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Topic: Analysis | Area report tool

I have just been using the area report tool to find the number of Scottish Biodiversity List species in a designated area. The query works fine, but the area of the polygon chosen (presented in sq km) appears to be wildly incorrect. I have crosschecked the site area with our own GIS and via MAGIC maps and the NBN Atlas comes up with a completely different area. Is this a bug? Am I missing something obvious? I tried this with another site and it too stated the polygon search area what appears to be incorrectly.

Mark

Mark Pollitt
SWSEIC (formerly DGERC)

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Re: Analysis | Area report tool

Hi Mark

Sorry you are have detected a problem with the Area Report tool.  It sounds like a bug (not one I am aware of) but to investigate we do need some extra information so that we can replicate the problem. So it would be helpful to have details about:

1. What you were trying to achieve
2. The exact steps you took
3. What you expected the result to be
4. What the actual result was
5. Screenshots would be helpful too.

Feel free to post the details here or email me directly if you prefer.  Good to hear from you anyway and hope all well at SWSEIC.

Many thanks,
Christine

Christine Johnston
NBN Atlas Project Officer

3 (edited by ChristineJ 16-07-2020 17:08:06)

Re: Analysis | Area report tool

Hi Mark

I have just tested creating an Area Report for two sites and have compared the area calculations with calculations made in QGIS using the original shapefiles for the two sites.  The values I get for area are:

Site name: Threave Castle (from the NTS layer):  NBN Atlas area report area = 6.28 sq km; original shapefile area calculation = 628.96 ha

Site name: South Solway Mosses (from the NNR layer for England): NBN Atlas area report area = 9.659 sq km; original shapefile area calculation = 967.554 ha

[The conversion from ha to sq km is x 0.01.]

There is therefore a small variance in area but I think this is probably within the tolerance expected for such calculations.  To explore this further it would be useful to know which sites you were reporting on as it may be there is a particular problem with a layer or layers that we need to check out.

Many thanks,
Christine

Christine Johnston
NBN Atlas Project Officer