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From your diagram it appears that you're interested in the points where the change in gradient is the most. Since the gradient of a line measures the rate of change (i.e. can be considered the derivative), then the gradient of the gradient is the rate of change of the gradient (i.e. can be considered the second derivative). So from this assumption we can say ...


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It sounds to be like you have not assigned the nodata values correctly. To correct this, try: Spatial Analyst Tools -> Conditional -> SetNull. Select your raster as the input conditional raster AND the input false raster and type in the “Expression” box: Value < -10 AND Value > 9000 (case and space sensitive). This means: “Set to Null all the points ...


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You do not say if you are in academia? If you are then the obvious place to go would be edina and digimap. If you are not then have a look here for free elevation data. Of cause you could go to OS the national mapping agency of the UK and get a 50m terrain model...


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Free of charge i would say: Get either ASTER or SRTM from earthexplorer. Both are available at 1 arc-sec., respectively ~20m vertical rmse.


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Set both the scale and the vertical exaggaration ("z-factor") to 1. The equation you found for calculating the scale only applies if you're working with geographical coordinates (i.e. degrees longitude and latitude) that need to be converted to metres, but the data you have is in a projected coordinate system (NAD83 / UTM zone 17N) that already uses metres.


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Based on the added information in your comment, I would suggest to use the GRASS module r.in.xyz. There are some issues lately with the QGIS GRASS plugin, so I'd work directly in GRASS, standalone. First, when you start GRASS, you're required to setup the GRASS database, and LOCATION. The LOCATION is defined by the coordinate projection parameters. Make sure ...


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The viewshed analysis plugin will help you, but I have never tried it with the cumul of all pixels (this would need as many tests as you have pixels, so it might become VERY heavy if you have a large DEM). However, it can take a set of points as inputs for the analysis in order to have the number of points that can be seen (or that can see your pixel). With ...


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BradHards is right. If you let us know the environment you are working in the stackexchange community can narrow down the answers specific to your tools. For now I will answer the high level question of what 1.4m resolution means. Forgive me if I provide basic info you already know, but I am unaware of your level of understanding and don't want to skip ...


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There are some tools that will meet your needs: GRASS GIS r.sunmask tool - which will perform fully automatic shadow cast computation based on DEM. It is based on SOLPOS 2.0 sun position algorithm. Please refer to detailed description on GRASS manual webpage. SAGA-GIS Analytical Hillshading module - this tool will also derive shadow cast but it's not as ...


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You can use gdaldem. I suggest you to have a look on http://blog.thematicmapping.org/2012/06/creating-hillshades-with-gdaldem.html You can can produce hillshade for all the azimut and elevation angles and then combine them together.



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