Say I have the coordinates: N: 5413457.7 E: 1528677.3

If I were to add 10 to the northing value would that make the new coordinates point 10 meters north of the original point?

  • How are they in a table? is it Text N: 5413457.7 E: 1528677.3 or Northings field and Eastings field? I would use field calculator but need to know if the text needs to be broken down and reassembled or if it's just adding to numbers. – Michael Stimson Feb 3 '15 at 0:36
  • @MichaelMiles-Stimson Sorry, I don't understand your question. I'm very new to dealing with coordinates, but I am storing simply a North and South value in an application I'm developing. I have the functionality built in to allow easy conversion between ECEF, NZTM and WGS84. What I need to be able to do is "move" a coordinate north by 10 meters and east by 3 (That is north/east as in north/east that would be on a compass). – Adrian773 Feb 3 '15 at 0:39
  • Yes, just add 10 to the north, 3 to the east and done! But that's not true north, if you want that kind of refinement the question is much more complex. What software are you using? I assumed ArcGis (in the absence of any other) but it sounds like you're developing a program? is it .net, Java.... Geographic coordinates however you can't just add 10 and 3. – Michael Stimson Feb 3 '15 at 0:44
  • Awesome, want to put that as the answer and I'll accept? C# application which I'm using to produce .kml files for Google earth (among other things). I need to be able to calculate the change of distance so that I can recalculate the start/end positions of a pole that is on a lean. – Adrian773 Feb 3 '15 at 0:48
  • The true answer is much bigger than you think. Roughly you can add/subtract values and get within a few centimetres, I have done this before for AGD66 to AGD84 which was close enough at the time. Mostly GIS folk use software like ArcGis or GDAL/OGR to do this sort of calculation for them - projection instead of adjustment. Proj.4 trac.osgeo.org/proj is an open source projection utility that you might want to consider using if more accuracy is required; this will also allow you to project to WGS84/Geographic which is more than just adjusting numbers. – Michael Stimson Feb 3 '15 at 0:53

Yes, but to explain why:

I can tell that you have projected coordinates (as I assume you're in New Zealand) the numbers are quite large, much bigger than -180 to 180, which is probably New Zealand Transverse Mercator 2000:

Projection type:Transverse Mercator 
Reference ellipsoid:GRS80
Origin latitude:0° 00' 00" South
Origin longitude / central meridan:173° 00' 00" East
False Northing:10,000,000 metres North
False Easting:1,600,000 metres 
EastCentral meridian scale factor:0.9996 - See more at: 

Which is in metres, so you can add 10 to go 10 metres north... approximately. Zones are slightly banana shaped so it's not a true north but roundabout. You can expect to be within a few centimetres of the correct location; the larger the displacement and the further from the centre of the zone the more you are likely to be off.

To get a more accurate figure use software like GDAL/OGR (OGR is for points, GDAL is for raster but they're distributed in the same package); GDAL uses the PROJ.4 library for coordinate transformation. This is open source software so is free to use. It's been a while since I've done OGR and I think it goes a little like this:

OGRpoint myPoint = new OGRPoint(Xcoord,Ycoord);
OGRSpatialReference fromSR = new OGRSpatialReference();
fromSR.importFromEPSG(2193); // NZTM is 2193, WGS84 UTM 59 south is 32759
OGRSpatialReference toSR = new OGRSpatialReference();
OGRGeometry myGeom = (OGRGeometry) myPoint;
myGeom.assignSpatialReference(fromSR); // assign the spatial reference
myGeom.transformTo(toSR); // convert to the 'to' spatial reference
myPoint = (OGRpoint) myGeom;
outX = myPoint.getX();
outY = myPoint.getY();

This is more accurate than simply adjusting the X and Y... WGS84/Geographic is EPSG:4326.

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