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4

Without seeing specific screenshot examples of what you are seeing, based on research I would say yes, the DEMs are fine and those structures do exist. I pulled up Google Maps and took a look at the terrain and satellite imagery from some of the counties you list. Armstrong shows them with the greatest frequency and proximity, for example at ...


3

Probably because the projection was not in meters. Slope with DEM projected in meters (UTM/31N: EPSG 25831): Slope with the same DEM projected in degrees (WGS 84: EPSG 4326) and z = 1: Slope with the same DEM projected in degrees (WGS 84: EPSG 4326) and z = 111320 (at the equator one horizontal unit, 1°, would correspond to about 111320 m):


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DTM is used interchangeably with DEM sometimes, but since you are asking to go from DEM to DTM then you must have something specific in mind. DEM format is normally a raster where each pixel's value represents an elevation. DTM sometimes refers to non-raster formats like a Triangulated Irregular Network (TIN). If that's what you want, you could use the ...


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Height data can come in the form of vector or raster data. Normally "posting" or "posts" is used in conjunction with vector height data and "horizontal resolution" refers to the grid/pixel size of a raster height model. The terms 'horizontal resolution' and posting sometimes get used interchangeably, so I wouldn't get too hung up on the vector vs raster ...


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Okay, I've provided this answer to try and consolidate my comments above and to serve as a resource for others contending with the issue of stream burning. As I stated in my answer to this question Shapefile and DEM: check rivers behaviour, you would expect a mapped vector stream data set to deviate from a corresponding DEM-extracted stream network because ...


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Aster DEMs are in EPSG 4326 (lat lon WGS84). According to the Gdal DEM documentation "For LatLong projections near the equator, where units of latitude and units of longitude are similar, elevation (z) units can be converted to be compatible by using scale=370400 (if elevation is in feet) or scale=111120 (if elevation is in meters). For locations ...


2

Hillshade computes the local illumination from a light source located at infinity (like the sun). Basically, it yields the cosinus of the normal to the face of the terrain and the light ray. This can be used for : visualisation and cartography : the light source is then located near the north, which then gives a nice picture of the relief. analysis ...


1

You write that you have reprojected the DEM from WGS84 to UTM, but the -projwin coordinates you give are in degrees. That does not work. You have to work either in degrees, or a projected CRS in metres (or else). Turning On-the-fly-reprojection OFF and work solely in one CRS is a good way to avoid such errors in raster operations.


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Stelios is kind of on the right lines in his comment. However, you are using Projected coordinates in the dialog box and that is fine but it throws the error because the y value of corner 2 is less than the y value of corner 1. Fix it simply by swapping them over (i.e. go lower right to upper left instead of UL to LR).


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There are several resources available according to a basic Google search on "Mars GIS data". For instance: USGS Planetary GIS Web Server (PIGWAD, and no I'm not making that up) Mars Open Planetary Data Arizona State University Mars Global Datasets


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You can use the raster package: library(raster) dem = raster.open("a_dem') # plot with R library(rasterVis) plot3(dem) # convert the raster to a matrix (as Volcano) demmat = as.matrix(dem) Now, you can apply the same procedure as in r2stl/demo/Maungawhau.R z = demmat x = 1:dim(demmat)[1] y = 1:dim(demmat)[2] library(r2stl) r2stl(x, y, z, ...


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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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You can generate new cross sections using Hec-Ras, you draw a line like a center of your river then you need to use the coordinates of your cross sections (I used Covadis software to get them). this video expalin the process https://www.youtube.com/watch?v=VlsTNNIi6Kc


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Have you considered "burning in" the main drainage channel? This is a process which is explained well in another thread here: How to 'burn' a stream network into a DEM layer in ArcGIS 10? It can help to account for common errors in elevation data (like bridges or roads crossing the river). It should force the flow in that area and produce a more ...



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