS
A geographic information system (GIS) is a configuration of computer hardware, software, and personnel specifically designed for the acquisition, maintenance, and use of geographically referenced data.
Modification of Dana Tomlin’s definition Geographic Information Systems and Cartographic Modeling (1990)

4. Why bring historic maps into GIS?
Use historic maps within GIS as a tool for understanding the spatial relationships of past phenomena
Deforestation
Shoreline change
Socio-economic characteristics of a state or a neighborhood
Place-names
Railroads and transportation networks
Disease

5. Why bring historic maps into GIS?
Context: What exists within one’s study area at a given point(s) in time?
Overlay modern GIS data over historic maps
Early 20th century USGS topographic map of central Mass.

6. Why bring historic maps into GIS?
Context: What exists within one’s study area at a given point(s) in time?
Overlay modern GIS data over historic maps
Early 20th century USGS topographic map of central Mass.
Overlay modern Quabbin Reservoir in semi-transparent blue

7. Why bring historic maps into GIS?
Context: What exists within one’s study area at a given point(s) in time?
Close up of northern Quabbin over early USGS topographic map.
Features flooded: Towns, roads, railroads, etc.

8. Why bring historic maps into GIS?
Feature Extraction (heads-up digitizing) and encoding
Vectorize: discrete data made up of ordered lists of points and represented by points, lines, and polygons
Trace features and encode those graphics with information
Surface of the earth
Anthropogenic features
Places, place-names, roads, railways, trails, buildings, bridges, etc.
Natural features
Rivers, lakes, shoreline, elevation, etc.
Abstract/Administrative geography
Country, state/province, municipal, parcel/property boundaries, census tracts, etc.

9. Why bring historic maps into GIS?
Feature Extraction (vectorization)
1898 USGS topographic map of Portland, Maine

10. Why bring historic maps into GIS?
Feature Extraction (vectorization)
1898 USGS topographic map of Portland, Maine
Built area extracted (vectorized) in red.
Perhaps trace roads, railroads, shoreline, contours, etc.
Note edge.

11. Why bring historic maps into GIS?
Resource/Research Management Tool
More and more researchers using spreadsheets to manage their research to collect information about places and source material
Think of GIS as sort of a spatial spreadsheet or database, which can be used to join that information to spatial representations

12. Why bring historic maps into GIS?
Analysis
Simple
Finding inns that are located within 5 miles of towns with a population over 10,000 in southern France around 1910.
More complex
Archaeological predictive modeling
Spatial analysis techniques to model fire density or disease patterns

13. Why bring historic maps into GIS?
Analysis
Interpolated fire density of Constantinople, 1660.

14. Why bring historic maps into GIS?
Graphic presentations or visualization
Make maps, charts, graphs, etc.
Very powerful and useful
See David Rumsey Example

15. Historic Map as a GIS Data Source
Historic maps are made for communicating, not for serving as a basemap/source data for a modern GIS.
Positional accuracy: features often moved slightly for clarity (i.e., clustered places, roads along rivers, etc.)
Scale distortion
Edge-matching
Insets
Paper streets
1890 map vs map

16. Data Conversion/Development Process
Convert maps to digital form
Georeference the digital maps: assign them meaningful spatial coordinates
Feature extraction and data modeling ($$)
Generally around 80% of project cost
Heavy overhead before one gets results, which is one of reasons why so many GIS fail.

17. Convert Printed Map to Digital Image
Digital Image (Raster) is composed of a grid of pixels
1898 U.S. railroad map

18. Convert Printed Map to Digital Image Equipment
Large-format scanner
Expensive
Scarce
Overhead digital photography
Be careful using photocopies
Distortion along edges

19. Convert Printed Map to Digital Image Resolution
Resolution can be expressed as the number of pixels per inch (PPI)
Different from spatial resolution of remotely sensed imagery, which is a measure of the smallest object that can be resolved by the sensor or the dimension on the ground represented by each pixel (i.e., 30 meters)

