nearby.org.uk blog » mgrs

MGRS coordinate entry

Barry — Fri, 12 Dec 2008 01:26:53 +0000

Prompted by one of those infernal* posts on a Google Maps group, have finally been inspired to cobble together a MGRS -> Lat/Long conversion. It seems trvial, the UTM->MGRS conversion is quite simple, but there are a few gotchas!, so after much puzzleing over some C code from GeoTrans (and Trial&Error for good measure!), I think** have something working.

Anyway try it out here:

Coordinate Flyto for Google Earth/Maps

also added today is a tickbox to open the result direct in Google Maps (rather than Google Earth).

I’ll tidy it up and post the code, which is based on the PHPcoord conversion class, incase others have a use. I’ll also add it to the API – and possibly even back port it into Perl for use on the on site coordinate covertor.

Finally possibly of interest is the realisation that the MGRS Google Earth Gridlines layer, will actully load directly in Google Maps, so:

MGRS Gridlines in Google Maps

the lines should update a few seconds after dragging/zooming. Ideally will suppress the big blue pins (which are show as numbers in GE) , but not tonight…

* in the nicest possible sence!

** I tested it by converting utm->mgrs->utm globally on a worldwide 1 degree grid – all check out with absolute precision.

MGRS fix for < 1km gratitules

Barry — Thu, 29 Nov 2007 23:08:38 +0000

Following the update in July for hiding the 100km numbers from the gridline labels, it seems the same fix broke the sub KM lines, thanks to a comment on the original post for letting me know.

Anyway, the online hosted version has been updated (and checked at all scales as best I can!), and the same file pushed into the downloadable zip for the offline version, so can download the latest code from the file. And just for completeness the diff.

Tweaking the number of the MGRS layer

Barry — Mon, 25 Jun 2007 10:13:27 +0000

Ever since releasing the MGRS layer for Google Earth, I’ve been asked a number of times (well about 10) about tweaking the numbers on the gridlines, to be more ‘MGRS like’. To be honest havent had a clue what this means, but a recent email made me twig whats going on.

Basically the numbers included the hundreds of KM, but in fact that number is already represented in the Grid Letters so doesnt make sence to include again (it was there because the layer was an almost direct port of the UTM code, which of course needs it).

So the server hosted version has been updated, and also the file inside the zip for the offline version (which are in fact identical code!), and if really interested heres the diff.

Enjoy!