1

I am currently making a landcover change map for a Kinabatangan, Sabah, Borneo for my undergrad dissertation. I downloaded landsat MSS and 8 images. These were pre-processed and both classified using unsupervised isodata classifications. Due to the restricted resolution I had to then use Google Earth Pro to delineate and map palm oil concessions (large palm oil sites) and smallholders (small farmers). I made polygons for each type and converted these to KML for GIS. These polygons were then changed to raster format so everything was the same. Both rasters were combined to make one palm oil layer. I standardised all the data e.g. all had the same projected coordinate system and cell size.

What I can't figure out though is how to combine my palm oil raster data with my 2014 landcover map (this was the only year the palm oil was seen). I essentially want three maps

1) 1973 Base landcover map, with these classes: Water; Forest and Non-forest

2) 2014 landcover map with combined palm oil data, with these classes: Water; Forest; Non-forest; Smallholders; Large Concessions

3) 1973 - 2014 Landcover change map, with these classes: Water; Forest; Non-forest; Smallholders; Large Concessions.

I have tried to use the raster calculator and also merge to new raster tools. Any comments of what I can do / am already doing wrong would be appreciated! P.S. I have attached some pictures of what I am working on [1: Overview of map; 2: Overview of classes].

16
  • 1
    Hey Nick thanks for your reply. The change I am wanting to show is from the 1973 map to the 2014 map. With the third map I'll change the class names to e.g. "Forest changed to large concessions etc". Regards to the raster calc how would I combine the "2014 land cover" raster with "Palm oil" raster? would it simply be an addition ("2014 land cover" + "Palm oil")? – Connor R Apr 7 '20 at 15:41
  • 1
    Hello Nick, I've just checked and both the palm oil layer and 2014 land cover layer are both in the same coordinate system etc. I standardised these to start. I have also looked at the attribute tables. The issue here lies that neither have common classes between them: 2014 landcover class: "Water", "Forest", "Other"; oil palm class: "Smallholders" and "Large concessions". Basically lots of areas that are forest in the 2014 landcover map are actually oil palm (either oil palm class) so hence pixels which are two things e.g. oil palm in the oil palm layer or forest in the landcover layer I want – Connor R Apr 7 '20 at 16:21
  • 1
    to be represented by oil palm layer instead. So essentially when combined (2014 land cover and oil palm), areas which are forest stay as forest, areas which are oil palm change to oil palm? Does that make sense? – Connor R Apr 7 '20 at 16:22
  • 1
    Hey Nick It won't let me chat there as I'm new. Is anywhere else appropriate? Being able to send images would be useful for us both. – Connor R Apr 7 '20 at 16:32
  • 1
    Yeah it is weird. I tried adding images again and it didn't work. Could we use whatsapp maybe ? – Connor R Apr 7 '20 at 16:41
0

You can try to use the set of following commands which I found useful - using gdal library:

Creating list of rasters that are in folder: dir /s/b/a *.tif > list.txt

Creating an image mosaic: gdal_merge --optfile list.txt -o output_raster.tif

Compression of raster: gdal_translate -co "COMPRESS=LZW" input_raster.tif output_raster.tif

Compression of rasters in a batch: for %i in (*.tif) do gdal_translate -co "COMPRESS=LZW" %i compress_%i

Hope it helps, Cheers

3
  • 1
    Hey thank you! I Don't want to sound dumb as I'm pretty new to GIS but is gdal within ArcGIS? – Connor R Apr 7 '20 at 14:36
  • I don't think so, however, it is an open-source library so you can use it outside of ArcGIS – Arsic Mladen Apr 7 '20 at 14:40
  • 1
    Ok no worries! I'll check it out now. Cheers – Connor R Apr 7 '20 at 14:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.