National Grid References

Jansson's Hampshire 1646
NGRs Simple mathematics was used to crudely superimpose the national grid on Jansson's map. The difference between the map projections used by the NGR system and used by Johannes Jansson 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 JAN1PTS.txt has readings of positions of recognisable places on the old map, using (x,y) coordinates on the old map.

Points
file 

@t Jansson 1646
@pl Alton @ngr SU717396 @xy (38.10,30.12)
@pl Andover @ngr SU365458 @xy (21.70,30.40)
@pl Basingstoke @ngr SU634527 @xy (34.06,35.56)
@pl Burghclere @ngr SU469610 @xy (25.70,37.38)
@pl Buriton @ngr SU740200 @xy (39.12,21.36)
@pl Christchurch @ngr SZ159925 @xy (13.66,3.66)
@pl Fareham @ngr SU575061 @xy (33.42,13.80)
@pl Fordingbridge @ngr SU150145 @xy (13.80,14.32)
@pl Grately @ngr SU275420 @xy (15.84,27.36)
@pl Havant @ngr SU717062 @xy (39.42,13.62)
@pl Kingsclere @ngr SU525586 @xy (28.74,37.68)
@pl Lymington @ngr SZ322954 @xy (21.60,6.98)
@pl Nether Wallop @ngr SU304364 @xy (17.42,25.44)
@pl Odiham @ngr SU740509 @xy (38.54,35.62)
@pl Overton @ngr SU514500 @xy (28.00,33.94)
@pl Petersfield @ngr SU744235 @xy (39.46,23.24)
@pl Ringwood @ngr SU149054 @xy (14.04,9.52)
@pl Romsey @ngr SU351212 @xy (22.48,19.22)
@pl Stockbridge @ngr SU355351 @xy (21.56,25.32)
@pl Tangley @ngr SU334524 @xy (19.64,33.52)
@pl Whitchurch @ngr SU460478 @xy (25.86,33.38)
@pl Winchester @ngr SU478293 @xy (26.74,23.34)
@w 52.40 @h 66.08
@sc 5.62 @m 6

The results from OLDMAPS.exe are given in file: JAN1NGR.txt. The file was designed for use by JandMN and is not terrifically friendly, sorry! The essential data is given here; some data is for information rather than use. 

Centroids of points

The centroids of the towns in (x,y) space and in ngr space 
are reported:-

(x,y) centroid is (26.31,24.31)
NGR centroid is SU458312; numerical ngr 445.80,131.20

Map scale

The map's scale is calculated by comparing the distances of the 
towns from the centroids.
 
scale = 2.07 (Alton)
scale = 2.27 (Andover)
scale = 2.03 (Basingstoke)
scale = 2.31 (Buriton)
scale = 2.02 (Christchurch)
scale = 2.18 (Fareham)
scale = 2.19 (Fordingbridge)
scale = 1.95 (Grately)
scale = 2.13 (Havant)
scale = 2.08 (Kingsclere)
scale = 2.13 (Lymington)
scale = 1.81 (Nether Wallop)
scale = 2.07 (Odiham)
scale = 2.01 (Overton)
scale = 2.25 (Petersfield)
scale = 2.09 (Ringwood)
scale = 2.30 (Romsey)
scale = 2.27 (Stockbridge)
scale = 2.16 (Tangley)
and averaged, and rounded off so as not to mislead the user with 
false accuracy:-

map scale 1 to 212133 (range 181348 to 230863)
about 1 to 212000

Map heading

The map's heading is calculated by comparing the headings of the towns from the centroids, and averaging:-

NGR north on map is -7.8 degrees from map north

Check points

The position of the ngr grid on the old map is now 'known' by 
the software. The location of the towns on the map and in ngr space 
can be compared, and an error calculated, in Km.

place               true ngr  map ngr   error

Alton               SU717396  SU722400  0.64
Andover             SU365458  SU378453  1.39
Basingstoke         SU634527  SU653526  1.90
Burghclere          SU469610  SU482588  2.56
Buriton             SU740200  SU718213  2.56
Christchurch        SZ159925  SZ132914  2.92
Fareham             SU575061  SU577070  0.92
Fordingbridge       SU150145  SU166137  1.79
Grately             SU275420  SU246406  3.22
Havant              SU717062  SU702049  1.98
Kingsclere          SU525586  SU547586  2.20
Lymington           SZ322954  SZ309961  1.48
Nether Wallop       SU304364  SU274361  3.01
Odiham              SU740509  SU747514  0.86
Overton             SU514500  SU521509  1.14
Petersfield         SU744235  SU731251  2.06
Ringwood            SU149054  SU157036  1.97
Romsey              SU351212  SU362216  1.17
Stockbridge         SU355351  SU361346  0.78
Tangley             SU334524  SU344524  1.00
Whitchurch          SU460478  SU474503  2.87
Winchester          SU478293  SU464290  1.43
average                                 1.81
 
Map sheet corners

The grid references of the maps corners is given (the corners from 
which measurements were made):-

bottom left SY835876
top left SP024265
top right TL125115
bottom right SZ936726

This could be useful as an indexing tool. The map's coverage could 
be drawn in a GIS system. We have not done this for a set of county 
maps which too fairly closely.

Grid lines
The software provides marker points by which to drawn ngr grid lines 
on the original map (on an overlay! or on the scanned map image). 
These are: x positions on bottom and top edges, y positions on left 
and right edges.

easting grid lines

Eing      bottom edge    top edge

390        3.07          -5.92
400        7.83          -1.17
410       12.59           3.59
420       17.35           8.35
430       22.10          13.11
440       26.86          17.86
450       31.62          22.62
460       36.38          27.38
470       41.13          32.14
480       45.89          36.89
490       50.65          41.65
500       55.41          46.41
510       60.16          51.17
520       64.92          55.92

northing grid lines

Ning      left edge      right edge

80        -3.63           3.50
90         1.12           8.26
100        5.88          13.02
110       10.64          17.77
120       15.40          22.53
130       20.15          27.29
140       24.91          32.05
150       29.67          36.80
160       34.43          41.56
170       39.18          46.32
180       43.94          51.08
190       48.70          55.83
200       53.46          60.59
210       58.21          65.35
220       62.97          70.11
230       67.73          74.86
 
Scale line

The scale line on the map is used to calculate what it says the 
map's scale is:-

scale line length 5.62 cm
representing 6 miles
scale 1 to 171816


Jansson's Hampshire 1646, index grid
General index
Old Hampshire Mapped
Map HMCMS:ACM1934.14