# How to find bounding coordinates (lat/long) for UTM zones?

I want to error check incoming lat/lng points by checking if the point resides within the given UTM zone. (This would work for the data im using because sometimes there is a missing sign or lat/lng is reversed and the UTM zone can still be correct)

So given a UTM zone, how would you find the bounding coordinates for that zone?(Either the lat/lng for SW and NE corners or a range of lat/lng values for a given zone)

Also: Since I am supplied with both UTM and lat/lng I can convert both and cross compare as a way to validate incoming points but I thought it would be interesting to know how to calculate a UTM zone's bounding box in lat/lng form just given a zone (and possibly a hemisphere).

## 1 Answer

I'm not sure what environment you're working in, but because UTM zones are referenced to a unique central meridian, the longitude of a point should be within +/- three degrees centered on the central meridian of your target UTM zone.

Regarding a projectable/renderable bounding box of a UTM zone, ESRI datasets that come with ArcGIS should contain a UTM zone shapefile, but you could also roll your own pretty easily. The northing coordinates will always be 180/-180, and simply walk your way through every 6th line of longitude, and there are of course 60 zones in the world.

You'd have to watch out for the exceptions Dan mentions in his comment as well as the polar zones which @whuber pointed out.

• You mean "within three degrees," not six. Note that polar zones are constructed differently (but may be of no interest). Also, to be complete, it's necessary to know that the central meridians are all congruent to 3 modulo 6: -177, -171, -165, ..., -3, 3, 9, ..., 171, 177 degrees. For longitudes in the range [-180, 180], a simple calculation of the zone number is `1 + Int((longitude + 180)/6)`. Mar 27, 2012 at 22:47
• @whuber yes you're right, I was assuming centered on the CM Mar 27, 2012 at 22:56
• Im computing the central meridian of the zone like so: `// Central meridian of zone \$zcm = 3 + 6 * (\$this->UTMGridZone - 1) - 180;` so I would check +/- 3 degrees from this number eh? Thanks for your help BTW. Mar 27, 2012 at 23:22