Archivos de diario de octubre 2019

30 de octubre de 2019

41. looking-for-inaturalist-observation-map-visualisation-suggestions

the and URLs above won’t actually take you anywhere. but they do provide a GIS tool – in this case, ArcGIS Online – the instructions needed to get map tiles from iNat and GBIF.

you may have noticed that when you load many online maps, they get rendered a section or a tile at a time, not all at once. as you pan beyond the original extent of the map, new sections or tiles get loaded and added to the map. as you zoom in and out, new tiles get loaded to provide a better representation of the map at the given zoom level.

you’ll notice in the tile URLs i provided above, they all contain a {level}, a {col}, and a {row}. ArcGIS will dynamically replace these with a zoom level, an x value (or column index), and a y value (or row index). that tells the API to return a map tile that represents a particular section of the Earth at a given zoom level. when the API provides ArcGIS that tile (usually a picture file – in these cases, all *.png files), ArcGIS puts that tile on the appropriate place in the map, along with all the other tiles needed to fully display the map.

here’s how you can create a map with one of these tilesets in ArcGIS Online:

go to 1
at the top of the screen, find Maps, and click on it. (you don’t have to sign in.)
that should get you to a screen with a blank map. at the top right of that screen, click Modify Map.
that wll add some editing options to the toolbar below. find Add in that tool bar (on the left side of the screen), and click on that, then select “Add Layer from Web” from the drop list.
that will give you a pop up. in that pop-up, select “A Tile Layer”, then fill in the URL (using one of the URLs i provided before), a title for it (which is what show up in the left Contents pane in the screenshots), and credits (which is what shows up in the bottom right corner of the map in the screenshots). then click Add Layer.
finally, you may want to use a basemap that is less busy than the default topo basemap. you can either select one by clicking the Basemap button in the map toolbar, or searching for one via Add > Search for Layer. (ArcGIS has lots of layers available.)
if you don’t like ArcGIS, you can also do something similar in other GIS tools. the specific steps will differ, of course, but the concept is the same. (the URLs may differ in the other tools, too. for example, QGIS and Leaflet.js expect {z}, {x}, and {y} in the URL instead of {level}, {col}, and {row}.)

hope that helps. if you have other questions, feel free to ask.

also note there are a few more advanced things that can be done. for example, you can use different tilesets for different zoom level ranges. so for example, the hexagons that GBIF provides may look okay at that size in my example at a continent level, but they might look too much like points at a higher (more granular zoom level). so you might choose to use relatively bigger hexagons at higher zoom levels by changing the hexPerTile value in the URL (smaller values result in bigger hexagons in this case). you can also modify the transparency of the tiles within your particular GIS tool.



it occurred to me last night / this morning that i could probably take the results from the UTFGrid tiles that the iNaturalist API serves up and use them to create my own custom observation maps. so when i got some time this evening, i tried to create my own custom map based on UTFGrid data, and it actually worked out better than i expected. i think UTFGrids might be a little less precise, but they are much more customizable than either iNat’s standard observation tiles or GBIF’s tiles, and they offer all the query options that iNat provides. below is an example of all observations from iNat. i compared it against another map i created from GBIF (, and it looks similar (which is good from a data quality perspective). i’ll probably work on it a little bit more when i get time just for fun, but if anyone is interested in it, i’ll clean it up a little bit more and can share the code when it’s more functional.

tbd utfgrid alternative implementation.jpg
1534×1330 133 KB
UPDATE: i was doing some more sanity checks on the data before i got too far down the road of coding something that turned out later to be flawed – so far, things look ok – and i just wanted to share some more maps that i thought were interesting.

here’s a map that shows observations over the last 4 years (r=2019, y=2018, g=2017, b=2016, brightest dots represent at least 20k observations). you can sort of see how iNat usage is spreading across the world:
tbd obs by year r2019 y2018 g2017 b2016 max20000.jpg
1535×790 102 KB
this map shows observations over the last 4 months (r=Oct, y=Sept, g=Aug, b=July, brightest dots represent at least 2500 observations):
tbd obs by 2019 month r10 y9 g8 b7 max2500.jpg
1536×785 120 KB
this map shows observations Monarchs over the last 4 months (r=Oct, y=Sept, g=Aug, b=July, brightest dots represent at least 25 observations). you can sort of see a shift in observations over these months related to migration:

k… i’ve been coding a bit, and i’m at a point of diminishing returns for further coding, i think. i didn’t get to the point of producing a mapping interface, but the code is here ( 2), and hopefully it’s relatively easy to understand and tinker with. you’re welcome to adapt it as you please.

here are some examples of different custom maps i created using the UTFgrids: 2 1 1 1 1 1 1 1 1


one last contribution here:

the previous examples were built in a static map viewer that i cobbled together. but this new example is built as an extension of Leaflet.js. so it might be easier to tinker with for those who are familiar with Leaflet.js, and this example is also easier for exploration since you can pan and zoom. the markers are also created a little differently here, in a way that is less resource intensive but is a little less flexible (tradeoffs).

that’s it for now.

hmm… if you’re trying to do heatmaps, then you should try the tilesets served up by iNat 1 and GBIF 1, if you haven’t already.

iNaturalist’s tiles are a little bit uglier in most cases (in my opinion), but they can be set to any color using the color parameter. GBIF’s tiles look a little better (in my opinion), and the polygon tilesets in particular offer lots of options for formatting, though there are fewer color options available.

here are 4 quick examples of observation tilesets for Diloma concameratum (Wavy Top) that i pulled up in ArcGIS Online over a dark basemap (each snapshot is preceded by the tileset URL i used for that layer):{level}/{col}/{row}@1x.png?srs=EPSG:3857&style=orange.marker&taxonKey=5797922 2
tbd heatmap gbif marker.jpg
1236×957 117 KB{level}/{col}/{row}@1x.png?srs=EPSG:3857&style=iNaturalist.poly&taxonKey=5797922&bin=hex&hexPerTile=16 2
tbd heat gbif hex 16.jpg
1236×957 120 KB{level}/{col}/{row}.png?color=orange&taxon_id=861925 1
tbd heatmap inat heat.jpg
1236×957 111 KB{level}/{col}/{row}.png?color=purple&taxon_id=861925



Here's the link for creating a traditional project:

Publicado el 30 de octubre de 2019 por ahospers ahospers | 3 comentarios | Deja un comentario
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