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Topic: Absence Records

I have just been looking at an interactive for Bee Wolf (Philanthus triangulum) and was surprised to see Absence records were shown as well as presence. When I drew a bounding box and queried the records, exactly the same list was shown for presence as for absence. The same happened when I looked at Hornet (Vespa crabro), but no absence records were offered when mapping Hairy legged Mining Bee (Dasypoda hirtipes) or Wall Butterfly (Lasiommata megera).
I guess this is happening because none of the records include an abundance figure and the software has equated zero abundance with absence. There are a great many records in our dataset which have no abundance data and it wouod be very misleading to represent these as absences. Is there any way these could automatically be given an abundance level of 1?
I do not understand why the absence records are shown for some species and not for others.

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Re: Absence Records

Hi, the gateway makes a distinction between absence and presence records as part of the record, and has nothing to do with attributes associated with the records themselves. So we only display absence layers when we have absence recrods for that species, if you notice that the absence records are shown on a white background with a hashing applied to them, that is where the actual record is in this case.

The issue here purely appears to be with the api not properly distinguishing between absence and presence records on the requests from the Interactive Mapper, I will see if I can find and resolve the issue here for you.

Thanks for bringing this to our attention,
Matt

Matt Debont
Application Developer
Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough PE1 1JY, UK

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Re: Absence Records

Hi, I have fixed this issue and the requests should return correctly now, thank-you for bringing this issue up with us and we apologise for any inconvenience or confusion that this has caused.

Thanks,
Matt

Matt Debont
Application Developer
Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough PE1 1JY, UK

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Re: Absence Records

Looking at the interactive map for Great Crested Newt, I notice there are a couple of datasets that generate "Absence" records. 

When the map is drawn, at 10k resolution, the "Absence" records overlay the "Presence" records, thus suggesting there are a couple of big blocks of the country where GCN are absent.  This is not the case as zooming in the map will show.   I am unable to test this at lower resolutions without applying for better access to the datasets, but my guess would be the same thing will be happening at whatever level of zoom is employed.  Surely "Presence" dots for a species should overlay "Absence" dots at whatever resolution the maps are displayed at otherwise the maps give completely the wrong impression.

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Re: Absence Records

Both the absence and presence records in this case are separate layers on the IMT, these can be re-ordered by dragging them up and down the list. You can also change the colour/opacity of the layers by clicking on the spanner icon next to each item in the list.

Hope that helps,
Matt

Matt Debont
Application Developer
Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough PE1 1JY, UK

6 (edited by Matt Smith 02-06-2014 10:23:31)

Re: Absence Records

Thanks for the reply Matt, I didn't know about the ability to re-order layers by dragging the list.  As for the "default" map, I still think it would be a good idea to have the various layers ordered such that "Presence" records overlay "Absence" records.

(Can of worms time..)  In relation to the above comments, is there any progress on getting multi-layered maps to display "Combined" dots, at least for, say, the first 4 layers.  At the moment the layer at the "top" of the list overlays anything below it so making multi-species (or even presence/absence) maps a little difficult to visualise.

7 (edited by matt.debont 02-06-2014 10:31:34)

Re: Absence Records

You should be able to change the opacity of each layer as I mentioned that way you should see the dots below the layer on top (i.e. set them to very different colours and have them transparent to at least some extent) then you should get a sort of combined view of the data.

Just click on the spanner button beside each layer to modify the properties of those layers which should have an opacity slider to control this. Its not 100% in all cases but its currently what we have.

Matt

Matt Debont
Application Developer
Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough PE1 1JY, UK