aerial photography slide rule
Date: circa 1951
Inventory Number: 2004-1-0341
Classification: Slide Rule
Subject:
Maker: Pickett & Eckel, Inc. (1943-1985)
Maker: United States Air Force (1947-present)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
0.8 × 15.5 × 3.6 cm (5/16 × 6 1/8 × 1 7/16 in.)
case: 1.3 × 16 × 4.8 cm (1/2 × 6 5/16 × 1 7/8 in.)
Accessories: brown leather case with table of equivalents
DescriptionAluminum slide rule with three slides, faced with white enamel (?). The top and bottom slides are bolted to aluminum end pieces on both sides of both ends. The center slide moves to left and right. A clear plastic runner, with a vertical indicating line and and aluminum frame, moves to left and right on both sides of the rule.
Eleven scales are printed on the face of the rule. Near the top edge of the top, fixed slide are two scales sharing a baseline, "L" (top) and "A" (bottom). "L" has values ranging from 0 to 1; "A" is composed of two logarithmic scales (values 1 to 10) placed side by side.
Printed along the bottom edge of the top slide is a logarithmic scale "DF", which has values ascending from [pi] to 10, then from 1 to [pi]. An identical scale "CF" is printed along the top edge of the center, moveable slide. Below this is an inverted logarithmic scale "CIF", with values descending from 3.15 to 1, then from 10 to 3.15. Directly to the left of each value on the "CIF" scale is a sideways chevron.
Third and fourth from the top of the center slide are two scales sharing a baseline, "T" and "S", respectively. Both scales have two sets of values: the first set is marked with a sideways chevron pointing left; the second set is marked with a sideways chevron pointing right. The first set of values on the "T" scale descends from 84.3 to 45; the second set ascends from 5.7 to 45. The first set of values on the "S" scale descends from 84.3 to 0; the second set ascends from 5.7 to 90.
A logarithmic scale "C", with values ranging from 1 to 10, is printed along the bottom edge of the center, moveable slide. An identical scale "D" is printed along the top edge of the bottom, fixed slide. Below the "D" scale is an inverted logarithmic scale "DI", with values descending from 10 to 1. Directly to the left of each value on this scale is a sideways chevron.
Printed near the bottom edge of the bottom slide is a scale "K" composed of three logarithmic scales (values 1 to 10) placed side by side.
Five scales are printed on the back of the rule. Along the bottom edge of the top, fixed slide is a scale for "GROUND SPEED (FEET)", with values descending from 10000 to 1. The values from 1000 to 100 are also labeled for "GROUND SPEED (M.P.H. OR KNOTS)". Printed above the mark for 3.6 is an arrow pointing down, labeled, "60% O.L. on 9'' ".
The top two scales on the center, moveable slide, are for "IMAGE SIZE". The top scale, for "CM.", has values descending from 100 to .03. The bottom scale, for "FT.", has values descending from 4 to .001. The mark for 1 on the "CM." scale is also labeled "CYCLING TIME".
Printed along the bottom edge of the center slide is a scale for "FOCAL LENGTH (INCHES)", with values descending from 240 to 1. Superimposed on the marks for 18, 9, 8, and 7, are small arrows pointing down. These are labeled "18'' COV.", "9'' COV.", "KNOTS", and "M.P.H.", respectively. Above the mark for 12 is an arrow pointing down, labeled, "SCALE". Above the mark for 1 is an arrow beginning at the top of the slide and pointing down, labeled, "FT. PER IN."
Along the top edge of the bottom slide is a scale for "ALTITUDE (FEET)", with values descending from 250000 to 100.
Instructions for using the gauge points on the back of the rule are printed on the backs of all three slides. The slide rule is stored in a brown leather case. A table of unit equivalents is visible through a clear panel on the back of the case.
The slide rule is corroded. The center slide is stuck in place.
Eleven scales are printed on the face of the rule. Near the top edge of the top, fixed slide are two scales sharing a baseline, "L" (top) and "A" (bottom). "L" has values ranging from 0 to 1; "A" is composed of two logarithmic scales (values 1 to 10) placed side by side.
