topic Re: Reprojecting raster land cover data in ArcGIS Pro Questions

Reprojecting raster land cover data

ErikaMae — Thu, 07 Sep 2023 10:16:10 GMT

Hi all,

My ultimate goal is to conduct change detection analysis on mangrove and non-mangrove extents for my study area over the years 2012, 2017, and 2021. I acquired my data through supervised classification on Google Earth Engine and exported my mangrove extents as GeoTiffs. It was exported at a scale of 30m (as I used Landsat) and the default coordinate reference system EPSG:3857. The image below is a screenshot of one of the exported tiffs properties.

My study area of Moreton Bay, Queensland is set to the coordinate system Geocentric Datum of Australia 1994. I will go on to use the Change Detection Wizard tool to map the changes between study years.

For what I am setting out to do, do I need to reproject to the Australian geographic coordinate system? Also, if I have exported the GeoTiff at a scale of 30m, why in the ArcGIS Pro layer properties is the cell size 0.000269?

Re: Reprojecting raster land cover data

DuncanHornby — Thu, 07 Sep 2023 10:50:20 GMT

Unless the change detection wizard requires your data to be projected you can probably leave your data in a WGS84 coordinated system and use it without projecting.

30m at the equator is 0.000269 in decimal degrees, you can have a play using this web page.

If you are attempting to report change in m2 then you are best projecting your raster into a coordinate system where the units are in metres and not decimal degrees. Summary lengths /area will make more sense.

You'll need to do a little research for what's best for mapping area in the region of Moreton Bay, Queensland.

Re: Reprojecting raster land cover data

ErikaMae — Thu, 07 Sep 2023 11:21:03 GMT

Thank you for your response Duncan!

As far as I'm aware the change detection wizard doesn't require reprojection, but I wonder if calculating the area for the catchments later would be impacted by not reprojecting?

I've seen mangrove extents measured in hectares which I was planning on using too, however, the extents are quite small so I think a smaller unit like m2 might be more fitting.