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Scale on old maps

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The ratio of distances on a map, globe, relief model, vertical section or other ... Say you have a map of England on which there is no scale statement at all. ... – PowerPoint PPT presentation

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Title: Scale on old maps


1
Scale on old maps
  • Yale University Library
  • Cataloging and Metadata Services

2
Scale
  • What is scale?
  • The ratio of distances on a map, globe, relief
    model, vertical section or other cartographic
    item to the actual distances they represent on
    earth.
  • Linear or bar scale
  • Verbal scale
  • Varying scale
  • More than one scale on the item being described

3
Why is it important in the bib record?
  • The information is critical in identifying a map
    and differentiating it from other maps with
    similar titles.
  • The information is of crucial importance to the
    user in determining if the map will show the
    level of detail they require.
  • Because cataloguing rules say it is!

4
How is scale recorded?
  • The representative fraction
  • Record in this form at least
  • Allows comparison between maps
  • Useful in automated searching when also recorded
    in coded form in the 034
  • 163,360
  • 1 of any unit on the map equals 63,360 of the
    same unit on the ground

5
Types of scale statements found on rare maps
  • Representative fraction
  • 16,842,880
  • Verbal scale
  • 108 English Miles to 1 Inch
  • Graphic or bar scale
  • No scale information at all

6
A word of warning
  • Unless the scale is 11, there are limitations to
    the accuracy of the methods used to derive the
    scale data.
  • This is especially true on older materials, where
    the scale may vary considerably over the face of
    the map depending on the methods available to the
    cartographer.
  • On modern maps, the projection used will affect
    the scale variation and distortion over the map.

7
Verbal scale statement
  • The relationship that a small distance on a
    graphic bears to the corresponding distance on
    the Earth, expressed as an equivalence, such as 1
    inch (on the graphic) equals 1 mile (on the
    ground).
  • Some users may be more familiar with this type
    of information.
  • However, it is very difficult to compare verbal
    scale statements in order to select the most
    appropriate map from the catalogue record, and
    virtually impossible to search or compare verbal
    scale statements in an automated catalogue.

8
The verbal scale statement
  • Scale may also be recorded in the record as a
    verbal scale statement, in other words, as it may
    appear on the map in addition to the RF.
  • Format for verbal scale statement
  • 1 1 mi.
  • 2 in. to the mi.
  • 255 __aScale 163,360. 1 in. to the mi.
  • Note its ok to abbreviate in the verbal
    statement portion of the 255.

9
Converting verbal scale information to a
representative fraction
  • 1 inch to the mile
  • 1 (on map) 1 mile (on Earth)
  • 1 5280 ft/mi x 12 in/ft
  • 1 63,360 in
  • RF 163,360

10
Graphic scales (1)
  • Bar scale statement

11
Measuring to convert graphic or bar scale
information to a representative fraction
12
Graphic scales (2)
  • Distances between parallels of latitude
  • Latitude is the measurement of degrees between
    the equator and the poles.
  • Latitude figures run along the sides of a map
    (when north is at the top).
  • Measure the natural scale indicators edge for 1
    of latitude against the latitude figures near the
    center of the map.

13
Graphic scale (3)
  • The map itself
  • If all else fails, and you are determined to
    figure out a scale, compare a measurable distance
    on the map to the same distance on a map of known
    scale, for instance, in a modern atlas.
  • Theres a formula for figuring the scale on the
    map youre cataloging in CM, or

14
Calculations to construct a representative
fraction using the comparison method
  • Say you have a map of England on which there is
    no scale statement at all.
  • Measure the distance between two known points,
    for example, the distance on the map between
    London and Cambridge.
  • On the map, London -gt Cambridge 10 inches
  • On the Earth, London -gt Cambridge 60 miles
  • 10 (on the map) 60 mi. (on the Earth)
  • 10 60 mi x 63360 in/mi
  • 10 3801600
  • 1 380160
  • RF 1380,160 highly approximate!

15
Recording the RF The 255 is an odd mixture of
recording exactly as it the data appears on the
item and recording according to a standard
formula.
  • If it appears as an RF on the map, record as is.
  • Scale 124,000.
  • If youve calculated from a verbal scale, record
    in brackets.
  • Scale 163,360.
  • If you measured against a bar or a map of known
    scale, record in brackets using ca.
  • Scale ca. 1120,000.

16
So, if you have to record the scale as an RF but
that is not given on the map, what do you do?
  • If you have a verbal scale statement on the map
  • CONVERT!
  • If you have a bar scale on the map
  • CALCULATE!
  • If you have no scale at all on the map
  • COMPARE!

17
Troublesome units of measurement on old maps
  • Chain
  • Furlong
  • Heures de marche
  • League
  • Lieue
  • Miles (that arent statute)
  • Milliaria Germanica, Hispanica, etc
  • Pole
  • Toise

18
Coding the scale in the 034
  • Indicators
  • First - Type of scale A value that indicates the
    type of scale contained in the field.
  • 0 - Scale indeterminable/No scale recorded ?No
    representative fraction is given in field 255.
  • 1 - Single scale
  • 3 - Range of scales
  • Second - Type of ring

19
Coding the scale in the 034
  • a - Category of scale (NR) A one-character code
    that indicates the type of scale of the item.
  • a - Linear scale
  • b - Angular scale (used for celestial charts)
  • z - Other type of scale
  • b - Constant ratio linear horizontal scale
    (R) The denominator of the representative
    fraction for the horizontal scale.
  • c - Constant ratio linear vertical scale (R) The
    denominator of the representative fraction for
    the vertical scale of relief models and other
    three-dimensional items.
  • d - Coordinates--westernmost longitude (NR)
  • e - Coordinates--easternmost longitude (NR)
  • f - Coordinates--northernmost latitude (NR)
  • g - Coordinates--southernmost latitude
    (NR) Subfields d, e, f, and g always appear
    together.

20
034 and 255 fields
  • 255 __ aScale 125,000.
  • Or
  • 255 __ aScale 125,000.
  • Or
  • 255 __ aScale ca. 125,000.
  • 034 1_ aab25000

21
Other possible scale statements
  • Scale ca. 1500,000. Map says scale is
    approximate
  • Scale 125,344. 2½ to the mi. Map says scale
    is 2½ to the mile
  • Scale 150,000. Scale is taken from cover etc
  • Scale ca. 163,360. Measured from bar scale
  • Scale not given. Not on map and cant or wont
    figure it out!
  • Scale varies. As on birds eye views
  • Scales differ. More than 1 map being described
    in 1 record
  • Not drawn to scale. Often with manuscript maps
  • Scale indeterminable is now out of fashion.

22
A few things not to worry about
  • Longitude
  • Meridians
  • Graticules
  • 69½ miles to a degree
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