australiacoordinate systemqgis
I am using QGIS to observe and analyse spatial distribution of earthquakes in Western Australia. I want to measure polygon areas, and create buffers, for which I need to use a projected coordinate system.
What projected coordinate system should I use for Western Australia?
I took your data and plotted it using WGS 1984 (in the ArcMap Coordinate System menu under Predined > Geographic Coordinate Systems > World > WGS 1984), which, in most cases is a good world standard to go with when you don't know the source coordinate system.
If you are creating Vector data, then it's best to keep the data in a geographic coordinate System with WGS84 as the datum.
With today's technology, there is no specific advantage to keep your vector data in a custom projection. 6 decimal points are enough to have meter level accuracy, and you aren't going to need any more. Projection on demand is fast enough in today's world; And you have the advantage of being compatible with most global sources like Satellite Imagery and GPS devices etc.
You shouldn't use a UTM zone, since India is covered by several zones, and big states like AP & MP themselves are covered by several UTM zones.
If you are dealing with any Governemt body, do note that you need to follow the NNRMS standards given in the NNRMS document. While the document clearly states (page 47 section 66.4) that you should store the data in Geographic Coordinate system, all government organizations that I have worked with, store even the vector data in the national or state projections.
Update In Feb 2016, these coordinate systems were added to the EPSG Database. For example, look at https://epsg.io/7755
Second Update This projection is now available both in the ArcGIS platform, as well as QGIS, Gdal and other projects which use the updated PROJ library.
If you are digitizing from SOI TopoSheets, It is even more complicated. Firstly, many experts believe that it is not legal to scan and digitize SOI TopoSheets. Secondly these toposheets are in a poly-conic projection, based on the Everest Spheroid & Modified Everest Datum. The coordinates on these maps are shifted quite a bit when compared to coordinates in the WGS84 datum. Hence you need to take care of this datum transformation.
Best Answer
If you're using a small area, you can use one of the MGA zones:
The CRS for these is
EPSG:283XXwhere XX is one of the numbers.It sounds like you want to cover all of Western Australia, though, so you probably want to use the Australian Albers, which is
EPSG:3577.