decimal degrees vs UTMs

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Kevin Messenger
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decimal degrees vs UTMs

Post by Kevin Messenger »

So a friend and I were having a debate the other night - I'm curious to get other opinions. Whenever I contribute specimens (photographic or vouchers) to museums, they prefer coordinates being documented in decimal degrees. Massive databases like GBIF (Global Biodiversity Information Facility) does the same.

They seem to prefer decimal degrees over UTMs, and I was just curious to know why? For me, decimal degrees seem vastly simpler to comprehend. If I know the latitude of a given place on the planet, I can take a stab in the dark at what the climate will be like (though this varies with water currents and air currents, but I can be in the ballpark). I can also have a gut feeling for when the sun may set based on what season it is. So for me, it makes biological sense to view the map in an X, Y coordinate system. UTMs have 3 "settings" - first a zone, then your northing and your easting.

anyway, can anyone provide answers/ clarity to my question? Any UTM advocates out there that can speak up for the same sort of intuition that knowledge of a latitude may provide. If you tell me "your campsite will be located at S10 degrees - I will immediately know a bunch of facts: A) that it will be hot, year round, and B) that the sunset is not going to fluctuate much over the course of the year and that the light/dark cycle is going to be close to 1:1.

Or if you say it will be at N34 degrees, I will know that the site is likely going to have 4 seasons, that sunset fluctuates greatly, and that weather will be approximately temperate.

I am just naming side-benefits to preferring lat/long over UTMs.

opinions??

-thanks!
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klawnskale
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Re: decimal degrees vs UTMs

Post by klawnskale »

Kevin: since most of the projects I have been involved with have been with federal and state government agencies, I have primarily utilized UTM's. This is the format they desire. When I have submitted roadkill specimens to a museum or university they prefer Lat/ Long. It doesn't make a difference to me
since I don't compose research studies or write reports. Whatever data is requested, I provide. It's just a matter of switching units on my GPS . So in so far as one being more informative to me than the other, it really doesn't make much of a difference. The location point is still the same whether it is represented in Lat/Long or UTM's.
Jimi
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Re: decimal degrees vs UTMs

Post by Jimi »

UTMs require a grid zone. There are 60 different zones, thus there are up to 60 unique points on Earth where a single specific e.g. northing & easting, or southing & westing could fall. If a data record does not include the grid zone, or it provides the wrong one, the record could be garbage. Or at least "off" by as much as (25,000/60) - over 4000 - miles. So, uh...that's not great. Ha ha.

Decimal degrees do not require as this ancillary information and are therefore superior. Less chance of a "naked data point". There's only one point on Earth a decimal degree coordinate falls.

At least that's how I understand things.

Cheers,
Jimi
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klawnskale
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Re: decimal degrees vs UTMs

Post by klawnskale »

Maptools provides information on which GPS coordinates system to use and which works best for specific conditions and criteria:
http://www.maptools.com/coordsys/
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Carl Brune
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Re: decimal degrees vs UTMs

Post by Carl Brune »

I am with you, Kevin. For the usual herper purposes, (lat,lon) in decimal degrees is the simplest, maybe also with some datum information. UTM is useful if you need to plot points on an x-y grid yourself (old school), but modern mapping programs take care of this projection stuff for you -- so there is not much need for it any more.
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Don Becker
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Re: decimal degrees vs UTMs

Post by Don Becker »

I prefer decimal Lat/Lon myself. The primary advantage I see to UTM is easier calculation of distance. Given any two points, the distance in meters can be calculated using Pythagoras theorem.
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Kevin Messenger
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Re: decimal degrees vs UTMs

Post by Kevin Messenger »

yep, so far that's been the only advantage I've seen
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Gluesenkamp
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Re: decimal degrees vs UTMs

Post by Gluesenkamp »

Cavers prefer UTM for a few reasons, primarily, because it is easier to find a precise point (i.e. a tiny, obscured cave entrance) when navigating the landscape. Choice of datum generally isn't that important in this day and age when conversion can occur at our fingertips. The most important thing is to note which one you used.
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