The big goal with the TN 911 project is to eliminate steps and still enter good data.
I’d like to fill out as much of the database as I could with minimal work from the person putting in data. Hence I’ve riddled the database with triggers and made drop down lists of about everything I could. I’m learning what makes for a good drop down list. Not using every value I could is a good start.
One thing I haven’t taken the time to do is the elevation attribute on the address. By the state standard I need a height in meters for every address. Not that hard in QGIS if you’re running the drape command at the end BUT I’d prefer to not run that and let QGIS do the work as I enter data.
Where do you stick the Elevation model? In one spot? On each machine? Geoserver? Database?
I spent a few spare hours messing around with a 10GB County wide DEM and a Virtual machine running linux. I loaded postgresql, postgis, Geoserver, and a few other things and ran some tests. The tests weren’t solely based on speed. They were more “what’s going to be the least hassle”.
What I learned:
- I like the idea of sticking the DEM in the database but that inflates the size of my database more than I want. That leads into another rant on the state of IT at these small 911s – that comes later.
- My thought has been after the last “sales job” to start running this in the cloud. How big of VM do I need? I’m currently using Digital Ocean.
- I merged this all together and didn’t do much beyond using gdal_translate. All my fancy tricks of output type and compression usually blew back with some sort of error. I probably should do something to the nearly 700 img files before merging them all together into a 10GB tiff. Maybe.
- Geoserver or COG – I think COG for this. I loaded apache on the VM and shared it out and it was fast. Of course this was all local so it’s going to be quick. Maybe today I shove it into the “cloud” and test it out. That may change my opinion on things. I do love me some Geoserver so that’s still in play.
So how did I grab the elevation? The TN standard is an integer and in meters and for this test I’m just grabbing it in feet. I can fix that. So I Start with:
I’m using forms in QGIS to apply the raster_value function as a point is placed or updated. Of course back to the whole meters and integer problem. Then:
I solved on more small problem with this – granted it’s not a problem anyone cares about at the moment but it’s nice to collect as much as you can collect without bugging the user. I can hide the elevation attribute and just let QGIS do it’s thing.
The last question – Can I grab the elevation of the start and end nodes for streets into this? That’s next.
