Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
2017-03-30 16:02 GMT-06:00 Rich Shepard : > On Thu, 30 Mar 2017, Laurent C. wrote: > >> In that case, you will not see the accumulation upstream the culvert that >> should normally occur if the pipe is actually higher than the ground. > > > Laurent, > > Both invert and outfall are above ground level and below the road. If > r.carve used the mean elevation between the two then the 'stream' is higher > than the bottom of the roadside swale. This should accumulate water until > the elevation matches the invert, correct? Rich, As far as I understand, r.carve interpolate the elevation using as starting points the DEM bellow the extremities of the vector lines. So if the DEM at these points is equal to the invert elevation of your culvert, you're good. Laurent >> Please note that in a future version, Itzï will be able to model culverts >> more accurately thanks to a coupled drainage model. But this might be in a >> few months. > > > I'd like to do the best that Itzi can with the current version. I may have > opportunities to do more flat land hydrologic models so the more fluent in > Itzi I am the easier it will be and the less I'll be asking for help. :-) > > > Rich > ___ > grass-user mailing list > grass-user@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Laurent C. wrote: In that case, you will not see the accumulation upstream the culvert that should normally occur if the pipe is actually higher than the ground. Laurent, Both invert and outfall are above ground level and below the road. If r.carve used the mean elevation between the two then the 'stream' is higher than the bottom of the roadside swale. This should accumulate water until the elevation matches the invert, correct? Please note that in a future version, Itzï will be able to model culverts more accurately thanks to a coupled drainage model. But this might be in a few months. I'd like to do the best that Itzi can with the current version. I may have opportunities to do more flat land hydrologic models so the more fluent in Itzi I am the easier it will be and the less I'll be asking for help. :-) Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
2017-03-30 12:38 GMT-06:00 Rich Shepard : > On Thu, 30 Mar 2017, Laurent C. wrote: > >> You can create a new vector map and create a line that link the two >> points. However, r.carve will interpolate the elevation between the start >> point and the end point. > > > Laurent, > > Have this line in a vector map called 'stream.' > >> If you culvert invert have a lower elevation, this will not show up. But >> considering the amount of simplification you're already applying, it could >> be acceptable. > > > The invert has a slightly higher elevation than the outfall. Both are > lower than the elevation of the road over the culvert. Rich, In that case, you will not see the accumulation upstream the culvert that should normally occur if the pipe is actually higher than the ground. Please note that in a future version, Itzï will be able to model culverts more accurately thanks to a coupled drainage model. But this might be in a few months. Regards, Laurent ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Laurent C. wrote: You can create a new vector map and create a line that link the two points. However, r.carve will interpolate the elevation between the start point and the end point. Laurent, If my visual interpretation of the output (detail of culvert attached) is correct, this new DEM (with metric elevations) is suitable for input to Itzi. The culvert depth is clearly less than the road surface. Thanks, Rich___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Laurent C. wrote: You can create a new vector map and create a line that link the two points. However, r.carve will interpolate the elevation between the start point and the end point. Laurent, Have this line in a vector map called 'stream.' If you culvert invert have a lower elevation, this will not show up. But considering the amount of simplification you're already applying, it could be acceptable. The invert has a slightly higher elevation than the outfall. Both are lower than the elevation of the road over the culvert. Will try this and see how it compares to the base map. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Laurent C. wrote: You need first to create a new vector map (or edit an existing one) and select "digitize new line". Laurent, Oh. Didn't notice the combo box on the extreme left side. Sigh. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
2017-03-30 12:09 GMT-06:00 Rich Shepard : > On Thu, 30 Mar 2017, Rich Shepard wrote: > >> Would the process be to use v.edit on a copy (called 'stream') of the >> culvert point map to generate a straight line between the two points? That >> would provide the vector input r.carve wants. > > > How do I add a line between two specific points using the vector digitizer > in the GUI map display window? > > Clicking on one point, then on the other point does not show a line > between the two points. > > Clicking on one point and dragging the cursor to the other point before > releasing the button also does not display a line between the two points. > > Clue stick needed. You need first to create a new vector map (or edit an existing one) and select "digitize new line". Laurent ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
