Armored 
Medical Research Laboratory 
Port Knox, Kentucky 
Fourth Partial Report 
On 
PROJECT NO. 37 - STUDY OF ERRORS IN FIELD ARTILLERY PRACTICE 
Su&jsfitu An Analysis of the Sources of Error in the Use of the Aiming 
APMYoirele and Development of an Improved Instrument 
Project No. 37 
28 March 1945 ARMORED MEDICAL RESEARCH LABORATORY 
Fort Knox, Kentucky 
Project AMRL No. 37, NDRC SOS-11 
SFMEA 413*74-4 
28 March 1945 
FOURTH PARTIAL REPORT 
STUDY OF ERRORS IN FIELD ARTILLERY PRACTICE 
lo PROJECT: No. 37 - Study of Errors in Field Artillery Practice, Fourth 
Partial Report; Subject; An Analysis of the Sources of Error in the Use of the 
A lifting Circle and Development of an Improved Instrument* 
a0 Authority: Letter AGF, 413*68 (R) (8 Apr 1944) GNRQT-10/78261 
dated 8 April 1944* 
b0 Purpose: (1) To determine the principal causes of error in reading 
horizontal angles with the standard Ml aiming circle$ and (2) to develop basic 
improvements in principles of design which will eliminate such sources of error 
and to incorporate these in a practical field instrument. 
2C DISCUSSION: 
a® In the First Partial Report of this study (18 September 1944) fre- 
quency of errors at the battery contributed by the executive were reported to be 
as high as 20 per cent0 Presumably* these were mainly errors in reciprocal laying, 
contributed for the most part by mistakes in reading the aiming circle® Similarly, 
errors in the use of the aiming circle account for many incorrect surveys0 Further 
evidence of weakness in this instrument is seen in the results of tests at the 
Field Artillery School® Approximately sixteen (15«7) per cent of a series of angle 
measurements made with the aiming circle, Ml, by 110 student officers were in error 
by more than three (3) mils0 
b0 A proposed new design of aiming circle is presented in Appendix I, 
and the comparative results of field tests with the present MI instrument and the 
German aiming circle, which possess to some degree the proposed design features, 
are smnarised in Appendix II0 
3o CONCLUSIONS; 
a0 Analysis of present form of aiming circle* MI* employed for measuring 
angles and laying the battefy indicates that it is basically similar to the pano- 
ramic sight with respect to design of scales and possesses the same inherent weak- 
nesses from the standpoint of potential error in use0 
b0 The major deficiencies of the azimuth scale of the present instru 
ments are: 
1 (1) Use of two separated coarse and fine scales, displaced in a 
direction opposite to the order of reading the whole asimuth value0 
(2) Continuous movement of the coarse scale relative to its index 
with rotation of the micrometer, resulting in uncertainty and 
confusion concerning the true hundreds scale value when the 
micrometer reading is in the danger sons just below 100 or above 
sero. 
(3) Inadequacies of design and numbering of both coarse and micrometer 
scales, requiring frequent interpolation in unnumbered portions. 
