c# - How to find nearby objects using Easting and Northing range

I have a bunch of objects which have associated Eastings and Northings in format OSGB36

for example:

265397  869562

547297  179002

If I have a starting Easting and Northing, and wanted to find related objects within X km is it possible to compute a Start/End Northing and Start/End Easting range that I can search for programatically?

I am using C#.

I.e. searching for objects using pseudo-code :

Easting >= 265390 && Easting <= 265400 &&
Northing >= 869560 && Northing <= 869564

would this find nearby objects? What resolution do these coordinates operate to? I can operate in miles or km, just need to know the scale - if such a thing is possible.

Sorry this is new to me.

Answer

See National Grid Reference Converter for help on the precision of OSGB map references.

If you just use a search range to create a box surrounding your query point, as indicated by

(east_QP - range)  <= east  <= (east_QP + range)
(north_QP - range) <= north <= (north_QP + range)

a variation on your pseudo code, it is fast but biased.

If you "create a circle" around your query point

hypot ((east_QP - east), (north_QP - north)) <= range

where hypot() computes distance, it is a tiny bit slower but less biased as it cuts out the box corners.