In 1992, Rusty Dodson and Waldo Tobler digitized John Snow’s cholera map. Unfortunately, they did not include the names of roads (e.g., Broad Street) in their data set. While not strictly necessary for analysis or visualization, having the names can be useful so I appended the actual street names from the map to the
roads data set.
Before discussing the details, some discussion of the structure of
roads is warranted. The data contain 1241 pairs of x-y coordinates that define the endpoints of straight line segments used to describe some 528 numerically identified “streets”.
head(roads) > street n x y id name > 1 1 2 16.73800 18.69600 1 Map Frame > 2 1 2 17.66000 18.71200 2 Map Frame > 3 2 2 14.46200 18.65500 3 Map Frame > 4 2 2 16.73800 18.69600 4 Map Frame > 5 3 2 12.79388 18.61613 5 Map Frame > 6 3 2 14.46200 18.65500 6 Map Frame nrow(roads) >  1241 length(unique(roads$street)) >  528
The correspondence between these 528 “streets” and streets in the real world is not one-to-one. Excluding the 50 “streets” used to draw the map’s frame, the remaining 478 “streets” actually describe 206 real world roads (e.g., Oxford Street, Regent Street).
This discrepancy emerges because real world streets are approximated using straight line segments. In fact 40% of the “real world” roads are composed of multiple “street” segments: for example, Oxford Street consists of 26 line segments and Broad Street consists of 6.
# Map Border "Streets" # <- c(1:12, 14) top <- c(37, 62, 74, 142, 147, 205, 240, 248, 280, 360, 405, 419, 465) right <- c(483, seq(487, 495, 2), 498, 500, seq(503, 519, 2)) bottom <- c(31, 79, 114, 285, 348, 397, 469) left <- sort(c(bottom, left, top, right)) border length(border) >  50
The primary source for road names is Snow’s map (a high resolution version is available here. While great effort was made to correctly record and cross-reference names, there may still be errors. Error reports and suggestions for amendments are welcome.
Some roads on the map do not have a name. In those cases, I attach unique labels like “Unknown-C”.
Some names appear multiple times even though they lie at different locations. For these, I use Roman numerals to distinguish them (e.g., “King Street (I)” and “King Street (II)”).1
There is one apparent coding error in Dodson and Tobler’s road data. Queen Street (I) extends too far: the water pump #5 is clearly located on Marlborough Mews (see map, cited above) but ends up on Queen Street (I).
I amend this by moving the end point of Queen Street (I) westward so that the street only runs in a north-south direction. I do so by reassigning the segment that runs east-west to be part of Marlborough Mews.
<- HistData::Snow.streets snow.streets $id <- seq_len(nrow(snow.streets)) snow.streets # Data frame of road names <- read.csv("~/Documents/Data IV/Snow/road3b.csv", road.data stringsAsFactors = FALSE) <- merge(snow.streets, road.data, by = "street", all.x = TRUE) roads is.na(roads$name), "name"] <- "Map Frame" roads[ $id == 277, "street"] <- 116 roads[roads$id == 277, "name"] <- "Marlborough Mews" roads[roads$id == 277, c("x", "y")] <- roads[roads$id == 276, c("x", "y")] roads[roads$name == "Queen Street (I)", "n"] <- 4 roads[roads$name == "Marlborough Mews", "n"] <- 3 roads[roads<- roads[order(roads$id), ]roads
To help locate and visualize streets and road segments (including the map frame segments), you can use
streetNameLocator() uses the names from the
roads data set and tries to corrects for case and for extra spaces:
streetNameLocator("Oxford Street") and
segmentLocator() provides more granular analysis. It uses individual road segments as the unit of observation.
