Slide for State of the Map Japan 2020 presentation.

1. A vision to make OSM data the
backbone of history across time
and space - Introduction to HTGCL -
Kohei Otsuka – Code for History
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2. NOTICE
This announcement is an introduction to , the open
source product of Code for History, and a conceptual
presentation on potential areas of future collaboration
between and OSM. There is nothing specific about
collaboration at this time in terms of actual implementations
or future timelines, so we hope you understand that.
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3. Table of contents
• What is Code for History?
• Introduction to
• Make OSM data the backbone of history across time and
space
• Conclusions
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4. What is Code for History?
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5. A community that uses information
technology to solve historical problems
(practically one person)
https://code4history.dev/
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6. Characteristics
• I want to emphasize that for us, information technology is a
"means" and not an “objective".
• The "objective" is to solve a historical problem, and if
necessary, to utilize non-IT means.
• The first priority is always to solve the problem.
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7. Introduction to
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8. Map viewer technology that allows you to
enjoy walking around the city using
historical maps and pictorial maps
© OpenStreetMap © Utouto Tanken-tai
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9. We recently changed it’s logo 9
Maplat

10. Features of
• Not distorting historical maps
• Adjusting not only the location of the center point, but also the direction
and scale
• Bidirectional one-to-one conversion (Returning to the original display
position after multiple map changes)
• Converting lines to lines (Roads to roads, rivers to rivers, etc.)
• It's open source, so anyone can create their own site with it
• Project Sites:
Library: https://github.com/code4history/Maplat/wiki
Editor: https://github.com/code4history/MaplatEditor
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11. Not distorting historical maps
• Existing technology (GIS) distorts historical maps
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12. Not distorting historical maps
• overlays historical maps without distorting them
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13. Adjusting the direction and scale
• Existing technology (Stroly) can't adjust the right orientation
and scale
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14. Adjusting the direction and scale
• fits the direction and scale almost perfectly
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15. Bidirectional one-to-one conversion
(homeomorphic conversion)
• Existing technology (Stroly) shifts the display position when
continuously switching maps
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16. Bidirectional one-to-one conversion
(homeomorphic conversion)
• does not shift the display position when
continuously switching maps (Japan patent JP-6684776)
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17. • In the past, used to get misaligned on the road at
times.
Converting lines to lines
Modern mapHistorical map
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18. • In the past, used to get misaligned on the road at
times.
Converting lines to lines
Modern mapHistorical map
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19. • Latest can accurately convert a point on the road to
a point on the road
Converting lines to lines
Modern map
Corresponding lines
(HTGCL)
Historical map
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20. • Latest can accurately convert a point on the road to
a point on the road
Converting lines to lines
Modern map
対応線
Historical map
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Corresponding lines
(HTGCL)

21. Make OSM data the backbone of
history across time and space
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22. What is the HTGCL?
• Abbreviation for Historical Topographic Ground Control Line
• Naming of the corresponding lines between modern geographic
coordinates and historical map coordinates which are used in
's "converting lines to lines" function.
• The concept is borrowed from Ground Control Points (GCPs),
which are the points in existing GIS that correspond to
inaccurate maps and accurate maps.
• Relying on points alone for coordinate transformations between
maps makes it difficult to maintain homeomorphism throughout
the transformations, and it is not possible to convert lines to lines.
Therefore, transformations using HTGCL are valuable not only
for but also for existing GIS.
• More on that in tomorrow's FOSS4G 2020 announcement.
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23. • HTGCL consists of a road/waterway network on the modern
map side and that on the historical map side.
• Is there a need to map the modern map side network every
time we map different historical maps?
• If we have an existing current map network data, could it be
used? => OSM could be used.
We could use OSM as a base for HTGCL 23

24. • Specify the area
where you want to
load OSM in the
map UI on the
modern map side
of the editor
• Read OSM data of
the area as a
network of modern
map side
• Then, specify the
corresponding
points and lines on
the historical map
Ideas on how to read OSM data 24
Download OSM
network

25. • OSM's network of roads and
waterways, created as a modern
map, could become a backbone
axis of data connecting regional
changes over history.
• The use of clear, common
modern map-side network data
could also provide valuable
data for mechanical analysis of
changes in history, such as a
river becoming a culvert and
turning into a road or a new
road being built.
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OSM data as the backbone
of regional history

26. Conclusions
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27. • is an open-source map viewer technology that allows you
to walk around town using historical maps.
• One of the features of is the ability to convert lines to
lines in the coordinate conversion between historical maps and
modern maps.
• The corresponding lines networks those are set up when
converting lines to lines is named HTGCL.
• There is a plan to use OSM data for the network of the modern
map side of HTGCL.
• The OSM may become a backbone axis that connects maps over
history, making it easier to analyze historical changes
mechanically.
Conslusions 27

28. • I used to be an avid OSM activist, but since starting Maplat, I
haven't done much OSM activity because I've been too busy with
's activities.
Since deals with history, while OSM deals with the
present, I was wondering if I would have less opportunity to get
involved with OSM in the future.
But now, I am happy to have the possibility to get involved with
OSM with an unexpected idea.
• However, at any rate, is being developed by just one
person, so I have no timetable yet for when this feature will be
implemented.
I have a lot of other features that I need to prioritize and develop,
so it's likely to be years in the future.
• is an open source activity, so if any OSM expert
developers are interested in this presentation, please help me.
Last comments 28

29. End
User: kochizufan
Github pages: https://code4history.dev/
E-mail: kochizufan@code4history.dev
Slide: https://speakerdeck.com/kochizufan/sotm-japan-2020 29