(4) Lack of sufficient definition and clarity of engraved lines and 
numbers on the scales0 
Co Comparative tests conducted with the aiming circle, Ml and a German 
aiming circle (R0 Ka 12m beh 1025 KF), indicated clearly the advantages offered 
by an in-telescope, direct reading instrument from the standpoint of relative 
certainty of reading and easier understanding of how to use the instrument<, A 
proposed near instrument, employing this principle of operation and other improve- 
ments has been designedo 
4o RECCMMENDATIONS: 
That an in-telescope, direct reading aiming circle, of the type presented 
in Appendix be developed and sufficient pilot models be constructed for field test* 
5o ACKNOWLSDCffiMSNT: 
Thie project is a Joint undertaking with NDRC and the field teats reported 
herein were jointly conducted with the staff of NDRC, Project SOS-11, Dr0 John Pc 
Hafe, Directoro 
Submitted by: 
Theodore F0 Hatch, Lt0 Col,, SnC 
Frederick S* Brackett, Lt0 Col,, SnC 
Steven Mo Horvath, Captain, SnC 
3 Inclse 
#1 - Appendix 1 
#2 - Appendix II 
#3 - Figures 1-9 
APPROVED 
WILLARD MACHLB 
Colonel, Medical Corps 
Commanding 
2 APPENDIX I 
PROPOSED AIMING CIRCLE DESIGN 
lo With respect to design and placement of azimuth scales and likelihood 
of error in reading the scales or in setting off desired angles, the aiming 
circle, Ml (Pigo 1 ) is similar to the panoramic telescope M12 in that it has 
the same basic deficiencies0 Evidence of this is seen in the reported errors 
which occur in its use (First Partial Report, 18 September 1944) together with 
the additional experience presented herewith (Appendix II)• The instrument has 
certain other features not found in the panoramic sight which increase the like- 
lihood of error, notably, the presence of the plateau and drum scales adjacent 
to the main azimuth scales which add unnecessary confusion and the multiplicity 
of knobs for the upper and lower motions which are not readily distinguished 
from each other0 Since the aiming circle is a primary instrument, employed in 
initial laying of batteries and even in surveying, it is especially desirable 
that its operation be free from error and, at the same time, that it be capable 
of use with speed and dispatch* The battery executive has so many responsibilities 
that he should be relieved, so far as possible, of worry with respect to potential 
errors in the use of his aiming circle0 
a. Owing to the placement of rotation knobs and other basic design 
features of the present instrument, the principle of the spiral micrometer disc 
bearing on the coarse scale, recommended for the panoramic telescope (See Second 
Partial Report, 22 March 1945)# i» not readily applicable to the aiming circle 
as a means of improving scale design and reducing the likelihood of errors0 More- 
over, since the instrument is employed primarily for measuring horizontal angles 
and in view of the speed desired, the use of external scales may not give the 
most desirable arrangement. It is believed that definite advantages are gained 
from the use of internal scales which are read directly in the telescope field0 
The speed of operation is increased, but more important, the operator has a 
visual picture of the relationship between the target and the azimuth scales0 
The scale design must, of course, possess the necessary attributes for insuring 
the maximum certainty of readingo In the proposed new instrument, described 
below, a portion of the continuous azimuth scale, graduated in mils, is projected 
into the telescope field and is seen as a reticle upon which the target is super- 
imposed , as in Pig. 3* The scale is numbered every 10th mil and one reads the 
position of the target along the 10 d section much as one reads a foot-rule. In 
Figo 3, for example, the reading is 1573 do The technic of reading, it will be 
noted, is one with which practically everybody is familiar0 Experience with a 
somewhat similar instrument (Appendix II) shows that an understanding of the 
reading procedure is readily acquired with minimum training and that, compared 
with aiming circle, 1C, the frequency of errors in reading, is markedly reduced0 
b0 Description of Instrument. 
(1) Measurement of Horizontal Armies0 The proposed instrument 
represents a complete departure from the basic design of the 
Inclo #1 
1 Ml aiming circle, as shown in Fig. 2. In place of the 
accurate gear and micrometer worm for angle measurement, the 
proposed instrument makes use of a direct scale graduated at 
1 mil intervals on a glass ring (A) mounted concentrically in 
the basec A 100 |l( portion of this scale, which is numbered 
every 10 )4, is projected optically into the telescope field 
where it is seen as a section of a graduated "measuring stick" 
on which any targets in the field are superimposed. The magni- 
fication of the mil scale in projection is such that the angle 
subtended at the eye is the same as that in the telescope field. 
To measure the angle to a target it is only necessary to bring 
it into the telescope field and read its position on the grad- 
uated mil scale (Fig. 3)» Thus, it is not necessary to adjust 
the target exactly to a vertical cross-hair with consequent 
saving in the time required to complete the angle measurement. 
Furthermore, all targets appearing simultaneously in the tele- 
scope field can be measured without rotating the instrument. 
