Hot answers tagged terrain
15
There are different possible implementations, but most procedures will start from a grid and not from a TIN.
The simplest one is most likely the D8 procedure: you calculate the direction where water would be flowing. There are 8 possibilities, the 8 cells that are next to a central grid cell. You can first calculate these directions, than how cells are ...
13
Curvature is a complex terrain derivative to compute, the equation that you use depends on the resolution of your input data, as you have to ensure that the curvature results you compute can be distinguished from noise in the data.
A lot of research has been done recently on curvature calculations on high resolution LiDAR data which showed that a scaling ...
10
It is all very dependent on your needs. You know that TIN is a vector-based representation whereas DEM is represented as a raster from grid of squares. Actually TIN is a type of DEM and derived from the raster DEM.
The TIN representation has information about altitude, slope and aspect and you can use them to extract the areas you require.
There is an ...
10
ESRI's version of Raster Analysis for calculating curvature might be helpful to develop a plugin for QGIS.
For each cell, a fourth-order polynomial of the form:
Z = Ax²y² + Bx²y + Cxy² + Dx² + Ey² + Fxy + Gx + Hy + I
is fit to a surface composed of a 3x3 window. The coefficients a, b, c, and so on, are calculated from this surface.
The ...
9
There are several open data initiatives on elevation (terrain) data.
A website with several alternatives (I have not checked them all) is available on this website:
http://www.terrainmap.com/rm39.html
For 90 meter accuracy dataset I would try the Shuttle Radar Topography mission (wikipedia article). I have used it on several occasions. An example of ...
6
ArcGlobe
http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=ArcGlobe_3D_display_environment
Lots of RAM required.
Though Google Earth might be a better option. (as comes with a flight sim)
http://earth.google.com/intl/en/userguide/v5/flightsim/index.html
6
Compute the focal range grid using a 2 x 2 neighborhood. (Use the option where NoData cells are ignored.)
Any two adjacent pixels will be included within at least one neighborhood. Therefore, if any pair of cells differ by more than 16 m, they will cause at least one surrounding neighborhood to have a focal range exceeding 16 m.
If the focal range of a ...
6
Mike Migurski (of Stamen Design) recently made a major new open terrain map: details on his blog and I put up a quick map viewer for it. It does terrain relief shading with various DEM sources combined with roads, labels, etc from OpenStreetMap. The source code to generate the map is on GitHub.
6
TopOSM has terrain tiles - though limited coverage (US Only)
http://www.toposm.com/us/
Full Details
http://wiki.openstreetmap.org/wiki/TopOSM
All the Rendering and Source files are available
http://svn.openstreetmap.org/applications/rendering/toposm/
License is the same as Open Street Map
OpenStreetMap Data is available under the Creative Commons ...
6
I think gdal_tranlate is going to be your best bet. I too am having to do this now to get elevation data in Vue for 3D simulations. Right now, I am going from whatever grid format to tif, then using gdal_translate to go to dem. If there is a way to do this natively using ESRI tools, I'd love to know about it. You can use the -projwin flag to clip as you ...
5
An original approach is the one proposed in this paper:
Fisher, P., J. Wood, and T. Cheng (2004). Where is Helvellyn? Fuzziness of multiscale landscape morphometry. Transactions of the Institute of British Geographers 29, 106-128.
It proposes a method based on fuzzy and multi scale representation. I am not sure but this method may be the one implemented ...
5
You can generate your own using Maperitive:
generate-relief-igor command
generate-tiles command
A sample hiking map using such tiles.
5
ArcGIS claims to be able to do this at 10 with new 3D Analyst tools: Virtual City Template Enables 3D City Modeling. I say claims because I haven't personally used these tools yet. Here's the documentation for the tool discussed in that article: How Skyline Barrier (3D Analyst) works
5
I provide a number of sample LiDAR files at http://liblas.org/samples that you can download. These are mostly example data, but many are quite interesting. You can use the las2txt utility that libLAS provides (or Isenburg's las2txt version as well) to convert them to XYZ ascii files.
Isenburg's tools also provide a number of fantastic triangulation ...
5
The algorithm is fairly simple. In a nutshell, it searches different possible platform elevations, computes the cut volume, dumps that into the fill area, and checks whether there is any left over or lacking.