20. Convert Printed Map to Digital Image Resolution (Cont.)
Generally between ppi, average ppi
Determine resolution that captures the smallest significant feature
Use consistent resolution if working with a map series
Capture uncompressed as TIFF (Tagged Image File Format)
Consider using image compression for working file
If map is in grayscale, capture it in grayscale color model
reduce file size
If map repository, consider capturing very high quality for archiving & resampling to lower resolution for GIS work

21. Georeference the Digital Image/Map
Georeferencing converts a digital image (raster dataset) from a nonreal-world coordinate system (image space) to a real-world coordinate system such as latitude and longitude.
Makes it “line up” with other GIS data.
Allows the digital map image to be viewed with other GIS data.

22. Georeferencing Process
Need to know locations of at least 3 recognizable features
Use more than 3
Locations used to create control points
Spread out throughout the map
1898 U.S. railroad map

23. Georeferencing Process
Lat/Long
Lat/Long
Lat/Long
Need to know locations of at least 3 recognizable features
Use more than 3
Locations used to create control points
Spread out throughout the map
Link real-world coordinates to the control points
Links used to transform the map image to real-world coordinates

24. Georeferencing: Transformation
Transformation adjusts the digital map to make it fit in this real-world coordinate system
Affine Transformation - most common
Scale
Skew
Rotation
Shift (Translation)

25. Affine Transformation: Scale
Changes the image scale by expanding or reducing

26. Affine Transformation: Skew
Before
After X Y

27. Affine Transformation: Rotation
Rotates x and y axes so that the image is correctly oriented
Before
After X Y

28. Affine Transformation: Shift (Translation)
X and Y origin are shifted
Before
After X Y

29. Georeferencing: Transformation Complete
1898 railroad map with modern vector shoreline overlaid
Software creates associated files that contain the coordinate information (i.e., .tfw)
Digital map can then integrated with other GIS data

30. Root Mean Square (RMS) error
Describes the deviation between the control points in the output image and the values calculated by the transformation
A measure of the accuracy of the control points
In general, lower number the better, with 0 being perfect
Record RMS error
Save control points

31. Georeferencing Techniques for Historic Maps
Use existing coordinates or tics
Link features on map to features within GIS datasets that have known real-world coordinates.
Global Positioning System (GPS)

32. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Over 134 types of features: towns, municipal boundaries, road types, railways, hydrology, rice fields, pasture land, post offices, churches, castles, inns, etc.
Austro-Hungarian Monarchy Topographic Series,
Scale: 1:75,000; Date:

33. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Topographic map misaligned with modern GIS municipal boundaries (red)

34. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Step 1: map research
Map projection: polyhedric projection (antiquated)
Coordinate system: Bessel 1841 spheroid
Spheroid: estimated shape of the earth as a sphere
Prime meridian: Ferro
Metadata is often located on the topographic map itself
However, not in this case
Significant role for the historian

35. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Step 2: Create a point layer
From geographic coordinates of the 4 corners
Based on the historic coordinate system (Bessel 1841) and prime meridian (Ferro)

36. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Step 3: Project points into the historic map projection
Polyhedric antiquated
Used a polyconic

37. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Step 4: Link tic marks on the map to the projected corner points.

38. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Step 5: Transform the map
Georeferenced topo with modern GIS municipal boundaries and rivers overlaid

39. Use Existing Coordinates or Tics to Reference the Map in Real-World Coordinates
Close up: modern municipal boundaries (gemeinden) overlaid on topo
Disparate datasets never match up perfectly
Off by around feet
Detail on map: churches, road types, pastures, etc.