The dimensions of the mil scale graduation approximate those of 
a good reticle and therefore no unusual difficulties are pre- 
sented in the construction of the scale. Accuracy of the in- 
strument depends upon uniformity of etching of the scale and 
correct centering in the instrument. A rack mechanism (B) and 
gear and worm (C) are provided but only for the purpose of fine 
adjustment in the upper and lower motions, respectively0 
(2) Compass Setting, The compass needle (D) is viewed through a 
window (E) in the instrument housing for rough setting, but for 
accurate adjustment it is viewed through the telescope where its 
magnified image is seen in relation to the mil scale,, To orient 
the instrument on the North line, the lower slow motion is ad- 
justed until the compass needle is seen to coincide with the 
declination constant on the mil scale, as shown in Fig 4o 
(Declination constant, 6257). As an alternative, the telescope 
may be first adjusted by the upper motion to bring the vertical 
cross-hair into coincidence with the declination constant and 
the compass needle then adjusted, by lower motion, to the 
vertical line as a reference point. 
(3) Measurement of Vertical Angles. Changes in vertical line of 
sighting are accomplished by rotation of the prism (F) without 
altering the position of the telescope eyepiece0 The vertical 
range of the instrument is from -300 to + 700 A spiral- 
edge micrometer dial in conjunction with the hundreds scale 
is employed to indicate the vertical angle0 This feature, 
together with the alternate numbering of the micrometer values 
on the large diameter dial, minimizes the likelihood of 100 
errors or errors caused by the necessity for interpolation on 
sparsely numbered scales (See Second Partial Report, 22 March 
1945)o 
Inclo #1 
2 (4) Telescope. Two forms of telescopes are shown (Figs. 2 and 5), 
one centrally mounted with a vertical eyepiece and the other 
with its eyepieces set at 45°* Both forms have the advantage of 
more comfortable viewing position, as compared with the horison- 
tal arrangement in the Ml aiming circle and the vertical in- 
strument has the added advantage that the eyepiece remains in 
one position when the instrument is rotated, making it unneces- 
sary for the operator to follow the telescope around in the 
initial adjustment0 The second design has the advantages of 
less overall height and a simpler optical system„ In both 
telescopes, the magnification is 4x and an apparent field 70° 
is obtained by use of Erfle type eyepieces0 
(5) Structural Featuresd Provisions are made for rapid upper 
rotation by means of a rack and a clamp provides for throwing 
out the lower motion,, Three-point leveling of the instrument 
on its base is provided together with the necessary circular 
and two cross-leveling vials, A new feature is the combination 
tripod and carrying case. This device (Figo 6) has the neces- 
sary features of sturdiness and adjustability required of the 
tripod and, when folded back over the instrument, it forms an 
enclosure for carrying, thus eliminating the separate carrying 
case0 The combination is proposed for consideration as a con- 
venient and weight-saving measure0 
No means of illumination is shown in the design but no difficulty 
should arise in applying suitable lighting devices to the mil 
scale and to the telescope© 
Incl0 #1 
3 APPENDIX II 
FIELD TESTS 
lo A partial measure of the degree of improvement in relative certainty 
of correct reading of horizontal angles which may be expected with the proposed 
new aiming circle over the Ml was obtained in comparative tests with the German 
aiming circle, R„K. 12* beh 1025 KF© This latter instrument (Fig© 1) does not 
provide for the single scale reading which is found in the proposed design*, 
Angles arc read directly in the telescope field, however, with a reticle pro- 
vided for this purposeo The findings may therefore be considered indicative 
of the improvement which may be expected from the proposed instrument© Horizontal 
angles are measured with the German instrument in the following manner: having 
no micrometer rotation in its upper motion, it is pointed toward the target to the 
nearest even hundred mil value, greater or smaller as the case may be, where it 
is held by a positive detent© The target is then seen in the telescope field 
superimposed on a reticle, graduated to i yl and numbered frcm 40 pt( on the extreme 
left to 100 - 0 at the center of the field and extending to 60 jf. on the right© 
The reticle scale is numbered every 10 as shown in Fig. 7© The two adjacent 
100 yl values for the particular setting of the instrument are projected optically 
from the coarse scale into the telescope field and viewed in the manner shown in 
Fig© 7© Thus the total value of the angle can be read directly in the field by 
combining the proper hundreds value with the reticle reading of the target 
position© If the target is on the left of the vertical cross-hair (100 - 0) the 
left-hand hundreds value is taken and similarly for a target position to the 
right, one reads the corresponding hundreds value. Opportunity for misreading 
by 100 yl has not been eliminated but the probability of occurrence has been 
reduced, owing to the positional relationship between the target on the reticle 
and the corresponding hundreds value, which is quickly learned, Of greatest 
interest in the present study, however, was the fact that this instrument pro~ 
rides for direct reading of the angle within the telescope in a manner similar 
to that provided in the proposed new instrument0 
2C Field Tests with American* and German Aiming Circles. 
