It is not uncommon for projects to use a local grid which may not be correspond exactly with the OS grid. One reason for this is that modern GPS surveying techniques reveal errors in the original OS work and adjustments made to fix alignment problems*, so for consistency, the new design may be based on new GPS surveys. However, noise spreads way beyond the immediate confines of the project and you need to use existing surveys to extend the study area. How do you make the two join up?
NoiseMap contains functions to 'Edit Object co-ordinates'. These allow you to shift (move) the selected objects in the X (east-west) and/or Y (north-south) directions by a given amount. Heights can also be shifted (increased or reduced) by a given amount. You can also rotate the axes to change the north-south direction and you can scale (stretch or shrink) the map in the east-west and north-south directions.
You will need to do some careful measurements using the co-ordinates of reference points to work out exactly what change is required. Of course, you can select and drag objects to a new position, and perform a rotation on-screen, but you cannot re-scale objects on-screen.
Beware that only selected objects will be moved, so ensure that you have selected the whole area that you need to move, otherwise the map could get into a mess. It is probably best to set up a temporary model on which to test your work before doing it for real.
Also note that no objects are permitted in the negative co-ordinate region. If you inadvertently move objects into this area, they will not be saved to the database.
(it is debatable whether it's best to move the new scheme to the main grid or the other way round - this will depend on the project)
* alignment problems are inevitable when projecting a curved earth onto a flat map
