Page 2 – Geographic Information Systems (GIS) Library

Remote Desktop:

Question: I am struggling with the remote desktop interface again. I don’t think it is just because it is falling asleep. I am only really able to get 1-2 clicks in before it freezes again and I have to wait another 5 minutes for it to decide to kick me off so I can log on again. When I return to the interface it is where I left it, but it kicks me off again soon after. I am never going to finish the lab at this rate. Is this happening to anyone else? Any tips to fix this?

Response Per IT Staff: There is no internal forced timeout/disconnection mechanism within the ArcGIS Remote Access pool, but as an entirely network-dependent service, any network interruption lasting more than a few seconds can cause a disconnect. If a session becomes disconnected while using it, then typically some external force precipitates it: network drops, inadequate bandwidth, wireless interference, VPN drop, computer sleep (which would cause a network drop), etc. There is an auto-logout timer of 20 minutes where a Windows session will log out after a session disconnect, but again, nothing that would force a disconnect in and of itself. Users working from home and experiencing disconnect issues are encouraged to examine their home network setup; wireless users in particular may have better experience when using a wired connection (most home routers have at least one Ethernet jack), particularly when wireless connectivity is weak, of low bandwidth, or in an area with high interference or many competing signals. The individual computer’s wireless card, age, protocol capabilities (802.11a/b/g/n and so forth), software drivers, antennae, etc. can all play a role in this, so using a wired connection can eliminate a lot of these variables. If the connection is more stable over a wired connection, then an audit of the home wireless environment would be required to know what issues were present in order to return to wireless use.

February 25, 2021March 3, 2021

Lab 6 Q&A: Public Data & Metadata

By Learn @ UVM

Question: I’ve used up all my ideas to answer this, now at a deadend. Anyone know how to find the scale of a map?

Response: Take a look at the Horizontal Accuracy section of the metadata to find the scale the data were mapped at.

Question: In the analysis section of the lab, you create an intersect of the hotspots and representative landscapes. I noticed that the intersect created redundant features, where two representative landscapes overlapped the same hotspot. My conclusion so far is that we don’t want those, as they are just repeats of the same places. But if I delete the duplicates, the answer no longer matches the options.
Is there a way to deal with this? See below for one example hotspot that shows up twice in the datasheet b/c two rep landscapes overlap it.

Response: I think you’re looking at the data in more detail than me. In “real life” I’d look at the Attribute Table and compare the values between / among the overlapping polygons of the same dataset. There’s likely a reason they are presented this way. If I couldn’t determine the “why”, I’d consult the metadata / reach out to the data provider or use the Dissolve tool to “break down” the borders of the overlapping polygons. For class purposes, please do not do this. Treat each polygon individually (so you derive the “correct” response). As long as you’re using the Intersect tool here, you’re ready to move on to the next step. When you run the zonal operation to summarize the tree canopy cover data, it’s the collection of pixels within each polygon that matter, not whether a pixel is in >1 polygon.

February 25, 2021March 3, 2021

Lab 5 Q&A: Remote Sensing & GPS

By Learn @ UVM

I’ve succeeded in getting the landsat data in, in creating an NDVI composite band and visualization on the map. My problem….I can’t seem to figure out how to extract an attribute table so I can sort/use the raster calculator/summarize/etc. I tried making the NDVI a layer, raster to geodatabase, zonal statistics to table…all sorts of the tools I barely understand. ;P Any suggestions on how to turn a raster into something with attributes or a table you can open/sort/etc? I hit this before and think I solved it then, but have NO recollection of how. This is an area I’ve struggled with repeatedly, so clearly I’m not getting it. Google hasn’t helped me much.

Response: Seems like there’s an issue with the NDVI data. Did you download the July 2017 scene? Are you using the Near infrared and red bands for the calculation?

Lab Portal Connection
I’m trying to compute the NDVI and the raster analysis button is unavailable to me. It says it can’t be run because it has to be connected to a portal with raster analysis rools. The top right corner shows I am logged in, so I found some ArcGIS Pro help instructions that directed me to the portal section of the project tab, where I need to enter the URL of the portal. I have no idea what that is or how to find it, why this happened or how to prevent it in the future.

Response: You want to use Raster Functions to compute NDVI, not Raster Analysis. See the attached image below. You’re on the correct tool bar, just need to move a few buttons to the right.

I was surprised by some of the answers in the knowledge check to the band combination codes. From checking online resources, it seemed like Landsat 8 has many different combinations, and none matched the correct answers for the knowledge check. Is there a better resource for looking up band combinations? Seems there are so many, it would be great to know where to look. The only thing I can think is that the knowledge check was asking about Landsat 7?? Here’s one of the more reputable sources I thought I found:

Response: That is a great resource for understanding Landsat bands. The questions about band combinations were asking aerial imagery, not satellite imagery. Apologies if the question was not clear / I did not make a distinction between the two. Think aerial photography (from a plane, drone, hot air balloon) v satellite imagery (collected from space by a sensor in orbit). The sensors employed are different, and so too are the “bands” of information they collect.