40. Issue: study area falls on edge of a topo sheet

41. Area Obscured by Overlap

42. Mosaic: Match Adjoining Map Sheets
Image processing software
Adobe Photoshop
ERDAS Imagine
ArcGIS Spatial Analyst
Time consuming

43. Other Useful Maps with Coordinate Systems
Topographic series
USGS 1890s – 1950s: 1:62500
England & Wales: , 1:63,360
German Karte des Deutschen Reiches: ; 1:100,000
China Ministry of National Defense Land Survey: ; 1:100,000
Survey of India: ; 1:253,440.
Nautical charts
Shorelines, soundings, etc.
World and regional maps
Historic places, national and provincial boundaries, transportation networks, etc.
Globes

44. Georeferencing Techniques for Historic Maps
Use existing coordinates or tics
Link features on map to features within GIS datasets that have known real-world coordinates
Global Positioning System (GPS)

45. Feature Linking
Use control points to link features on the map to features within a GIS dataset that have known real-world coordinates
2001 MassGIS Digital Orthophoto
1797 Street Map of Boston

46. Feature Linking Steps Acquire GIS reference dataset to link the map to
Should be of equal or slightly better scale
Map research
Map projection, coordinate system/datum
Identify additional map sources for reference
Establish reference points to use as links
Cultural features such as street intersections, bridges, buildings, landmarks, monuments, etc.
Try to avoid using natural features such as shoreline, rivers, lakes, etc. because they fluctuate greatly
Check dates of features on the map used as links
Project GIS data to match the projection of the map

47. Feature Linking Steps (Cont.)
If georeferencing multiple maps, start with the most current map and work backwards in time
Provides more features to link to
1797
1835
1895
2001

48. Feature Linking Steps (Cont.)
Add at least 3 control points spread out throughout the map
Transform the map
2001 MassGIS Digital Orthophoto
1797 Street Map of Boston

49. City-Wide Maps: Boston
Useful for tracing the historical development of:
Streets
Districts & wards
Shoreline
Town boundaries
Monuments
Churches
Schools
Significant buildings
shoreline change

50. City-Wide Maps: Cambridge Full View
1865 street map of the City of Cambridge, MA

51. City-Wide Maps: Cambridge Detail
Detail of 1865 street map of the City of Cambridge, MA

52. City-Wide Maps Georeferenced
Georeferenced 1865 map of Cambridge
GIS reference data
City of Cambrige GIS street centerline (shown in red)

53. Integrate Additional GIS Data with Georeferenced Map
Georeferenced 1865 map of Cambridge overlaid with 3D buildings

54. Integrate Additional GIS Data with Georeferenced Map
Georeferenced 1865 map of Cambridge overlaid with 3D buildings and modern shoreline of the Charles River

55. Urban/Fire Insurance Atlases
Publishers: Bromley, Beers, Hopkins, Sanborn, Ordnance Survey (OS)
Begin around mid 19th century, early 1800s for OS.
Scale of 1:5000 or better
Wealth of information
Property: boundaries, owners, addresses
Building: footprints, composition, heights, stories, use, roof types
Other info: streets, fire hydrants, etc.

56. Urban/Fire Insurance Atlases Detail
Detail of 1867 Boston Sanborn

57. Urban/Fire Insurance Atlases Full View
Issues
Bound editions make digital conversion difficult
Insets
Mosaicing or edge-matching
Ungeoreferenced 1867 Boston Sanborn

58. Urban/Fire Insurance Atlases Georeferenced Mosaic Full View
Georeferenced 1867 Boston Sanborn with inset mosaiced

59. Urban/Fire Insurance Atlases Georeferenced Mosaic Detail
Georeferenced 1867 Boston Sanborn with inset mosaiced

60. Urban/Fire Insurance Atlases Integration of Modern and Historical Data
Georeferenced 1867 Boston Sanborn with modern buildings overlaid in red

61. Reconstructing the New Orleans Yellow Fever Epidemic of 1878 Andrew Curtis & John Anderson, LSU
Example of using historic urban atlases and city-wide maps
Textual descriptions
Automated data conversion
Historical geocoding of death residences
Spatial Analysis

62. Other Useful Types of Maps
Census Maps
Most common request
Enormous amount of vectorization work
Scarce
Minor Civil Divisions, NY, 1930.

