Re: OS 50k versus 25k accuracy?
The message <313030303131343449F8AF1A69@xxxxxxxxxxxxxxxxxxx>
from Roger <roger@xxxxxxxxxxxxxxxxxxx> contains these words:
The interesting thing about Terry Pinnel's example was that the
same GPS track appeared to be systematically shifted NE on one map with
respect to the other.
You sure about that? ISTM that the track is in the same place relative
to the grid lines but the various features on the map are not.
I am now all but convinced that the difference is down entirely to
sloppy map making. The centre of the footbridge over the reservoir is,
near as damn-it, at TQ332308 (that's a point, not a bloody square) on
the 1:25,000 but that grid reference is some 44 metres away from the
bridge on the 1:50,000 and almost on the East shore of the reservoir.
Given that the track agrees the 1:50,000 it would seem that the 15,000
is at fault.
Graham will no doubt be along shortly to correct me if I am wrong but
ISTR that he said that traditionally different scale maps were all drawn
up independently from basic data. No marks then for the Herbert who did
this 1:25,000 then. :-)
--
Roger Chapman
Nearest Marilyn still to be visited - Great Orme.
89 miles as the crow flies,
considerably more as the walker drives.
.
Relevant Pages
- Re: 2D Tile Game - Keeping location data between Map & Things synced up (longish)
... OK, as you noted, that strongly argues for some notion of 'tile' that has terrain and Things associated with it. ... That's fine because Thing.moveis just executing the mechanics of shifting position from one grid position to another grid position. ... If the move involves more than simply changing grid locations, the moveresponsibility may need to be broken up into more atomic activities and some of those may be more logically abstracted in a different object that collaborates with Thing to actually do the move. ... That argues for subdividing Map into distinct Tiles again because that captures the important notions better about how distinct different locations are. ...
(comp.object) - Re: Garmin Geko - Accuracy of conversion to Bristish National Grid
... > drawn on the map, ... not give accurate Grid References not because the GPS can not determine its true ... the significance of your use of OziExplorer to calcuate the a Grid Reference ...
(sci.geo.satellite-nav) - Re: World map embedded in userform.
... Those are simply edited "workings" to show how to convert grid coordinates ... Peter T ... Hereby the requested co-ordinates might be different than the last, ... coordinates are put into a sheet, a marker of some kind shows on the map ...
(microsoft.public.excel.programming) - Re: World map embedded in userform.
... Those are simply edited "workings" to show how to convert grid coordinates ... Peter T ... Hereby the requested co-ordinates might be different than the last, ... coordinates are put into a sheet, a marker of some kind shows on the map ...
(microsoft.public.excel.programming) - Re: Expanation of datum/grid terms requested
... > grid and datum in my Magellan MeriPlat: ... Whilst WGS84 is a good average fit to the whole world it doesn't ... and is the only line where there is no distortion of the projected map. ... where this point is relative to the actually origin of the map projection. ...
(sci.geo.satellite-nav) |
|