a0 Teat Procedures. Determination of the relative number of error® in a 
series of angle measurements with the two instruments was made at Fort Knox and the 
Field Artillery School, Fort Silie The tests at Fort Knox consisted in the measure- 
ment of sixteen angles varying in magnitude from less than 100 mils to over 3000 
mils© Approximately half of the angles were in the micrometer danger zone of 85 to 
10 milSo The stakes for these angles were placed along a full circle approximately 
200 yards from the aiming circles0 A new zero point was designated for each angle 
measured, thus requiring considerable mechanical manipulation of the instruments 
in the test* For these measurements a total of 17 subjects from the 414th Field 
Artillery Battalion were employed0 These men had had a moderate amount of ex- 
perience with the Ml aiming circle, and were given only limited instruction in 
the use of the German instrument0 The subjects were rotated in a random manner 
♦ Plateau scale removed 
Incl© #2 
1 in use of the two instruments0 
b„ The tests at the Field Artillery School consisted in the measurement 
of a series of twenty horizontal angles, varying in magnitude from 100 mils up to 
3100 mils and well distributed so as to avoid an undue weighting with respect to 
position on the coarse and fine scales. The two aiming circles were spaced about 
30 yards apart* A series of twenty-one stakes were located along a semi-circle 
of approximately 100 yards radius and carefully positioned by an aiming circle 
at the first point to give a predetermined series of twenty angles from the zero 
stakeo The angles from the second point did not differ markedly in value from 
this pre-selected group. Each man measured the twenty angles with each of the 
two instruments* For these measurements a total of 43 test subjects drawn from 
School Troops were employed* They included nineteen (19) officers and twenty- 
four (24) enlisted men from survey sections of the School* These men had had 
from six to thirty-six months training in survey, although about one-fourth had 
not been actively engaged in survey work for about two months* Each group of 
eight (8) or sixteen (16) men was divided into two sub-groups* At the outset 
of each test period the two sub-groups were assigned to the two aiming circles 
and remained at their assigned positions until all men had measured the twenty 
angles, after which the groups shifted* The order of reading the angles 
was suitably altered from one aiming circle to the other so as to equalize as 
much as possible all variables not under study* Only minimum instruction was given 
to the men on the method of operation of the German aiming circle* The maximum 
period for any group was eight minutes, approximately one-half minute per man. 
This time was devoted primarily to instruction in the reading of the scale, 
especially the reading of the hundred mil values in relation to the position of 
the target in the visual field of the telescope. 
ce Results of Test80 
(1) Relatively inexperienced men. The comparative results of teste 
with seventeen (17) men from the 414th Field Artillery Battalion, 
having only a moderate amount of experience with aiming circles, 
are presented in Table 1. Considering the errors from all 
sources and all magnitudes, the per cent of errors for the 
American aiming circle was approximately 40%, of which &05% 
were in the nature of mistakes in reading greater than £ 3 jf*0 
Analysis of the errors in respect to source brings out clearly 
the deficiencies in scale design (see similar breakdown for 
the panoramic telescope 1H2 in the Second Partial Report, 
22 March 1945)o The errors less than 100 ails in magnitude 
are directly traceable to the confusion arising out of the 
necessity for constant interpolation along the sparsely 
numbered micrometer scale of the Ml aiming circle together 
with the fact that only a limited portion of the scale is 
visible at a time,, Despite the lack of familiarity with the 
German aiming circle, 69o5 per cent of the angles were measured 
correctly by the test group, ten per cent more than with the 
*All errors of 4 3 and less have been arbitrarily called instrumental errors 
to distinguish them from mistakes in scale reading, in spite of the fact that 
seme of the small errors were undoubtedly true mistakes. 