63. Other Useful Types of Maps
Aerial Photography
Vertical photography from mid 1930s to present; developed during WWII
Great for context
Distortion/displacement: scale, relief, and tilt
Use building footprints not rooftops, street intersections, etc. for control points
1952
2001
Boston 1952 USDA aerial photo over 2001 MassGIS color orthophoto

64. Other Useful Types of Maps
Map to Map Georeferencing
Compare one map to another
Don’t need real-world coordinates
Map of Paris, 1832
Map of Paris, 1865

65. Georeferencing Techniques for Historic Maps
Use existing coordinates or tics
Link features on map to features within GIS datasets that have known real-world
Global Positioning System (GPS)

66. Global Positioning System (GPS)
A system of satellites & receiving devices used to compute positions on the Earth

67. Global Positioning System (GPS)
Collect ground control points for significant features on the map: building corners, street intersections, monuments, site remains, etc.
Lat/Long
1815 map of early 16th century waterworks in Istanbul

68. Global Positioning System (GPS)
Useful for georeferencing when one does not have any reference data or coordinates on the map
Primarily used for city-scale or larger scale maps, not for maps of very large regions

69. Georeferencing Techniques and Historic Maps for GIS
Use existing coordinates or tics
Link features on map to features within GIS datasets that have known real-world coordinates
Global Positioning System (GPS)

70. Rubber Sheeting
Expression is used many different ways

71. Rubber Sheeting
“The process of transforming an image from one x,y coordinate system to another”
ArcInfo manual
Includes linear (Affine) transformations

72. Rubber Sheeting Higher order transformations (warping)
2nd order or higher (nonlinear) that transform through curves
Need minimum of 6 control points
Maps of large areas and unknown projection
Aerial photography

73. Rubber Sheeting Piecewise Transformation
Uses different transformations in different parts of the map
Used when map is badly warped and data matching is essential
Used for edge-matching
Generally use a full transformation first
How does one record this in the metadata?
Sometimes easier with vector data

74. Rubber Sheeting - What to Do?
Start with a first-order (Affine) transformation
Research projection of your map
Find good control points
Understand there is a fuzziness of inaccuracy in all maps and GIS data.
Then move on to higher order transformations and then piecewise transformations

75. Getting Started Source Materials
Historic & contemporary maps
Map & government document libraries
Special collections
Archives
Government agencies
Commercial vendors
GIS data
Universities
Libraries

76. Getting Started Software
Image processing software
Adobe Photoshop, Photoshop Elements
GIS software
ArcView, ArcGIS, IDRISI, AutoCAD, etc.
Advanced spatial image processing software (optional)
ArcInfo Grid, Spatial Analyst, ERDAS Imagine, etc.
Advanced wavelet image compression software (optional)
If want to disseminate georeferenced maps
ECW, MrSID, JPEG2000

77. Getting Started Hardware
Computer with minimum 512 megs RAM
For large processing 1-2 gigs of RAM
Access large format scanner or overhead digital photography

78. Getting Started People
GIS skills
Usually takes about 1 to 2 weeks to get up to speed

79. Do you need to bring your historic map into a GIS?
Maybe NOT
Making a map of an historical period.
Using the map as reference to encode pre-existing GIS data.
Digitizing tablet
to extract/trace features.

80. General Future of Bringing Historic Maps into GIS
History of cartography community needs more research concerning technical aspects (i.e., map projections and coordinate systems), mentioned by David Woodward at ICHC 2003
GIS community needs to develop more historic projections, coordinate systems, and transformations.
Development of geo-historical datasets that can be widely used
must include metadata
Accuracy assessment
Outreach concerning the use and significance of historical materials for GIS

81. Future of Bringing Historic Maps into GIS at the Harvard Map Collection
Harvard Library Digital Initiative
Georeferencing and disseminating maps online through the Harvard Geospatial Library (HGL) as JPEG2000
Civil War collection
Early Africa
Chinese topos
Historic USGS topos
Experimenting with automated raster to vector data conversion
Conducting workshops and developing instructional materials concerning GIS and the humanities/social sciences

82. Useful Internet Sites The Harvard Map Collection
Harvard Geospatial Library
David Rumsey Map Collection
The Boston Atlas

83. Comments and Questions?