How Gwulo's new maps help date old Hong Kong photos

Submitted by David on

I’ve just finished adding new features to make Gwulo’s maps more useful. One feature in particular can help you to work out what year an old Hong Kong photo was taken.

Here’s a short video introducing the new features, and showing how to use them:

  • 00:00 Introduction to Gwulo’s maps
  • 01:16 Problem with the original map
  • 01:35 New feature 1: Only show Places in a Range of Years
  • 03:04 How to use it to date an old photo of Hong Kong
  • 09:15 How to use it to trace Hong Kong’s development
  • 13:07 New feature 2: Only show Places in a specific Year
  • 14:16 Tip: Share a map
  • 14:53 Tip: Show all Places

If you run into any problems, or have any questions about using these, please let me know in the comments below.

Comments

Hi David. This is helpful, especially for questions where you showed solutions in your video (new buildings at the praya in 1900-1910).

I tried this myself, but there are some things I do not fully understand. Here is the map showing places 1860-1870.

https://gwulo.com/map-of-places-in-year-range?startYear=1860&endYear=1870#19~22.28128~114.15638~Map_by_GovHK-Markers~100

Hong Kong Club building (1st generation) / Yee Sang Fat Building - IL 16 [1846-1930] has a red marker, General Post Office - Queen's Road at Pedder St - (2nd location) [1865-1921] has a green one. There are a few more on this map (e.g. Dent & Co. (Centre) / Holiday & Wise / later Melcher's - ML 7 Sec B [1858-c.1904] (red) and Dent & Co. (West - Praya and Pedder) / Melcher's Building - ML 7 Sec C [1863-1889] (green)). 

If I understood your explanation correctly, the marker for the GPO is green, as it opened in 1865. The HK Club building has a red marker, because nothing happened in this decade. It's a bit confusing because it should have a green marker as it was there.

Posssibly the text  Places that existed in a range of years should read: Places that changed their state in a range of years.

Hi Klaus,

Thanks for testing this, and for the helpful feedback. Let me try and give a better explanation.

Here is the 'Map of all Places' for the area we're discussing:

https://gwulo.com/map-of-places#19~22.28128~114.15638~Map_by_GovHK-Markers~100

A Place's marker colour represents what its condition is today. If it's a green marker the Place still exists - go there today and you'll see the Place. If it's a red marker there's nothing to see there today, the Place has already been demolished.

Now switch to the map of 'Places that existed in a range of years':

https://gwulo.com/map-of-places-in-year-range?startYear=1860&endYear=1870#19~22.28128~114.15638~Map_by_GovHK-Markers~100

This acts as a filter, only showing the Places that existed in the specified years (1860-1870 in this case) and hiding all the others. There's no change in the meaning of the marker colours, they still reflect what you'd see if you went there today.

The new dot colours are different, as they reflect changes that happened during the specified range of years. On your example map, a Place with a green dot was completed sometime during the years 1860-1870, while a Place with a red dot was closed or demolished during that time.

I hope that helps make things clearer, but let me know if I can explain anything else.

Regards, David

Hi David,

thank you for explaining. For my (hopefully) final understanding, the following examples:

Post Office Building -Queens Road Central - 1st Generation [1846-c.1864]
colour red inside the red marker- it was demolished between 1850 and 1860, therefore does not exist today.

General Post Office - Queen's Road at Pedder St - (2nd location) [1865-1921]
colour green inside the red marker- it opened between 1850 and 1860. It was demolished in 1921, and therefore does not exist today.

Hong Kong Club building (1st generation) / Yee Sang Fat Building - IL 16 [1846-1930]
(standard full) red marker - it existed unchanged between 1850 and 1860. It was demolished in 1930, and therefore does not exist today.

Marine Lot 5 (ML5) [1841- ]
(standard full) green marker - it existed unchanged between 1850 and 1860. It still exist today.
 

Places that existed in a range of years (e.g. link) 

Whenever we adjust the range under it and press the [Update map] button, the chosen paper map in use is cleared away.
I guess this may be one limitation of a sessionless webpage for users.

For easier usage, could we suggest to default End of Range year as the paper map to be attached, if that year's map exists ?
Alternatively, some checkbox for users to keep the current filter/choice may be used (one example here)  
 e.g. we may have this option, to carry the user's choice of paper map forward ? 
         [ ]  keep the map source

Either one of above may make 'Places that existed in a range of years' searching more handy, but I am not sure if easy to adapt under Drupal, or need much coding.

observation about the dot colours

e.g.
dot of Nathan Theatre (1938-1948) is left-half green, right-half red under range start 1935, end 1950
It is interpreted like 1938 completion is within range (so, left-half green) and closed year 1948 is within range (right-half red). Correct ?

dot of Koon Chung Theatre (c.1931-1939)
1931 is outside range, so left-half of dot is showed as red;
1939 is within range, so right-half of dot is showed as red too

With such observations, I think it may be better for users to put an estimated closed/demolished date, as far as possible, instead of leaving it BLANK (viz. open-ended).
Otherwise, some green dot may appear for places with current condition demolished/no longer exists, causing confused interpretation.