topic Re: Raster to Polygon Super slow then not working in Data Management Questions

Raster to Polygon Super slow then not working

DXXX — Thu, 30 May 2013 09:30:31 GMT

I have a bunch of rasters that I want to convert into polygons, but when I use the tool it is so slow. 3 hours working on 1 .tif gets too 1%. Anyone have any ideas how I can convert my raster data set into polygons?

Re: Raster to Polygon Super slow then not working

SamCoggins1 — Thu, 30 May 2013 15:05:09 GMT

How big are the rasters?

You should probably try to run the Raster to polygon tool on a small subset to determine whether it's your tool or the size of the rasters. If the tool is still slow on the subset, then it's a problem with the tool. If it process the rasters perfectly you can probably set up a Python script that uses splits the raster up, converts to polygon, and then merges the polygonised raster back together.

Let me know if you need a hand with the scripting...

Re: Raster to Polygon Super slow then not working

JeffreySwain — Thu, 30 May 2013 16:10:06 GMT

Depending on the original raster there are a few things that can be done. I would recommend considering why you are converting it as it may not be necessary. Some of the spatial analyst tools can be used in place of the polygon version of the file with zonal statistics. If you really want to convert the raster still, then I would recommend using some of the generalization tools to clean up the edges and reduce the number of polygons. You may also consider the multivariate classification to further reduce the variability and create relatively homogenous zones prior to conversion. Also consider the output format, feature classes are a must as they are not required to be under ~2 Gigs as shapefiles. The output from these conversions is usually rather large.

Re: Raster to Polygon Super slow then not working

SteveLynch — Thu, 30 May 2013 16:20:31 GMT

They key to this discussion is the version of ArcGIS.

Prior to ArcGIS 10 all the rasters are processed as grids and then converted to your raster format and all feature classes are written to shapefile and then finally converted to your format. So if you are using pre 10, your .tif will be converted to grid prior to RasterToPolygon doing it's thing.

In ArcGIS 10 we process the data in it's native format.

-Steve

Re: Raster to Polygon Super slow then not working

DXXX — Fri, 31 May 2013 04:53:19 GMT

Thanks for the response. I am using 10.1. I need to do this process as we need to make payment to a client that has delivered us the aerial imagery so we need to work out how much has been delivered and how much extra we need to cover our work area.

I have tried running the convert Raster to Polygon tool on just 1 aerial photo, not the full set and it still doesn't work.

In the end I need 1 polygon with the area covered by the aerial photos.

Re: Raster to Polygon Super slow then not working

JeffreySwain — Fri, 31 May 2013 10:49:33 GMT

Ok so you are not looking for a classified polygon, you are looking for the outer extent. I would recommend creating a mosaic dataset and then you will have one polygon per raster. With that description, you should be able to see the amount of work completed. The polygons created are called footprints and should represent all the rasters delivered. You could look at the count of the rasters(footprints) but be sure you do not create overviews and accidentally count them.

Re: Raster to Polygon Super slow then not working

DXXX — Sat, 01 Jun 2013 09:07:53 GMT

I have the Raster dataset already in a Mosaic. How ever the footprints do not match up to the actual imagery. See picture. in the end I need to have a polygon the same size of the imagery (picture) and not a polygon the same size as the footprints.

Any ideas? If I have to digitize it will take me days.

Re: Raster to Polygon Super slow then not working

GeospatialTechnology — Mon, 03 Jun 2013 09:22:45 GMT

What resolution is your raster dataset? If it is high resolution it will take a long time to process. Can you cope with a reduced resolution raster? How about using Resample and altering the cell sizes.

Re: Raster to Polygon Super slow then not working

DXXX — Mon, 03 Jun 2013 10:26:19 GMT

What resolution is your raster dataset? If it is high resolution it will take a long time to process. Can you cope with a reduced resolution raster? How about using Resample and altering the cell sizes.

Thanks for your response. Can you tell me what options to check to reduce the size? See attached picture.

Re: Raster to Polygon Super slow then not working

JeffreySwain — Mon, 03 Jun 2013 11:42:59 GMT

All you need to do is build the footprints. Simply use the ID tool to see the pixel values of the white space in your mosaic dataset and then adjust the settings in the build footprints tool. By default they are set to eliminate the 0 and 255 pixels. If your rasters have additional values then adjust the min or max values.

You should not have to resample the rasters for this workflow.

