[Qgis-user] USGS 3DEM question: export to kml/kmz

[Brent Wood]

One comment - have the LIDAR set to hillshade in grayscale (set symbology to hillshade) with the imagery overlayed & symbology partially transparent (or partially opaque).
You can adjust the opacity to what looks good & you don't need to switch between them - you can see them both at once.

You can play with the Z multiplier to tweak the hillshade to get the degree of contrast you want, also change the direction of the light source as desired.

And a different (manual) workflow you might try (if I correctly understood what you are trying to do)...

Create a new vector linestring layer (shapefile is probably simplest), make this editable.

you should be able to see the railroad tracks of interest from the LIDAR & satellite layers on the screen,
create a new linestring for each one (called digitising) by using the mouse to click on map where you want the line to go

When you have got all the lines you want to export to kml saved in the shapefile, you can export the layer as kml. It will not be a large file...


Brent Wood

Principal Technician, Fisheries
NIWA
DDI:  +64 (4) 3860529

________________________________
From: QGIS-User <qgis-user-bounces at lists.osgeo.org> on behalf of John W. Blue via QGIS-User <qgis-user at lists.osgeo.org>
Sent: Friday, November 15, 2024 07:01
To: qgis-user at lists.osgeo.org <qgis-user at lists.osgeo.org>
Subject: Re: [Qgis-user] USGS 3DEM question: export to kml/kmz

Bernie,

Thank you for the suggestion.

As I was checking out the plugins I did see "Quick Maps" and thought of the same workflow but have not tried it yet.  My only hesitation at the time was wanting to be able to mark the old roadbed as trail.  With some more google searching today I found:

https://ultrajourneys.org/digitizing-trails-in-qgis/<https://ultrajourneys.org/digitizing-trails-in-qgis/>

Have not attempted to follow the tutorial so if you know of a better one all ears.  Marking an old roadbed as a trail and getting that trail into a GPX format is the ultimate goal here.

Thanks!

John


From: Bernie Connors [mailto:bernie.connors at unb.ca]
Sent: Wednesday, November 13, 2024 9:03 PM
To: John W. Blue
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] USGS 3DEM question: export to kml/kmz

Here is a suggestion. Keep the USGS DEM tif in QGIS and symbolize it as a hillshade.  It will be very easy to spot abandoned railways in the hillshade.  Then use the Quick Maps plugin to add the Google Satellite map to QGIS.  You can easily switch back and forth between Google Satellite layer and the USGS DEM hillshade.

Cheers,
Bernie.
On Wed, Nov 13, 2024, 10:11 p.m. John W. Blue via QGIS-User <qgis-user at lists.osgeo.org> wrote:
Thanks for the file composition info.

Using that I was able to convert the downloaded 3DEM .tif from a raster to vector using Raster > Conversion > Polygonize (Raster to Vector) option.  The resultant exported .kml file size was almost 1 Gb and while Google earth was to load it, it was nothing but a white square.

I did find that Raster > Analysis > Hillshade was able to produce some remarkable and useable results.  What is strange is that the conversion of the hillshade raster to vector .kml never completes.  It quickly gets to 7% and then seemly stalls out.

Am I not waiting long enough?

John



From: oisin.kelly.wild at gmail.com [mailto:oisin.kelly.wild at gmail.com]
Sent: Tuesday, November 12, 2024 3:01 PM
To: John W. Blue
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] USGS 3DEM question: export to kml/kmz

The tif file is a raster.
Kml is a vector format.
You need to use one of the processing tools to extract contours or spot heights and then export the results to kml.
Get BlueMail for Android
On 12 Nov 2024, at 20:06, "John W. Blue via QGIS-User" <qgis-user at lists.osgeo.org> wrote:
Hello,

QGIS newbie here.  I want to use USGS LiDAR to search for abandoned railroad grades as a layer in Google Earth.

I am able to download the 1 meter tif from USGS and I am able to add it as a layer in QGIS.  I cannot, however, figure out how export the layer as a kml/kmz file.

I right-click on the layer and choose “Export” and then “Save As” followed by dropping the “Format” menu down.  Heaps and heaps of options to choose from but none for kml/kmz.

Any help in what I am missing or doing wrong would be appreciated.

John
________________________________________


[https://www.niwa.co.nz/static/niwa-2018-horizontal-180.png] <https://www.niwa.co.nz/>
Brent Wood
Principal Technician - GIS and Spatial Data Management
Programme Leader - Environmental Information Delivery
+64-4-386-0529

National Institute of Water & Atmospheric Research Ltd (NIWA)
301 Evans Bay Parade Hataitai Wellington New Zealand
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