2017-03-30 12:00 GMT-06:00 Rich Shepard : > On Thu, 30 Mar 2017, Laurent C. wrote: > >> If you want to 'open' the culvert, you'll have to cut through the road. >> You can do this with r.carve, for example. > > > Certainly worth doing. The r.carve manual page requires as input a vector > map containing streams. Having only two points (culvert inlet and outlet), I > suppose the idea is to create a stream between those two points. > > Would the process be to use v.edit on a copy (called 'stream') of the > culvert point map to generate a straight line between the two points? That > would provide the vector input r.carve wants. Rich, You can create a new vector map and create a line that link the two points. However, r.carve will interpolate the elevation between the start point and the end point. If you culvert invert have a lower elevation, this will not show up. But considering the amount of simplification you're already applying, it could be acceptable. Regards, Laurent ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Rich Shepard wrote: Would the process be to use v.edit on a copy (called 'stream') of the culvert point map to generate a straight line between the two points? That would provide the vector input r.carve wants. How do I add a line between two specific points using the vector digitizer in the GUI map display window? Clicking on one point, then on the other point does not show a line between the two points. Clicking on one point and dragging the cursor to the other point before releasing the button also does not display a line between the two points. Clue stick needed. Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Laurent C. wrote: If you want to 'open' the culvert, you'll have to cut through the road. You can do this with r.carve, for example. Certainly worth doing. The r.carve manual page requires as input a vector map containing streams. Having only two points (culvert inlet and outlet), I suppose the idea is to create a stream between those two points. Would the process be to use v.edit on a copy (called 'stream') of the culvert point map to generate a straight line between the two points? That would provide the vector input r.carve wants. Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
Rich, If I understand well, you have a 'raw' DEM and you want to open the culvert in that DEM. If it is an under-road culvert, your 'raw' DEM will show the road elevation, and the culvert will not be shown. i.e the culvert is blocked. If you want to 'open' the culvert, you'll have to cut through the road. You can do this with r.carve, for example. Regards, Laurent 2017-03-30 10:04 GMT-06:00 Rich Shepard : > On Thu, 30 Mar 2017, Nikos Alexandris wrote: > >>> For the record: there is a "differences" color table which is useful for >>> this. > > >> Don't forget to try r.colors with -e or -a -g if the first attempt does >> not >> show much differences. > > > I _had_ not noticed the 'differences' color table. Applying that produces > interesting results (see attached .png). > > The four blue cells are ~0.6m higher in the blocked map than in the open > culvert map. I don't know the reason for the lighter blue cell to the > southwest of the group of four. I suspect, but don't know, that the pinkish > cells represent slightly higher water accumulation in the blocked map than > in the open map. > > Germane to what Markus M. wrote, "The point locations used to edit the > original DEM are probably wrong (not close to the center), ..." I now think > that's where I made one mistake. When I isolated those four cells and > queried them I truncated the easting and northing coordinates to the integer > value assuming that all elevations in a 1m x 1m cell were the same. If this > assumption is incorrect then I'll re-create the change and start the model > running again with a slightly different set of elevations for those cells. > > If anyone can suggest other changes to the model input to better show > where water accummulates behind a blockage please let me know. > > Rich > > ___ > grass-user mailing list > grass-user@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Rich Shepard wrote: Germane to what Markus M. wrote, "The point locations used to edit the original DEM are probably wrong (not close to the center), ..." I now think that's where I made one mistake. Nope. I zoom in to isolate those 4 cells in in the blocked map. No matter where within the cell I click the elevation is the same. However, ... I'm now wondering if the issue is the elevation in feet rather than meters. The source DEMs were run through r.proj to convert from feet to meters. This converted the coordinates but apparently not the elevations. If Itzi wants all input in SI units then having elevations in feet with rainfall in mm/hr would certainly get the model's briefs in a twist. If having elevation data range from ~147 to ~168 feet rather than ~45m to ~51m would produce incorrect results then I suppose I need to multiply both input maps (open and blocked) by 0.305 using r.mapcalc, then run both models again. Comments? Thoughts? Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, 30 Mar 2017, Nikos Alexandris wrote: For the record: there is a "differences" color table which is useful for this. Don't forget to try r.colors with -e or -a -g if the first attempt does not show much differences. I _had_ not noticed the 'differences' color table. Applying that produces interesting results (see attached .png). The four blue cells are ~0.6m higher in the blocked map than in the open culvert map. I don't know the reason for the lighter blue cell to the southwest of the group of four. I suspect, but don't know, that the pinkish cells represent slightly higher water accumulation in the blocked map than in the open map. Germane to what Markus M. wrote, "The point locations used to edit the original DEM are probably wrong (not close to the center), ..." I now think that's where I made one mistake. When I isolated those four cells and queried them I truncated the easting and northing coordinates to the integer value assuming that all elevations in a 1m x 1m cell were the same. If this assumption is incorrect then I'll re-create the change and start the model running again with a slightly different set of elevations for those cells. If anyone can suggest other changes to the model input to better show where water accummulates behind a blockage please let me know. Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Thu, Mar 30, 2017 at 2:46 AM, Rich Shepard wrote: > > On Wed, 29 Mar 2017, Vaclav Petras wrote: > >> As Soeren mentioned in the other part of the thread, use r.univar to get >> the statistics. Don't rely on just looking at the resulting raster map. >> There can be things like outliers which may throw the visualization off. > > > Vaclav, > > Here are the results of r.univar on the output of r.mapcalc "output_diff = > blocked_h_max - open_h_max": > > [...] > min=-1.89342188835144 > max=0.00093058729544282 > [...] > > [...] I see a small range and many null > cells, but I expect that because 4 cells on one input DEM are set about 0.6m > higher elevation than those on the other input DEM. Apparently something went wrong because min should be 0 and max should be about 0.6. The point locations used to edit the original DEM are probably wrong (not close to the center), and the computational region might have been changed somewhere in the process of editing the original DEM. Markus M ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Wed, Mar 29, 2017 at 8:46 PM, Rich Shepard wrote: > n=140652 > null_cells=71271 > cells=211923 > Relatively hight number of null cells. > min=-1.89342188835144 > max=0.00093058729544282 > range=1.89435247564688 > Probably small differences, but there is at least one outlier. > mean=-5.03205256742558e-05 > mean_of_abs=5.24979771199771e-05 > sum=-7.07768257713542 > median=0 > The overall differences are small or cancel out as they are distributed around zero. Looking at histogram may also help you interpret these statistics. ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
Rich Shepard wrote: No differences? Wrong syntax? GRASS hung due to an initial syntax error; corrected. Now I have the difference map which is a solid color using the elevation color table. Ergo, no differences. Moritz: For the record: there is a "differences" color table which is useful for this. Don't forget to try r.colors with -e or -a -g if the first attempt does not show much differences. Nikos ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Wed, 29 Mar 2017, Vaclav Petras wrote: As Soeren mentioned in the other part of the thread, use r.univar to get the statistics. Don't rely on just looking at the resulting raster map. There can be things like outliers which may throw the visualization off. Vaclav, Here are the results of r.univar on the output of r.mapcalc "output_diff = blocked_h_max - open_h_max": n=140652 null_cells=71271 cells=211923 min=-1.89342188835144 max=0.00093058729544282 range=1.89435247564688 mean=-5.03205256742558e-05 mean_of_abs=5.24979771199771e-05 stddev=0.00847518705371129 variance=7.18287955953955e-05 coeff_var=-16842.4056389523 sum=-7.07768257713542 first_quartile=-7.4142e-09 median=0 third_quartile=2.60843e-09 percentile_90=7.45058e-08 With no experience interpreting r.univar output I'm not sure what the above tells me about the two maps. Yes, I see a small range and many null cells, but I expect that because 4 cells on one input DEM are set about 0.6m higher elevation than those on the other input DEM. Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Tue, Mar 28, 2017 at 4:30 PM, Rich Shepard wrote: > Now I have the difference map which is a solid color... > ...Ergo, no differences. > As Soeren mentioned in the other part of the thread, use r.univar to get the statistics. Don't rely on just looking at the resulting raster map. There can be things like outliers which may throw the visualization off. Vaclav ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On 28/03/17 22:30, Rich Shepard wrote: On Tue, 28 Mar 2017, Rich Shepard wrote: No differences? Wrong syntax? GRASS hung due to an initial syntax error; corrected. Now I have the difference map which is a solid color using the elevation color table. Ergo, no differences. For the record: there is a "differences" color table which is useful for this. Moritz ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.mapcalc: compare two maps [RESOLVED]
On Tue, 28 Mar 2017, Rich Shepard wrote: No differences? Wrong syntax? GRASS hung due to an initial syntax error; corrected. Now I have the difference map which is a solid color using the elevation color table. Ergo, no differences. Rich ___ grass-user mailing list grass-user@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-user
