New answers tagged dem
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The threshold is not directly related to the scale, but it controls the level of detail in your network. If you consider the scale from a cartographic point of view, the scale is more related to the size of your pixels, which is constant when you change the threshold.
In hydrology, the threshold is set on the "flow accumalution", which is a count of the ...
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There wouldn't be a specific tool, but a work flow you could follow to do this. I have done something similar in ArcMap, and can describe the concept.
Firstly decide what the fixed elevation is of your dam. Then you can convert your rectangular polygon to a raster file (matching parameters such as cell size with your DEM). There should be a tool for this.
...
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You may want to check out the relatively new MERIT-DEM, which is mostly SRTM but heavily corrected (especially north of 60 degrees). You can download it in tiles. They also have corresponding hydrologic models (MERIT-Hydro) that include flow directions, flow accumulations, channel widths, height above nearest drainage, and a depression-filled DEM. All global....
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You can download a 90-m resolution DEM from http://srtm.csi.cgiar.org/download. It covers both Uruguay and all of South America.
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16 bit signed integers can only store whole numbers between -32768 to 32767.
Either keep in 32 bit floating point (and compress) or multiply by 10 before saving to 16 bit int to keep 1 decimal place, ie 483.41 becomes 4834.
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I think it is because you use WMS layer which can be served like a tiled image - not "real" DTM. Why not to use SRTM or EU-DEM?
SRTM
http://dwtkns.com/srtm30m/
EU-DEM
https://www.eea.europa.eu/data-and-maps/data/copernicus-land-monitoring-service-eu-dem
This is an example of using EU-DEM data. I cropped some part using a polygon layer in SAGA-GIS and then ...
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I believe the reason you cannot access the values from this DTM is because it is being served as a WMS, which QGIS is unable to obtain data from.
Sometimes some WMS work as WFS if this one does, the second answer here might be of help.
3
How about something like this:
radius=5000 # Maximum distance
X=200000 # X coordinate of lookout
Y=500000 # Y coordinate of lookout
r.import dem.tif output=elev
g.region -a rast=elev
r.viewshed input=elev output=vshed max_distance=$radius coordinates=${X},${Y}
r.to.vect input=vshed output=vshed type=area
This should leave you with a raster named "...
4
The problem you're seeing occurs when you load multiple tiles but the the gray scale interpretation of min/max is based on only one of the tiles. If other tiles have a different range, parts may be "blown out". Probably the easiest way to deal with this is to combine the tiles into a single raster, then load that raster. Alternatively, if you have only a few ...
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Given a DEM and DSM:
Use raster calculator to compute height:
Compute zonal statistics for your shapefile using height raster:
Join table to shapefile and extrude geometries using fields created with Zonal statistics process:
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This is possible, and not very complicated in most GIS software. The best way to learn it will be to figure out which tools/algorithms will be used, and find the relevant section of the software manual. If the manual doesn't have enough detail, find tutorials for those tools in your chosen software by using the name of the software and the name of the tool ...
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You are trying to clip a raster using a mask layer.
Using Qgis, you can follow the following procedure.
Load your dem and polygon on the canvas
In the raster menu, go to Extraction -> Clip raster by mask layer
There, put your DEM as input layer, your polygon as mask layer. You can pretty much leave the other fields as default
In the Clipped(mask) field, ...
3
Picking the contour interval has less to do with horizontal resolution of the DEM, 3m in your case, and is instead mediated by the accuracy of the elevation values.
Specifically, to produce valid contours without forcing the interpolation software to "guess" more than it reasonably should, the smallest interval you can make contours of is limited at ...
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The answer depends on your landscape, but generally your contour interval can be much less than the resolution of the DEM. Are you looking at a normal flat-ish or hill-y area, or is this something like a Rocky Mountain range with very, very intense vertical change?
If you think about vertical changes versus horizontal distance, there is generally a much ...
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Your idea is correct, however you might incur into some practical issues.
The first is that the DTM and the stereos you are using seem to have a different height reference system.
For example, as you suggest, one might use ellipsoidic heights, the other geoidic heights.
While it is possible to convert ellipsoidic <-> geoidic heights using geoid models, ...
2
This can be done with R, visualized with the rgl package, and converting the DEM and image to mesh3d form with the quadmesh package.
Here I use another package ceramic from github to obtain the DEM and image, but you can replace those by reading the DEM with raster::raster() and the image with raster::brick().
## install.packages(c("remotes", "quadmesh", ...
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to generate terrain files i used cesium terrain builder
if you want to have quick result use docker to simplify generate process.
after generate terrain files i put them on tomcat in test folder and use it:
this.map = new Map({
target: 'map',
layers: [
new TileLayer({
source: new OSM()
})
],
view: new View({
center: [0, 0],
...
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If you retrieved the data from LRO LOLA (LDEM GDR), you do need to multiply vertical (height) values by a "Scaling Factor" of 0.5:
From the documentation:
Conversion to local height (meters) is accomplished via the following equation:
Height = (Pixel Value * Scaling Factor)
Conversion to local Radius (meters) is computed as follows:
Radius = (Pixel ...
1
You can use the Raster Calculator to do arithmetic on a raster.
Enter an expression like moon@1 / 2 into the Raster Calculator Expression box and set an output layer path and format.
But I would check first that your data really is in half-metre units - check the metadata carefully and check that the basis you are comparing it with is right too.
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