Inclo #2 
2 TABLE 1 
SUMMARY OF ERRORS IN ANGLE MEASUREMENT BY AMERICAN AND GERMAN AIMING 
CIRCLES 
S0 P* ARTILLERY TROOPS - FORT KNOX 
AMERICAN A 
O Co 
GERMAN A. 
Co 
Microo Value of Angle 
80-10 
10-80 
Total 
80-10 
10-80 
Total 
Jfumber of Angles 
7 
9 
16 
8 
8 
16 
lo No0Correct Me&80 
68(57)* 
94(61) 
162(60) 
94(69) 
95(70) 
189(70) 
IIo Nooof Instr0 Errors 
39(33) 
48(31) 
87(32) 
36(27) 
31(23) 
67(24) 
11 
35 
44 
79 
25 
18 
43 
+ 2 4 
3 
4 
7 
7 
9 
16 
+ 3 i 
1 
1 
4 
4 
8 
IIIo Mistakes 
U(9) 
12(8) 
23(8<>5) 
6(4) 
10(7) 
16(6) 
Read wrong side major 
gradB 
3 
1 
4 
- 
- 
am 
Read nearest major 
grade 
2 
4 
6 
- 
- 
- 
100 ft or more 
6 
5 
11 
2 
4 
6 
TranspoOf Figures 
- 
1 
1 
2 
3 
5 
Failure to lock Instr0 
- 
- 
- 
2 
2 
4 
Record reverse Angle 
- 
1 
1 
- 
- 
- 
Unexplained 
- 
- 
- 
- 
1 
1 
Total Readings 
118 
154 
272 
136 
136 
272 
1 
* Percentage values in ( ) 
Xnclo #2 
3 American instrument, with which they were familiar0 The 
number of mistakes was also smaller and these arose from 
entirely different causes than did the incorrect readings 
with the American aiming circle0 Four of the mistakes were 
from mechanical causes0 Two of the three transposition 
errors resulted from failure to include the zero in a state- 
ment of size of anglej viz,, calling out 13 instead of 103© 
The six 100 mil errors (four were made by a single individual) 
are chargeable to lack of inderstanding of the principle of 
the German instrument, the larger of the two figures seen in 
the lower field being read regardless of the position of the 
target on the reticle* This indicates a basic defect of the 
system which allows a choice of values, a weakness which has 
been avoided in the proposed new instrument^ 
(2) The greater number of errors 100 mils or more in magnitude 
observed with the Ml (11 against 6) arose from the well-known 
cause, namely the displaced coarse and fine scales and un- 
certainty of relation between the two0 Six of these errors 
occurred in the reading of seven angles having micrometer values 
from 80 - 100 and 0 - 10 and the other 5 in the reading 
of the remaining 9 angles. Another point of considerable interest 
is the failure of any of the subjects to make errors greater 
than 100 yi with the German instrument whereas three subjects 
made such errors (up to 800 mils) with the Ml, 
(3) Experienced Men. Nineteen (19) officers and twenty-four (24) 
enlisted men from School Troops at Fort Sill, who had had 
considerable experience in survey and in use of the American 
aiming circle, took part in the next group of tests0 The time 
to read and report the twenty angles was measured. Despite their 
unfamiliarity with the German aiming circle, the average time 
required for the twenty angles was a half minute less than for 
the corresponding angles measured with the American instrument 
—6 minutes, compared with 6j minutes0 
(a) The greater certainty of reading angles correctly when the 
value is obtained directly from a scale in the telescope 
Itself is strikingly demonstrated by the results of this 
test. Over 78 per cent of angles were measured correctly 
with the German instrument in contrast to only 40 per cent, 
in the case of the Ml aiming circle0 Furthermore, only 
two mistakes, both questionable in nature, were recorded 
with the German aiming circle as compared with 63 mistakes 
in the use of the American instrument0 One of the two was 
of a type which can never be entirely eliminated; The 
correct angle of 1819 was reported as 1919, despite the 
fact that the figure 19 did not appear in the visual field, 
