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After loading the DEM, you can use the Raster | Raster calculator menu option to modify values.
For example, here the raster 'Tsavo.dem' was loaded (it appears as band Tsavo@1), and the calculator will produce a new TIF called tsavoMinus30.tif using the calculation "Tsavo@1" - 30
3
You need points in both sides of the road to interpolate. In the process we will get also a buffer to clip the raster.
Create a buffer of your lines with a proper radius for a road (let's assume that 30m is a proper radius).
Dissolve the buffers.
Densify by interval the dissolved buffer, by a proper distance to get enough nodes (let's assume that 10m ...
3
QGis is trying to be helpful by "stretching" the the "colours" of the tiles for you. The easy way around this to add all of the tiles as a single layer. This is quite easy as you can create a virtual layer so instead of this:
You can go to Raster->Miscellaneous->Build Virtual Raster, unclick place each input file into a different band and select all ...
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You don't need to create a DEM from the contours and spot heights, you can download the DEM directly. Select "ASCII Grid and GML (Grid): 162 Mb" on the OS Terrain® 50 download page.
If you really want to interpolate from the contours and spot heights... The contours do contain elevation. As per the user guide, the elevation of each contour is stored in the ...
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Convert to numpy Array, find out which indices your coordinates correspond to and fetch values from array:
import arcpy, os
import numpy as np
raster = r"C:\GIS\data\SomeDEMraster.tif"
coords = [[364764, 6283003],[383872, 6215199],[352822, 6257659]] #Or read from a csv file etc.
arr = arcpy.RasterToNumPyArray(raster)
def giveRasterValue(x,y,nparr): #Might ...
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To read your raster into a numpy Array you can try:
import gdal
ds = gdal.Open(r'C:\path\to\raster\dsm.tif')
band1 = ds.GetRasterBand(1).ReadAsArray()
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This error comes from the inappropriate layer input.
First of all we must save our imported .csv layer in the .shp format. In the geometry type it would be good to include the z-dimension and select the point layer.
Then we can run the plugin and everything is fine
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Try to use Profile tool which you can download from Plugin Manager. The tool can use your existing line layer to extract the profile from the raster data.
Have a look at this video: Using the Profile Tool plugin in QGIS which I selected randomly to show how to use Profile tool.
To use for existing vector layer:
Select the raster image
Add Layer
From the ...
1
Let's say your DEM layers have the names DEM1 and DEM2.
The following expression (in the QGIS Raster Calculator) returns 0 for the differences that have an absolute value that is less than 0.005, and the calculated difference larger absolute differences:
"DEM1@1" - "DEM1@1" * (("DEM1@1" - "DEM1@1" > 0.005) OR ("DEM1@1" - "DEM1@1" < -0.005))
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TRI algorithm was made according to this science paper "Riley, S.J., De Gloria, S.D., Elliot, R. (1999): A Terrain Ruggedness that Quantifies Topographic Heterogeneity. Intermountain Journal of Science".
First, you have to know which pixel size you have? If your pixel size 20x20 then you have some calculations.
TRI Riley classification is based on 1km x 1km ...
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Geospatial Data Abstraction Library (GDAL) will allow you to convert many open raster file types to a USGS DEM. The QGIS GDAL processing toolbox has a tool called Translate (convert formats). Translate (convert formats) allows you to choose USGS DEM as the output.
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