coordinate systemqgis
I'm severely confused by projection systems in GIS softwares and need some help with it.
For my project I need projections which allow me to measure distances and areas in meters or meters squared etc.
From what I know, WGS projections don't allow you to do that, but UTM projections do.
What if I'm using EPSG 32643, WGS 84/ UTM zone 43N? Will this give me measurements in meters?
ArcMap has a Geoprocessing Tool that Adds XY Coordinates as two new fields in the attribute table. If you're set up in a projected coordinate system, you'll need to first change over to the geographic system in order for the output of the tool to be in Lat Long.
Alternatively you can open a new map, set the data-frame to WGS 84 (Right-click 'Layers' in the table of contents, choose properties, Coordinate system). Add your point shapefile (or feature class) add two fields for x and y coordinates, right click -> Calculate Geometry -> X-Coordinate -> Use Data frame's coordinate system.
Data Frame Properties (right click 'Layers' in TOC):
Calculate Geometry Dialog Box:
You use a UTM zone when your area of interest fits completely within it or very nearly so. A UTM zone is not appropriate when your area of interest spans several zones such as in your case. A little overlap into a neighboring zone might be ok, but the further away from the zone you pick, the more distortion there will be and the more it matters. I found this page with a graphic example.
You actually want a projection designed to cover that area and minimize the appropriate distortions (shape, area, distance, direction - can't have them all minimized in one projection), as mdsumner suggests. Note that you can always take a standard projection and modify it to best suite your particular area of interest by changing the detailed settings. That does take a level of understanding to know the impact your choices have on distortions and whether or not they are acceptable. And of course the larger the area you look at, the greater the compromise you make in distortions for some areas. This Esri pdf is a good introduction to projections.
You could also get the length calculations you need on a per zone basis if you want to stick with UTM and its level of distortion/error.
As an experiment, you can always add another length field, set a different projection that covers more than just a UTM zone, such as EPSG:3001 I mentioned earlier in a comment, field calculate that length, and compare it to your UTM lengths to see what kind of difference it makes.
Best Answer
WGS is a combination of several things. The WGS84 coordinate system uses geographic coordinates, so no meters there. You can use the WGS84 ellipsoid/datum as base for a metric coordinate system though. That's what the WGS84/UTMxx projections are. Based on the WGS84 ellipsoid, but not a plain geographic coordinate system.
UTM coordinate systems are metric so EPSG 32643 will give you metric measurements. But be aware that UTM systems are only valid for specific zones, don't use a zone for China to measure in Europe, that would give you bad distortions.