the double set of figures being (17ol8)o The other, 30 
in magnitude, resulted from failure to seat the instrument 
properly in detent, and did not involve an error in scale 
reading* 
4 
Indo #2 TABLE 2 
SUMMARY OP ERRORS IN ANGIE MEASUREMENTS BY AMERICAN AND GERMAN AIMING CIRCLES 
P. A» SCHOOL TROOPS - PORT SILL 
AMERICAN A 
. Co 
GERMAN A 0 C0 
Micros Value of Angle 
80-10 
10-80 
Total 
80-10 
10-80 
Total 
Number of Angles 
7 
13 
20 
7 
13 
20 
lpNOpOf Correct Ueas<, 
103(37)* 
232(40) 
335(39) 
I 217(78) 
456(76) 
673(78) 
Instr.Errors 
150(54) 
312(53) 
462(54) 
60(22) 
125(22) 
185(22) 
4 x i 
97 
206 
303 
48 
104 
152 
i 2 i 
41 
75 
116 
10 
21 
31 
4 3 
12 
31 
43 
2 
- 
2 
III. Mistake* 
24(8.7) 
39(6.7) 
63(7.3) 
- 
2(0.5) 
2(0.25) 
• f 4 d 
1 
1 
2 
- 
- 
- 
4 5 i 
14 
26 
40 
- 
- 
4 10 i 
2 
3 
5 
- 
- 
- 
4 20 i 
2 
1 
3 
- 
flk 
- 
4 33 fi 
- 
1 
i 
_ 
- 
- 
4 35 ft 
- 
1 
1 
! ~ 
1 
1 
4 ioo 4 
3 
2 
5 
mm 
1 
1 
4 200 
2 
4 
6 
mm 
' 
- 
Total readings 
277 
583 
660 
277 
583 
860 
* Percentage Y&luee in ( ) 
Inol #2 
5 (b) Mot only did the men read a greater proportion of the 
angles correctly with the unfamiliar German instrument 
but more than 94 per cent of the angles were read to 
£ 1 mil of the correct angle in contrast to less than 
three-quarters of the measurements of equal accuracy made 
with the American instrument*, In this group, as with the 
inexperienced group, no errors in excess of 100 mils were 
made with the German aiming circle, whereas six (6) were 
made with the Mlo 
(c) The comparative results of these tests ars so striking as 
to leavs little doubt of the improved perfbraance, from the 
standpoint of frequency of errors, to be expected from the 
proposed instrument* Moreover, the experience shows clear- 
ly that little difficulty may be expected in training men 
in the correct use of the instrument. 
3o Other Features of German Aiming Circlt 
&o The German aiming circle possesses certain other features of design 
which indicate that in the development of the instrument, the required functional 
characteristics hare been studied and an attempt made to provide for them more 
successfully than in past designs* This is of particular interest in view of 
the fact that the instrument which it replaced was very similar to the present 
Uo Se standard Ml* Of interest, from the standpoint of reduction of errors, is 
its special provision for reciprocal laying of the battery* A secondary project- 
ing system is provided parallel to and below the sighting telescope (Pig* 1) 
which includes a reticle carrying the vertically repeating and evenly spaced 
markings shown in Pig* 60 The reticle of the German panoramic sight Rbl P 32 
has a single line of corresponding symbols (Pig* 9)o When the aiming circle 
telescope is directed toward the gun sight to the nearest 100 jrf and the gun 
sight similarly directed toward the aiming circle, one of the symbols or a line 
and portions of the two adjacent symbols on the aiming circle reticle can be 
seen through the panoramic sight0 The particular symbol which is seen depends 
upon the angle of offset between the line of sighting of the aiming circle 
telescope and the true line fras the panoramic sight to the aiming circle* The 
procedure in reciprocal laying is simplified as compared with that required with 
the American instrument„ Thus, the executive rotates his instrument from the 
0-32CX) line toward the gun sight and fixes it at the nearest hundreds value* 
He calls off to the gunner only the right-hand whole hundreds value as read in 