In detail, the algorithm deals with a digital representation (TIN or grid) of an idealized surface which we can think of as the graph of an ...
5
try or read this page for some good information. and second link show you the way of random digital elevatin model...
Numerical and Scientific Python and Data Visualisation
creating elevation/height field gdal numpy python
i hope it helps you
5
I've done maps like this before in ArcGIS years ago. I would clip the elevation raster (usually NED from USGS) to the vector polygon of the study area. Next, create a hillshade of the elevation raster, drape that over the source NED raster, then play around with the transparency/contrast/color ramp of the hillshade to get it to look like I wanted - you might ...
5
Natural Earth has many top-notch free products that may work for you, including:
Natural Earth I with Shaded Relief, Water, and Drainages
Shaded Relief Basic
4
It seems like there should be a way to derive AS from a skyline graph created using the ArcGIS 10.0 3D analyst. If you have a skyline (3D polyline) that surrounds an observation point, it should be able to step through each vertex on the skyline and find some portion of a sphere that is visible.
Or, if you moved each vertex so that it is one unit ...
4
If you have access to arcinfo-workstation (that is: command line arcinfo) then use the LATTICEDEM command to convert from raster to USGS DEM. If you have Arcinfo License level then workstation is available from the original installation media (up to v10.0) but isn't installed by default.
Arc: latticedem
Usage: LATTICEDEM <in_lattice> <out_dem> ...
4
I actually like using the Rugosity index from Lundblad et al.
http://dusk.geo.orst.edu/esri04/p1208_cc.html
http://proceedings.esri.com/library/userconf/proc04/docs/pap1208.pdf
(I think this was only published as a paper presentation, but it is one of the most cited posters in oceanography.)
4
Have you tried to perform any histogram stretching? If you are using a raw satellite image it will be less visually appealing without any stretching. If you are thinking of using osgearth I would assume that you are using the satellite image for a 3D application? I have worked in the 3D visualization industry for the better part of a decade and all raw ...
4
You've got a projection issue. Chances are you've not specified the projection of the DEM correctly.
There are typically two indicators to this and you have both:
You have spikes.
You have a cell size that looks like: 0.000278 (it should be a whole number).
So make sure you've set the correct projection for the DEM as well as the drape (if memory serves, ...
4
In this Wiki we maintain a list of free data sets:
http://grass.osgeo.org/wiki/Global_datasets#Elevation_data
For several also the import commands for GRASS GIS are stated (in many cases read with GDAL, hence the GDAL tools should work as well).
3
The folks at telascience are starting to revive the OpenAerialMap.org project which is on hold for now. They have already processed NAIP which can be found at http://hyperquad.telascience.org/naip/ They also have world coverage of Landsat done.
As far as contours, elevation, shaded relief, etc, part of the plan is to include SRTM http://srtm.csi.cgiar.org/ ...
3
If you have the Esri Interoperability Extension, then you can extend it using the FME ArcGIS Data Interop Edition. This gives access to most of the raster formats supported by FME:
http://safe.com/solutions/for-applications/esri/esri-arcgis/data-interop-comparison/
3
You could try using Perlin noise to create some random fractal terrain. This answer on Stackoverflow explains a way you could get started in Python. The trick would be to zoom in on a very small area of the noisy grid so it's not too irregular looking.
3
Here is an R solution using a Gaussian Kernel to add autocorrelation to a random raster. Although, I have to say that the GRASS r.surf.fractal function, suggested by @markusN, seems like the best approach.
require(raster)
# Create 100x100 random raster with a Z range of 500-1500
r <- raster(ncols=100, nrows=100, xmn=0)
r[] <- runif(ncell(r), ...
2
This is really a comment on Kirk Kuykendall's excellent answer (why has no one been perspicuous or generous enough to vote it up yet?), but I don't have the rep to post a comment.
Kirk suggests
It seems like there should be a way to derive AS from a skyline graph created using the ArcGIS 10.0 3D analyst.
I haven't seen that graph, but presumably it ...
2
Both ArcGlobe & ArcScene are capable of providing 3D terrain Visualization, but the Navigation tools are horrendous.
You could use Google Earth, but when you load your own data, the capabilities are limited:You cannot add your own DEM, The memory consumption goes up with the amount of images that you load, and garbage collection in memory is limited.
...
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