Recommended Projection for Queensland

BenNadler · ‎08-22-2019

Hi Melita.

Any thoughts about a good projection that covers Queensland, minimizes reprojection errors, uses meters as the units and preserves length?

Need to standardize data from GDA 1994 MGA – Zone 56 (meters), GDA 1994 MGA - Zone 55 and 56 and lots of Geographic data (latitude, long)

SimonKettle · ‎08-22-2019

I think I'm following your request....

Couldn't you convert your data projected in GDA 1994 MGA Zones using the GDA94 datum into something like the GDA94 Lambert Projection? The Lambert projection is conformal and will preserve shape...otherwise some Azimuthal Equidistant projection would work to preserve length but only from a single point...it kind of depends on the scale of the information you're trying to re project etc...

For your other lat longs do you know their CRS as you'll need to know to find the appropriate transformation method?

MelitaKennedy · ‎08-22-2019

Queensland is pretty big. Latitude range is 19° (10S to 29S) and longitude range is 16° (138E - 154E). My colleague, Bojan, looked at it with me. Some possibilities are below:

Lambert azimuthal is equal area which is not what you want, but given as an option (distorts distances and angles). He used WGS84, but GDA2020 would be another option.

PROJCS["ProjWiz_Custom_Lambert_Azimuthal",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Azimuthal_Equal_Area"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",146],PARAMETER["Latitude_Of_Origin",-19.5],UNIT["Meter",1.0]]

Stereographic is conformal (good angles), will distort distances and areas

PROJCS["ProjWiz_Custom_Stereographic",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Stereographic"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",146],PARAMETER["Scale_Factor",1.0],PARAMETER["Latitude_Of_Origin",-19.5],UNIT["Meter",1.0]]

My first thought was equidistant conic. Distances are true along longitude lines and the standard parallels. It's impossible to maintain or preserve all distances. If you can work large scale and have a projection customized for the area, distances shouldn't be too bad.

PROJCS["ProjWiz_Custom_Equidistant_Conic",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Equidistant_Conic"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",146],PARAMETER["Standard_Parallel_1",-25.8333333],PARAMETER["Standard_Parallel_2",-13.1666667],PARAMETER["Latitude_Of_Origin",-19.5],UNIT["Meter",1.0]]

Another some distances-preserved option is azimuth equidistant as Simon suggested.

PROJCS["ProjWiz_Custom_Azimuthal_Equidistant",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Azimuthal_Equidistant"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",146],PARAMETER["Latitude_Of_Origin",-19.5],UNIT["Meter",1.0]]

You'd have to compare the last two to see if one gives better results than the other for, say, area calculations.

Melita