National Grid References

Blaeu's Hampshire 1645
NGRs Simple mathematics was used to crudely superimpose the national grid on Blaeu's map. The difference between the map projections used by the NGR system and used John Blaeu has been ignored. 'Centres' of the the old and the Ordnance Survey maps of the county were superimposed at an average position of twenty or so prominent towns; the orientations and scales were matched by averaging the directions and distances of these places from the centres on each map; it is then possible to draw the NGR from the modern map upon the image of the old. The calculations were done by a computer using a program written by MN, OLDMAPS.exe; fuller notes about the process are provided in the software notes, OLDMAPS.rul.

File BLA1PTS.txt has readings of positions of recognisable places on the old map, using (x,y) coordinates on the old map.

Points
file 


@t Blaeu 1645

@pl Alton @ngr SU717396 @xy (39.56,35.11)
@pl Andover @ngr SU365458 @xy (20.42,34.26)
@pl Basingstoke @ngr SU634527 @xy (34.71,40.54)
@pl Burghclere @ngr SU469610 @xy (24.96,42.70)
@pl Buriton @ngr SU740200 @xy (40.49,23.84)
@pl Christchurch @ngr SZ159925 @xy (12.03,3.77)
@pl Fareham @ngr SU575061 @xy (34.07,15.38)
@pl Fordingbridge @ngr SU150145 @xy (11.93,15.92)
@pl Grately @ngr SU275420 @xy (14.24,30.72)
@pl Havant @ngr SU717062 @xy (41.02,15.15)
@pl Kingsclere @ngr SU525586 @xy (28.26,42.96)
@pl Lymington @ngr SZ322954 @xy (20.81,7.62)
@pl Nether Wallop @ngr SU304364 @xy (15.77,28.53)
@pl Odiham @ngr SU740509 @xy (39.61,40.66)
@pl Overton @ngr SU514500 @xy (27.62,38.43)
@pl Petersfield @ngr SU744235 @xy (40.92,26.18)
@pl Romsey @ngr SU351212 @xy (21.66,21.40)
@pl Stockbridge @ngr SU355351 @xy (20.39,28.42)
@pl Tangley @ngr SU334524 @xy (18.10,38.07)
@pl Whitchurch @ngr SU460478 @xy (25.13,37.82)
@pl Winchester @ngr SU478293 @xy (26.38,26.23)

@w 60.56 @h 50.40

@sc 4.39 @m 4


The results from OLDMAPS.exe are given in file: BLA1NGR.txt:-

Map Blaeu1
  Data file: BLA1PTS.txt
Output file: BLA1NGR.txt


OLDMAPS

Plotting a NGR grid on an old map
version 7.2
MN: 11.10.2001


Given points

 no  place                    ngr         (x,y)

  1  Alton                    SU717396    (   39.56,   35.11)
  2  Andover                  SU365458    (   20.42,   34.26)
  3  Basingstoke              SU634527    (   34.71,   40.54)
  4  Burghclere               SU469610    (   24.96,   42.70)
  5  Buriton                  SU740200    (   40.49,   23.84)
  6  Christchurch             SZ159925    (   12.03,    3.77)
  7  Fareham                  SU575061    (   34.07,   15.38)
  8  Fordingbridge            SU150145    (   11.93,   15.92)
  9  Grately                  SU275420    (   14.24,   30.72)
 10  Havant                   SU717062    (   41.02,   15.15)
 11  Kingsclere               SU525586    (   28.26,   42.96)
 12  Lymington                SZ322954    (   20.81,    7.62)
 13  Nether Wallop            SU304364    (   15.77,   28.53)
 14  Odiham                   SU740509    (   39.61,   40.66)
 15  Overton                  SU514500    (   27.62,   38.43)
 16  Petersfield              SU744235    (   40.92,   26.18)
 17  Romsey                   SU351212    (   21.66,   21.40)
 18  Stockbridge              SU355351    (   20.39,   28.42)
 19  Tangley                  SU334524    (   18.10,   38.07)
 20  Whitchurch               SU460478    (   25.13,   37.82)
 21  Winchester               SU478293    (   26.38,   26.23)
number of points = 21


Centroids of points


(x,y) centroid is  (   26.58,   28.27)
  NGR centroid is  SU472324
    numerical ngr  447.28 132.43