Re: Raster to Polygon Super slow then not working

GeospatialTechnology — Mon, 03 Jun 2013 11:56:58 GMT

Thanks for your response. Can you tell me what options to check to reduce the size? See attached picture.

Just put the new cells size you want in the x and y bits. You can find your current cell size in Source section of layer properties.

Re: Raster to Polygon Super slow then not working

GeospatialTechnology — Mon, 03 Jun 2013 12:10:53 GMT

Actually please ignore me I just read you comment further up.

How about using the 'Build Boundary' tool on your mosaic dataset?

http://resources.arcgis.com/en/help/main/10.1/index.html#/Build_Boundary/001700000086000000/

Re: Raster to Polygon Super slow then not working

DXXX — Mon, 03 Jun 2013 12:25:35 GMT

All you need to do is build the footprints. Simply use the ID tool to see the pixel values of the white space in your mosaic dataset and then adjust the settings in the build footprints tool. By default they are set to eliminate the 0 and 255 pixels. If your rasters have additional values then adjust the min or max values.

You should not have to resample the rasters for this workflow.

The result is ok but still needs a lot of cleaning. Have a look at the screen shot in the attachment. Its a pity the Raster to polygon doesn't work as it should. I am hoping Mark will get back to me and show me what drop downs to select. Please Mark Please.

Re: Raster to Polygon Super slow then not working

GeospatialTechnology — Tue, 04 Jun 2013 13:53:20 GMT

I already did deedug. Have you tried right clicking on the mosaic dataset in arc catalog then selecting modify and build boundary?

Re: Raster to Polygon Super slow then not working

SteveLynch — Tue, 04 Jun 2013 15:08:24 GMT

If you are only interested in the area then you can run the IsNull tool, open the attribute table which will have 0 and a count and 1 and a count.
The count for 0 is the number of cells that are not nodata. Multiply this by the squared cell size.

Steve

Re: Raster to Polygon Super slow then not working

EricRice — Tue, 04 Jun 2013 16:06:39 GMT

Its a pity the Raster to polygon doesn't work as it should.

The Raster to Polygon tool isn't really meant for imagery. The tool is primarily designed for single band integer raster datasets. If you input a multi-band "image", the tool operates only on the first band. It will essentially create a polygon for every cell in the input unless of course two or more adjacent pixels share the same value. If you give it a small raster that is 10k x 10k you'll potentially end up with 100,000,000 polygons. Raster to Polygon does not and is not intended to create a radiometrically correct footprint feature class.

See Recalculating footprints radiometrically which basically takes you to the Build Footprints tool previously mentioned. Note, it usually takes playing around with the values, shrink distance, and vertice counts a couple times before you get the desired output.

Best Regards,
Eric

Re: Raster to Polygon Super slow then not working

EricRice — Tue, 04 Jun 2013 16:15:58 GMT

Actually please ignore me I just read you comment further up.

How about using the 'Build Boundary' tool on your mosaic dataset?

http://resources.arcgis.com/en/help/main/10.1/index.html#/Build_Boundary/001700000086000000/

The boundary merges all the footprint polygons to create a single boundary representing the extent of the valid pixels. So, you have to fix the footprint polygons first, since the boundary layer is basically a 'merge' and 'dissolve' of the footprints.

You can get the footprints very close to how you want them, then build the boundary, and if some minor edits are still required then manually editing shouldn't be all that bad by this point.

I would hold off on optimizing the mosaic dataset (building overviews) until the footprint/coverage is sorted out.

Best,
Eric

Re: Raster to Polygon Super slow then not working

AmandaGibson1 — Sat, 08 Jun 2013 12:57:19 GMT

Any suggestions if I do not have the mosaic dataset extension?

Any word on getting the "create raster index shapefile" extension for 10? It worked splendidly on 9.3.

Thanks,
Amanda

Re: Raster to Polygon Super slow then not working

JeffreySwain — Mon, 10 Jun 2013 11:15:43 GMT

All you need is access to 10 or 10.1 and the ArcEditor or Standard license. The Image Server Extension only comes into play when you want to publish the mosaic dataset.

Re: Raster to Polygon Super slow then not working

EricRice — Mon, 10 Jun 2013 16:48:53 GMT

Even if you have just the basic license you can create a raster catalog to get the footprints. They will be the extent of each image and do not have options like calculating by radiometry which the mosaic dataset has, but it can get you mostly what you want.

Best,
Eric