There are 206 “valid” road names; 207, if we include “Map Frame”:
1 Adam and Eve Court Maidenhead Court 2 Air Street Margaret Court 3 Albany Street Margaret Street 4 Albemarle Street Market Court 5 Allens Court Market Place 6 Angel Court Market Row 7 Archer Street Market Street (I) 8 Argyll Place Market Street (II) 9 Argyll Street Marlborough Court 10 Arundel Place Marlborough Mews 11 Arundel Street Marlborough Row 12 Batemans Buildings Marshall Street 13 Beak Street Marylebone Street 14 Bentinck Street Masons Arms Yard 15 Berners Street Meards Court/Street 16 Berwick Street Mill Street 17 Black Lion Court Nags Head Yard 18 Blenheim Mews Naylors Yard 19 Blenheim Street New Bond Street 20 Boyle Street New Burlington Mews 21 Brewer Street New Burlington Street 22 Bridle Street New Street 23 Broad Street New Street/Husband Street 24 Bruton Street Newman Street 25 Bull Yard Noel Street 26 Burlington Arcade Norris's Place 27 Burlington Gardens North Coventry Street 28 Cambridge Street Old Burlington Mews 29 Carlisle Street Old Burlington Street 30 Carnaby Court Old Compton Street 31 Carnaby Street Orchard Place 32 Castle Street East Oxendon Street 33 Catherine Wheel Yard Oxford Street 34 Chapel Place Panton Street 35 Charles Street Perrys Place 36 Church Street Peter Street 37 Clifford Street Pews Place 38 Coach & Horses Yard Phoenix Yard 39 Cock Court Picadilly 40 Conduit Street Plough Yard 41 Cork Mews Poland Street 42 Cork Street Pollen Street 43 Coventry Street Portland Mews 44 Cross Street Portland Street 45 Crown Court Princes Street (I) 46 Dean Street Princes Street (II) 47 Dover Street Princes Street (III) 48 Duck Lane/Ham Square Princes Street/Hanover Square 49 Dufours Place Pulteney Court (I) 50 Edward Street Pulteney Court (II) 51 Falconberg Court Queen Street (I) 52 Falconberg Mews Queen Street (II) 53 Fouberts Place Queen Street (III) 54 Francis Street Queens Head Court 55 Frith Street Rathbone Place 56 George Court (I) Regent Street 57 George Court (II) Regents Quadrant 58 George Place (?) Richmond Buildings/Mews 59 George Street Richmond Street 60 George Yard Rupert Street 61 Glasshouse Street Sackville Street 62 Golden Place Saville Row 63 Golden Square Sherrard Street 64 Grafton Street Ship Yard 65 Great Castle Street Sidney Alley 66 Great Chapel Street Silver Street 67 Great Crown Court Smiths Court/Yard 68 Great Marlborough Street Soho Square 69 Great Pulteney Street South Row 70 Great Windmill Street St Anns Court 71 Greek Street St Anns Place 72 Green Dragon Yard St James Workhouse 73 Greens Court St James's Market 74 Ham Yard Sutton Street 75 Hanover Street Swallow Place 76 Hanway Street Swallow Street 77 Haymarket Tent Court 78 Heddon Court Tichborne Street 79 Heddon Street Titchfield Street 80 Hollen Street Turks Head Yard 81 Hopkins Street Tyler Court 82 Jermyn Street Tyler Street 83 John Street Tylers Court 84 Kemps Court Unknown-A1 85 King Street (I) Unknown-A2 86 King Street (II) Unknown-B 87 Kings Arms Yard Unknown-C 88 Leicester Street (I) Upper James Street 89 Leicester Street (II) Upper John Street 90 Lisle Street Upper Rupert Street 91 Little Argyll Street Vigo Street 92 Little Chapel Street Vine Street 93 Little Crown Court Walkers Court 94 Little Dean Street Wardour Mews 95 Little Marlborough Street Wardour Street 96 Little Pulteney Street Warwick Street 97 Little Windmill Street Wellington Mews 98 Lower James Street Wells Street 99 Lower John Street West Street 100 Lowndes Court Whitcomb Court 101 Macclesfield Street White Bear Yard 102 Macclesfield Street/Gerrard Street William and Mary Yard 103 Maddox Street Winsley Street
The original map is 14.5 x 15.5 inches with a stated nominal scale of 30 inches per mile.
Dodson and Tobler write that “The scale of the source map is approx. 1:2000. Coordinate units are meters.” By my estimate, one unit on the map is approximately 177 feet or 54 meters per unit.2
Streets with the same name were not an unusual occurrence. See Judith Flanders. 2012. The Victorian City: everyday life in Dickens’ London. New York: St. Martin’s Press, 57-58.↩︎
According to Dodson and Tobler’s data, the length of Carnaby Street from its intersection with Great Marlborough to its intersection with Cross Street is 2.61 units. According to Google Maps, the approximate analog of that segment is the distance along parts of Great Marlborough Street and Carnaby Street between 19-21 Great Marlborough Street and 43 Carnaby Street (at Ganton Street): 463 ft. This translates into approximately 177 feet/unit or 54 meters/unit.↩︎