Creating a map of slopes is common practice when looking at slope stability. Some examples of when you may want to create slope maps would be to identify areas with high slope to indicate avalanche or landslide danger. Another example may be to present slope maps of the seabed so that a structure with set tolerances for inclination could be located. Slope and gradient maps can be easily generated using Surfer.
Slope information can be easily computed from grid, raster or digital elevation models (DEMs) using options under the Grid | Calculus menu command in Surfer. The slope values can be expressed either in degrees or as a decimal (rise/run) which can then be computed as a percentage. For example, using Grid | Calculus you could select:
Using a digital elevation model (or any grid file), create slope maps either by calculating terrain slope in degrees or the gradient of the slope in percent.
Let’s walk through an example. Let’s say we have an area that is prone to avalanches and we want to indicate on a map the areas where the slope is greater than 30°. To do this, follow these steps:
Create a 3D surface map and drape a georeferenced image on top of it to visualize the DEM.
Select the Terrain Modeling | Terrain Slope option in the Grid Calculus dialog.
Add slope contours to the 3D surface map
Set the contour levels to visualize the areas that have a slope above a 30° angle.
Another way to visualize this data is to create a base map of a USGS DRG file showing the elevation contours, and overlaying that map with a contour layer of the slope data.
Additionally visualize the slope results on a 2D map of elevation contours. Print this map to take with you in the field.
Please note that when calculating slopes from DEM or grid files, Surfer uses the X, Y and Z values proportionally when calculating the slope values. Therefore, the X, Y and Z values must be in the same units, and the units must be linear (e.g. feet or meters) for the slope calculation to be correct. If the X and Y units in the grid file are in lat/lon, then the slope calculated for each node will be almost vertical because the X and Y extents (the lat/lon ranges) are so small compared to the difference in Z values. In this case, convert the coordinate system of your data, DEM or grid file from lat/lon to another system with linear units prior to calculating the slope. For instructions on how convert the XY coordinates for raw data, DEMs, please see our newsletter article: Converting the Coordinate System of Data, Image, Vector, and Grid Files in Surfer .
Slope maps can be powerful tools when evaluating sites for safety, field engineering, projecting road layouts or drainage patterns, and many other applications. Surfer can also calculate other terrain modeling information, such as aspect and curvature to make sure you get the information you need to make informed decisions.
Yes, it is possible to visualize areas where the slope is greater than 100%. A slope of 100% is where the vertical distance is the same as the horizontal distance (a 45° slope). To do this, click Grids | Calculate | Calculus. Select your input grid, choose Differential & Integral Operator | Gradient Operator, specify the output grid, choose to create a new contour map and click OK.
The Z value in this grid is rise/run. To convert it to a %, click Grids | Calculate | Math. In the Grid Math dialog, click Add Grids, select the new grid and click Open. Enter a function A*100 to multiple the Z values in the grid by 100 to convert them to a %.
Then to visualize the areas where Z is over 100%, create a contour map (Home | New Map | Contour Map, select the grid file and click Open). Select the Contours layer and in the Properties window, click the Levels tab, change the Minimum contour value to 100. You can change the Contour interval to something greater than the difference between the new contour minimum and contour maximum value to get a single interval for the area above 100%. You can then fill the contours if you wish or overlay it with other maps.
Your is really helpful create 3d surface for architectural modelling and rendering.
Is it possible export obj or fbx file format for 3d software ?
3d Motion Studio
Thanks for the kind comment! It is not currently possible to export to OBJ or FBX file formats, but I have added votes for this functionality to our feature request file.
GS Technical Support
Thanks for your kind reply.
3d Motion Studio
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3D Rendering Studio.