Map scale

scale =     1.73 (Alton)
scale =     2.00 (Andover)
scale =     1.76 (Basingstoke)
scale =     1.97 (Burghclere)
scale =     2.02 (Buriton)
scale =     1.78 (Christchurch)
scale =     1.89 (Fareham)
scale =     1.93 (Fordingbridge)
scale =     1.75 (Grately)
scale =     1.84 (Havant)
scale =     1.81 (Kingsclere)
scale =     1.86 (Lymington)
scale =     1.81 (Odiham)
scale =     1.77 (Overton)
scale =     1.97 (Petersfield)
scale =     1.96 (Romsey)
scale =     1.88 (Tangley)
scale =     1.60 (Whitchurch)

map scale  1 to   185087
  (range   159724 to   201818)

or         1 to   185000



Map heading

Map heading
NGR north on map is -7.8 degrees from map north



Check points

 no  place                    true        map
                              ngr         ngr

  1  Alton                    SU717396    SU728416  error 2.28
  2  Andover                  SU365458    SU375449  error 1.35
  3  Basingstoke              SU634527    SU652528  error 1.80
  4  Burghclere               SU469610    SU479592  error 2.06
  5  Buriton                  SU740200    SU716207  error 2.50
  6  Christchurch             SZ159925    SZ144911  error 2.05
  7  Fareham                  SU575061    SU577068  error 0.73
  8  Fordingbridge            SU150145    SU173134  error 2.55
  9  Grately                  SU275420    SU252400  error 3.05
 10  Havant                   SU717062    SU704047  error 1.98
 11  Kingsclere               SU525586    SU540589  error 1.53
 12  Lymington                SZ322954    SZ314960  error 1.00
 13  Nether Wallop            SU304364    SU275356  error 3.01
 14  Odiham                   SU740509    SU743518  error 0.95
 15  Overton                  SU514500    SU517507  error 0.76
 16  Petersfield              SU744235    SU730249  error 1.98
 17  Romsey                   SU351212    SU365210  error 1.41
 18  Stockbridge              SU355351    SU359342  error 0.98
 19  Tangley                  SU334524    SU342525  error 0.81
 20  Whitchurch               SU460478    SU470503  error 2.69
 21  Winchester               SU478293    SU464287  error 1.52


Map sheet corners

 bottom left SY914872
    top left SU041797
   top right TQ151644
bottom right TV024720



Grid lines

x positions on bottom and top edges,
y positions on left and right edges,
by which to draw lines on map

easting grid lines

Eing      bottom edge    top edge

 400          4.68          -2.25
 410         10.13           3.20
 420         15.59           8.66
 430         21.04          14.11
 440         26.50          19.56
 450         31.95          25.02
 460         37.40          30.47
 470         42.86          35.92
 480         48.31          41.38
 490         53.76          46.83
 500         59.22          52.29
 510         64.67          57.74
 520         70.13          63.19

northing grid lines

Ning      left edge      right edge
  80         -3.98           4.35
  90          1.48           9.81
 100          6.93          15.26
 110         12.38          20.71
 120         17.84          26.17
 130         23.29          31.62
 140         28.75          37.08
 150         34.20          42.53
 160         39.65          47.98
 170         45.11          53.44
 180         50.56          58.89



Grid baselines

10Km square corner with
north-south and west-east grid line points,
by which to draw lines on map

  NGR base point  SU472324
  x,y base point  (   22.86,   26.44)

        mark x,y  (   22.12,   31.79)
        mark x,y  (   21.39,   37.14)
        mark x,y  (   20.65,   42.49)
        mark x,y  (   19.91,   47.85)
        mark x,y  (   19.18,   53.20)

        mark x,y  (   23.60,   21.08)
        mark x,y  (   24.33,   15.73)
        mark x,y  (   25.07,   10.38)
        mark x,y  (   25.80,    5.03)
        mark x,y  (   26.54,   -0.33)

        mark x,y  (   28.21,   27.17)
        mark x,y  (   33.56,   27.91)
        mark x,y  (   38.92,   28.64)
        mark x,y  (   44.27,   29.38)
        mark x,y  (   49.62,   30.12)
        mark x,y  (   54.97,   30.85)
        mark x,y  (   60.33,   31.59)
        mark x,y  (   65.68,   32.33)

        mark x,y  (   17.51,   25.70)
        mark x,y  (   12.15,   24.96)
        mark x,y  (    6.80,   24.23)
        mark x,y  (    1.45,   23.49)
        mark x,y  (   -3.90,   22.76)



Scale line

scale line length     4.39 cm
representing    4 miles
scale 1 to   146637


Blaeu's Hampshire 1645, index grid
General index
Old Hampshire Mapped
Map HMCMS:FA1998.149