topic Re: Just started using ArcMap - is this kind of analysis possible? in Spatial Data Science Questions

Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Wed, 24 Jun 2015 17:03:02 GMT

I have 2 files, a shapefile (.shp) and a raster file (.tif). The .tif is merely 2 bands (0 and 1) where 0 represents no forest loss and 1 represents forest loss (file is from here: http://earthenginepartners.appspot.com/science-2013-global-forest/download_v1.1.html) The .shp consists of polygons that represent protected areas (file is from here: http://www.protectedplanet.net/).

What I'd like to do is try a statistical analysis that would simply tell me how much forest loss ("1" points in the .tif) lies within the protected areas and how much loss lies outside the protected areas (in the .shp).

I'm wondering if it's possible to do this in arcmap/arcgis and if so how would I do this?

Sorry if this seems like a stupid question, I haven't been using the software for long and I couldn't find anything online.

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Wed, 24 Jun 2015 17:12:55 GMT

He Elio, if you have the spatial analyst extension I would try using the zonal statistics tool: ArcGIS Desktop.

Re: Just started using ArcMap - is this kind of analysis possible?

DarrenWiens2 — Wed, 24 Jun 2015 17:14:46 GMT

Tabulate Area will give you the areas of 0 and 1 inside your shapefile.

You will have to define what is "outside". If it's your whole raster, just calculate the total areas of 0 and 1 and subtract those inside. If some other area for "outside", draw a polygon and use Tabulate Area.

Re: Just started using ArcMap - is this kind of analysis possible?

DarrenWiens2 — Wed, 24 Jun 2015 17:25:12 GMT

Just a note that Tabulate Area is a better choice for categorical area analysis because:

a.) it calculates area directly. Zonal Statistics will provide a sum of cells that you will have to calculate to an area later.

b.) it will handle more than one class. Zonal Statistics provides one final statistic per zone (sum, mean, etc.) so unless you are only interested in summing the number of cells with the value 1, this is not a good tool to use. Tabulate Area will provide sums for each class, regardless of it's original value.

Re: Just started using ArcMap - is this kind of analysis possible?

JayantaPoddar — Wed, 24 Jun 2015 18:02:57 GMT

Darren,

I think OUTSIDE means the part of the Forest Loss area in Raster that lies outside the protected area polygon.

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Elio,

Apart from the above suggestions bu Sephe and Darren, you could also try Raster to Polygon to convert the raster to polygon. Also go to Environment Settings > Raster Storage. Define NoData value as 0. (This will ensure that no polygon is created out of No Forest area.)

Now you have polygon feature (shapefile) of Forest Loss area

Then use Union between the two shapefiles. In the resulting shapefile, use Select by Attributes and Statistics (attribute table) to identify the total area of Forest Loss inside /outside protected area.

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Wed, 24 Jun 2015 19:17:06 GMT

Thank you Sephe, Darren and Jayanta for your suggestions. I will try them all and see which works best for me

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 02:02:36 GMT

Hi Sephe, I couldn't really understand the output this created I think it's a bit too complex for what I'm trying to achieve, perhaps I did it wrong? I'm just trying to find out how many points lie within protected areas and how many lie outside the protected areas. This translates as "1" data points in the .tif, and polygons in the .shp.

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 02:07:53 GMT

Hi Darren, this method seems like it could work for me but it appears to get stuck on "executing tabulated area..." when I run the tabulate area tool (I gave it at least 30 mins but no change). Perhaps the files I'm using are too big? I did select and create a new shapefile of the area I needed from the original shapefile (as it's 2GB+). The shapefile ends up being about 20mb and the tif is about 40mb. I have a quadcore PC, do you think I just need to give it more time? Or I might be setting it up wrong. I'm just trying to find out how many points lie within protected areas and how many lie outside the protected areas.

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 02:15:44 GMT

Hi Jayanta I liked the look of this approach but I couldn't get it to work, my resulting attribute table after the union is a mess and looks completely wrong haha. I I will give it another try tomorrow, I think merging the polygons in each layer first might help. Perhaps you could try running the sequence yourself using the same data

http://commondatastorage.googleapis.com/earthenginepartners-hansen/GFC2014/Hansen_GFC2014_loss_00N_060W.tif

http://www.protectedplanet.net/downloads/WDPA_June2015?type=shapefile (I just created a new shapefile using the polygons that cover the .tif to reduce file size)

Is this the easiest way to find out how many points lie within protected areas and how many lie outside the protected areas?

Thanks for your help.

Re: Just started using ArcMap - is this kind of analysis possible?

DarrenWiens2 — Fri, 26 Jun 2015 03:21:27 GMT

If you're only dealing with points to raster, you can use Extract to Points http://resources.arcgis.com/en/help/main/10.1/index.html#//009z0000002t000000

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 03:49:43 GMT

I don't have anything to put into the "Input point features" that would be compatible. I only have a shapefile with polygons and a tif with 2 bands (loss and no loss/1 and 0) so I'm not sure how I'd make this work?

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Fri, 26 Jun 2015 04:57:40 GMT

Oh Elio, could you not upload a subset of the shapefile? Nobody is super keen to download a 2GB shapefile.

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Fri, 26 Jun 2015 05:00:24 GMT

Elio, what is the area you are interested in analyzing? This raster is 10x10 degrees. That's quite a large area of the earth.

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Fri, 26 Jun 2015 05:02:56 GMT

Select the polygons you're interested in, right click the shapefile in the table of contents and select export. Save the shapefile, then zip all the individual files with that name (they are all parts of the same shapefile) and zip it up. Then you can attach the zip in a comment here.

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 05:05:49 GMT

Good point, I'm running on little sleep and so wasn't really thinking, sorry. I just uploaded it to mediafire i hope this works: http://www.mediafire.com/download/aaaluh55bo86d6m/loss_0n_60w_shapefile.shp

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Fri, 26 Jun 2015 05:07:41 GMT

Thank you sir

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 05:08:09 GMT

I am trying to analyse as much area as I can, do you think 10x10 is too large? Originally I was planning on analysing the whole earth but I can now tell that is not really possible to do all at once

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Fri, 26 Jun 2015 05:09:54 GMT

Urm, yeah, you only uploaded the .shp file. ALL the different files are needed to use this in ArcMap. Can you zip them all up together and try again? There should be 5 to 7 files, all with the same name.

Re: Just started using ArcMap - is this kind of analysis possible?

ElioD_Aversa — Fri, 26 Jun 2015 05:14:49 GMT

Ah I didn't realise, my inexperience really is showing now... you'll have to forgive me. Hopefully this is what you need: http://www.mediafire.com/download/9y2ofx4n5da636t/loss_0n_60w_shapefile.zip

Re: Just started using ArcMap - is this kind of analysis possible?

SepheFox — Fri, 26 Jun 2015 05:16:59 GMT

Don't worry about it--common rookie error