# Tag Info

1

You can use Geotools //create reference system WGS84 Web Mercator CoordinateReferenceSystem wgs84Web = CRS.decode("EPSG:3857", true); //create reference system WGS84 CoordinateReferenceSystem wgs84 = CRS.decode("EPSG:4326", true); //Create transformation from WS84 Web Mercator to WGS84 MathTransform wgs84WebToWgs84 = CRS.findMathTransform(wgs84Web, ...

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Zone 1 covers longitude 180° to 174° W, hence it's origin is (177° W,0° N). similarly moving eastward Zone 2 covers longitude 174° to 168° W, with origin (171° W,0° N). so Zone 18 is 78° W to 72° W, with origin (75°W, 0°N)

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Many projected coordinate systems use a false Easting and/or a false Northing to avoid negative coordinates and/or to reduce potential ambiguities with other CRS of the same region. In the case of UTM 18N, the origin of the projection, in lat long, is (0°, -75°), but the false easting is 500 000 m meaning that the XY coordinate system has been shifted. ...

1

The units of WGS84 are degrees, so your result says 79 degrees west of the Greenwich prime meridian. Generally, UTM coordinates have a false easting of 500km, so the origin is really 500km west of the UTM 18N meridian at 75° West cutting the equator.

0

I used this code to convert wgs84 to utm and utm to wgs84. Caution: Accuracy of this code is about one meter. <script> function Wgs2Utm( lan1,fi) { var a=6378137.000; var b=6356752.314; var f=(a-b)/a; var e2=Math.sqrt((Math.pow(a,2)-Math.pow(b,2))/Math.pow(b,2)); var e=Math.sqrt((Math.pow(a,2)-Math.pow(b,2))/Math.pow(a,2)); var zone; var lan0; if ...

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You thought to reproject to UTM by using Set Layer CRS, which is wrong. You have altered the CRS, but not the extent. You need Raster -> Projections -> Warp to reproject raster data correctly to another filename and CRS.

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This is how you change it to UTM, First you have yo change it to wgs, and then call the function to do the rest function showCoordinates(evt) { var wgs = webMercatorUtils.webMercatorToGeographic(evt.mapPoint); var mp = evt.mapPoint; // Converting The WGS to UTM ...

2

I think we can over complicate this answer. It is meters, as UTM Zones are almost always going to use meters as their unit (exceptions are so rare as to not be worth a mention). If you suspect you are using something that is not meters it will say so. Use this site as it is software independent if you must look it up. http://spatialreference.org/ Then ...

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The unit of the projection is used for area calculation, meter or decimal degree or feet. Check Settings/Options/Crs, see screenshot:

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I think that you should check a few items: check layer CRS check project CRS (set automatically reprojection on the fly in: Settings > Options > CRS) After open vector layer in QGIS use tool "identify Feautures" and select one feauture In "Identify Results" dock window "expand all" and look for area units Now you can use "Filed calcuator" or Vector > ...

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