SOSC301 Web App – Part 2
In part 1 of this series, the specifications and data needed for a field trip web app for SOSC301 were outlined. In this post we look at how the data were prepared and published for use in the app .
In our previous post, we looked at the requirements for a web app to be used on a SOSC301 field trip map. Once all the data have been compiled, the next step is making those data available on the web as web services. Perhaps a good way to think about web services is like a song streamed on Spotify. The song is out there as a piece of information that can be consumed (as the industry would say) in the Spotify app. We can do the same thing with GIS data, funnelled through a GIS server and consumed by an app on a smartphone, or by Pro or ArcMap. In essence, this is what the likes of Google Maps, or Earth, or Open Street Map are doing.
You’ll recall that the students will need some layers just to get a sense of what’s there – glacial geology, terrain, rainfall, etc – and also a layer that they can add their own field data to. This brings up two flavours of web services: map services and feature services. The difference between the two is that a map service is really just an image of a data layer while a feature service is the actual data that can be edited. We’ll need both for this.
Since we’re wanting these data to be available on the web, we’ve got to use a web server that makes the data from my desktop open to the rest of the world. For the most part, we’ll use ArcGIS Online for this but our raster layers make things a bit difficult. More on that below.
As the blurb says, ArcGIS Online is a cloud based mapping system. LU has its own site and anyone at the university can have an account to store their own data and access others’ data and maps within the organisation and further afield. It has much of the basic functionality of a desktop GIS with the added bonus that anyone can access your maps and data, depending on how you set things up. I will often use web maps to share analysis results with my less spatially-enabled colleagues and they don’t need to know a thing about driving ArcGIS (lucky them). The next question is how do I get data from my desktop onto ArcGIS Online?
One the design ideas behind Pro was greater connection to ArcGIS Online, making it quite easy to share your data. Let’s start with the simplest layer on the map – the Glenmore Station boundary – to illustrate this:
Nothing more than a polygon but useful to have on the map. I’ll just change the symbology so that it’s hollow, leaving just the station boundary with a slightly larger line width:
Next step – publish this layer to ArcGIS Online. Pro makes it pretty simple – right-click on the layer and pick Sharing > Share as Web Layer:
This opens a new pane as shown to the right:
A few notes on this:
The Summary is just a layer description while the Tags make searching for this layer later easier.
Feature means the service is a vector layer.
The SOSC301 folder is part of my ArcGIS Online account.
I can chose to share this layer with the whole world (Everyone) or limit it to people on the Lincoln system.
It’s not visible in this image but I’ve also shared the layer with a particular group on the Lincoln ArcGIS site for SOSC301
(Note: I have the option to share the whole map directly to a webmap from the Share tab > Web Map. I’m going to share each layer individually so I have a bit more flexibility later on.)
How does Pro know where to save this?
When I first log on to Pro, I use my username and password for our ArcGIS Online site – this automatically connects Pro to my account and the wider LU site. If I click Publish above, it will first analyse the layer to make sure there aren’t any major problems and publish it if there aren’t. Switching over to my ArcGIS Online (AGOL) account and the SOSC301 folder in particular, I can see this newly published layer as a “Feature Layer (hosted) at the top of the list:
I can then view that on an AGOL map:
With one fell swoop, this layer has now been unleashed on the world. Anyone on the LU system could view this layer and either add it to their own AGOL map or add it to a Pro or ArcMap map. For the SOSC301 web app, I’ll need to gather all of my layers onto one webmap so we might as well make that our next step.
In AGOL I can start this by clicking on Map across the top of the page (or New Map from the map above), which takes me to a new blank map:
To add the station boundary layer, click Add > Search for Layers. By default, it’s looking in My Content and there’s my boundary layer – I add it by clicking the wee “+” in a circle. I’ve also saved this map with the name “Glenmore Station”:
Subsequent layers I publish can be added to this map until we’ve got everything we need.
There are three more vector layers to publish: geological faults, geological units and the glacial geomorphology layer. Before publishing I’ll want to symbolise them more appropriately.
The faults layer was relatively easy but the other two had some interesting issues.
There’s a standard symbology for the QMAP geological units layer that’s used on published maps. Frequent users of those maps would be looking for that same symbology so I’d like to try and match it. To save me the trouble of trying to manually recreate the symbols to the standard, the good people at GNS have made a layer file available with their preferred symbology – but wait, this just in…Peter’s requested that the QMAP, glacial geomorphology and hillshade layer be available at the Canterbury scale rather than just the Glenmore Station scale (he’s such a taskmaster…) – no biggie, just a bit more judicious clipping.
Anyway, for the Canterbury QMAP layer, I’ll add it to my Pro map and then import the symbology from the layer file, et voila! It now looks like any other QMAP map:
I’ll publish this layer and add it to the AGOL map. The CSIGG unfortunately doesn’t have a layer file so I’ll do my best to recreate the legend. I quickly see that this is going to be a nightmare – below is the legend used by GNS for some (but not all) of the landforms from the published report:
There are 47 unique landforms listed in my spatial layer…not sure how I want to handle this just yet so I’m going to kick it to touch for now and return to it later.
So that’s the vector layers I can get on the map for now:
The raster layers will be a bit more problematic for one big reason: AGOL does not support publishing raster layers, or, to be more specific, I can’t currently publish a raster layer to AGOL. Time for plan B.
Plan B is our own, campus based, GIS server, affectionately known locally as V-ArcGIS02 but to the rest of the world as gis.lincoln.ac.nz. With the GIS Server software running on this machine, I can publish raster layers and then share them with my AGOL account. I won’t go into all the gory details, suffice it to say that from the user’s point of view, they won’t be able to tell what’s going on behind the scenes. It just means a bit more, behind the scenes work for me. But that’s why they pay me the big bucks, right? (Roslyn?)
Below is my web map with all the layers on it (except for CSIGG):
That’s probably enough about this for now…next time, I hope to have that CSIGG layer finished and we’ll see to setting up the editable layer. Join me then if you haven’t been put into a deep coma by this post.