the telescope* The gunner sets this hundreds value on his panoramic sight and 
then traverses the gun until the corresponding symbol on his reticle is super- 
imposed on the symbol seen in the projecting telescope of the aiming circle* 
The spacing of symbols (Pig0 B) is equal to 2 and from any symbol to ths 
adjacent line is 1 Thus, if the true deflection of the gun sight from the 
0-3200 line of the aiming circle is 1676, for example, the panoramic sight 
would be set at 1900 and the gun traversed until the symbol & is superimposed 
on the corresponding symbol projected from the aiming circle0 For deflection 
0637# the reticle pattern to be matched would be: i 
4 j>(4 * 36 *(;> =3® I( ) 
with the panoramic sight set at 0600* In both cases the gun would then be 
parallel to the 0-3200 line of the latter instrument0 Certain advantages are 
Inclo #2 
6 immediately suggested by this procedurej first, the command from the executive 
to the gunner is simplified since the deflection is given as a whole hundreds 
value only, thereby reducing the probability of errors in communication and 
execution of command; secondly, no secondary error arises from sight displace- 
ment when the gun is traversed to bring the panoramic sight into line with the 
aiming circle* This latter error, although generally small (1 to 3 *() is a 
common source of annoyance with the Uo S0 aiming circle and is eliminated only 
by checking and relaying0 There are certain obvious disadvantages, foremost 
of which is that the instrument must remain pointed toward a particular gun 
until the gunner has completed his laying, whereas with the American aiming 
circle the executive can pass to the second gun while No0 1 is laying, etc0, 
returning to Mo0 1 for re-check after measuring the angle to No* Another 
is that there is no check on correctness of the laying of a particular piece 
as there is with the American technic which involves an exchange of instrument 
readings, although there is nothing to prevent such check readings being made© 
b0 The facilities for reading angle of site in the German instrument 
are not improved over earlier designs with respect to certainty of scale reading <> 
It will be noted, on the contrary, in the proposed new aiming circle the spiral 
disc principle has been employed on the angle of site scales to minimise errors 
of readingo 
*It is of interest, however, that in some limited tests, it was found that the 
speed of laying the battery with the German instrument was 
the greater despite thls0 
DmIo #2 
7 AIMING CIRCLES 
AMERICAN MI (LEFT) AND GERMAN (RIGHT) 
ARMORED MEDICAL RESEARCH LABORATORY 
FORT KNOX, KY. 
Project No. 37 
Figure 1 FIG. 2 TELESCOPE FIELD W H HHUJLUILU 
SHOWING INDICATION OF TARGET ON SCA_E 
(APPROXIMATE PROPORTIONS) 
READING - 1573 rh 
FIG. 3 ' 
IndU #3 TELESCOPE HELD mm rPOJcxrrcv rn— SCALE 
AND PROJECTED COMPASS NEEDLE 
DEFLECTION CONSTANT — 6257// 
FIG.4 
Inclo #3 MG. b FIG. 6 TELESCOPE—FIELD "OT—(it H MAM AIMING CIRCLE 
SHOWING ADJACENT HUNDREDS VALUES AND 
RETICLE SCALE AND 
ILLUSTRATING TARGET READING 
FIG.7 reticle Kirai i» mojKcrruo mxacon 
or omuN inaw circle 
ARMORED MEDICAL RESEARCH LABORATO^ 
POST KNOX, KY. 
?lfwr« 0 
Project Ho. 37 wlo #3 
RETICLE PATTERN OF GERMAN PANORAMIC TELESCOPE ( Rbl F 32) 
NOTE THAT ON THIS HALF OF THE RETICLE 
THE 6,S,8 AND Z HAVE A BAR THROUGH 
THE LARGEST OPEN SECTION 
ENLARGEMENT OF FIGURES IN RETICLE 
®OMie2Z3D4V5F667i8AC HTUNG 
FIG. 9 
NOTE THAT ON PROJECTION FIELD ON THE AIMING CIRCLE 
THE SAME PATTERN IS PRESENT 
THE CENTER IS DISTINGUISHED BY-^-AND-AND I LINES 
FIG. 9