I need to calculate the share of the area within a 50km radius of major German city centers that is covered by water with either Arcmap 10.3.1 or Qgis 2.14. My plan is to use the Global Lakes and Wetlands Database as a source , but if there is a dataset publicly available with higher resolution which would also include all the rivers I am very open to a recommendation.

I have already created a shapefile that represents the area of interest around each city in an EPSG:3035 projection. How can I now calculate the share of the area within each polygon covered by water? I have already tried to follow these instructions How to calculate a percentage of an area covered by polygons ArcGIS 10.1 but the intersect tool does not show any results while the tabulate intersect tool shows errors.Tabulate intersect shows error and intersect does not find and intersection What would be the suitable approach for this task?

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    "but the intersect tool does not show any results"... do you mean that no polygons are produced when you run this tool, or that it doesn't give you the area (this would not be an automatic task in the tool)? – Tangnar May 18 '16 at 13:20
  • Also what is your error with the tabulate intersection tool? – Tangnar May 18 '16 at 14:03
  • The shapefile created by the intersect operation is empty. As you can see in the screenshot, the shapefile "überlappend" does not show anything and in the results column "Warning 00117 empty output" is shown. Likewise if I run the tabulate intersection tool I get Error 999999, the geometry is not M-aware – Altbau May 18 '16 at 14:27

Sorry I didn't realize the errors were in your image. The approaches that you have tried are correct, you just have an issue with the data. Try removing the m-values from whichever dataset is m-aware. While you're going through this process, I'd make the outputs the same projection/crs just to be safe. I always feel more comfortable with these types of operations/calculations when I am aware of all projections.

As far as your task goes, you chose the right tools... The quickest is tabulate intersection. Use a unique ID for the input Zone Field (e.g. FID or OBJECTID) so you can relate or join it back to your polygons. You can choose your units of area to be output to the table. Make sure you give your table a proper name with file extension if you're saving outside of a geodatabase (.dbf), or you might get an error.

If you want to keep the polygons, you can use intersection and run the summary statistics tool as indicated in your original post.

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    Short follow up: The error 99999 just arose because I did not add the .dbf file extension in the tabulate intersect tool. The interface really is not that intuitive... Removing m-values did not solve the problem. Thank you very much for your help. – Altbau May 21 '16 at 20:48

A newer version of ArcGIS solves the overlapping zones problem: https://blogs.esri.com/esri/arcgis/2013/11/26/new-spatial-analyst-supplemental-tools-v1-3/

ESRI's Spatial Analyst Supplemental Toolbox v1.3 has two tools - "Tabulate Area 2", and "Zonal Statistics as Table 2" that improve on the original geoprocessing tools by "fully handling overlapping polygons" in a feature zone input. These tools are for versions 10.1 SP1 and beyond.

According to the comments from users who have downloaded (http://www.arcgis.com/home/item.html?id=3528bd72847c439f88190a137a1d0e67) the toolbox, there are some issues and inaccurate results reported for these tools.

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  • The tabulate area and tabulate intersection are different tools. The tabulate area is a zonal tool that is generally recommended for rasters (even with feature class inputs, it converts to rasters). I don't think the overlapping polygons are the problem in the original question. – Tangnar May 19 '16 at 12:34
  • Please include key information in your answer so it does not lose all value due to link rot. – underdark Jan 6 '17 at 13:50

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