Transcript Scale on old maps Yale University Library Cataloging and Metadata Services Scale • What is scale? The ratio of distances on a map, globe,

Scale on old maps
Yale University Library
Cataloging and Metadata Services
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
Why is it important in the bib
record?
1. The information is critical in identifying a
map and differentiating it from other
maps with similar titles.
2. The information is of crucial importance
to the user in determining if the map will
show the level of detail they require.
3. Because cataloguing rules say it is!
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
1:63,360
1 of any unit on the map equals 63,360 of the
same unit on the ground
Types of scale statements found on
rare maps
• Representative
fraction
– 1:6,842,880
• Verbal scale
– 108 English Miles to 1
Inch
• Graphic or bar scale
• No scale information
at all
A word of warning…
Unless the scale is 1:1, 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.
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.
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 1:63,360. 1 in. to the mi.
Note: it’s ok to abbreviate in the verbal statement portion of the 255.
Converting verbal scale information to a representative
fraction
1 inch to the mile
1” (on map) =
1”
=
1”
=
1 mile (on Earth)
5280 ft/mi x 12 in/ft
63,360 in
RF 1:63,360
Graphic scales (1)
• Bar scale statement
Measuring to convert graphic or bar scale information to a
representative fraction
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 indicator’s edge
for 1° of latitude against the latitude figures
near the center of the map.
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.
There’s a formula for figuring the scale on
the map you’re cataloging in CM, or:
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 -> Cambridge = 10 inches
On the Earth, London -> Cambridge = 60 miles
10” (on the map) =
60 mi. (on the Earth)
10”
=
60 mi x 63360 in/mi
10”
=
3801600”
1”
=
380160”
RF
1:380,160
highly approximate!
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 1:24,000.
If you’ve calculated from a verbal scale,
record in brackets.
Scale [1:63,360].
If you measured against a bar or a map of
known scale, record in brackets using ca.
Scale [ca. 1:120,000].
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!
Troublesome units of measurement
on old maps
Chain
Furlong
Heures de marche
League
Lieue
Miles (that aren’t statute)
Milliaria Germanica, Hispanica, etc
Pole
Toise
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
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.
034 and 255 fields
255 __ $aScale 1:25,000.
Or
255 __ $aScale [1:25,000].
Or
255 __ $aScale [ca. 1:25,000].
034 1_ $aa$b25000
Other possible scale statements
•
•
Scale ca. 1:500,000. {Map says scale is approximate}
Scale [1:25,344]. 2½” to the mi. {Map says scale is
•
•
•
Scale [1:50,000]. {Scale is taken from cover etc}
Scale [ca. 1:63,360]. {Measured from bar scale}
Scale not given. {Not on map and can’t or won’t figure it
2½” to the mile}
out!}
•
•
•
•
Scale varies. {As on bird’s 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.
A few things not to worry about…
•
•
•
•
Longitude
Meridians
Graticules
“69½ miles to a degree”