Printed along the bottom edge of the top slide is a logarithmic scale "DF", which has values ascending from [pi] to 10, then from 1 to [pi]. An identical scale "CF" is printed along the top edge of the center, moveable slide. Below this is an inverted logarithmic scale "CIF", with values descending from 3.15 to 1, then from 10 to 3.15. Directly to the left of each value on the "CIF" scale is a sideways chevron.
Third and fourth from the top of the center slide are two scales sharing a baseline, "T" and "S", respectively. Both scales have two sets of values: the first set is marked with a sideways chevron pointing left; the second set is marked with a sideways chevron pointing right. The first set of values on the "T" scale descends from 84.3 to 45; the second set ascends from 5.7 to 45. The first set of values on the "S" scale descends from 84.3 to 0; the second set ascends from 5.7 to 90.
A logarithmic scale "C", with values ranging from 1 to 10, is printed along the bottom edge of the center, moveable slide. An identical scale "D" is printed along the top edge of the bottom, fixed slide. Below the "D" scale is an inverted logarithmic scale "DI", with values descending from 10 to 1. Directly to the left of each value on this scale is a sideways chevron.
Printed near the bottom edge of the bottom slide is a scale "K" composed of three logarithmic scales (values 1 to 10) placed side by side.
Five scales are printed on the back of the rule. Along the bottom edge of the top, fixed slide is a scale for "GROUND SPEED (FEET)", with values descending from 10000 to 1. The values from 1000 to 100 are also labeled for "GROUND SPEED (M.P.H. OR KNOTS)". Printed above the mark for 3.6 is an arrow pointing down, labeled, "60% O.L. on 9'' ".
The top two scales on the center, moveable slide, are for "IMAGE SIZE". The top scale, for "CM.", has values descending from 100 to .03. The bottom scale, for "FT.", has values descending from 4 to .001. The mark for 1 on the "CM." scale is also labeled "CYCLING TIME".
Printed along the bottom edge of the center slide is a scale for "FOCAL LENGTH (INCHES)", with values descending from 240 to 1. Superimposed on the marks for 18, 9, 8, and 7, are small arrows pointing down. These are labeled "18'' COV.", "9'' COV.", "KNOTS", and "M.P.H.", respectively. Above the mark for 12 is an arrow pointing down, labeled, "SCALE". Above the mark for 1 is an arrow beginning at the top of the slide and pointing down, labeled, "FT. PER IN."
Along the top edge of the bottom slide is a scale for "ALTITUDE (FEET)", with values descending from 250000 to 100.
Instructions for using the gauge points on the back of the rule are printed on the backs of all three slides. The slide rule is stored in a brown leather case. A table of unit equivalents is visible through a clear panel on the back of the case.
The slide rule is corroded. The center slide is stuck in place.
Signedface, center slide, right center: 59 / [Pickett trademark] ;
back, center slide, center right: U.S. AIR FORCE / AERIAL PHOTO / SLIDE SLIDE RULE / TYPE A-2 ;
front of case, top center: U.S. AIR FORCE / AERIAL PHOTO / SLIDE RULE / TYPE A-2
back, center slide, center right: U.S. AIR FORCE / AERIAL PHOTO / SLIDE SLIDE RULE / TYPE A-2 ;
front of case, top center: U.S. AIR FORCE / AERIAL PHOTO / SLIDE RULE / TYPE A-2
Inscribedface, center slide, center left: MODEL / 7[obscured]
FunctionFor use in interpreting aerial photographs. This slide rule was designed and used by the United States Air Force.
For details on using the slide rule, see the manual (primary sources).
For details on using the slide rule, see the manual (primary sources).
Primary SourcesUSAF Air Materiel Command, How to Use the U.S. Air Force Aerial Photo Slide Rule. Chicago: Pickett & Eckel, Inc., 1951. Available for download here.
ProvenancePrivate Donor, Troy, New York.