Watershed OpenCV. In the remainder of this post, I’ll show you how to use the watershed algorithm to segment and extract objects in images that are both touching and overlapping. To accomplish this, we’ll be using a variety of Python packages including SciPy, scikit-image, and OpenCV.
Hi Jason,On the wish list or not, it's a fantasy. Any one who tells you they can doit has no knowledge of TIN models.Unless you pick a point which is exactly on a line in the model where thetwo triangles on each side of the line slope towards the line forming avalley, the catchment area to a point is a line. And, as you know a linehas zero area.You could make some sort a guess and get a catchment area which drains tothe triangle which you pick - or some other convention such as an assumptionof water depth at the point, or a nominal length of gutter at the point, butwould you rely on something like this without knowing what the conventionwas and whether that would be realistic in the circumstances of your design?The watersheds defined for the TIN model are areas bound by 'ridge lines' inthe model. They are a guide to the user in as much as water from outside acatchment cannot get into the catchment because it would have to flow over aridge line to do so.Obviously in practice, water in flat country can cross catchment boundariesas the water depth can exceed height of the ridge line above the invert inthe catchment area.As an example of this, I once had to analyse a 'maximum probable rainfall'event.
A rail embankment varying from 3 to 7m high (nominally horizontalfor the trains) ran across several valleys with 6m by 4m culverts at thevalleys. These culverts were no where near adequate for the event I wasanalysing and water would have flowed between the valleys had the stormevent occurred.At it's peak, it is likely the water would have flowed about a metre deepover the rail line over a length of about 6km and washed significantportions of the embankment away.-Laurie ComerfordCADAppswww.cadapps.com.auwww.civil3Dtools.com'Jason Hickey' wrote in messagenews:[email protected] wrote: I just tried using the watershed analysis routine. It left me somewhat confused. The model is in mountainous terrain and was developed from 24k contours.
I would like to be able to pick a spot on the surface and have the software delineate the drainage basin discharging at this point. Can this be done?It's on the wishlist.-Jason HickeyCivil 3D 2007, SP3Dell Precision M702 GIG RAM, 256 MB nVidia Quadro FX Go1400Intel Centrino 2 gHz Processorwww.civil3d.com.
I am trying to delineate watersheds automatically using Arcgis/Arc Hydro.I got the drainage area contribution of stream segment (part of stream) as shown in figure stream. The corresponding drainage area as shown in figure area. But I am looking for drainage areas/catchment areas as shown in figure Water Shed. In watershed figure, at any point on the stream, it calculates drainage area by considering entire upstream length of the stream. Suppose, if you choose point '8', its catchment/drainage area covers the area of points '9' and '10'.
Similarly for point '5' covers all points upstream of stream.I want to get similar automatic watershed delineations.Please guide me to the software/method to get the result as shown in figure watershed for my entire stream network of an area. The areas you are looking to create are called 'subwatersheds' or subsheds. You can use the 'Batch Subwatershed Delineation' tool in ArcHydro under the 'Watershed Processing' menu. This will calculate subsheds from a set of points you define. The other input is a flow direction grid. This is a raster where the value of each pixel represents the direction water would flow from this pixel (N, NE, E, SE, S, SW, W, NW).The data you have in your screenshots look like the 1:100,000 resolution National Hydrography Dataset (NHD).
If this is the case, the has a flow direction grid already calculated that you can download. Otherwise, you will need to use the 'Flow Direction' tool in ArcHydro under the 'Terrain Preprocessing' menu to manually calculate flow direction from an input digital elevation model (DEM).Note that the spatial resolution of your subwatersheds is limited to the spatial resolution of the input DEM. Thanks for your reply. I have given figure watershed with limited points(10) for understanding. If it is the case, I can choose each point and calculate corresponding areas by using batch process in archydro. But in my case, to my entire stream network, I have taken points at equal interval(say 100m).
So I got points in multiple of thousands along the stream (entire network include branches). In this case I cannot take each and every point along the main stream and branches and do batch process to get result.Hence I need a automatic process to calculate by any software or by any method.pls.–Aug 5 '12 at 14:56.
Comments are closed.
|
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |