JPG (1M) KMZ (2M) for Google Earth PDF (14M) they say "print optimized" TIFF (27M) they call this GeoTiffThe JPG is pretty pathetic, but easy to look at. The PDF is very good in quality. I have been encouraged to try the KMZ, but given the 2M file size, I don't expect much as far as quality.
pdfinfo USGS_I-614_1-prnt.pdf Page size: 3075 x 2906 pts
The big (27M as compared to the 14M PDF) GeoTiff file is a total mystery to me and I have no idea how to view it. My first goal with QGIS will be to open and view this file.
Using it will involve a signficant learning curve. There are plenty of online tutorials. Some videos are made by people in India, and while they may have good content, I find them a struggle to listen to. The tutorial by Matt Forrest seems well produced, he is easy to listen to and seems to know his stuff.
Here are some notes as I watch the video. He both talks and works very fast and often doesn't explain what he is doing, leaving you with a big of a puzzle -- which in a way is a good thing. And the video is 72 minutes long, so maybe we should be thankful.
Global --- f Enter/exit fullscreen j Skip behind 10s l Skip ahead 10s k Play / pause video m Mute / unmute video Esc Exit fullscreen Shift + , Reduce playback rate by 0.25 Shift + . Increase playback rate by 0.25 Shift + p Load previous video Shift + n Load next video Local --- c Toggle subtitles/CC b Change subtitles/CC background o Change subtitles/CC text opacity w Change subtitles/CC window opacity = Increase subtitles/CC text size (English keyboard) - Decrease subtitles/CC text size (English keyboard) 0 to 9 Skip to X0% of the video (X is a number from 0 to 9) Spacebar Play / pause video Home Skip to start of video End Skip to end of video Left arrow Skip behind 5s Right arrow Skip ahead 5s Up arrow Increase volume by 5% Down arrow Decrease volume by 5%
QGIS has thousands of plugins. There is one the tutorial calls QuickMapServices. I don't find it by looking under "Q" in the list, but typing into the search entry finds "NextGIS QuickMapServices". Apparently it has be renamed since the video was made (in 2024). Installing it takes only seconds.
The video shows me that I can add a directory to my Favorites, and I add /home/tom/qgis. Then I copy data files on interest into that directory (using the linux command line). Then QGIS can easily find them and show them to me. I drag USGS_I-614_1.tif from there to the layers dingus below and voila, the map is displayed in the canvas. This achieves my first goal! I can zoom in on it, pan around, and who knows what else.
I do some searches about how to add USGS topography to QGIS and I find that the QuickMapServices plugin will do it for me. There is also a USGS 3DEP Downloader" plugin that I should investigate.
Back to the tutorial. To use the QMS plugin I just installed, I use Web, the select QMS, then I get a menu. I select OpenStreetMap to continue with the tutorial, but I also notice that USGS is in the menu. It offers several options (unlike the tutorial) and I select the first (colorful), which seems to work.
Next he wants to change the projection. The text looks a bit slanted, and this will apparently fix that. At the lower right I see EPSG:4326 and I want to change to EPSG:3857 (which he says is sort of a standard for online maps). I click on the thing at lower right and it brings up a project properties gadget set to show me CRS (coordinate reference systems). I use filter, type in 3857, select it and say OK (Apply is apparently a non-sticky way to try different projections. Away we go.
The layers pane allows you to change the layer order. Layers at the start of the list hide layers below them. You can also turn layers on/off.
Next (26m) he gets into the "styling menu". You double click on a layer and get layer properties.
And now we get to the tree census data. The NYC site shows a PDF we can download, but that is not what we want. We use the Actions button at the top right and use "query data". This is a case where we ask "what the heck did he do?". I have discovered that the "J" key rewinds 10 seconds in Youtube and is a Godsend in cases like this. He clicks on "select a column to filter", then chooses the "borough" column and then selects Manhattan. Use "Apply" at the bottom, then "Export" at the upper right and CSV is the default. This gives us 2015_Street_Tree_Census_-_Tree_Data_20260729.csv which I move to my qgis directory.
He does not right click on the file and then "add layer to project". He uses the Layer tab at the very top, then Add Layer, and Add vector layer. I drag and drop the filename to the Source entry. Set "longitude" for X_POSSIBLE_NAMES and likewise for "latitude" Then click on Add and Close. He sees the data in the ocean, but I don't see it at all. I right click to get a menu and select Layer CRS and then select EPSG:4236. Voila. A bunch of green dots appear over Manhattan. He goes into a discussion of how to use stump diameter to change colors, but I skim this (it involves changing data types). He changes text to decimal, then he can use the value to fiddle with the symbols. You can even label symbols.
To get to layer properties, right click on the layer, then pick "properties" from the bottom of the menu. Note that you can set opacity here.
Polygons are vector data too, and you can edit them. You can drag vertices to new positions. You can add polygons to a layer, or you can use layer -- create layer to create a new layer. He does a shapefile layer. He clicks the little box at the upper right (to browse) I can trace a layer, but for some reason it won't let me type in an id and name. I don't know if this is a bug or some magic that I cannot see him doing in the video.
Now printing. Use project -- new print layout. Then he uses "Add Map" (an icon on the left) to copy the layers into the map. You can then use Layout -- export as PDF to spit out the map. You can add legends, north arrows, markers, ...
Plugins -- QuickOSM, qgis2web, google earth engine.
Spatial analysis -- use Processing -- toolbox and you get a big menu. I search on "spatial analysis" asking for examples and get:
Emergency planners overlay flood zones with population data to find high-risk neighborhoods, buffer a 1-mile radius around a toxic spill site to find affected homes, or calculate the shortest delivery path for a truck.In his video he uses "Vector geometry" -- Buffer, with the goal being to find the number of squirrels in each park polygon or within a given distance. He also does a whirwind tour of "model builder".
Raster data -- he wants to input the "1 foot elevation model (DEM)" from the New York portal. DEM is "digital elevation model". I began downloading this, but canceled it as it was taking forever. He wants to select a portion of this, namely central park. There are various select tools (yellow boxes) as icons at the top. He uses "select features by area or single click", then he exports central park as a new layer. Then he uses "clip raster by mask layer". Once he has this, he uses "hillshade" from under "raster terrain analysis" in the processing toolbox to get a very nice shaded relief map.
He also does contours. Type "contour" into the Processing toolbox search entry. It is under GDAL (whatever that is) in Raster extraction. I search on GDAL and find:
GDAL (Geospatial Data Abstraction Library) is an open-source, cross-platform software library used to read, write, convert, and manipulate geospatial data formats.Next he uses Raster terrain analysis -- Relief to get a shaded relief map (how is this different from Hillshade). Relief is fancier, uses color, and takes longer.Network analysis -- i.e. streets, bike paths, and such. You can find Network analysis in the processing toolbox Given the bike path layer, you can set points in another layer, then ask for shortest or fastest path. The bike path layer should indicate 1-way roads as appropriate.
He wraps up by generating a web map and showing you how nice it is online.
Feedback? Questions? Drop me a line!Tom's Geology Info / tom@mmto.org