Coordinate conversion

This topic has 5 replies, 6 voices, and was last updated 14 years, 6 months ago by Sit Rep.

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May 25, 2010 at 5:53 pm #3549

bob
Participant

Newbie technical question:

I saw the "BP live video feed" of the leak in the Gulf.
They show what look like some kind of GPS coordinates.
E 1201871.44 and N 10431526.18

Are these GPS coords? Is there a way to convert them into something more familiar to a non technical person, perhaps Decimal Degrees?

I thought with the coordinates they display, it would be easy to map.
This has not been the case.

May 25, 2010 at 10:20 pm #28025

James
Participant

Hi Valkyrie:

For your reading enjoyment:

http://www.uwgb.edu/dutchs/usefuldata/utmformulas.htm

I am sure our Survey Brethen can give a better answer but in laymen terms the E=Eastings and N=Northing is feet (or meters maybe).

Why they do not use Lat and Long?

Regards,

May 26, 2010 at 3:09 am #28026

tc1
Participant

eastings and northings are what we used before gps in the old style Decca Navigators for position finding.

May 26, 2010 at 6:54 am #28027

Ray Shields
Participant

Eastings Northings, or Universal Transverse Mercator (UTM), is used by survey companies.

UTM assumes a "flat" earth, Going from 1 degree in Lat or Long to another is not necessarily the same distance (think of the difference in miles between a degree at the equator and one up near the north pole)

Some more info on

http://en.wikipedia.org/wiki/United_States_National_Grid

or http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system

June 30, 2010 at 7:15 am #28028

hermawan
Participant

as far i know, just convert like that, must be using id zone, central meridian, if you want detail asking surveyor guys who actually know about that,

i see some display rov just showing easting,northing too

June 30, 2010 at 9:51 am #28029

Sit Rep
Participant

Comment from a non-survey type (and relying on memory):

measurement is based on metres from a datum

The datum in use depends on geographic coordinate system in use, see http://en.wikipedia.org/wiki/Geographic_coordinate_system e.g. WGS84, AGD94

It basically all arises because our planet is neither perfectly round (spherical) nor is it flat, so a model has to be developed to allow the "real" 3D coordinates of a point to be determined with repeatability.

Hopefully it helps
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